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Article
A Presumptive Standard For Environmental Flow Protection
Abstract
The vast majority of the world's rivers are now being tapped for their water supplies, yet only a tiny fraction of these rivers are protected by any sort of environmental flow standard. While important advances have been made in reducing the cost and time required to determine the environmental flow needs of both individual rivers and types of rivers in specific geographies, it is highly unlikely that such approaches will be applied to all, or even most, rivers within the forseeable future. As a result, the vast majority of the planet's rivers remain vulnerable to exploitation without limits. Clearly, there is great need for adoption of a “presumptive standard” that can fill this gap. In this paper we present such a presumptive standard, based on the Sustainability Boundary Approach of Richter (2009) which involves restricting hydrologic alterations to within a percentage-based range around natural or historic flow variability. We also discuss water management implications in applying our standard. Our presumptive standard is intended for application only where detailed scientific assessments of environmental flow needs cannot be undertaken in the near term. Copyright © 2011 John Wiley & Sons, Ltd.
... Normally, the natural-or close to unimpaired-historical flow regime is seen as a reference desirable state to conserve or restore freshwater ecosystems, and hydrology-based approaches have delivered multiple reference values that range from ecologically relevant hydrological indices to percentages of the mean annual runoff (MAR) [3,[6][7][8][9]. Furthermore, those reference values have been strategic inputs for many national, regional, or basin-scale programs to assess eflow requirements and track progress on environmental water allocation at a planning level as a response to recognizing the environment as a legitimate user [3,[10][11][12][13][14]. However, such reference values are commonly used regardless of the nature of the hydrological behavior of different river types. ...
... This is because of the weighing in the new reference values of frequency factors of flow components occurrence. Such values are in line with the original method [24]; however, unlike the values provided in previous studies [11,12,22], the ones proposed in the present research differentiate between streamflow types. These were developed based on the recognition that they depend differently on hydrological conditions, inter-annual and seasonal variability, consistent with the PCA outcomes (Appendix A Figure A3), the related characteristics of each class, and the significant differences among them. ...
... Furthermore, at a water planning level, the reference values of EWRs expressed as a percentage of the MAR provide streamflow type frequency-based volumes adjusted to a four-class system of environmental objectives. Such reference values have been proposed based on comprehensive assessments [3,[9][10][11][12] and widely used throughout the world (i.e., "look-up tables") to track progress on eflow implementation, i.e., Sustainable Development Goal 6.4.2., the "water stress" indicator and the Global Environmental Flow Information System [14], or to assess the water scarcity accounting for the gap between people's and environmental water needs [44]. ...
Environmental flow (eflow) reference values play a key role in environmental water science and practice. In Mexico, eflow assessments are set by a norm in which the frequency of occurrence is the managing factor to integrate inter-annual and seasonal flow variability components into environmental water reserves. However, the frequency parameters have been used indistinctively between streamflow types. In this study, flow variability contributions in 40 rivers were evaluated based on hydrology, climate, and geography. Multivariate assessments were conducted based on a standardized contribution index for the river types grouping (principal components) and significant differences (one-way PERMANOVA). Eflow requirements for water allocation were calculated for different management objectives according to the frequency-of-occurrence baseline and an adjustment to reflect the differences between river types. Results reveal that there are significant differences in the flow variability between hydrological conditions and streamflow types (p-values < 0.05). The performance assessment reveals that the new frequency of occurrence delivers climate-smart reference values at least at an acceptable level (for 85–87% of the cases, r2 ≥ 0.8, slope ≤ 3.1), strengthening eflow assessments and implementations.
... Hydrological methods are usually based on annual minimum flow thresholds such as 7Q10, the lowest flow that occurs for seven consecutive days once in ten years (Telis and District 1992) or Q 90 , where the flow exceeded 90% of the period of record (NGPRP 1974 Richter, Baumgartner et al. (1997) divided the Indicators of Hydrological Alteration (IHA) into five groups: magnitude, timing, duration, frequency, and rate of change; they determined some environmental flow components (EFCs), such as the maintenance flow, during dry and normal years (Mathews and Richter 2007). Alternatively, EFRs can be calculated using a method called the Range of Variability Approach (RVA) which in nonparametric analyses calculates EFRs as a range between the 25 th and 75 th monthly flow percentile (Armstrong, Todd et al. 1999, Babel, Dinh et al. 2012 or in parametric analyses as a range of mean monthly flow (±standard deviation) (Smakhtin, Shilpakar et al. 2006, Richter, Davis et al. 2012. The advantage of hydrological methods is that they are simple and fast EF methods for use in preliminary assessments or when ecological datasets are not available. ...
... because of the lack of global ecohydrological data (Richter, Warner et al. 2006, Poff andZimmerman 2010 (Hanasaki, personal communication). evaluated monthly EFRs by applying the presumptive environmental flow standard defined by Richter, Davis et al. (2012). Although limited water consumption to 20% of total discharge, this did not imply that 80% of the total discharge was unavailable; they show, however, the period of the year in which net water availability fails to meet water demand. ...
... Smakhtin and Q90_Q50) are overestimating EFRs of perennial rivers and underestimating EFRs of intermittent rivers. The only global method that used monthly proxies based on study cases was found in , however, their study was based on the presumptive method developed by Richter, Davis et al. (2012) which only used four temperate study cases. Furthermore, Richter et al. ...
Freshwater ecosystems are among the most threatened ecosystems on Earth. At the same time, water demand for food is projected to increase with projected increase in population and diet shift putting part of the population under pressure in terms of food security. These projections are likely to be exacerbated by climate change. Over the past decades, irrigated areas have nearly tripled to meet actual human food requirements. Today, 40% of food production comes from irrigated production and about 30% from irrigated areas. This increasing share of irrigated production has come at the expense of freshwater ecosystems and river health. About half of the rivers have been fragmented and altered via the constructions of dams and reservoirs and via diversion of river flow to irrigated fields. Furthermore, water demand for industry, household and hydropower is predicted to increase and competition between water sectors will intensify. Under actual water competition, water availability for freshwater ecosystems has often been neglected.Over the past decade, awareness was given to define planetary boundaries for natural resources especially freshwater ones. While irrigation withdrawals and industries and household withdrawals already reach respectively about 2600 km3 yr-1 and 1000 km3 yr-1, planetary boundaries for freshwater have been defined to 4000 km3 yr-1. With the expected rise in water demand for food and industries, freshwater boundaries are likely to be exceeded in the coming decades and it is urgent to define global water availability and demand with accurate time and spatial resolutions. More specifically, it is necessary to develop a method that enables the calculation of water demand for freshwater ecosystems known as “Environment Flow Requirements” (EFRs). EFRs were often neglected in global assessments and/or defined with annual proxies.The overall objectives of this thesis were to redefine global water demand for freshwater ecosystems (EFRs) and set these last as a priority in global integrated assessments. For that, it was necessary to design a robust methodology that can be easily implemented in Global Hydrological Models (GHMs) and in global integrated assessments. In chapter 2, existing global and local Environmental Flow (EF) methods were reviewed. Three methods were selected among existing global methods, including the Smakhtin method, which is based on a combination of annual quantiles and proxies of annual flow, the Tennant method, which is based on annual proxies of flow, and the Tessman method, which is based on monthly proxies of flow. Two other methods were designed for this study: the Variable Monthly Flow (VMF) method, which is based on the allocation of the percentage of monthly flow to the environment and the Q90_Q50 method, which is based on the allocation of flow quantiles. These methods were compared with 11 local case studies from different ecoregions, for which EFRs have been defined locally with ecological and hydrological data collection. The VMF method showed the best performance against local case studies and demonstrated easiness of use and validation with different flow regime types. Among the five global EF methods, EFRs represent 20 to 50% of mean annual flow to maintain EFRs in “fair” ecological conditions.In chapter 3, the concept of “Environmental Flow (EF) deficit” was designed. It represents the lacking flow to meet EFRs. EF deficit was defined on a monthly basis at 0.5 deg. The originality of this study is that the origin of the deficit was characterized by the natural deficit and the anthropogenic deficit. Natural deficit is defined when EFRs are not met due to natural climate variability and anthropogenic deficit is defined when EFRs are not met due to water extractions for irrigation or other users. The frequency, timing and magnitude of each deficit were also calculated at global scale. The EF deficit was also studied for 23 river basins, which are located in different ecoregions, and it was shown that flow regime type, origin of deficit, magnitude of deficit and level of flow alteration were correlated. Perennial rivers such as the Congo River showed only natural deficit while very altered river such as the Godavari river showed high respective natural and anthropogenic deficit. In chapter 4, we set EFRs as a priority user in the global vegetation model LPJmL. It was shown that to sustain EFRs in “fair” ecological conditions, irrigation water use should be reduced by 30%, which would lead to 30% less food coming from irrigated area and a total of 5% loss in food production. Calorie loss per capita was really high in developing countries where population density is high such as in South-East Asia. This loss in food production can however be compensated by an increase of 50% in irrigation use efficiency.In chapter 5, we used an economic optimization model (GLOBIOM) to study future global change including different constrains of EFRs. It was shown that, under future climate change (RCP 8.5) and socio-economic development (SSP2), international trade should be increased by 15% to compensate for EFRs implementations compared to a business-as-usual scenario. The positive outcome is that it was demonstrated that food and water security for humans and ecosystems can be sustained with three levees: use of trade (+15%), conversion of irrigated land to rainfed land (60Mha) in South Asia and expansion of rainfed land into natural area in Latin America.In the chapter 6, we reviewed and analyzed each chapter as an ensemble. The new development of the VMF method is acknowledged thanks to its application in all chapters of this thesis and in many other global assessments. Among them, two studies redefined the freshwater planetary boundaries at 2,800 km3 yr-1 which is lower than previous estimates defined by Rockstrom et al. (2009). This thesis allowed the inclusion of EFRs in global integrated assessments with refined temporal and spatial scales and water demand for ecosystems are now recognized and acknowledged. The limitations of the VMF method are also discussed such as its weakness to be compatible with inter-annual studies considering extreme events such as floods and droughts. Further data collection on eco-hydrological relationships should be organized and harmonized at global scale to further improve EFRs at global scale. Characterization of EF deficit with differentiation of the anthropogenic and natural deficit can be used as a tool to prioritise actions in terms of river restoration/protection. In face of meeting future SDGs, we highlighted the complexity in meeting food and water security for humans and ecosystems. Competition between different water sectors already exist and require local, regional and international consensus to satisfy all water users while safeguarding water availability for freshwater ecosystems. For that, future improvement in agriculture and water management is fundamental to provide future sustainable water access to humanity.
... Furthermore, aquatic species have evolved within and adapted to the natural flow regime, and alterations to it may facilitate invasive species. Therefore, although riverine ecosystems are extremely complex, the association between flow regime alteration and riverine ecosystem integrity is strong (Poff and Zimmerman, 2010;Rolls et al., 2018). ...
... These methods assume that not transgressing EFRs will retain a fair state of riverine ecosystems. Even though this proxy relationship is uncertain and varies across spatial and temporal scales (Bunn and Arthington, 2002;Poff and Zimmerman, 2010;Rolls et al., 2018), the hydrological EF methods are often used in global studies as presumptive standards of sustaining riverine ecosystems (Gerten et al., 2020(Gerten et al., , 2013Hanasaki et al., 2008;Hoekstra and Mekonnen, 2011;Hogeboom et al., 2020;Pastor et al., 2014Pastor et al., , 2019Steffen et al., 2015). In addition to ecological uncertainty, discharge data used for determining EFRs in global studies are uncertain; runoff and discharge estimated by global hydrological models (GHMs) that are forced with modelled climate from general circulation models (GCMs) tend to be highly dispersed between different GHMs and GCMs (Gädeke et al., 2020;Hattermann et al., 2018;Müller Schmied et al., 2016;Schewe et al., 2014;Veldkamp et al., 2018;Zaherpour et al., 2019). ...
... Moreover, hydrological EF methods often only set a minimum discharge boundary, disregarding the potentially adverse effects of flows increasing significantly above natural levels -especially in floodplain ecosystems (Hayes et al., 2018;Junk et al., 1989;Schneider et al., 2017;Talbot et al., 2018). Although reviews of EFs have recognised the threat of increased upper extreme flows (Acreman et al., 2014;Poff and Zimmerman, 2010;Richter, 2010), and limiting upper extreme flows has been conceptually proposed (Richter et al., 2012), a global scale methodology to quantify this does not yet exist. ...
Human actions and climate change have drastically altered river flows across the world, resulting in adverse effects on riverine ecosystems. Environmental flows (EFs) have emerged as a prominent tool for safeguarding the riverine ecosystems, but at the global scale, the assessment of EFs is associated with high uncertainty related to the hydrological data and EF methods employed. Here, we present a novel, in-depth global EF assessment using environmental flow envelopes (EFEs). Sub-basin-specific EFEs are determined for approximately 4400 sub-basins at a monthly time resolution, and their derivation considers the methodological uncertainties related to global-scale EF studies. In addition to a lower bound of discharge based on existing EF methods, we introduce an upper bound of discharge in the EFE. This upper bound enables areas to be identified where streamflow has substantially increased above natural levels. Further, instead of only showing whether EFs are violated over a time period, we quantify, for the first time, the frequency, severity, and trends of EFE violations during the recent historical period. Discharge was derived from global hydrological model outputs from the ISIMIP 2b ensemble. We use pre-industrial (1801–1860) quasi-natural discharge together with a suite of hydrological EF methods to estimate the EFEs. We then compare the EFEs with recent historical (1976–2005) discharge to assess the violations of the EFE. These violations most commonly manifest as insufficient streamflow during the low-flow season, with fewer violations during the intermediate-flow season, and only a few violations during the high-flow season. The EFE violations are widespread and occur in half of the sub-basins of the world during more than 5 % of the months between 1976 and 2005, which is double compared with the pre-industrial period. The trends in EFE violations have mainly been increasing, which will likely continue in the future with the projected hydroclimatic changes and increases in anthropogenic water use. Indications of increased upper extreme streamflow through EFE upper bound violations are relatively scarce and dispersed. Although local fine-tuning is necessary for practical applications, and further research on the coupling between quantitative discharge and riverine ecosystem responses at the global scale is required, the EFEs provide a quick and globally robust way of determining environmental flow allocations at the sub-basin scale to inform global research and policies on water resources management.
... We model three different environmental flow levels for protecting the rights of waters. There is debate within conservation ecology over how to determine minimal flow requirements for preserving the ecological function of rivers (Richter et al. 2012, Pastor et al. 2014, Ziegler et al. 2017. Protecting rights of waters could conceivably entail different levels of protection from extractions. ...
... By 2100, this scenario reaches conditions inconsistent with robust-to-moderate values of environmental flows (e.g., EF = 80% or 20% of runoff, respectively), representing different conceptions of the rights of waters, shown as ceilings in figure 1. The so-called regional rivalry pathway (SSP3) Note: High and low environmental flow scenarios correspond to the case with EF equal to 80% (Richter et al. 2012) or 20% of runoff, respectively. We calculate the limit to water consumption in land equipped with irrigation (based on data from circa 2000) and in rainfed cropland suitable for irrigation. ...
Although a wide body of scholarly research recognizes multiple kinds of values for water, water security assessments typically employ just some of them. In the present article, we integrate value scenarios into a planetary water security model to incorporate multiple water-related social values and illustrate trade-offs among them. Specifically, we incorporate cultural values for environmental flows needed to sustain ecosystem function (rights of waters), the water requirements of a human right to food (rights to water), and the economic value of water to commercial enterprise (commercial water rights). Pairing quantitative hydrological modeling with qualitative systems of valuing, we suggest how to depict the available water for realizing various combinations of the values underlying those rights. We account for population growth and dietary choices associated with different socioeconomic pathways. This pluralist approach incorporates multiple kinds of values into a water security framework, to better recognize and work with diversity in cultural valuation of water.
... Although locally, empirical quantitative relationships between various degrees of flow alteration and ecological responses have been derived, EFs are still unknown for the vast majority of freshwater and estuarine ecosystems 11 . With over 200 existing EFs methods 10 , it is a challenge to quantify how much water should be reserved to sustain ecosystems and how much water is available for direct human use such as agriculture, industry, cities and energy. ...
... Here we assess national per capita renewable water availability worldwide, accounting for high respectively low aquatic ecosystem protection by means of two well established EF methods. As a measure for high ecosystem protection, we use the presumptive standard for EFs by Richter et al. 11 , which attributes 80% of natural monthly river flows as EF (EF PROT ). As a measure representative for minimum flow recommendations (EF MIN ), we use the monthly Q 95 , that is, the flow exceeded for 95 per cent of each month. ...
Global freshwater biodiversity has been decreasing rapidly, requiring the restoration and maintenance of environmental flows (EFs) in streams and rivers. EFs provide many ecosystem services that benefit humans. Reserving such EFs for aquatic ecosystems, implies less renewable water availability for direct human water use such as agriculture, industry, cities and energy. Here we show that, depending on the level of EF protection, global annual renewable water availability for humans decreases between 41 and 80% compared to when not reserving EFs. With low EF protection, currently 53 countries experience different levels of water shortage, which increases to 101 countries for high EF protection. Countries will carefully have to balance the amount of water allocated to humans and the environment.
... The first two case studies use RCT depth as the independent variable to quantify the effect of water diversion on the magnitude and timing of ecological responses. These case studies are particularly relevant to top-down instream flow management applications, such as the presumptive standard (Richter et al. 2011) or the modified percent-of-flow (MPOF) approach (Mierau et al. 2017). The MPOF is explicitly based on the assumption that diversion rates that do not exceed a 5% reduction in RCT depth will have a negligible effect on aquatic habitat and stream-dwelling organisms (Mierau et al. 2017). ...
... The combined effects of physical habitat, prey and food web dynamics, ecological interactions, and the range of biotic responses are not fully captured by any single model used to develop flow-ecology relationships, and certainly cannot be described by any single hydraulic relationship. For these reasons, top-down holistic instream flow management approaches that allow diversion as a percent of the natural hydrograph have become prominent in environmental flow management (Richter et al. 2011). However, top-down holistic instream flow approaches still require resource managers to determine an acceptable increment of departure from the unimpaired hydrograph or baseline condition (Tharme 2003). ...
Riffle crests are important hydraulic controls in riffle‐pool‐dominated streams, influencing pool hydraulics and water quality that collectively control lotic habitat for many organisms. We define a simple stream depth measurement, the riffle crest thalweg (RCT), describe measurement methods and utility, and suggest that RCT depth is a better independent variable than streamflow (Q) for many instream flow and habitat assessment applications. Using RCT depth as an independent variable, rather than streamflow, reduces the need for gauging or streamflow measurements in many management applications. Unlike streamflow, RCT depth varies directly with fundamental elements of riverine habitat such as channel morphology and bed roughness. We also suggest that relationships between RCT depth and streamflow (RCT‐Q curves) can be used to evaluate the risk of streamflow alteration at ungauged sites. We describe three case studies to demonstrate the utility of RCT depth and RCT‐Q rating curves in stream ecosystem management: (1) evaluating the effect of a top‐down flow prescription on modeled salmonid habitat, (2) estimating the risk from the incremental reduction of RCT depth on habitat and ecological responses, and (3) identifying relationships between RCT depth and dissolved oxygen in ungauged streams. An easy‐to‐measure, inexpensive, and ecologically sensitive metric, RCT depth holds promise as a useful tool in stream ecosystem management.
... In addition, ELOHA could not be applied to many areas with low spatial coverage of biological data. Therefore, Richter et al. [2,3] proposed the sustainable boundary approach (SBA) as a reference for the ecological flow management of these areas. The SBA, which is extended from the "percent-of-flow" approaches, proposes to set an allowable variation range called sustainable boundaries around the natural flow conditions as an approach to express the requirements of environmental flow management. ...
... Richter [2,3] suggested that the protection of environmental flows should be viewed as an integrated management of water resources for long-term sustainability, not as water distribution. From this point of view, the sustainable boundaries of ecological flow were established to protect the hydrological regime of rivers, and the ecological target is to maintain the flow within the sustainable boundaries. ...
In this study, a model was proposed based on the sustainable boundary approach, to provide decision support for reservoir ecological operation with the dynamic Bayesian network. The proposed model was developed in four steps: (1) calculating and verifying the sustainable boundaries in combination with the ecological objectives of the study area, (2) generating the learning samples by establishing an optimal operation model and a Monte Carlo simulation model, (3) establishing and training a dynamic Bayesian network by learning the examples and (4) calculating the probability of the economic and ecological targets exceeding the set threshold from time to time with the trained dynamic Bayesian network model. Using the proposed model, the water drawing of the reservoir can be adjusted dynamically according to the probability of the economic and ecological targets exceeding the set threshold during reservoir operation. In this study, the proposed model was applied to the middle reaches of Heihe River, the effect of water supply proportion on the probability of the economic target exceeding the set threshold was analyzed, and the response of the reservoir water storage in each period to the probability of the target exceeding the set threshold was calculated. The results show that the risks can be analyzed with the proposed model. Compared with the existing studies, the proposed model provides guidance for the ecological operation of the reservoir from time to time and technical support for the formulation of reservoir operation chart. Compared with the operation model based on the designed guaranteed rate, the reservoir operation model based on uncertainty reduces the variation range of ecological flow shortage or the overflow rate and the economic loss rate by 5% and 6%, respectively. Thus, it can be seen that the decision support model based on the dynamic Bayesian network can effectively reduce the influence of water inflow and rainfall uncertainties on reservoir operation.
... hydrological, hydraulic, habitat simulation and holistic). The 'presumptive environmental flow standard' proposed by Richter et al. (2012), and earlier applied in many WF sustainability assessment studies (e.g. de Miguel et al., 2015;Kaur et al., 2019;Veettil and Mishra, 2018), was used here. According to this standard, the EFR accounts for an 80% share of the natural flow regime (R nat ). ...
... Schyns et al. (2019) recommended that future work focus on better estimating WA green , especially with regard to ET env and ET unprod . Meanwhile, in the current study, the procedure proposed by Richter et al. (2012) for EFR accounting was adopted. However, a large number of methods exist for estimating EFR, and these can give significantly different results (Arthington, 2012). ...
The evaluation of water shortages and pollution levels is crucial for watershed management and sustainable development. This paper proposes a water footprint (WF) sustainability assessment approach to analyse water security in a river basin under human pressures. The methodology involves a comprehensive assessment of the current water security at different spatial and temporal levels, and identifies suitable response formulations to achieve sustainability. Field surveys and measurements (streamflow, water quality) were carried out, and the Soil and Water Assessment Tool model was used for assessing water balance components and water quality. The study was carried out in the Canale d’Aiedda river basin (Taranto, Italy), which is part of the ‘area of environmental crisis’ of Taranto, which requires remediation of surface water, groundwater, soil and subsoil. Considering all the anthropogenic activities in the basin, including agriculture and the treated effluent disposed of via wastewater treatment plants (WWTPs), the average WF was 213.9 Mm3 y-1, of which 37.2%, 9.2% and 53.6% comprised respectively for WFgreen, WFblue and WFgrey. The WF sustainability assessment revealed that pollution was the main factor affecting surface water security. In particular, point sources contributed with 90% to the total WFgrey, and lower pollutant thresholds should be fixed for effluent from WWTPs in order to increase water quality of the receiving water body. In addition, for assuring water security the extension of the natural areas should be increased to support biodiversity in the river basin and soil management strategies should be improved to allow more water to be retained in the soil and to reduce nutrients in surface runoff. This study demonstrates that the WF sustainability assessment is a feasible approach for integrated water resources management, as well as offering a much broader perspective on how water security can be achieved in a Mediterranean basin affected by multiple anthropogenic stressors.
... The negative impacts of stored and diverted water on ecosystems are well understood (Poff and Zimmerman, 2010); but understanding the aspects of flow quantity, quality, place, and timing that are needed to restore and sustain native aquatic ecosystems has been a key focus of research studies for decades (Poff et al., 1997;Arthington, 2012;Poff, 2018). The natural flow regime (Poff et al., 1997) characterizes the dynamic and nuanced characteristics of stream flow that integrate to sustain ecosystems, acknowledgement of which has led to the development of environmental flow approaches that recognize the importance of natural flow variability and related ecological responses Richter et al., 2012). More recent research has increasingly recognized the role of physical and biogeochemical factors in mediating the relationship between flow and ecology (Beechie et al., 2010;Wohl et al., 2015;Yarnell et al., 2015), and resource managers have advocated for holistic environmental flow assessment methods designed to support the physical, chemical, and biological functions of streams that sustain ecosystem health (Poff and Matthews, 2013;Palmer and Ruhi, 2019;Tickner et al., 2020). ...
... When compared to exceedance flow strategies, percent-of-flow regimes have been shown to provide the highest energy production (Kuriqi et al., 2017), but they had yet to be compared to a functional flows strategy prior to this study. Generally, a hydrologic alteration of <20% of unimpaired flow is the standard to maintain ecosystem function (Richter et al., 2012), though allocations of 40-60% of unimpaired flows for the environment have been explored for their ability to support hydropower and other societal objectives (McManamay et al., 2016;Zamani Sabzi et al., 2019). While the 40% FNF strategy in this study more closely aligned with the baseline strategy flow releases and hydropower production, it failed to address the need for wet season peak flows and curtailed critical snowmelt recession function during wet years. ...
Environmental flow management in watersheds with multi-objective reservoirs is often presented as an additional constraint to an already strained and over-allocated stream system. Nevertheless, environmental flow legislation and regulatory policies are increasingly being developed and implemented globally. In California, USA, recent legislative and regulatory policies place environmental flows at the forefront of the state's water management objectives; however, the increased reliance on hydropower to support climate change mitigation goals may complicate efforts on both issues. This study modelled alternative environmental flow strategies in the major tributaries to the San Joaquin River in California. Strategies included detailed water management rules for hydropower production, flood control, and water deliveries, and three methodological approaches to environmental flow releases: minimum instream flows ("baseline") year-round, 40% of full natural flow (FNF) during the spring runoff season and minimum releases the remainder of the year, and functional flows year-round. Results show that environmental flow strategies affect downstream flow releases in each of the San Joaquin's four sub-basins differently depending on infrastructure capacity, water management objectives, and hydrologic year types. While hydropower production was comparable or declined in the Stanislaus, Tuolumne, and Merced basins, functional flow and 40% FNF strategies increased hydropower production in the Upper San Joaquin basin by 11%. Uncontrolled spill of high flow events decreased when high flow releases were based on hydrologic cues rather than exclusively on flood storage capacity. Water deliveries were reduced in all years regardless of environmental flow strategy. The 40% FNF and functional flow strategies both increased water released to the river relative to baseline, but in different ways. The functional flow strategy allocated water in a holistic approach that enhanced ecological functions in all years, but particularly in moderate and wet years. In contrast, the 40% FNF strategy provided increased flows relative to baseline and some ecological benefit in dry years, but less ecological benefit in other years. This study shows that alternative environmental flow strategies will have different and important trade-offs for integrated water management, and may mutually benefit seemingly conflicting objectives.
... A driving force such as population growth, resulting in land use change, potential growth of industries and extraction of water for industrial operations, coupled with climate change will create major stress on the existing ecosystem. Determination of the ecological threshold for flow variability is an intricate and tedious procedure, and many researchers have focused on this research area (Gain et al., 2013;Ghanbarpour et al., 2013;Jiang et al., 2014;Knight et al., 2008;Konrad et al., 2008;Mathews & Richter, 2007;Meijer & Beek, 2011;Richter et al., 2011;Zhang et al., 2011). However, there has been no study carried out in Brunei Darussalam to identify E-flows which would keep its rich biodiversity intact. ...
... Environmental flow is considered as the flow which exceeds 90% of the monthly average flow (Arthington & Pusey, 2003;King et al., 2003;Richter et al., 2011;Snelder et al., 2011) and based on these principles the flow for three different scenarios are computed as 3.94, 1.46 and 2.7 m 3 /s as shown in Figure 7. The environmental flow is calculated as 2.7 m 3 /s, and the average flow is based on three different scenarios. ...
The concept of environmental flows and its application and enforcement is a main challenge in several developing countries. The services and benefits derived from the ecosystem are indispensable for sustaining the livelihood of people particularly living in coastal areas. Decision-makers often ignore ecosystems when referring to water allocation, as the supporters of ecosystems are less vocal as compared to other stakeholders. This study focuses on establishing guidelines for maintaining the minimum amount of flow known as environmental flow of Brunei River in Brunei Darussalam for the sustainability of its rich ecosystem. In this study, the flow of the river was simulated based on land use, climate change, and potential growth of industries using a Water Evaluation and Planning System as a computing tool. The study finds that the months of March and June (1.48 and 3.92 m ³ /s) are more vulnerable to low flow. It recommends a threshold value of 2.7 m ³ /s for the environmental flow of Brunei River essential to preserve its rich and diversified ecosystem.
... For decades, river scientists have been working to understand the quantity, quality, and timing of flows needed to sustain healthy river ecosystems. This work has resulted in the development of approaches for defining enviornmental flows that recognize the importance of natural flow variability and ecosystem functions (Poff et al., 2010;Richter et al., 2012;Horne et al., 2017). In addition to the direct, predictable impacts of flow changes on ecological condition (Poff et al., 1997;Bunn and Arthington 2002;Arthington 2012), researchers have increasingly recognized the role of other factors in mediating the relationship between flow and ecology, including the physical form and structure of the stream channel, impairments to water quality, and biological interactions among species (Beechie et al., 2010;Wohl et al., 2015;Yarnell et al., 2015;Mazor et al., 2018). ...
Environmental flow programs aim to protect aquatic habitats and species while recognizing competing water demands. Often this is done at the local or watershed level because it is relatively easier to address technical and implementation challenges at these scales. However, a consequence of this approach is that ecological flow criteria are developed for only a few areas as dictated by funding and interest with many streams neglected. Here we discuss the collaborative development of the California Environmental Flows Framework (CEFF) as an example process for developing environmental flow recommendations at a statewide scale. CEFF uses a functional flows approach, which focuses on protecting a broad suite of ecological, geomorphic, and biogeochemical functions instead of specific species or habitats, and can be applied consistently across diverse stream types and spatial scales. CEFF adopts a tiered approach in which statewide models are used to estimate ecological flow needs based on natural functional flow ranges, i.e., metrics that quantify the required magnitude, timing, duration, frequency, and/or rate-of-change of functional flow components under reference hydrologic conditions, for every stream reach in the state. Initial flow needs can then be revised at regional, or watershed, scales based on local constraints, management objectives, and available data and resources. The third tier of CEFF provides a process for considering non-ecological flow needs to produce a final set of environmental flow recommendations that aim to balance of all desired water uses. CEFF was developed via a broad inclusive process that included technical experts across multiple disciplines, representatives from federal and state agencies, and stakeholders and potential end-users from across the state. The resulting framework is therefore not associated with any single agency or regulatory program but can be applied under different contexts, mandates and end-user priorities. The inclusive development of CEFF also allowed us to achieve consensus on the technical foundations and commitment to applying this approach in the future.
... These conservative thresholds clarify manager's interest of carrying out comprehensive hydrological, geographical and biological studies to estimate them. In addition, minimum and maximum flow thresholds can be used to provide a range of possible environmental flows as the sustainability boundaries proposed by Richter (2009) or the presumptive standards method (Richter et al. 2012). However, the assessment of flow thresholds is a huge task rendered more difficult because of the paucity of ecological information to match with the definition of environmental flow. ...
Through a case study in Southern Quebec (Canada), the assessment of environmental flows in light of the effects of climate change is investigated. Currently, the 7Q2 flow metric (7-day average flow with a 2-year return period) is used for water abstraction management. Several flow metrics were calculated using flow time series simulated by a deterministic hydrological model (HYDROTEL) and climate change scenarios as inputs. Results were compared within homogeneous low flow regions defined using ascendant hierarchical clustering, for the 1990, 2020 and 2050 horizons and annual, summer and winter periods. The impact of each flow metric on the potential availability of physical habitat was analyzed using the wetted perimeter as a proxy. Results indicated that: (1) the increasing non-stationarity of simulated flow data sets over time will complicate the use of frequency analysis to calculate the 7Q2 flow metric; (2) summer low flow values are expected to be lower than winter low flows; and (3) flow-duration curve metrics like the LQ50 (median discharge value of the month with the lowest flow) may become relevant environmental flow metrics by 2050. Results question current water abstraction management tools and permit us to anticipate future local and regional issues during low flow periods. HIGHLIGHTS
This is an environmental flow (EF) study considering climate change effects in Southern Quebec rivers.;
Two flow thresholds and a wetted perimeter threshold were used, both theoretical, to compare the results and their impact on how river ecosystems protection may evolve.;
Low flow regions defined using multivariate analyses reveal the evolution of low flows between 1990 and 2050 horizons and identified local issues.;
Frequency analysis is not recommended for EF assessment in the future, due to the increasing non-stationarity of flow time series with climate change effects.;
Water managers should consider adjusting EF approaches to account for climate change effects on low flows in Southern Quebec rivers.;
... Therefore, EFR has a significant role in quantifying the accurate level of blue water scarcity of a region. Although different methodologies (e.g., low streamflow method, Adapted Smakhtin methodology) are developed to evaluate EFR, the presumptive standard method developed by Richter (2010), Richter et al. (2012) is widely used (Liang et al., 2021;Veettil and Mishra, 2018;Zeng et al., 2012). According to the presumptive standard method, water withdrawal from streamflow greater than 20% will cause degradation in ecosystem health, and this available water for withdrawal is termed blue water availability (Veettil and Mishra, 2016). ...
Over the last four decades, water security assessment has attracted much political and economic attention. An improved understanding of the relationships between water demand and supply is needed to mitigate the impacts of diminishing water resources. This study provides an overview of water security assessment by focusing on the various water security indicators and the concept of water footprint (blue, green, and grey water). The water security indicators based on the water footprint concept is currently receiving more attention because it accounts for the return flow from the total water withdrawn from a watershed. We also investigate the application of different physically-based hydrological models, such as Soil and Water Assessment Tool (SWAT) and Variable Infiltration Capacity (VIC), on water security assessment at a regional to continental scale. However, hydrological/agricultural system models cannot quantify evapotranspiration from irrigation and rainwater separately. Therefore, independent quantification of blue and green water footprint from the irrigated field is challenging. For illustration purposes, we apply the fully distributed Agricultural Ecosystems Services (AgES) model in the Big Dry Creek Watershed (BDCW), an intensively managed and irrigated watershed located in semiarid Colorado. The results indicate that the blue water footprint is higher than the green water footprint in the watershed. In addition, the spatial distribution of grey water footprint is highly correlated with the amount of fertilizer application. The variation of grey water footprint in the irrigated fields is higher than blue and green water footprints. We conclude that applying a physically distributed model can provide useful insight into the impact of climate and anthropogenic activities on water security at different scales.
... For advanced determination of EWR thresholds, particularly with regard to water impact assessment, several methods have been introduced and discussed (cf. [49,[76][77][78][79][80]). Thus, there are different recommendations for EWS thresholds in the existing literature, varying considerably between authors and across river regimes [52]. ...
The consumption of freshwater in mining accounts for only a small proportion of the total water use at global and even national scales. However, at regional and local scales, mining may result in significant impacts on freshwater resources, particularly when water consumption surpasses the carrying capacities defined by the amount of available water and also considering environmental water requirements. By applying a geographic information system (GIS), a comprehensive water footprint accounting and water scarcity assessment of bauxite, cobalt, copper, iron, lead, manganese, molybdenum, nickel, uranium and zinc as well as gold, palladium, platinum and silver was conducted to quantify the influence of mining and refining of metal production on regional water availability and water stress. The observation includes the water consumption and impacts on water stress of almost 2800 mining operations at different production stages, e.g., preprocessed ore, concentrate and refined metal. Based on a brief study of mining activities in 147 major river basins, it can be indicated that mining’s contribution to regional water stress varies significantly in each basin. While in most regions mining predominantly results in very low water stress, not surpassing 0.1% of the basins’ available water, there are also exceptional cases where the natural water availability is completely exceeded by the freshwater consumption of the mining sector during the entire year. Thus, this GIS-based approach provides precise information to deepen the understanding of the global mining industry’s influence on regional carrying capacities and water stress.
... Another example is the abstraction of surface water, which must not threaten the sufficiency of environmental flows (e.g. Richter et al., 2012) and water abstraction for other human activities. ...
The Circular Economy (CE) is a concept that has gained considerable global attention during the past decade amongst private and public sector actors, politicians and policymakers, citizens and media, and scientific communities. Water and water-related ecosystems, despite their vital role in practically all human activities, have been largely missing from conceptualisations and scientific definitions of the CE. Therefore, this paper presents a definition and concept for a water-smart CE that incorporates water and water-related ecosystems. A water-smart CE would (i) reduce losses of water, energy and valuable substances, (ii) improve water efficiency and productivity, (iii) reuse treated wastewater, and (iv) better protect and lessen pressure upon water-related (both aquatic and groundwater) ecosystems. The paper also touches upon the potential risks of the CE to water-related ecosystems. Policy instruments that could be used to promote a transition towards a water-smart CE in Finland – the setting of the present study – and beyond were also sought. Additionally, actors who provide and/or use water-smart CE solutions were interviewed to shed light on their perceptions about the drivers of, barriers to and potential policy instruments for promoting a transition towards a water-smart CE. Based on the analyses of policy instruments and stakeholder interviews, a mixed use of economic, regulatory and informative instruments is suggested to support the desired transition towards a water-smart CE in Finland and elsewhere.
... Per province, local water availability was calculated as local natural runoff minus environmental flow requirement 7 . The latter was assumed as 80% of the local natural runoff following Richter et al. 55 . BWS ≤ 1 implies that part of the local water availability is still left for the environmental flow; hence, total · blue WF p is sustainable. ...
Ending hunger and ensuring food security are among targets of 2030’s SDGs. While food trade and the embedded (virtual) water (VW) may improve food availability and accessibility for more people all year round, the sustainability and efficiency of food and VW trade needs to be revisited. In this research, we assess the sustainability and efficiency of food and VW trades under two food security scenarios for Iran, a country suffering from an escalating water crisis. These scenarios are (1) Individual Crop Food Security (ICFS), which restricts calorie fulfillment from individual crops and (2) Crop Category Food Security (CCFS), which promotes “eating local” by suggesting food substitution within the crop category. To this end, we simulate the water footprint and VW trades of 27 major crops, within 8 crop categories, in 30 provinces of Iran (2005–2015). We investigate the impacts of these two scenarios on (a) provincial food security (FSp) and exports; (b) sustainable and efficient blue water consumption, and (c) blue VW export. We then test the correlation between agro-economic and socio-environmental indicators and provincial food security. Our results show that most provinces were threatened by unsustainable and inefficient blue water consumption for crop production, particularly in the summertime. This water mismanagement results in 14.41 and 8.45 billion m³ y⁻¹ unsustainable and inefficient blue VW exports under ICFS. “Eating local” improves the FSp value by up to 210% which lessens the unsustainable and inefficient blue VW export from hotspots. As illustrated in the graphical abstract, the FSp value strongly correlates with different agro-economic and socio-environmental indicators, but in different ways. Our findings promote “eating local” besides improving agro-economic and socio-environmental conditions to take transformative steps toward eradicating food insecurity not only in Iran but also in other countries facing water limitations.
... The presumptive standard method allows abstracting 20% of the river flow for consumption (BW availability) and left 80% for sustaining the environment (Richter et al., 2012). ...
This paper presents a physical metric that is defined as “difference of water footprint and availability in a given region” during either normal or dry periods, based on blue and green water concepts. Proposed metric quickly highlights water-stressed regions and directly provides volume of water surplus/deficit in the region of interest. Evaluated green water surplus/deficit for agricultural areas can be applied to assess optimum irrigation water requirement while blue water surplus/deficit can be used to assess potential growth of agricultural-based economy and sustainable water use and allocation within a watershed. We assessed surplus/deficit volumes of blue and green waters for three watersheds of Karaj, Latian and Mamlu dams located in Tehran and Alborz Provinces of Iran. Blue and green water resources are quantified using well-calibrated hydrologic model of the Soil and Water Assessment Tool during the period 1995-2013. Results denote that minimum and maximum water deficit occur during wet and dry seasons, respectively. Study area does not experience green water deficit during normal periods, but a few regions encounter green water deficit during droughts. Annual blue water metrics show that one (sub-basin 7) and three sub-basins (sub-basins 5, 6, 7) are ecological hotspots during normal and dry periods, respectively. Results also indicate that farmers should reduce applied irrigation water from 4.86 m³/s to 3.165 (-35%) and 3.4 (-30%) m³/s during normal and dry periods, respectively while cultivated area (agricultural production) in Karaj, Latian and Mamlu watersheds can respectively be increased by 31 km² (46.5 × 10⁶ kg), 52 km² (65.6 × 10⁶ kg) and 31.4 km² (47.6 × 10⁶ kg) during droughts.
... However, this would depend on many local factors like discharge, nutrients, temperature and ecological status, which has led most global studies to neglect them entirely. Several studies have therefore used a discharge requirement as proxy value to determine EFRs , Richter et al 2012, Pastor et al 2019. We implemented the variable monthly flow (VMF) method developed by Pastor et al (2014). ...
p>With a growing population and a changing climate, competition for water resources in the water-energy-food (WEF) nexus is expected to increase. In this study, competing water demands between food production, freshwater ecosystems and utilities (energy, industries and households) are quantified. The potential trade-offs and related impacts are elaborated for different SSP scenarios with the integrated assessment model IMAGE, which includes the global vegetation and hydrology model Lund-Potsdam-Jena managed Land (LPJmL). Results for the 2045-2054 period are evaluated at the global scale and for a selection of 14 hotspot basins and coastal zones. On the global scale, we estimate that an additional 1.7 billion people could potentially face severe water shortage for electricity, industries and households if food production and environmental flows would be prioritized. Zooming in on the hotspots, this translates to up to 70% of the local population. Results furthermore show that up to 33% of river length in the hotspots risks not meeting environmental targets when prioritizing other water demands in the nexus. For local food production, up to 41% might be lost due to competing water demands. The potential trade-offs quantified in this study highlight the competition for resources in the WEF nexus, for which impacts are most notably felt at local scales. This emphasizes the need to simultaneously consider different dimensions of the nexus when developing scenarios that aim to achieve multiple sustainability targets. </p
... In their Emergency Recovery Plan for dampening or reversing declines in freshwater biodiversity, Tickner et al. 1 lay out several major actions, the first being the widespread implementation of environmental flows, i.e., the quantity and timing of streamflow volumes required to sustain the ecological integrity of river systems. With competing demands for limited water quantities, the inevitable question that follows is "How much water do river [ecosystems] need?" 12,13 . Prescribing environmental flows for rivers requires understanding dependencies or linkages between essential stream flow components (e.g., magnitude, duration, frequency of flows) and ecological processes. ...
Environmental flows are critical for balancing societal water needs with that of riverine ecosystems; however, data limitations often hinder the development of predictive relationships between anthropogenic modifications to streamflow regimes and ecological responses – these relationships are the basis for setting regional water policy standards for rivers. Herein, we present and describe a comprehensive dataset of modeled hydrologic alteration and consequences for native fish biodiversity, both mapped at the stream-reach resolution for the conterminous U.S. Using empirical observations of reference conditions and anthropogenically altered streamflow at over 7000 stream gauges, we developed a predictive model of hydrologic alteration, which was extended to >2.6 million stream reaches. We then used a previous nationwide assessment of ecological responses to hydrologic alteration to predict fish biodiversity loss in stream reaches resulting from streamflow modification. Validation efforts suggested hydrologic alteration models had satisfactory performance, whereas modeled ecological responses were susceptible to compounded errors. The dataset could ameliorate regional data deficits for setting environmental flow standards while providing tools for prioritizing streamflow protection or restoration.
... Different simple and complex methods have been proposed to assess environmental flow (reviewed by Richter et al. (2012)). For example, hydrologic desktop methods are the simple and inexpensive methods to assess environmental flow in which ecological values are not highlighted (Sedighkia et al. 2017). ...
Balancing the benefits and environmental degradations of the reservoirs is a challenging issue in the reservoir management. The present study proposes and evaluates an integrated framework to optimize reservoir operation in which hydropower loss and economic loss of irrigation supply are minimized while ecological degradations at downstream river are alleviated. The ecohydraulic simulation was utilized in the structure of the reservoir operation optimization. Reservoir operation losses and environmental degradations were minimized in three hydrological conditions including dry years, normal years and wet years. Moreover, the cropping pattern optimization was applied to mitigate the economic loss of irrigation supply as the main responsibility of the reservoir in the study area. Particle swarm optimization was applied in the reservoir operation optimization. Based on the results in the case study, reliability indices of hydropower production and farmers’ revenue are 15–25 and 30–60%, respectively. Moreover, the physical habitat loss is considerably reduced in all hydrologic conditions by proposing optimal environmental flow. The proposed method is able to provide a fair balance between downstream environmental degradations and economic benefits of the reservoir including farmers’ revenue and hydropower production. Low computational complexities are the most important strength point for the developed model. HIGHLIGHTS
A novel optimization method for reservoir operation.;
Linking ecological impacts and energy and food production in an integrated model.;
Ecohydraulic simulation was carried out by fuzzy approach.;
Cropping pattern model was applied to maximize net revenue.;
... Funding provided by the Australian Government developed tools and frameworks for managing river flows (both environmental and consumptive) at a whole-of-basin scale. However, there was variable investment in social, economic, indigenous, and ecological research, as is typical for many large river basins worldwide (Nilsson, Reidy, Dynesius, & Revenga, 2005;Richter, Davis, Apse, & Konrad, 2012). Assessing environmental water needs in the Murray-Darling Basin was predicated on targeting flows to generate ecological responses at a few sites and a few ecological assets considered representative of the entire system (Swirepik et al., 2016). ...
In the face of mounting environmental and political challenges in river management, accurate and timely scientific information is required to inform policy development and guide effective management of waterways. The Murray–Darling Basin is Australia's largest river system by area and is the subject of a heavily contested series of water reforms relying comprehensively on river science. River scientists have specialised knowledge that is an important input into evidence‐based decision‐making for the management of the Murray–Darling Basin, but despite extensive literature on the interface between science and policy, there is little guidance on achieving policy relevance for practicing scientists. Here, we provide a set of important discussion points for water scientists to consider when engaging with policy‐makers and environmental water managers. We place our considerations in the context of a broader literature discussing the role of natural‐resource scientists engaging with policy and management. We then discuss the different roles for river scientists when engaging in this space, and the advantages and pitfalls of each. We illustrate the breadth of modes of engagement at the science‐policy‐management interface using the Murray–Darling Basin as an example. We emphasise the need for effective governance arrangements and data practices to protect scientists from accusations of operating as advocates when working to inform management and policy.
... E-flow recommendations based on simple hydrologic rules [80,81] have been widely recognized to be inadequate for sustaining the biological structures and the functionality of aquatic ecosystems [82]. Current state-of the-art approaches, e.g., [83][84][85][86], specifically advocate that e-flow recommendations should be based on the mechanistic Environments 2022, 9, 27 8 of 14 relationships between flows and ecological outcomes. For instance, a recent study accounting for the status of the benthic macroinvertebrate communities of both unregulated and regulated Alpine streams in Lombardy highlighted that the shift from unimpacted conditions was more significant at reaches below reservoirs than at reaches below intakes, since seasonal streamflow variation was partly preserved in the latter [87]. ...
Monitoring of freshwaters allows the detection of the impacts of multiple anthropic uses and activities on aquatic ecosystems, and an eco-sustainable management of natural resources could limit these impacts. In this work, we highlighted two main issues affecting inland waters, referring to findings from the most inhabited Italian region (Lombardy, approximately 10 M inhabitants): the first issue is lake pollution by old generation pesticides, the second is river development for hydropower. In both cases, some management strategies reducing the anthropic impacts on freshwaters were discussed: organic farming and biocontrol as an alternative to diffuse pollution by agrochemicals; environmental flows and controlled sediment flushing operations to limit the hydropower impact on rivers. Although the two mentioned issues were discussed separately in this paper, the management of water resources should be carried out in a comprehensive way, accounting for the multiple impacts affecting freshwater ecosystems, including those related to the climate changes.
... Following earlier studies, basin-level water scarcity is then calculated based on water consumption and water availability: total surface runoff from TerraClimate estimation minus environmental flow requirement (i.e. following the 80% rule by Richter et al [50], which suggests runoff depletion should be below 20% to maintain normal ecosystem service [2]). ...
Water competition between the food and energy sector is a critical component of the food-energy-water nexus. However, few studies have systematically characterized the geospatial and, especially, the sub-annual variations in such competition and the associated environmental impacts and targeted mitigation opportunities. This study characterizes competing water uses for crop-specific irrigated agriculture and fuel-specific power generation across global major river basins to reveal their resulting impacts on local water scarcity for global population under both current and a warming climate. Under annual (and most seasonal) accounting, almost all basins currently suffering from extremely high water scarcity are dominated by agricultural water consumption (e.g. accommodating 26%-49% of basin-total population across seasons), which are often simultaneously exposed to potentially decreasing seasonal water availability under a 4 °C warming scenario. Only 13%-20% of population are located in basins dominated by seasonal power sector water uses, which are predominantly with low water scarcity. Agriculture sector provides the most basin-specific water mitigation opportunities across mid-latitude basins in all four seasons. Nevertheless, power sector becomes more important in affecting seasonal water scarcity and provides unique seasonal water mitigation opportunities, particularly in basins among higher northern latitudes in winter. This analysis highlights irrigated agriculture is currently and will likely remain the key in global water management for basins facing the severest water scarcity, yet increasing attention on the seasonal and spatial variations in cross-sector water use competition is needed to better identify region- and season- specific mitigation opportunities.
... To prevent future detrimental effects on freshwater ecosystems and restore already degraded ecosystems, it has been advocated to restrict human water withdrawals (Arthington et al., 2018;Hogeboom, Bruin, Schyns, Krol, & Hoekstra, 2020;Richter, Davis, Apse, & Konrad, 2012). By setting a water withdrawal cap at the river basin scale, human water appropriation could be kept within ecological boundaries. ...
... Schmutz and Sendzimir (2018) emphasize, that fish act as an indicator of flow alteration and responds particularly sensitive to changes in the flow magnitude. Here, it has to be considered that the influence of discharge implies both the role as a trigger for fish migration as well as maintaining the ecological integrity of rivers for a fish population, known as environmental flow (Richter et al., 2012). The latter as such cannot be answered by the extent of this study when it comes to population dynamics, linked to the altered flow regime. ...
In dieser Studie wurde die kaum erforschte Laichwanderung der europäischen Seeforelle (Salmo trutta) in der Hasliaare in der Schweiz untersucht. Zwei Fischzählanlagen (Resistivity Counter) und ein multispektrales Unterwasserkamerasystem wurden eingesetzt, um eine uneingeschränkte Wanderung zu gewährleisten. Umweltparameter wie Abfluss, Wassertemperatur, Globalstrahlung und Luftdruck wurden statistisch auf ihren Einfluss auf die flussaufwärts und flussabwärts gerichtete Wanderung untersucht. Darüber hinaus wurde der Wanderkorridor zwischen zwei Zählanlagen im Hinblick auf Limitierungen durch Abfluss und Wassertiefe während Niedrigwasserperioden analysiert. Insgesamt 129 Fische, die anhand ihres Punktmusters individuell unterschieden werden konnten, gaben Rückschlüsse auf das Wanderverhalten und die Faktoren, die für ihre Wanderung im Untersuchungsgebiet verantwortlich sind. In Übereinstimmung mit anderen Studien kamen die größten Seeforellen zuerst im Laichgebiet an, gefolgt von kleineren Exemplaren gegen Ende des Beobachtungszeitraums. Die Wanderung selbst fand überwiegend in der Dunkelheit statt. Das Geschlechterverhältnis wurde mit 67 zu 33 % zugunsten der Weibchen dokumentiert. Es zeigte sich, dass die Wassertiefe während der Laichzeit kein limitierender Faktor war. Die Entscheidungsbaumanalyse zeigte, dass die Wassertemperatur der Hauptfaktor für die stromaufwärts gerichtete Wanderung ist, während der Abfluss den Großteil der flussabwärts gerichteten Bewegungen erklärt. Die Wandergeschwindigkeiten im Untersuchungsgebiet zeigten keinen Trend hinsichtlich der Fischgröße oder des Geschlechts. Die Männchen hielten sich wesentlich länger in der Restwasserstrecke auf als die Weibchen. Die Ergebnisse zeigen, dass sowohl der Resistivity Counter als auch das multispektrale Kamerasystem effektive Methoden zum Monitoring von wandernden Salmoniden in freien Gewässern darstellen.
This study examines the barely investigated upstream and downstream migration of the European lake-run brown trout (Salmo trutta) in the Hasliaare river in Switzerland. Two resistivity fish counters and a multi-spectral underwater camera system were used as a monitoring technique to provide an uninterrupted migration. Environmental parameters including discharge, water temperature, global radiation and atmospheric pressure have been statistically analyzed with regard to their influence on upstream and downstream migration. Further, the migration corridor between two fish counters was analyzed towards limitations in discharge and water depth during low flow periods.
A total of 129 fish, individually differentiated through their spot pattern, allowed conclusions to be drawn about their migratory behavior and drivers for their migration in the study reach. Consistent with other studies, the largest lake trout were first to arrive in the spawning area, followed by smaller individuals towards the end of the monitoring period. The migration itself took place predominantly in the darkness. Sex ratios have been observed with 67 to 33 % in favor of females.
It was shown that water depth is not a limiting factor within the spawning period. Regression tree analysis showed that water temperature is the main driver for upstream migration and discharge explained most of the downstream movements.
Migration speeds in the valley section of Innertkirchen showed no trend regarding fish size or sex. Males stayed in the river for much longer than females. The results demonstrate that both the resistivity fish counter and the multi-spectral underwater camera system provide harmless and effective upstream and downstream monitoring methods for migratory salmonids in open river stretches, especially regarding critically endangered fish populations.
... The use of scenarios within the adaptive management framework helps provide information for stakeholders to respond with management strategies through time. Presumptive methods that set minimum allowable deviations will still be required where resources do not allow for this level of detail (Richter et al., 2012). However, even in the case of these presumptive methods, consideration needs to be given as to how the system operation can adapt to accommodate uncertain futures. ...
The numerous environmental flows assessment methods that exist typically assume a stationary climate. Adaptive management is commonly put forward as the preferred approach for managing uncertainty and change in environmental flows. However, we contend that a simple adaptive management loop falls short of meeting the challenges posed by climate change. Rather, a fundamental rethink is required to ensure both the structure of environmental flows assessments, along with each individual technical element, actively acknowledges the multiple dimensions of change, variability and complexity in socio-ecological systems. This paper outlines how environmental flow assessments can explicitly address the uncertainty and change inherent in adaptively managing multiple values for management of environmental flows. While non-stationarity and uncertainty are well recognised in the climate literature, these have not been addressed within the structure of environmental flows methodologies. Here, we present an environmental flow assessment that is structured to explicitly consider future change and uncertainty in climate and socio-ecological values, by examining scenarios using ecological models. The environmental flow assessment methodology further supports adaptive management through the intentional integration of participatory approaches and the inclusion of diverse stakeholders. We present a case study to demonstrate the feasibility of this approach, highlighting how this methodology facilitates adaptive management. Rethinking our approach to environmental flows assessments is an important step in ensuring that environmental flows continue to work effectively as a management tool under climate change.
... EFR would also be significantly different for ecological conservation goals across regions. Richter et al. (2012) suggested that 80% of daily flow would maintain ecological integrity in most rivers, and 90% may be needed to protect rivers with at-risk species. The EFR suggested by the Tennant method can range from 10% to more than 100% of mean annual flow in different seasons for different ecological statuses (Tennant, 1976). ...
Climate change was projected to have negative effects on water availability and consequently a serious constraint to food production in many areas of the world. However, such effects have not been well understood, particularly over rainfed croplands, partly because of the poor representation of green water in associated assessments. In this study, we develop an integrated agricultural water scarcity index (WSIag) that incorporates blue and green water components to examine the agricultural water scarcity in the baseline (1981–2005) and future (2026–2050) periods under the Representative Concentration Pathway (RCP)2.6 and RCP6.0 scenarios. Results show that ∼3.8 million km² (∼39% of total) croplands experienced water scarcity in the baseline period and it would expand by more than 3% in the future. Under the two scenarios, WSIag projections are similar overall and are higher than that under the baseline in 83%–84% of global total croplands. Differences are found between the scenarios in Amazonia, Southern Africa, and South Asia. The increases in future WSIag are dominated by the decreased water availability in ∼60% of total croplands and ∼24% of which is dominated by the increased crop water requirement. Changes in green water availability have a significant contribution to changes in WSIag in 16% of global croplands, mostly in arid/semiarid regions (e.g., the South edge of the Sahel, Southern Africa, Northeast China, and Central America). This implies the important role of green water management for agriculture in these regions. The integrated assessment can help develop effective strategies for agricultural water management under climate change.
... For this analysis, 'unsustainable' is defined as situations where local surface and ground water (termed 'blue water') consumption for irrigation exceeds locally available blue water resources. Available resources are the amount of surface and subsurface runoff remaining after preserving environmental flows, which are often taken as 80% of runoff (Richter et al 2012). ...
Global analyses have revealed virtual drains and gains of water between trading countries, with Mexico ranking as one of the countries with the fastest increase in unsustainable water consumption in agriculture for export markets, since 2000. It is unclear, however, how Mexico has reshaped its crop production and associated reliance on freshwater resources to satisfy growing domestic and international markets, especially the United States (US). While the Mexico-US partnership has been identified as one supported by unsustainable irrigation water, the spatial understanding of its strain on water resources has remained at the national scale and without context of the crops driving the change. In this analysis, we focus on the evolution of Mexican agriculture since 1994, the year the North American Free Trade Agreement was enacted, to identify hotspots of water unsustainability in crop production in the domestic and US supply chain. Using a global process-based crop water model, we find that between 1994 and 2015, rainwater (or ‘green’ water) and irrigation (or ‘blue’) water consumed in the production of crops increased by one fourth nationally, while water in crops exported to the US doubled. Virtual export of blue water embodied in the trade of berries increased five orders of magnitude; a substantial growth in blue water export was also associated with trade to the US of cereals, fruits, nuts, vegetables, pulses, and tubers. Our results show that in Mexico irrigated water plays an increasingly prominent role in export agriculture, and that many healthy crops that dominate US imports from the world are grown in water scarce Mexican municipalities relying on unsustainable irrigation practices. This serves as a warning for the sustainability of future Mexican healthy food supplies, both for the domestic market and for export to the US.
... -calculates EWR as a range between the 25th and 75th monthly flow percentile using non-parametric analyses or as a range of mean monthly flow using parametric analyses -Can be implemented as a desktop tool. -gauged or modelled daily flows can be used -The number of parameters used is too large [74][75][76][77] Water 2022, 14, 893 8 of 21 ...
Anthropogenic activities such as damming have caused an alteration in the natural flow regime in many rivers around the world. In this study, the role of constructing a hydroelectric dam on the natural flow regime of the Kor River, Iran, is investigated. Nine different methods, which fall into the category of hydrological methods, were used to determine the environmental water requirement, EWR, of the Kor River. Also, two indexes are introduced to evaluate the environmental flow allocation in anthropogenic rivers. The results show that although the supply of environmental flow in some months is in relatively acceptable conditions on average, there is a deficiency in the allocation of EWR in the range of 1.92-30.2 % in the spawning period of the dominant fish species. The proposed indicators can provide a comprehensive picture of the status of environmental flow allocation in rivers where little ecological data is available and hydrological regime has changed due to human activities, particularly in case of rivers with hydropower plants. Also, after the construction of the dam, no major floods have occurred in the river, which has led to the loss of morpho-ecological balance in the river and disruption of the natural state of habitats. Therefore, the negative impact of dam construction on the environmental conditions of the river should be considered in the active management of the dam outlets.
... Existing approaches for managing environmental flows in effluentdominated rivers typically consist of limiting withdrawals to a fixed proportion of the natural flow regime. This approach may maximize water for reuse but may not guarantee that ecological objectives can be achieved (Richter et al., 2012). A functional flows approach offers a more holistic method that accounts for the complexity and variability of flow over space and time and aims to protect the ecological integrity of the river but allow for flexibility for water reuse during ideal times. ...
Flows in urban rivers are increasingly managed to support water supply needs while also protecting and/or restoring instream ecological functions, goals that are often in opposition to each other. Effluent-dominated rivers (i.e., rivers that consist primarily of discharged treated wastewater) pose a particular challenge because changes in effluent discharge may impact river ecology. A functional flows approach, in which metrics from the annual hydrograph correspond to ecological processes, was applied to understand the hydro-ecological implications of wastewater reuse in the Los Angeles River watershed (Los Angeles County, California, USA). The Los Angeles River, like many urban rivers, is dominated by effluent, particularly during dry weather. An hourly hydrologic model was created, calibrated, and validated in EPA SWMM for the Los Angeles River watershed to investigate how increases in wastewater reuse (i.e., decreases in discharge to the river) may impact river flows and subsequently ecology and recreation in the river. Current flows are shown to support freshwater marsh, riparian habitat, fish migration, and wading shorebird habitat, in addition to recreational kayaking. Functional flow metrics were assessed under future management scenarios including reducing discharge to increase recycling at three wastewater treatment plants within the watershed. Both wet-season and dry-season baseflows were most sensitive to increasing wastewater reuse, with an average decrease of 51–56% (0.93 cms) from current baseflows. Sensitivity curves that relate potential changes in wastewater discharge to changes in functional flows show that a 4% decrease in current wastewater discharge may negatively impact habitat for indicator species during the dry season. More opportunity exists for wastewater reuse during the wet season, when current wastewater discharge may be reduced by 24% with minimal impacts to ecology and recreation. The developed approach has the potential to inform similar tradeoff decisions in other urban rivers where flows are dominated by wastewater or stormdrain discharge.
... Fundamentally, determining instream flows requires selecting appropriate estimation methods based on spatial scale, temporal resolution, data availability, technical requirements, costs, and ecological management goals (Tharme 1996, Arthington and Zalucki 1998, Arthington 2012). More than 200 methodologies exist for estimating instream flows (Tharme 2003), most of which fall into three distinct categories: hydrologic (e.g., Tennant 1976, Escobar-Arias and Pasternack 2010, Richter et al. 2012, Yarnell et al. 2015, habitat simulation (e.g., Tharme 2003, Arthington 2012, and holistic (e.g., Poff et al. 2017). ...
The Rio Grande/Bravo is an arid river basin shared by the United States and Mexico, the fifth-longest river in North America, and home to more than 10.4 million people. By crossing landscapes and political boundaries, the Rio Grande/Bravo brings together cultures, societies, ecosystems, and economies, thereby forming a complex social-ecological system. The Rio Grande/Bravo supplies water for the human activities that take place within its territory. While there have been efforts to implement environmental flows (flows necessary to sustain riparian and aquatic ecosystems and human activities), a systematic and whole-basin analysis of these efforts that conceptualizes the Rio Grande/Bravo as a single, complex social-ecological system is missing. Our objective is to address this research and policy gap and shed light on challenges, opportunities, and success stories for implementing environmental flows in the Rio Grande/Bravo. We introduce the physical characteristics of the basin and summarize the environmental flows studies already done. We also describe its water governance framework and argue it is a distributed and nested governance system across multiple political jurisdictions and spatial scales. We describe the environmental flows legal framework and argue that the authority over different aspects of environmental flows is divided across different agencies and institutions. We discuss the prioritization of agricultural use within the governance structure without significant provisions for environmental flows. We introduce success stories for implementing environmental flows that include leasing of water rights or voluntary releases for environmental flow purposes, municipal ordinances to secure water for environmental flows, nongovernmental organizations representing the environment in decision-making processes, and acquiring water rights for environmental flows, among others initiatives. We conclude that environmental flows are possible and have been implemented but their implementation has not been systematic and permanent. There is an emerging whole-basin thinking among scientists, managers, and citizens that is helping find common-ground solutions to implementing environmental flows in the Rio Grande/Bravo basin.
... However, addressing flow alteration and determining the ecological flows needed to support ecosystem functions can be a challenge in systems where alteration is widespread. Traditional referencebased approaches, such as a percentage of unimpaired flow (Richter et al., 2011), the Tennant method using a percentage of mean annual unimpaired flow (Tennant, 1976), or the Tessman method considering monthly unimpaired flow (Tessman, 1980), can be implemented to determine minimum environmental flows that serve as a management target. However, reference-based environmental flow targets may not be relevant nor realistic in systems that are far from reference. ...
Flow alteration is a pervasive issue across highly urbanized watersheds that can impact the physical and biological condition of streams. In highly altered systems, flows may support novel ecosystems that may not have been found under natural conditions and reference-based environmental flow targets may not be relevant. Moreover, stream impairments such as altered channel morphology may make reference-based environmental flow targets less effective in supporting ecosystem functions. Here, we develop an approach for determining ecological flow needs in highly modified systems to support existing ecological uses utilizing the California Environmental Flows Framework (CEFF). CEFF was established to provide guidance on developing environmental flow recommendations across California’s diverse physical landscape and broad array of management contexts. This paper illustrates the application of CEFF in informing ecologically-based flow restoration in a highly altered region of South Orange County, California. The steps of CEFF were implemented including a stakeholder process to establish goals and provide input throughout the project; identifying the natural ranges of functional flow metrics, or distinct components of the natural flow regime that support ecosystem functions; refining ecological flow needs to account for altered channel morphology and the life history needs of riparian and fish species; and assessing flow alteration to inform management strategies. Key considerations and lessons learned are discussed in the context of developing ecological flow needs in highly altered systems including when non-flow related management actions (i.e., channel rehabilitation) are necessary to achieve ecological goals.
... In practice, however, a fixed percentage of mean annual flow is set arbitrarily as the 'default minimum acceptable threshold' or the 'lowest acceptable environmental flow allocation' without any scientific basis (Smakhtin et al. 2010;Richter et al. 2011;Chen et al. 2019). For example, the 'Physical habitat simulation' technique advocates for relatively constant flows although it is inadequate for sediment mobilisation (Gippel 2001). ...
The concept of environmental flows (E-flows) is not very old and is still evolving. The central theme associated with the E-flows is allocation of water for economic benefits and maintenance of sustainability of the riparian and instream ecosystems, riverine environment, and its habitats. Assessment of E-flows involves different methodologies with numerous criteria and thresholds. However, there is little consensus and more debate on criteria and flow thresholds, and regarding priority between development and environment. While many criteria and flow thresholds are relevant, some are inadequate or even inappropriate. Besides, there are other relevant and important issues related to flows and E-flows, which are either ignored or overlooked in the existing E-flows framework. This article through critical examination has pointed out the overlooked crucial issues (such as E-flows for temporary rivers, water quality criteria, impact of water stagnancy on water balance and hydrological cycle, and possible impact of climate change on E-flows), identified gaps in E-flows’ policy framework and has recommended modifications in the E-flows policy and practice. Incorporation of the recommended criteria will surely make the E-flows policy robust and effective.
Hydrologic alternation of river systems is an essential factor of human activity. Cascade-dammed waters are characterized by the disturbed outflow of material from the catchment. Changes in sediment, dissolved load and nutrient balance are among the base indicators of water resource monitoring. This research was based on the use of hydrological and water quality data (1984–2017) and the Indicators of Hydrologic Alteration (IHA) method to determine the influence of river regime changes on downstream transfer continuity of sediments and nutrients in the example of the Lower Brda river cascade dams (Poland). Two types of regimes were used: hydropeaking (1984–2000) and run–of–river (2001–2017). Using the IHA method and water quality data, a qualitative and quantitative relationship were demonstrated between changes of regime operation and sediment and nutrient balance. The use of sites above and below the cascade made it possible to determine sediment, dissolved load, and nutrient trapping and removing processes. Studies have shown that changes in operation regime influenced the supply chain and continuity of sediment and nutrient transport in cascade-dammed rivers. The conducted research showed that sustainable management of sediment and nutrient in the alternated catchment helps achieve good ecological status of the water.
Environmental flows are unanimously considered to be one of the most comprehensive indicators of the rivers health and their capacities to provide ecosystem goods and services. In this study, the objective was to predict the response of environmental flow components in a typical North African rivers network to future climate change. The study watershed is Bouregreg watershed (BW) in Morocco. To achieve this objective, a hybrid approach was build based on the semi-distributed model Soil and Water Assessment Tool (SWAT) and the Indicators of Hydrologic Alteration program (IHA). Data of two emissions scenarios (RCP4.5 and RCP8.5) from a downscaled Global Circulation Model were used to force the hybrid SWAT-IHA to calculate modifications of BW's environmental flow components in 2085-2100 period. Results showed that BW will experience climatic changes under both scenarios. Most of the environmental flow attributes will be modified within the study period: loss of natural flow variability due to shift in exceedance probability of low flows (up to 40%), decrease of monthly low flows, forward shift in high flow timing (up to 50%), and alteration of both the duration and the rise rates of floods. BW's streams responded unequally to the simulated changes in terms of the altered attributes as well as the degree of the alteration. This study confirmed the ability of the developed modeling approach to monitor environmental flow parameters for the first time in Morocco, and contributed in highlighting the necessity of proactive long term strategies to protect riverine ecosystems in North Africa watersheds .
Water scarcity is increasing across the globe. We discuss how the private sector and private investment can assist in the fight against water scarcity, especially in advanced and middle-income economies. We first lay out from an economic perspective why local, regional, and national governments have traditionally played an outsized role in providing water security. We next describe a whole set of possible roles for the private sector, ranging from a fully privatized water sector to more limited public–private partnerships (PPPs), corporate social responsibility (CSR), and impact investment that may take place independent of the public sector. The theoretical and empirical underpinnings of an argument for greater private involvement emerge from reassessing the traditional view of the water sector as a natural monopoly with increasing returns to scale, as well as from contract theory that emphasizes how carefully written contracts imply control but do not require public ownership at all times. Rising water scarcity and water infrastructures badly in need of an upgrade in many places point to public institutions and societies not meeting the social and environmental challenge, which opens the door for private initiatives in the form of corporate social responsibility and impact investing.
Hydrologic processes are often key determinants of successful recruitment of native fishes. However, water management practices can result in abnormal changes in daily and seasonal hydrology patterns. Rarely has fish recruitment across river‐reservoir landscapes been considered in relation to flow management, despite the direct relationship between reservoir water management and the resulting upstream and downstream hydrology. We evaluated the relationships between lotic and lentic hydrology and recruitment of two native broadcast‐spawning fishes, Freshwater Drum Aplodinotus grunniens and Gizzard Shad Dorosoma cepedianum. Four seasonal periods for each species were identified that related to species’ spawning biology, from which we derived our remaining hydrology variables. Annual hydrology variables were also considered in our analysis. We developed regression models in conjunction with a model‐selection procedure for each species and habitat type based on catch‐curve residuals from fish populations in hydrologically connected river‐reservoir systems in the Ozark Highland and Ouachita Mountain ecoregions, USA. Our results indicated that recruitment of reservoir Freshwater Drum was negatively correlated to annual reservoir retention time. In lotic habitats, Freshwater Drum recruitment was positively correlated with prespawn discharge conditions and negatively correlated with annual flow variability. Similarly, riverine Gizzard Shad recruitment was positively correlated to the frequency of high flow pulses during the spawning period. Our results indicate releasing reservoir water to best mimic relatively natural flow patterns may benefit some broadcast spawning species occupying both lentic and downstream lotic environments, especially during the spring. This information, combined with future efforts on additional spawning guilds, will provide a foundation for developing holistic river‐reservoir water‐allocation plans.
Environmental flow (e‐flow) practices were investigated for 100 class A rivers in Japan, which are managed by the central government. We examined how much e‐flow requirements (EFRs) are allocated for each river, and investigated the seasonally variable flow components, objectives, and target organisms. The EFRs of the 100 rivers ranged from 5 to 51% as a percentage of the mean annual discharge (MAD). Protecting physical habitat was an e‐flow objective for all target rivers. Protecting water quality and cultural scenery, preventing salt damage, and maintaining groundwater levels were also common objectives. However, the minimum flow required for the migration and spawning of 12 representative fish species was the most influential factor. The Japanese e‐flow framework is a holistic approach that takes not only individual species but also multiple aspects of ecosystem services, including its social and cultural value, into account. E‐flows for all target rivers were given as a form of minimum flow. Eighty‐six percent of the rivers considered seasonally variable flow targets, while 14% designed constant minimum flow throughout a year. The reason why the EFRs do not consider natural flow variability is that the storage and control capacity of Japanese dams is minimal, and that problems associated with the modified flow regime is not critical at present. The Japanese e‐flow framework has been successfully implemented, and it has been institutionally integrated into river management for 30 years. However, it will require adaptive management and adjustment in the future as social structure, climate, and hydro‐ecological characteristics change.
Clarifying specific water resources distribution and quantifying water security are vital for sustainable management. There is still unexplored gap regarding security indicators as the linkage between water footprint and availability. This study proposed a dynamic water security assessment framework considering the boundary consistency between green water footprint and provision at multi spatio-temporal scales and applied it to Yalong River Basin (YLRB) of southwest China. Results show: 1) The temporal variation of blue water was stronger than green water. Green water flow exhibited more homogeneous spatial distribution than blue water and green water storage. 2) The hotspots of green water crisis were observed in the middle reach with the higher scarcity/vulnerability. 3) Under anthropogenic disturbance, pastureland exhibited lower green water sustainability with scarcity >1 than forest. 4) Lower green water scarcity denoted the potential for rain-fed agriculture in the southeastern YLRB and higher blue water security indicated the water supply prospect for socioeconomic utilization. This work contributes to ensure water resources sustainable management in eco-socioeconomic nexus.
Flow variability determines the conditions of river
ecosystems and river ecological functioning. The variability of ecological
processes in river ecosystems gradually decreases due to river
channelization and incision. Prediction of the environmental flow allows us
to keep biological diversity and river health developed as a response to the
degradation of aquatic ecosystems overexploited by humans. The goal of the
study was to test the influence of river incision on environmental flow
estimation based on the Biological Monitoring Working Party (BMWP)
macroinvertebrate index. A total of 240 macroinvertebrate assemblages of 12
waterbodies differing in bed substrate and amplitude of discharge were
surveyed in southern Poland. Variations in the distribution of 151 466
macroinvertebrates belonging to 92 families were analysed. The similarity of
benthic macroinvertebrates reflects the typological division of the rivers
into three classes: Tatra mountain streams, mountain flysch rivers, and
upland carbonate and silicate rivers. As a response variable reflecting the macroinvertebrate distribution in the river, the BMWP_PL index was chosen. The river incision significantly
increased the values of e-flow calculations in relation to redeposited
channels. The area of optimal habitat for macroinvertebrates decreased with
the bed incision intensity. In highly incised rivers, the environmental flow
values are close to the mean annual flow, suggesting that a high volume of
water is needed to obtain good macroinvertebrate conditions. As a
consequence, river downcutting processes and impoverishment of optimal
habitats will proceed.
The amount of groundwater and surface water consumed in a river basin constitutes the blue water footprint (BWF). To safeguard the environment, it has been suggested to set a cap to the BWF based on blue water availability (BWA). BWA depends on the precipitation that becomes runoff and the need to reserve environmental flow requirements. Previous studies determined BWF caps based on the use-what-is-there principle, which assumes that all BWA in a sub-catchment may be consumed locally, without the need to reserve water for downstream. However, BWA in an upstream sub-catchment does not have to be consumed locally but could be consumed downstream instead, thereby mitigating blue water scarcity in downstream areas. Therefore, this study aims to investigate the effect of alternative allocation principles – that account for downstream demands – to set monthly BWF caps per sub-catchment on BWS levels across a large river basin. We take the Yellow River basin for the period 2010 to 2014 as a case study to evaluate four scenarios of BWF cap-setting. We compare the ‘natural’ and ‘reservoir’ scenario that both apply the use-what-is-there principle to determine the effects of reservoirs on BWF caps. We then apply two alternative allocation principles that take relative population size (‘population-based’ scenario) and historic blue water demand (‘demand-based’ scenario) as a basis to determine BWF caps per sub-catchment and compare the effects against the ‘reservoir’ scenario. Our results confirm previous finding on the effects of reservoirs on caps. We further find that blue water scarcity increases from upstream to downstream under the use-what-is-there principle. Both the population and demand-based scenarios reduce upstream-downstream differences in the degree of blue water scarcity. The demand-based scenario is most effective in this respect. On the other hand, the population-based scenario leads to the smallest upstream-downstream differences in BWA per capita. The results feed into a discussion on alternative approaches to set BWS caps in a large river basin which needs to take place for BWF caps to become effective and practical concepts in policy making.
Background
Increasing human demand for water and changes in water availability due to climate change threatens water security worldwide. Additionally, exploitation of water resources induces stress on freshwater environments, leading to biodiversity loss and reduced ecosystem services. We aimed to conduct a spatially detailed assessment of global human water stress for low to high environmental flow (EF) protection.
Methods
In this modelling study, we used the LISFLOOD model to generate daily natural flows without anthropogenic water use for 1980–2018. On the basis of these flows, we selected three EF methods (EF with high ecological protection [EFPROT], EF with minimum flow requirements [EFMIN], and variable monthly flow [EFVMF]) to calculate monthly EFs. We assessed monthly consumptive water use for industry, agricultural crops, livestock, municipalities, and energy production for 2010. We then estimated the corresponding number of people under water stress per month on a global and national level using a spatially detailed population database for 2010.
Findings
We estimate that 3·2 billion (EFPROT), 2·4 billion (EFVMF), and 2·2 billion (EFMIN) people lived under water stress for at least 1 month per year, corresponding to 46%, 35%, and 32% of the world's population in 2010, respectively. Around 80% of people living under water stress lived in Asia; in particular, India, Pakistan, and northeast China. Compared with EFMIN, imposing EFPROT globally would have put between 710 million (March) to 1 billion (June) additional people under water stress on a monthly basis, whereas this would have been 72 million (August) to 218 million (April) additional people if EFVMF were imposed.
Interpretation
Ensuring high ecological protection would put nearly half of the world's population (3·2 billion people) under water stress for at least 1 month per year. Policy makers and water managers have to make an important trade-off when allocating limited water resources between direct human needs and the environment. A better understanding of local ecosystem needs is crucial to alleviating current and future human water stress, while sustaining healthy ecosystems.
Funding
None.
Nowadays, constructing a new hydropower plant is one of the most attractive solutions to overcome energy requirements. The Kayan Hydroelectric, built in the Kayan River, is projected to generate electricity of nine hundred megawatts. However, the dams have to be managed appropriately since alteration of river discharge will have a significant impact on the environment. This paper proposes an environmental flow assessment as an appropriate indicator to manage sustainability. Three environmental flow assessment methods were used: Flow Duration Curve Analysis (FDCA), Tennant method, and Building Block method. The environmental flow pattern was used as a benchmark to evaluate whether the operation rule of the dams fulfilled the sustainable requirement, particularly on the hydrological pattern of the river. Regarding the Tennant and FDCA method, the minimum discharge that has to be maintained for the minimum environmental flow of the river is about twenty-five cms (corresponds to ten percent of AFF) and thirty-five cms, respectively. Meanwhile, the Building block method informs a range of discharge from a hundred cms to twenty thousand cms during the flood. The environmental flow should be managed to guarantee that the river’s ecosystem and carrying capacity can be preserved.
Humans and ecosystems are deeply connected to, and through, the hydrological cycle. However, impacts of hydrological change on social and ecological systems are infrequently evaluated together at the global scale. Here, we focus on the potential for social and ecological impacts from freshwater stress and storage loss. We find basins with existing freshwater stress are drying (losing storage) disproportionately, exacerbating the challenges facing the water stressed versus non-stressed basins of the world. We map the global gradient in social-ecological vulnerability to freshwater stress and storage loss and identify hotspot basins for prioritization ( n = 168). These most-vulnerable basins encompass over 1.5 billion people, 17% of global food crop production, 13% of global gross domestic product, and hundreds of significant wetlands. There are thus substantial social and ecological benefits to reducing vulnerability in hotspot basins, which can be achieved through hydro-diplomacy, social adaptive capacity building, and integrated water resources management practices.
The ongoing agrarian transition from smallholder farming to large-scale commercial agriculture promoted by transnational large-scale land acquisitions (LSLAs) often aims to increase crop yields through the expansion of irrigation. LSLAs are playing an increasingly prominent role in this transition. Yet it remains unknown whether foreign LSLAs by agribusinesses target areas based on specific hydrological conditions and whether these investments compete with the water needs of existing local users. Here we combine process-based crop and hydrological modelling, agricultural statistics, and georeferenced information on individual transnational LSLAs to evaluate emergence of water scarcity associated with LSLAs. While conditions of blue water scarcity already existed prior to land acquisitions, these deals substantially exacerbate blue water scarcity through both the adoption of water-intensive crops and the expansion of irrigated cultivation. These effects lead to new rival water uses in 105 of the 160 studied LSLAs (67% of the acquired land). Combined with our findings that investors target land with preferential access to surface and groundwater resources to support irrigation, this suggests that LSLAs often appropriate water resources to the detriment of local users.
The freshwater ecosystems around the world are degrading, such that maintaining environmental flow (EF) in river networks is critical to their preservation. The relationship between streamflow alterations and, respectively, EF violations, and freshwater biodiversity is well established at the scale of stream reaches or small basins (~<100 km2). However, it is unclear if this relationship is robust at larger scales even though there are large-scale initiatives to legalize the EF requirement. Moreover, EFs have been used in assessing a planetary boundary for freshwater. Therefore, this study intends to carry out an exploratory evaluation of the relationship between EF violation and freshwater biodiversity at globally aggregated scales and for freshwater ecoregions. Four EF violation indices (severity, frequency, probability to shift to violated state, and probability to stay violated) and seven independent freshwater biodiversity indicators (calculated from observed biota data) were used for correlation analysis. No statistically significant negative relationship between EF violation and freshwater biodiversity was found at global or ecoregion scales. While our results thus suggest that streamflow and EF may not be an only determinant of freshwater biodiversity at large scales, they do not preclude the existence of relationships at smaller scales or with more holistic EF methods (e.g., including water temperature, water quality, intermittency, connectivity etc.) or with other biodiversity data or metrics.
This paper discusses the role and limitations of using WEI+ as a water resource management tool for highly regulated river basins, with a conjunctive use of surface and groundwater resources. By considering flow regulation by reservoirs and aquifer systems, seasonality of water availability and demand, returns from water uses and environmental flow requirements, WEI+ constitutes an improvement to existing quantitative water scarcity indexes. However, the analysis the computation of WEI+ in complex river basins systems requires detailed data on water availability and water allocation to various uses, which are hard to obtain from monitoring records. The paper describes how the combined use of hydrological and water allocation models can help to overcome data gaps in water accounting and contribute to an improved analysis of water scarcity in heterogeneous and intricate river basins. It also examines the information provided by WEI+ and by other widely used water scarcity indexes, such as the Water Stress Index and the Criticality Ratio, as well as discusses the ability of WEI+ to measure the performance of hydraulic systems, usually evaluated by parameters such as reliability, vulnerability, and resilience. The Tagus River transboundary basin was selected as case study due to massive flow regulation by multi-purpose reservoirs and significant seasonality of water availability and demand. Results show the benefits of using WEI+ to define levels of water scarcity, over other indexes. Within the Tagus River systems, high values of WEI+ are reached during the summer months in regions with intensive agriculture, denoting severe water stress conditions in most sub-basins. The analysis also reveals the strong dependence of Portugal, the downstream country, on flows from Spain, the upstream country.
The conflicts between the utilization and conservation of water resources induced by blue water scarcity have become increasingly prominent. Aiming to balance the ecological and socio-economic benefits derived from blue water resources, this study proposed a regional eco-compensation assessment framework. Based on the blue water budget (deficit or surplus), the formulae for calculating the eco-compensation amount were developed. The blue water scarcity index and its explanatory variables were designed. Considering the spatial dependence of blue water scarcity, the spatial lag model was adopted to perform the spatial econometric analysis. The panel data in 21 prefecture-level cities of Guangdong Province in China from 2009 to 2018 was used for the case study. The findings suggested that blue water scarcity presented significant spillover effects. The precipitation had significantly negative total effects on blue water scarcity, while GDP per capita, population density and water use intensity exhibited significantly positive total effects. Thereupon, a modified coefficient was incorporated to adjust the eco-compensation amount to local condition, so as to achieve targeted restriction and advocate a more sustainable consumption pattern. We believe that the eco-compensation could serve as a potential tool for regional blue water management and contribute to the implementation of sustainable development goals.
Free-flowing rivers support diverse, complex and dynamic ecosystems, as well as provide societal and economic services. Globally, however, the water flow of many rivers has been regulated by hydropower or other sources. Flow modification affects crucial ecosystem functions and processes, and organism’s capacity to fulfil its life cycle requirements. In light of these widespread effects, it is urgent to mitigate ecological impacts caused by existing water infrastructures. To achieve environmental objectives, as well as to manage water uses in a sustainable way, a thorough understanding of ecological responses to hydrological alterations on different temporal levels (e.g., environmental flow, hydropeaking) is essential. This work aims to establish holistic approaches for restoring flows in modified rivers, and to develop environmental flows able to sufficiently mitigate the ecological effects of short-term and annual flow modifications in fluvial ecosystems.
This thesis disentangles the effects of multiple stressors and shows that flow regulation is a primary predictor of fish populations. Moreover, by assessing flow-ecology relationships on annual, seasonal, and sub-daily levels, this work identifies fundamental principles to implement flow restoration measures in rivers affected by water abstraction and hydropeaking. While more dynamic flows are generally recommended as environmental flows, flow restrictions are needed for hydropeaking mitigation. Regarding the latter, a seasonal framework for hydrological mitigation based on fish life-history stages is established, and thresholds are synthesized.
Overall, this thesis advances the establishment of guidelines for successful flow restoration in river systems affected by competing water uses by establishing holistic flow restoration schemes and by subsuming quantitative and qualitative hydropeaking thresholds. Moreover, this thesis sets the topic of flow restoration into the broader context of hydromorphological river rehabilitation. Hence, this work contributes to a more balanced discussion on trade-offs between societal and environmental water uses.
People use a lot of water for drinking, cooking and washing, but significantly more for producing things such as food, paper and cotton clothes. The water footprint is an indicator of water use that looks at both direct and indirect water use of a consumer or producer. Indirect use refers to the 'virtual water' embedded in tradable goods and commodities, such as cereals, sugar or cotton. The water footprint of an individual, community or business is defined as the total volume of fresh water that is used to produce the goods and services consumed by the individual or community or produced by the business. This book offers a complete and up-to-date overview of the global standard on water footprint assessment as developed by the Water Footprint Network. More specifically it: provides a comprehensive set of methods for water footprint assessment shows how water footprints can be calculated for individual processes and products, as well as for consumers, nations and businesses contains detailed worked examples of how to calculate green, blue and grey water footprints describes how to assess the sustainability of the aggregated water footprint within a river basin or the water footprint of a specific product includes an extensive library of possible measures that can contribute to water footprint reduction. Arjen Y. Hoekstra is Professor in Water Management at the University of Twente, the Netherlands; creator of the water footprint concept and Scientific Director of the Water Footprint Network. Ashok K. Chapagain was an irrigation engineer in Nepal for more than a decade, has worked as a researcher at the University of Twente and currently works for the WWF in the UK. Maite M. Aldaya works as a consultant for the United Nations Environment Programme (UNEP) and is a researcher at the Water Footprint Network.
Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of streamflow alteration and its potential ecological consequences have not been quantified on a national scale. We assessed streamflow alteration at 2888 streamflow monitoring sites throughout the conterminous US. The magnitudes of mean annual (1980–2007) minimum and maximum streamflows were found to have been altered in 86% of assessed streams. The occurrence, type, and severity of streamflow alteration differed markedly between arid and wet climates. Biological assessments conducted on a subset of these streams showed that, relative to eight chemical and physical covariates, diminished flow magnitudes were the primary predictors of biological integrity for fish and macroinvertebrate communities. In addition, the likelihood of biological impairment doubled with increasing severity of diminished streamflows. Among streams with diminished flow magnitudes, increasingly common fish and macroinvertebrate taxa possessed traits characteristic of lake or pond habitats, including a preference for fine-grained substrates and slow-moving currents, as well as the ability to temporarily leave the aquatic environment.
Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow ''rules'' to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological ''rules of thumb'' and more comprehensive environmental flow assessments and experimental flow restoration projects.
Sound management and protection of the Great Lakes Basin’s abundant freshwater
resources requires the ability to predict local habitat conditions and fish communities across
regional spatial scales. In response to concerns over increased use and potential diversion of its
plentiful freshwater resources, the State of Michigan enacted legislation in 2006 that required
creation of an integrated assessment model to determine potential for water withdrawals to cause
an adverse impact to Michigan’s waters or water-dependent natural resources. As part of this
effort, we developed a model to predict how fish assemblages in different types of Michigan
streams would change in response to decreased base flows. The model uses habitat suitability
information from Michigan (catchment size, base flow yield, July mean water temperature) for
over 40 fish species to predict assemblage structure and characteristic fish assemblages in
individual river segments under a range of base flow reductions. River segments were classified
into eleven strata based upon catchment size and July river temperature, and fish assemblages
were predicted for each category. By synthesizing model runs for individual fish species at
representative segments of each river type, we developed curves describing how typical fish
assemblages in each type respond to flow reduction. The strata-specific, fish response curves can
be used to identify streamflow reduction levels resulting in adverse resource impacts (ARIs) to
characteristic fish populations. Our model provides a framework for evaluating impacts of flow
withdrawals on biotic communities across a diverse regional landscape.
umans have long been fasci- nated by the dynamism of free-flowing waters. Yet we have expended great effort to tame i rivers for transportation, water sup- ply, flood control, agriculture, and ; f
Summary1. Environmental flows is now a widely accepted term that covers the quantity, timing, duration, frequency and quality of water flows required to sustain freshwater, estuarine and near-shore ecosystems and the human livelihoods and well-being that depend on them.2. The Water Framework Directive (WFD) of the European Union does not use the term environmental flows explicitly, but requires member states to achieve good ecological status (GES) in all waterbodies, which is assessed by reference to aquatic biology. Nevertheless, it is accepted that ecologically appropriate hydrological regimes are necessary to meet this status. Implementing environmental flows will be a key measure for restoring and managing river ecosystems.3. The WFD explicitly requires stakeholder involvement, but this has been interpreted as largely a dissemination exercise by national government agencies. Stakeholders are no longer involved in negotiation over ecological objectives as these are pre-set in the WFD. However, stakeholders may be more involved in reviewing standards and agreeing to measures to restore river ecosystems to the status required by the WFD.4. The U.K. has undertaken two major projects to set environmental standards for water resources (i) to define water abstraction limits that maintain a healthy river ecosystem and (ii) to define ecologically appropriate flow releases from reservoirs.5. Implementation of environmental flows remains a major issue, but new ideas such as time-limited licences and licence trading are being tried.
1. The flow regime is a primary determinant of the structure and function of aquatic and riparian ecosystems for streams and rivers. Hydrologic alteration has impaired riverine ecosystems on a global scale, and the pace and intensity of human development greatly exceeds the ability of scientists to assess the effects on a river-by-river basis. Current scientific understanding of hydrologic controls on riverine ecosystems and experience gained from individual river studies support development of environmental flow standards at the regional scale.
The Southwest Florida Water Management District has implemented a management approach for unimpounded rivers that limits withdrawals
to a percentage of streamflow at the time of withdrawal. The natural flow regime of the contributing river is considered to
be the baseline for assessing the effects of withdrawals. Development of the percent-of-flow approach has emphasized the interaction
of freshwater inflow with the overlap of stationary and dynamic habitat components in tidal river zones of larger estuarine
systems. Since the responses of key estuarine characteristics (e.g., isohaline locations, residence times) to freshwater inflow
are frequently nonlinear, the approach is designed to prevent impacts to estuarine resources during sensitive low-inflow periods
and to allow water supplies to become gradually more uvailable as inflow increases. A high sensitivity to variation at low
inflow extends to many invertebrates and fishes that move upstream and downstream in synchrony with inflow. Total numbers
of estuarine-resident and estuarine-dependent organisms have been found to decrease during low-inflow periods, including mysids,
grass shrimp, and juveniles of the bay anchovy and sand seatrout. The interaction of freshwater inflow with seasonal processes,
such as phytoplankton production and the recruitment of fishes to the tidal-river nursery, indicates that withdrawal percentages
during the springtime should be most restrictive. Ongoing efforts are oriented toward refining percentage withdrawal limits
among seasons and flow ranges to account for shifts in the responsiveness of estuarine processes to reductions in freshwater
inflow.
"Hydropower dam construction is expanding rapidly in Central America because of the increasing demand for electricity. Although hydropower can provide a low-carbon source of energy, dams can also degrade socially valued riverine and riparian ecosystems and the services they provide. Such degradation can be partially mitigated by the release of environmental flows below dams. However, environmental flows have been applied infrequently to dams in Central America, partly because of the lack of information on the ecological, social, and economic aspects of rivers. This paper presents a case study of how resource and information limitations were addressed in the development of environmental flow recommendations for the Patuca River in Honduras below a proposed hydroelectric dam. To develop flow recommendations, we applied a multistep process that included hydrological analysis and modeling, the collection of traditional ecological knowledge (TEK) during field trips, expert consultation, and environmental flow workshops for scientists, water managers, and community members. The final environmental flow recommendation specifies flow ranges for different components of river hydrology, including low flows for each month, high-flow pulses, and floods, in dry, normal, and wet years. The TEK collected from local and indigenous riverine communities was particularly important for forming hypotheses about flow-dependent ecological and social factors that may be vulnerable to disruption from dam-modified river flows. We show that our recommended environmental flows would have a minimal impact on the dam’s potential to generate electricity. In light of rapid hydropower development in Central America, we suggest that environmental flows are important at the local scale, but that an integrated landscape perspective is ultimately needed to pursue hydropower development in a manner that is as ecologically sustainable as possible."
The flow regime is regarded by many aquatic ecologists to be the key driver of river and floodplain wetland ecosystems. We have focused this literature review around four key principles to highlight the important mechanisms that link hydrology and aquatic biodiversity and to illustrate the consequent impacts of altered flow regimes: Firstly, flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic composition; Secondly, aquatic species have evolved life history strategies primarily in direct response to the natural flow regimes; Thirdly, maintenance of natural patterns of longitudinal and lateral connectivity is essential to the viability of populations of many riverine species; Finally, the invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes. The impacts of flow change are manifest across broad taxonomic groups including riverine plants, invertebrates, and fish. Despite growing recognition of these relationships, ecologists still struggle to predict and quantify biotic responses to altered flow regimes. One obvious difficulty is the ability to distinguish the direct effects of modified flow regimes from impacts associated with land-use change that often accompanies water resource development. Currently, evidence about how rivers function in relation to flow regime and the flows that aquatic organisms need exists largely as a series of untested hypotheses. To overcome these problems, aquatic science needs to move quickly into a manipulative or experimental phase, preferably with the aims of restoration and measuring ecosystem response.
Annear, T., I. Chisholm, H. Beecher, A. Locke, P. Aarrestad, N. Burkardt, C. Coomer, C. Estes, J. Hunt, R. Jacobson, G. Jobsis, J. Kauffman, J. Marshall, K. Mayes, C. Stalnaker, and R. Wentworth. 2004. Instream flows for riverine resource stewardship, revised edition. Instream Flow Council, Cheyenne, WY. 268 pp.
ABSTRACT / The flow regime is regarded by many aquatic ecologists to be the key driver of river and floodplain wetland ecosystems. We have focused this literature review around four key principles to highlight the important mechanisms that link hydrology and aquatic biodiversity and to illustrate the consequent impacts of altered flow regimes: Firstly, flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic composition; Secondly, aquatic species have evolved life history strategies primarily in direct response to the natural flow regimes; Thirdly, maintenance of natural patterns of longitudinal and lateral connectivity is essential to the viability of populations of many riverine species; Finally, the invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes. The impacts of flow change are manifest across broad taxonomic groups including riverine plants, invertebrates, and fish. Despite
growing recognition of these relationships, ecologists still struggle to predict and quantify biotic responses to altered flow regimes. One obvious difficulty is the ability to distinguish
the direct effects of modified flow regimes from impacts associated with land-use change that often accompanies water resource development. Currently, evidence about how rivers function in relation to flow regime and the flows that aquatic organisms need exists largely as a series of untested hypotheses. To overcome these problems, aquatic science needs to move quickly into a manipulative or experimental phase, preferably with the aims of restoration and measuring ecosystem response.
A quick, easy methodology is described for determining flows to protect the aquatic resources in both warmwater and coldwater streams, based on their average flow. Biologists do their analysis with aid of hydrological data provided by the U.S. Geological Survey (USGS). Detailed field studies were conducted on 11 streams in 3 states between 1964 and 1974, testing the “Montana Method.” This work involved physical, chemical, and biological analyses of 38 different flows at 58 cross-sections on 196 stream-miles, affecting both coldwater and warmwater fisheries. The studies, all planned, conducted, and analyzed with the help of state fisheries biologists, reveal that the condition of the aquatic habitat is remarkably similar on most of the streams carrying the same portion of the average flow. Similar analyses of hundreds of additional flow regimens near USGS gages in 21 different states during the past 17 years substantiated this correlation on a wide variety of streams. Ten percent of the average flow is a minimum instantaneous flow recommended to sustain short-term survival habitat for most aquatic life forms. Thirty percent is recommended as a base flow to sustain good survival conditions for most aquatic life forms and general recreation. Sixty percent provides excellent to outstanding habitat for most aquatic life forms during their primary periods of growth and for the majority of recreational uses.
1. This paper introduces a new approach for setting streamflow-based river ecosystem management targets and this method is called the `Range of Variability Approach' (RVA). The proposed approach derives from aquatic ecology theory concerning the critical role of hydrological variability, and associated characteristics of timing, frequency, duration, and rates of change, in sustaining aquatic ecosystems. The method is intended for application on rivers wherein the conservation of native aquatic biodiversity and protection of natural ecosystem functions are primary river management objectives.2. The RVA uses as its starting point either measured or synthesized daily streamflow values from a period during which human perturbations to the hydrological regime were negligible. This streamflow record is then characterized using thirty-two different hydrological parameters, using methods defined in Richter et al. (1996). Using the RVA, a range of variation in each of the thirty-two parameters, e.g. the values at ± 1 standard deviation from the mean or the twenty-fifth to seventy-fifth percentile range, are selected as initial flow management targets.3. The RVA targets are intended to guide the design of river management strategies (e.g. reservoir operations rules, catchment restoration) that will lead to attainment of these targets on an annual basis. The RVA will enable river managers to define and adopt readily interim management targets before conclusive, long-term ecosystem research results are available. The RVA targets and management strategies should be adaptively refined as suggested by research results and as needed to sustain native aquatic ecosystem biodiversity and integrity.
Many river restoration projects are focusing on restoring environmental flow regimes to improve ecosystem health in rivers that have been developed for water supply, hydropower generation, flood control, navigation, and other purposes. In efforts to pre-vent future ecological damage, water supply planners in some parts of the world are beginning to address the water needs of river ecosystems proactively by reserving some portion of river flows for ecosystem support. These restorative and protective actions require development of scientifically credible estimates of environmental flow needs. This paper describes an adaptive, inter-disciplinary, science-based process for developing environmental flow recommendations. It has been designed for use in a variety of water management activities, including flow restoration projects, and can be tailored according to available time and resources for determining environmental flow needs. The five-step process includes: (1) an orientation meeting; (2) a literature review and summary of existing knowledge about flow-dependent biota and ecological processes of concern; (3) a workshop to develop ecological objectives and initial flow recommendations, and identify key information gaps; (4) implementation of the flow recommendations on a trial basis to test hypotheses and reduce uncertainties; and (5) monitoring system response and conducting further research as warranted. A range of recommended flows are developed for the low flows in each month, high flow pulses throughout the year, and floods with targeted inter-annual frequencies. We describe an application of this process to the Savannah River, in which the resultant flow recommendations were incorporated into a comprehensive river basin planning process conducted by the Corps of Engineers, and used to initiate the adaptive management of Thurmond Dam.
Human demands on the world's available freshwater supplies continue to grow as the global population increases. In the endeavor to manage water to meet human needs, the needs of freshwater species and ecosystems have largely been neglected, and the ecological consequences have been tragic. Healthy freshwater ecosystems provide a wealth of goods and services for society, but our appropriation of freshwater flows must be better managed if we hope to sustain these benefits and freshwater biodiversity. We offer a framework for developing an ecologically sustainable water management program, in which human needs for water are met by storing and diverting water in a manner that can sustain or restore the ecological integrity of affected river ecosystems. Our six-step process includes: (1) developing initial numerical estimates of key aspects of river flow necessary to sustain native species and natural ecosystem functions; (2) accounting for human uses of water, both current and future, through development of a computerized hydrologic simulation model that facilitates examination of human-induced alterations to river flow regimes; (3) assessing incompatibilities between human and ecosystem needs with particular attention to their spatial and temporal character; (4) collaboratively searching for solutions to resolve incompatibilities; (5) conducting water management experiments to resolve critical uncertainties that frustrate efforts to integrate human and ecosystem needs; and (6) designing and implementing an adaptive management program to facilitate ecologically sustainable water management for the long term. Drawing from case studies around the world to illustrate our framework, we suggest that ecologically sustainable water management is attainable in the vast majority of the world's river basins. However, this quest will become far less feasible if we wait until water supplies are further over-appropriated.
Attempts to implement environmental flows have encountered many obstacles. Many water allocation systems include a system of prioritization among water uses that generally does not favor environmental flow protection, or do not allow for protection of high flow events for ecological purposes. It has proven very difficult to implement complicated environmental flow prescriptions that attempt to mimic natural flow variability within water allocation systems. Additionally, many water allocation systems do not adequately address interconnections between surface water and groundwater, or releases from dams. It is time to re-think our approaches to protecting environmental flows. As with water quality protection, environmental flows should be viewed not as an “allocation” of water, but rather as a desirable outcome of integrated management of water and land resources for long-term sustainability. In this sense, environmental flows should be managed in a manner similar to water quality protection, in which the influences of diverse land and water use activities are regulated to ensure that the ecological and social values of water are optimized. Both water quality and environmental flow management protect a vast array of important social benefits that are sustained by managing for healthy freshwater ecosystems. In this paper I offer a definition of sustainable water management that explicitly recognizes the fact that society derives substantial benefits both from out-of-stream extractions of water as well as by maintaining adequate flows of water within freshwater ecosystems. To help facilitate sustainable water management, a ”Sustainability Boundary Approach“ is described for use in setting quantitative water management goals. When the cumulative hydrologic impacts of water and land uses are managed within these sustainability boundaries, the full array of values associated with water can be more fully realized. Copyright © 2009 John Wiley & Sons, Ltd.
Instream Flow Protection is a comprehensive overview of Western water use and the issues that surround it. The authors explain instream flow and its historical, political, and legal context; describe current instream flow laws and policies; and present methods of protecting instream flow. They provide numerous examples to illustrate their discussions, with case studies of major river systems including the Bitterroot, Clark's Fork, Colorado, Columbia, Mimbres, Mono Lake, Platte, Snake, and Wind.Policymakers, land and water managers at local, state, and federal levels, attorneys, students and researchers of water issues, and anyone concerned with instream flow protection will find the book enormously valuable.
Understanding effects of flow alteration on stream biota is essential to developing ecologically sustainable water supply strategies. We evaluated effects of altering flows via surface water withdrawals and instream reservoirs on stream fish assemblages, and compared effects with other hypothesized drivers of species richness and assemblage composition. We sampled fishes during three years in 28 streams used for municipal water supply in the Piedmont region of Georgia, U.S.A. Study sites had permitted average withdrawal rates that ranged from < 0.05 to > 13 times the stream's seven-day, ten-year recurrence low flow (7Q10), and were located directly downstream either from a water supply reservoir or from a withdrawal taken from an unimpounded stream. Ordination analysis of catch data showed a shift in assemblage composition at reservoir sites corresponding to dominance by habitat generalist species. Richness of fluvial specialists averaged about 3 fewer species downstream from reservoirs, and also declined as permitted withdrawal rate increased above about 0.5 to one 7Q10-equivalent of water. Reservoir presence and withdrawal rate, along with drainage area, accounted for 70% of the among-site variance in fluvial specialist richness and were better predictor variables than percent of the catchment in urban land use or average streambed sediment size. Increasing withdrawal rate also increased the odds that a site's Index of Biotic Integrity score fell below a regulatory threshold indicating biological impairment. Estimates of reservoir and withdrawal effects on stream biota could be used in predictive landscape models to support adaptive water supply planning intended to meet societal needs while conserving biological resources.
Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow "rules" to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological "rules of thumb" and more comprehensive environmental flow assessments and experimental flow restoration projects.
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