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A Collaborative and Adaptive Process for Developing Environmental Flow Recommendations
Abstract
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.
... Likewise, alternative methodologies have emerged in flow management, including conceptual workshop-driven and participatory sciencedriven approaches , Richter et al., 2006. These methods engage stakeholders in the identification and definition of thresholds, providing a more comprehensive understanding of ecosystem dynamics and greater investment in implementation. ...
... Flow-ecology relationships and their derived thresholds should be viewed as testable hypotheses rather than prescriptions (Davies et al., 2013), and multiple lines of evidence may support or refute initial findings. For example, thresholds can serve as starting points for setting environmental flow targets, which are then iteratively refined through monitoring and adjustments, particularly under changing conditions (Richter et al., 2006;Poff, 2018). Unless extreme events above or below common conditions are Fig. 7. Plots of flow-ecology datasets with relationships best fit by linear or nonlinear trends, along with approximated potential thresholds. ...
... Management will always benefit from more data, but the availability of temporally and geographically extensive hydrologic data has been decreasing in the United States and globally (Vörösmarty et al., 2001;Ruhi et al., 2018). The most effective and consistent sources of these data may be the parties most invested in the systems of interest (Richter et al., 2006). Thresholds, whether in the literature or proposed as flow standards, represent an essential starting point for informed water resource management. ...
... In 2002, The Nature Conservancy (TNC) entered a national (US) partnership with the US Army Corps of Engineers (US-ACE) called the "Sustainable Rivers Program (SRP)" and focused on opportunities to re-operate USACE dams for ecological benefit as well as meeting basin stakeholder needs ( Table 6). As one of the earliest SRP trials, the Savannah River project demonstrated the potential for a collaborative approach to e-flows (Richter et al. 2006). In 2020, however, hydropower interests prevailed and the partnership between the TNC and dam owner operators was terminated for the foreseeable future, this despite the preference of many other stakeholders for the e-flow regime developed over many years of stakeholder consultations. ...
... Konrad (2010) and Richter et al. (2006). ...
... The provision of e-flows is most often enabled by modifying the water release rules of individual dams or dam cascades using existing infrastructure (Richter et al. 2006;Widen et al. 2022). In other cases, retrofitting or removing water infrastructure could facilitate and enhance e-flow implementation (Thieme et al. 2021). ...
Environmental flows (e-flows) aim to mitigate the threat of altered hydrological regimes in river systems and connected waterbodies and are an important component of integrated strategies to address multiple threats to freshwater biodiversity. Expanding and accelerating implementation of e-flows can support river conservation and help to restore the biodiversity and resilience of hydrologically altered and water-stressed rivers and connected freshwater ecosystems. While there have been significant developments in e-flow science, assessment, and societal acceptance, implementation of e-flows within water resource management has been slower than required and geographically uneven. This review explores critical factors that enable successful e-flow implementation and biodiversity outcomes in particular, drawing on 13 case studies and the literature. It presents e-flow implementation as an adaptive management cycle enabled by 10 factors: legislation and governance, financial and human resourcing, stakeholder engagement and co-production of knowledge, collaborative monitoring of ecological and social-economic outcomes, capacity training and research, exploration of trade-offs among water users, removing or retrofitting water infrastructure to facilitate e-flows and connectivity, and adaptation to climate change. Recognising that there may be barriers and limitations to the full and effective enablement of each factor, the authors have identified corresponding options and generalizable recommendations for actions to overcome prominent constraints, drawing on the case studies and wider literature. The urgency of addressing flow-related freshwater biodiversity loss demands collaborative networks to train and empower a new generation of e-flow practitioners equipped with the latest tools and insights to lead adaptive environmental water management globally. Mainstreaming e-flows within conservation planning, integrated water resource management, river restoration strategies, and adaptations to climate change is imperative. The policy drivers and associated funding commitments of the Kunming–Montreal Global Biodiversity Framework offer crucial opportunities to achieve the human benefits contributed by e-flows as nature-based solutions, such as flood risk management, floodplain fisheries restoration, and increased river resilience to climate change.
... The method is grounded on several time-varying hydrological conditions and individual flow events that play a key role in the performance and persistence of aquatic, semi-aquatic, and terrestrial species linked to a wide variety of rivers [3,18,33]. Likewise, frequency-of-occurrence-based management of such flow components contributes to exposing freshwater and riparian species to extreme conditions for coping with non-stationarity [8,18,24,[34][35][36]. ...
... The multivariate assessments provide scientific evidence of greater hydrological dependency of intermittent rivers and ephemeral streams than perennial rivers. Baseline parametrization cannot continue as it was designed because the aquatic phase of intermittent rivers and ephemeral streams is not equally resilient at an ecohydrological level as in perennial rivers and, in the extreme case, it condemns them to almost or completely disappear (i.e., environmental objective class D) [3,24,[33][34][35][36][37]. Thus, the model's "top roof" and "ground floor" parametrization need to be adjusted to avoid underestimations in non-perennial stream types. ...
... The rationale for the adjustment setting is that perennial rivers exhibit baseflows that impede flow secession, i.e., 90% exceedance time based on the flow duration curve criteria used in this study, notwithstanding high values of coefficient of variation between seasons. Due to the lack of such buffer capacity in the case of non-perennial rivers, keeping the original values imply significant changes at an ecohydrological level and, therefore, a further degradation would be expected than that anticipated by the original model in the performance and persistence of aquatic, semi-aquatic, and terrestrial species [3,8,18,24,[33][34][35][36][37]. Furthermore, the adjustment differentiates the wet conditions dependency between stream types (seasonally or annually). ...
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.
... There have been major efforts to define EFRs based on eco-hydrological relationships in individual rivers (Richter, Warner et al. 2006) but there has been limited upscaling of individual methods to global or regional scales. In general, eco-hydrological relationships are far from being linear at local scales. ...
... EF methods are classified into four types: hydrological methods; hydraulic rating methods; habitat simulation methods; and holistic methods (Table 2.1). These EF methods were mainly developed at river or basin scale, either in the context of flow restoration projects (Richter, Warner et al. 2006) or for assessing the ecological status of rivers at a regional, national, or continental level, as per, for instance, the Water Framework Directive 2000/60/EC (Council 2000). (Tennant 1976, Tessmann 1980, Richter, Baumgartner et al. 1997, Armstrong, Todd et al. 1999, Smakhtin, Shilpakar et al. 2006, Richter 2010, Babel, Dinh et al. 2012 Hydraulic Flow velocity, river crossing area R2Cross method (Armstrong, Todd et al. 1999) Habitatsimulation Flow velocity, river cross section, dataset of a fish specie PHABSIM, IFIM (Bovee 1986, Bovee, Lamb et al. 1998, Milhous 1999, Capra, Sabaton et al. 2003 (King and Louw 1998, Hughes 2001, Bunn and Arthington 2002, Arthington, Bunn et al. 2006) ...
... For example, if EFRs were defined by only 5 years average including a dry year such as 2003, the calculated flow could be lower than the required flows and vice versa, if EFRs are overestimated, this could lead to an overestimation of the EF deficit. EFRs can sometimes be adjusted to wet and dry years such as in Richter, Warner et al. (2006). It is also possible to give a range of EFRs to water managers by increasing or decreasing EFRs with its the standard deviation (in this study and in ). ...
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.
... Wolman & Miller 1960 [51] Leopold 1994 [76] Richter et al. 2006 [77] Pruitt & McKay 2013 [78] Petts 1996 [79] Montgomery & Bolton 2003 [80] Mise en connexion des annexes fluviales, inondation de la plaine alluviale > Q plein bord Richter et al. 2006 [77] Infiltration, recharge des nappes alluviales > Q plein bord Stanford & Ward 1988 [81] Tockner et al. 2000 [10] Maintien de la complexité des structures à l'échelle de la plaine d'inondation ...
... Wolman & Miller 1960 [51] Leopold 1994 [76] Richter et al. 2006 [77] Pruitt & McKay 2013 [78] Petts 1996 [79] Montgomery & Bolton 2003 [80] Mise en connexion des annexes fluviales, inondation de la plaine alluviale > Q plein bord Richter et al. 2006 [77] Infiltration, recharge des nappes alluviales > Q plein bord Stanford & Ward 1988 [81] Tockner et al. 2000 [10] Maintien de la complexité des structures à l'échelle de la plaine d'inondation ...
Cette étude contribue à cerner les impacts écohydrologiques des prélèvements de hautes eaux sur les écosystèmes aquatiques, (1) en identifiant des indicateurs écohydrologiques (c’est-à-dire des variables hydrologiques qui reflètent la qualité de l’habitat des organismes ou le fonctionnement écologique) adaptés à l’étude de ces impacts, et (2) en estimant comment ces indicateurs seraient affectés par des scénarios de prélèvements directs, en rivière.
... Ecological requirements should be addressed urgently to attain sustainability in water management and allocation [1]. Water supply planners are proactively addressing the water needs of aquatic ecosystems by reserving environmental flows for ecosystems to prevent ecological damage [2]. Many restoration projects are focused on restoring environmental flows to improve the health of the aquatic ecosystems. ...
... where Ex sp (kJ/g) is the special eco-exergy, Ex(kJ/m 3 ) is the ecoexergy, v i is the weight factor of specie i, C i (g/m 3 ) is the biomass of specie i, C t (g/m 3 ) is the biomass of all species. Implementing flow recommendations can improve the scientific understanding of flow conditions necessary to affect desired ecological changes or processes [2]. A multi-object reservoir operation model was developed, in which the environmental flow recommendations in step six were treated as limited conditions [47]. ...
... The methods employed are based on the RVA as seen in Richter et al. [45,[62][63][64][65], ...
... Nonparametric graphical and statistical study was analyzed using the software, V7 IHA [72] under the hypothesis that there are no differences between the medians of the preimpact period and the postimpact period (Ho: μ1 = μ2 and Ha: μ1 ≠ μ2). As can be seen below, the 33 IHA parameter (Figure 3), V7 IHA is compatible with Table 1 and Richter's thesis in terms of [65]. The indicators of hydrological alteration (IHA) provided a quantitative approximation of hydrology through the characterization of intra-annual variation of flow by the use. ...
Sustainability requires understanding and respecting the ecosystem functioning to plan the use of its resources. Improvised planning plus economic benefits can stimulate unsustainable decisions that lead to complications and obscures the application of appropriate adaptations when a change is required. This paper is a historical review of a reservoir when the dam changes its use from hydroelectric to water supply and then tourism is superimposed on the ecosystem. Data collected from the literature are systematically analyzed to see the effects on basin-reservoir dynamics. The main effect was the increase in the hydraulic retention time of the reservoir that facilitates the accumulation of nutrients and eutrophication, aggravated by the increase in the fixed and floating population stimulated by tourism. The consequent cyanobacteria blooms deteriorate the landscape, become a health risk and cancels the use of the reservoir to tourism. The increase in emerging compounds detected in the treatment plant effluent discharged into the reservoir poses a risk to aquatic species and the water supply. These results are analyzed in light of the objectives and dimensions of Sustainability. Recommendations include modifying Goal 1 of SDO 8, because it is shown that an annual growth of 7% of GDP in developing countries threatens their natural resources.
... (2) Changes in river morphology have directly affected biodiversity within river channels [42]. For example, there are obvious changes in the flow pulse count and duration at Dongbei Station [43], which are not conducive to the migration, spawning, and survival of aquatic organisms in the region [44]. ...
... However, it has also changed the size and occurrence time of peak flood flow, causing damage to the ecological flow of some river sections [41]. (2) Changes in river morphology have directly affected biodiversity within river channels [42]. For example, there are obvious changes in the flow pulse count and duration at Dongbei Station [43], which are not conducive to the migration, spawning, and survival of aquatic organisms in the region [44]. ...
Hydro power has provided significant economic benefits to society due to its cleanliness and convenience. As the number of hydropower stations has increased, many serious ecological issues have also emerged. This study uses Wan’an Reservoir as its research object and investigates single–multi-objective optimal operation and decision-making regarding reservoirs for ecology-oriented operation, to meet ecological water demand and seek the optimal operation schemes for energy generation and ecological benefits. The full-process research is conducted based on the “objective-modeling constraint optimization scheme decision-making” framework. The Mann–Kendall test and ordered clustering method were used to diagnose the hydrological variation in the basin. Based on this, a hierarchical and phased ecological flow process was derived. The objectives were defined according to the flow process, and optimal operation models were constructed. The differential evolution algorithm (DE) and improved non-dominated sorting genetic algorithm-II (NSGA-II) were used to solve the models. A non-fitting curve method was used to determine the approximate inflection point of the Pareto front curve, and the curve was fitted linearly according to the approximate inflection point to obtain the conversion formula between the objectives. Based on the coefficient of variation and Mahalanobis distance, a new multi-attribute decision-making method for reservoir operation, CV-ITOPSIS, was constructed by improving the traditional TOPSIS. The results show that: (1) There is a piecewise linear contradiction between energy generation and ecological objectives, and the contradiction intensifies with an increase in incoming water frequency. (2) Before the approximate inflection point, the head significantly influences the conversion rate from the energy generation to ecology, while the discharge flow is the major influencing factor after the inflection point. The inflection point and the formula for the piecewise straight line can reveal the conversion law between the two objectives. (3) CV-ITOPSIS considers the degree of differentiation of index data and fully considers the correlation between indicators while retaining the good evaluation performance of the traditional method. It recommends the optimal benefit scheme for a multi-objective non-inferior solution set. The research results provide a theoretical foundation and decision support for the optimal ecological operation of the Ganjiang River Basin.
... However, they are prohibitively expensive in terms of data requirement and computational time, which limits the prospect of their application in ecosystem management studies in developing nations. On the other hand, conceptual models are expert based and developed by reviewing data and knowledge about the river-floodplain system, native species and their flow regime dependencies on low, high and flood flows (Richter et al. 2006). The limitation of the review work, however, depends on the extent to which the river environment has been studied, the type and amount of information gathered and the availability of studies on similar ecosystems. ...
... The limitation of the review work, however, depends on the extent to which the river environment has been studied, the type and amount of information gathered and the availability of studies on similar ecosystems. The review work can be targeted to a keystone species because their flow needs are representative of an ecological guild (Richter et al. 2006). ...
The dominant plant species in many African wetlands is Cyperus papyrus. Its adaption to saturated and low oxygen conditions and its dense structure and height provide breeding and feeding grounds for unique flora and fauna. As a keystone species adapted to local hydrology, the flow regime of papyrus offers the full range of hydrologic conditions and events essential to ecosystem health. However, no study has attempted to link papyrus wetlands’ flow regimes to their biologically-relevant hydrologic attributes. The Indicators of Hydrologic Alteration (IHA) enable the evaluation of changes to flow regimes by examining hydrologic records and linking them to biologically-relevant hydrologic characteristics through the Environmental Flow Components (EFCs) approach. This study assesses hydrologic alterations of a papyrus wetland’s flow regime due to rice irrigation. We develop a conceptual ecological model linking papyrus to hydrologic attributes to determine the consequences of changed EFCs (extreme low flows, base flow, high flow pulses, and small and large floods) on papyrus as a habitat. We find that agricultural water management considerably alters the magnitude, duration, timing and rate of change of EFCs for the irrigated area to catchment area ratio greater than 1:153, affecting both sexual and asexual reproduction in papyri plants. Overall, a better understanding of the threats of water diversion for agriculture is made by linking papyrus’ flow regimes to biologically-relevant hydrologic attributes. Knowledge of the roles of the various EFCs could provide opportunities for conserving and protecting papyrus wetlands, especially for systems at risk of altered flows.
... Environmental flows (EFs) are defined as the quality, quantity, and patterns of the river flow required for maintaining ecosystem services and are associated with a river's natural flow regime before human settlement (LeRoy Poff et al., 1997;Richter et al., 2006). EFs support sedimentation transfer to coastal deltas formed at the river mouth. ...
... The environmental flow assessment methodologies currently in use depend on linkages to other local policy recommendations and stakeholder engagement (Hill Clarvis et al., 2014;Hannaford, 2015). There are ongoing efforts to define standards and methods to account for environmental flow methods in rivers based on the ecohydrological relationships in rivers (Richter et al., 2006). More than 200 environmental flow assessment methods exist globally (Tharme, 2003). ...
The Indus River Basin (IRB) is a severely water-stressed and rapidly developing home to an estimated 250 million people in South Asia. An acute deficit of environmental flows (EFs) in the basin’s delta negatively impacts geomorphology and surrounding ecosystems. Here, a sub-national model of the IRB’s integrated water–energy–land systems is applied to quantify multi-sector transformations and system costs for enhancing EFs to the Indus Delta. The results show that increasing the average outflows from the basin relative to historical policy levels by 2.5 and 5 times would increase sectoral costs for upstream water users between 17–32 and 68–72% for low and high ecological potential targets. The enhanced EFs result in more energy for pumping and treating water upstream from the delta and a net increase in irrigation and energy investments. The EF policy costs are minimized by 7–14% through cooperation across countries and 6–9% through the coordinated implementation of water efficiency measures in the irrigation, conveyance, power plant cooling, and water treatment sectors. The results underscore the crucial role of a multi-sector, multi-scale collaboration in achieving EF targets in water-stressed river basins for ecosystem adaptation to climate vulnerability, restoration of the delta, and socio-economic benefits.
... The methods employed are based on the RVA as seen in Richter et al. [45,[62][63][64][65], ...
... Nonparametric graphical and statistical study was analyzed using the software, V7 IHA [72] under the hypothesis that there are no differences between the medians of the preimpact period and the postimpact period (Ho: μ1 = μ2 and Ha: μ1 ≠ μ2). As can be seen below, the 33 IHA parameter (Figure 3), V7 IHA is compatible with Table 1 and Richter's thesis in terms of [65]. The indicators of hydrological alteration (IHA) provided a quantitative approximation of hydrology through the characterization of intra-annual variation of flow by the use. ...
Adaptation to climate change requires, among others, the modification of river flow regimes to account for the change in household, agricultural, industry, and energy water consumption as well as their short/medium/long-term socioeconomic impact. In this study, the comparative analysis of the variation of the precipitation in relation to the availability of water in the Yautepec and Cuautla rivers in Morelos, Mexico, for the previous period and subsequent period is carried out, to determine the change in the availability of water in the ecosystem. In winter (February), an increase in rainfall on the Yautepec and Cuautla River was observed, where annual seasonal agriculture and Pine and Oyamel forest are the characteristic vegetation. In autumn (October), a decrease in precipitation takes place. The flows in some regions do not coincide with the increase in the percentage of precipitation (Oaxtepec and Las Estacas Stations) and point out the synergistic effect of the human use of the water resource and the effects of climate change. On Ticumán Station, the depletion of the flow only can be associated with the use of the resource by human influence. The modifications caused by alteration of a river’s flow regime and climatic change must be studied through comparative multidisciplinary studies that give to decision-makers the design of environmental flows.
... One of the root causes behind this degradation is the anthropogenic alteration of the natural flow regime of a river -i.e. the magnitude, frequency, duration, timing, and rate of change in flow (Poff et al., 1997). Human actions impact the intra-and interannual variability, which are often considered as parts of the natural flow regime (Richter et al., 2006). These natural streamflow dynamics have already changed in major rivers across the globe (Grill et al., 2015). ...
... To date, many countries have initiated legislation that would support the establishment of EFs as a concrete means of conserving and restoring riverine ecosystems (Acreman et al., 2014;Arthington et al., 2018;Tickner et al., 2020). In an ideal case, EFs are quantified by assimilating observed hydrological data with local-scale expert knowledge in a collaborative process, resulting in EFs tailored to each unique river (Richter et al., 2006;Poff et al., 2017). Such holistic EF methods include, for example, ELOHA , DRIFT (King et al., 2003), and PROBFLO (O'Brien et al., 2018). ...
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.
... Los caudales ambientales, pueden ser definidos como el agua que se libera y se requiere en un sistema fluvial, o se deja correr con un propósito específico para mantener la condición natural y funcional del ecosistema (Richter, 2006). De acuerdo con la declaración de Brisbane, los caudales ambientales, incluyen la cantidad, periodicidad y calidad del agua que se requiere para sostener los ecosistemas dulceacuícolas, estuarios y el bienestar humano que depende de estos ecosistemas (Brisbane, 2007). ...
Nationally and internationally it is recognized the urgent need to maintain
healthy rivers with natural flow regimes since these are associated with a
large number of natural processes and eco-systemic services offered by the
rivers. The main objective of this study was to integrate spatial, hydrological
and environmental elements of the Verde River Basin in Oaxaca, Mexico, to
identify thresholds of environmental flow variability that can be assigned
monthly or seasonally to their streams under exploitation or water pressure
schemes, to maintain the functionality and connectivity of aquatic and
riparian ecosystems. A GIS was integrated with physical information such as
the sub-basins areas that account for a total basin of 18.366 km2
. For each
stream its length, slope and order was estimated, corresponding to the Verde
River basin 240 km, 1.04 % and 5th order, respectively. The hydrological
methodology IHA-RVN developed by TNC, was applied to establish flows
variability thresholds in 12 hydrometric gauges from Conagua and CFE, using
data records from 15 to 30 years. Both, intra-annual and historical interannual analysis defined the monthly and seasonal minimum and maximum
thresholds during dry, medium and rainy years. To justify and associated the
instream flow suggested strategies some resources to be protected were
identified, such as 18 fish species and 7 crayfish species recently identified in
the last part of the basin (60 km before its sea mouth). Besides, different
levels of eco-hydrological alteration were defined within the basin, being the
medium condition the most common (with low water use pressure). The
priority conservation sites were more abundant in the sea mouth and lagoon
system associated to the river. The tool developed in this research can serve
as a basis for consultation and for the balance between water use and
conservation in the basin.
... Los caudales ambientales, pueden ser definidos como el agua que se libera y se requiere en un sistema fluvial, o se deja correr con un propósito específico para mantener la condición natural y funcional del ecosistema (Richter, 2006). De acuerdo con la declaración de Brisbane, los caudales ambientales, incluyen la cantidad, periodicidad y calidad del agua que se requiere para sostener los ecosistemas dulceacuícolas, estuarios y el bienestar humano que depende de estos ecosistemas (Brisbane, 2007). ...
... There is still a lack of consensus to specify thresholds for the mentioned parameters (Costa et al., 2017). In this study, we will focus on how RRRs can contribute to flow management, including ramping rates, minimum flow, and peak flow which are critical criteria for hydropeaking mitigation Richter et al., 2010). ...
The role of hydropower as a renewable and balancing power source is expected to increase in a Net Zero Emissions by 2050 scenario. As a common phenomenon in hydropower plants, hydropeaking will become more prominent, resulting in additional stresses on the ecological status of rivers. Here we propose a novel approach to design and operate auxiliary reservoirs called re‐regulation reservoirs (RRR) that aim to mitigate the adverse impacts of hydropeaking on rivers. A re‐regulation reservoir aims at smoothing flow fluctuations caused by hydropeaking by diverting and retaining parts of high flows and returning them back to river corridors during low flows. Using actual data from a hydropeaking‐influenced river system, the operation and efficiency of potential reservoirs have been investigated. An open‐access algorithm was developed to analyze the influence of the reservoirs to mitigate hydropeaking, considering peak and minimum flow and up‐ and down‐ramping rates. The findings illustrate that, in most cases, the required reservoir volume increases as the flow thresholds become more stringent. Nonetheless, several exceptions were observed, where larger reservoir volumes were required compared with cases with more stringent thresholds. These findings highlight the importance of understanding the impact of flow adjustments, while carefully considering the river regime, sub‐daily flow patterns, and unique characteristics of the river's ecosystem. Our approach shows theoretical possibilities for regulating hydropeaking and provides a basis for optimizing re‐regulation reservoirs, contributing to practical and adaptable strategies for sustainable hydropower management without increasing the operational cost of power systems.
... On a global scale, it is estimated that approximately 65 % of the discharge (in terms of quantity) in rivers poses a moderate to severe threat to biodiversity (Vörösmarty et al., 2010), connectivity of 48 % of rivers is diminished (Grill et al., 2019), and fish biodiversity has been significantly altered in 53 % of rivers . The main causes of such degradation and alteration in river flow regimes around the globe are associated with anthropogenic activities and climate change (Richter et al., 2006;Stamou et al., 2018;Wineland et al., 2021). Therefore, there is a need to rethink and properly manage water resources in regions subjected to water scarcity and, most importantly, severe changes in regional climate. ...
The impact of drought on environmental flow (EF) in 27 catchments of the Indus Basin is studied from 1980–2018 using indicators of hydrologic alterations (IHAs). The standardized precipitation evapotranspiration index (SPEI) was systematically propagated from one catchment to another using principal component analysis (PCA). Threshold regression is used to determine the severity of drought (scenario 1, drought severity that causes low flows) and the month (scenario 2, months where drought has resulted in low flows) that trigger low flows in the Indus Basin. The impact of drought on low EFs is quantified using range of variability analysis (RVA), which is an integrated component of the IHA used to study the hydrological alterations in environmental flow components (EFCs) by comparing the pre- and post-impact periods of human and/or climate interventions in EFCs. The hydrological alteration factor (HAF) is calculated for each catchment in the Indus Basin. The results show that most of the catchments were vulnerable to drought during the periods of 1984 to 1986, 1991/1992, 1997 to 2003, 2007 to 2008, 2012 to 2013, and 2017 to 2018. On a longer timescale (SPEI-12), drought is more severe in the lower Indus Basin (LIB) than in the upper Indus Basin (UIB). The IHA pointed out that drought significantly impacts the distribution of EFCs, particularly extremely low flow (ELF) and low flow (LF). The magnitude and frequency of the ELF and LF events increase as drought severity increases. The threshold regression provided useful insights, indicating that moderate drought can trigger ELF and LF at shorter timescales (SPEI-1 and SPEI-6) in the UIB and middle Indus Basin (MIB). Conversely, severe and extreme droughts trigger ELF and LF at longer timescales (SPEI-12) in the LIB. The threshold regression also divided the entire study period (1980–2018) into different time periods (scenario 2), which is useful for quantifying the impact of drought on low EFs using the SPEI coefficient. Higher SPEI coefficients are observed in the LIB, indicating high alterations in EF due to drought. HAF showed high alterations in EF in most of the catchments throughout the year except in August and September. Overall, this study provided useful insights for analysing the effects of drought on EF, especially during low flows.
... There is still a lack of consensus to specify thresholds for the mentioned parameters (Costa et al., 2017). In this study, we will focus on how RRRs can contribute to flow management, including ramping rates, minimum flow, and peak flow which are critical criteria for hydropeaking mitigation Richter et al., 2010). ...
The role of hydropower as a renewable and balancing power source is expected to significantly increase in a Net Zero Emissions by 2050 scenario. As a common phenomenon in hydropower plants, hydropeaking will become more prominent, resulting in additional stresses on the ecological status of rivers. Here we propose a novel approach to design and operate auxiliary reservoirs called re-regulation reservoirs that aims to mitigate the adverse impacts of hydropeaking on rivers. A re-regulation reservoir aims at smoothing flow fluctuations caused by hydropeaking by diverting and retaining parts of high flows and returning them back to river corridors during low flows. The regulatory performance of re-regulation reservoirs is a function of its geometry and volume availability. It is defined (and optimized) by restricting various flow components thresholds. Using actual data from a hydropeaking-influenced river system, the operation and efficiency of potential re-regulation reservoir have been investigated by employing a range of thresholds for hydropeaking mitigation. A methodology and an open-access algorithm to operate re-regulation reservoirs, by establishing a hierarchy of conditions to restrict peak flow, minimum flow, up-ramping rates, and down-ramping rates was developed. Our calculations show clear theoretical possibilities for regulating hydropeaking with re-regulation reservoirs, while offering several advantages, including greater flexibility and adaptability to changing environmental conditions, power, and water demand without increasing the operational cost of power systems.
... (3) prediction and model parameterization in ungauged catchments [10][11][12][13][14][15][16][17][18]; (4) predictions under changed flow conditions [6,11,[19][20][21][22]; (5) assessment of environmental flows [23][24][25][26][27]; and (6) eco-hydrologic classification [28,29]. ...
Catchment classification plays an important role in many applications associated with water resources and environment. In recent years, several studies have applied the concepts of nonlinear dynamics and chaos for catchment classification, mainly using dimensionality measures. The present study explores prediction as a measure for catchment classification, through application of a nonlinear local approximation prediction method. The method uses the concept of phase-space reconstruction of a time series to represent the underlying system dynamics and identifies nearest neighbors in the phase space for system evolution and prediction. The prediction accuracy measures, as well as the optimum values of the parameters involved in the method (e.g., phase space or embedding dimension, number of neighbors), are used for classification. For implementation, the method is applied to daily streamflow data from 218 catchments in Australia, and predictions are made for different embedding dimensions and number of neighbors. The prediction results suggest that phase-space reconstruction using streamflow alone can provide good predictions. The results also indicate that better predictions are achieved for lower embedding dimensions and smaller numbers of neighbors, suggesting possible low dimensionality of the streamflow dynamics. The classification results based on prediction accuracy are found to be useful for identification of regions/stations with higher predictability, which has important implications for interpolation or extrapolation of streamflow data.
... The concept of an ecological drought was proposed to study the impact of droughts on ecosystems [19,20], and many indices have been developed based on different variables to identify ecological drought events in terrestrial ecosystems, such as the vegetable index and soil moisture for a drought in vegetable ecosystems [21,22]. Since the streamflow regime is one of the most important factors for aquatic ecosystem health, the ecological streamflow has been commonly used as a threshold for identifying ecological drought events in aquatic ecosystems [23][24][25]. It is feasible to forecast ecological droughts in rivers through a hydrological model when the values of the ecological streamflow for the rivers (i.e., the thresholds of ecological droughts in rivers) are available. ...
Ecological droughts in rivers, as a new type of drought, have been greatly discussed in the past decade. Although various studies have been conducted to identify and evaluate ecological droughts in rivers from different indices, a forecast model for this type of drought is still lacking. In this paper, a numerical weather forecast, a hydrological model, and a generalized Bayesian model are employed to establish a new general framework for the probabilistic forecasting of ecological droughts in rivers, and the Daitou section in China is selected as the study area to examine the performance of the new framework. The results show that the hydrological model can accurately simulate the monthly streamflow with a Nash–Sutcliffe efficiency of 0.91 in the validation period, which means that the model can be used to reconstruct the natural streamflow from the impact of an upstream reservoir. Based on a comparison of ecological drought events from the observed and model-simulated streamflow series, the events from the observed series have a larger deficit volume and a longer duration of ecological droughts after 2014, indicating that human activities may lead to a more severe situation of ecological droughts. Furthermore, due to the uncertainty of precipitation forecasts, a probabilistic precipitation forecast is employed for probabilistic ecological drought forecasting. Compared to the deterministic forecast, the probabilistic ecological drought forecast has better performance, with a Brier score decrease of 0.35 to 0.18 and can provide more information about the risk of ecological droughts. In general, the new probabilistic framework developed in this study can serve as a basis for the development of early-warning systems and countermeasures for ecological droughts.
... Adversely affected communities downstream of major dams and inter-basin diversion projects, such as Australia's Snowy Mountains Scheme, advocated for the restoration of flows based on claims about environmental and social justice (Erskine et al., 1999;Alexandra and Rickards, 2021). International organisations, such as the Nature Conservancy and the International Union for Conservation of Nature (IUCN), also campaigned for the formal adoption of Eflows (Dyson et al., 2003;Richter et al., 2003Richter et al., , 2006. ...
Environmental flows (or Eflows) refer to water that is allocated to the environment through the deliberate release of stored water or planned allocations. Since the late 20th century, Eflows have become increasingly influential in water policy. Over several decades, the research, policy and practice of Eflows has broadened from addressing flow requirements of specific river reaches or the needs of significant species such as salmon, to a broader focus on integrated strategies that aim to sustain rivers' diverse values. Eflow research has generated an extensive literature that is focused on the scientific and sociopolitical dimensions of managing river flows. We examine this literature critically, tracing the development, application and expansion of Eflows and exploring the shifting norms, framings and assumptions that underpin their theory and practice, including contestations about policy decisions. Our analysis indicates that the politics of environmental flows refracts socially constructed and contested views about nature and river systems and raises fundamental questions about how decisions are made and who decides. While there is a tendency to try to depoliticise Eflows by rendering decisions technical, we argue that, like all water allocation decisions and all water science, Eflows involve sociopolitical contestations about the control of rivers. These contestations are fundamentally about who has the power to make decisions on allocating water and what beliefs, worldviews and frameworks guide these decisions. We conclude that recognising the value-laden character of Eflows research and practice is an essential step towards recognising the value-laden character of river science and management. To achieve more equitable negotiations on deciding how rivers are managed, we argue for an explicit recognition of the political dimensions of Eflows, including a greater awareness of the cultural and ontological politics involved.
... to upstream. The ecological functions and health of rivers were gradually becoming more important around the world, M. C. Acreman (Acreman & Dunbar, 2004) reviewed the methods used by organizations to define "environmental flows" and pointed out that when using them, it is important to choose the appropriate method based on actual needs. Brian D. Richter(B. D. Richter, Warner, Meyer, & Lutz, 2006) put forward a "five-step process" for determining environmental flow. This method had been put into practice in the Savannah River, which made significant progress in environmental flow calculations. Line J. Gordon (Gordon, Peterson, & Bennett, 2008) pointed out that the changes in water flow caused by agriculture make ecological accide ...
With the gradual development of the restoration and protection of the water ecosystem, the research and safegard of ecological flow have received much attention. However, there is a lack of systematization of the literature in the field of “ecological flow” and a lack of in-depth understanding of the main and topical contents of the research in this field. In order to gain an in-depth understanding of the progress and current status of research on ecological flows, this paper searched Web of Science core databases for scientific papers published from 1999 to 2021 on the topic of “ecological flow”. The retrieved 18,128 research papers on ecological flows were also visualized and analyzed by using CiteSpace software for documents per year, category, country and institution distribution, co-citation, and clustering. The results show that research papers on ecological flows have shown an increasing trend since 1999. The categories of disciplines involved cover a wide range of disciplines such as environmental science and ecology, water resources, and so on. The United States ranks first in the number of publications and has a high influence. A total of five clusters were obtained through keywords clustering, with more overlapping areas, hydrological modeling, and aquatic ecosystems are the mainstream of research in the field of ecological flow. “Ecological flow” is still in a phase of rapid development, with the depth of research gradually increasing and the breadth of research expanding. In a long time, the keywords “r package”, “ecological flow”, “loess plateau”, “yellow river” and “emission” will be the center of the field of “ecological flow”.
... Assessing alterations in hydrological characteristics caused by climate change and the construction of terraces within a watershed system is a prerequisite for formulating strategies and plans pertaining to watershed management, restoration, and conservation [28,29]. Consequently, this study centered on the Laixi River basin (LRB) as the study area, aiming to analyze the impact of terraces on the temporal variations of the hydrological regime (including magnitude, duration, frequency, timing, and rate) under the influence of the climate variability from 2000 to 2020. ...
Terraces play a crucial role in regulating the water cycle. The management and restoration of, and the conservation strategies and plans for basins rely heavily on the assessment of alterations in hydrological characteristics, whether natural or man-made, within these basin systems. This study centers on evaluating the impact of terraces on temporal variations in the hydrological regime within the Laixi River basin, within the context of climate variability. To achieve this, we employed a hydrological model and applied the Indicators of Hydrologic Alteration and Range of Variability Approach (IHA–RVA). The results show that, under the influence of terraces, the annual flow exhibited an overall decreasing trend. There was a noticeable decrease in streamflow from March to July, while from October to December, there was a clear upward trend, with increases ranging from 4.76% to 8.10% at the Guanshenxindi (GSXD) and Watershed outlet (WO) cross-sections. The indicators related to the minimum flow showed an overall increasing trend, whereas all indicators related to the maximum flow exhibited a clear decreasing trend. Both high and low flow pulse counts decreased, while high and low pulse durations increased overall. The overall trend of flow reversal counts also showed a decrease. All hydrological indicators exhibited low levels of alteration, with hydrologic alteration values lower than 33.33%. However, the influence of terraces on the upstream hydrological conditions was more pronounced than their downstream effect. The terraces in the study area have played a beneficial role in the flood regulation, drought mitigation, and water resource conservation of the Laixi River. They have contributed to stabilizing the daily average flow during high flow periods and have had a positive impact on the ecological base flow during low flow periods, thereby improving the aquatic ecological environment. This study provides theoretical support for river regulation within the framework of soil and water conservation measures.
... Sustainable water resource development and the effective management of intermittent rivers relies on a thorough understanding of their hydrology (Poff et al., 1997;Richter et al., 2006); however, for many intermittent rivers, this is poorly understood. This is because many are not gauged (Callow and Boggs, 2013) and more importantly once flow ceases, which is a defining feature of intermittent systems, the gauges do not record information. ...
... At the national scale, there is a need for stronger policy frameworks and regulatory mechanisms to protect oxbow lakes and their associated ecosystems. This includes the development of legislation that recognizes the importance of oxbow lakes and provides clear guidelines for their management (Richter et al., 2006). The integration of oxbow lake management into broader environmental and development policies can also help to raise awareness and secure funding for conservation and restoration efforts (Zabala and Sullivan, 2018). ...
... Further suggestions included the development of full flow regimes (Richter et al. 2006, Staentzel et al. 2019b. One method to mitigate flow perturbations, and therefore restrictions to downstream sediment transport, is the augmentation of BLG. ...
Restoration of riverine ecosystems is a key aspect of river management, driven by concerns over water sustainability and declining biodiversity caused by anthropogenic and environmental perturbations. Anthropogenic perturbations include agricultural sedimentation and nutrient input, deforestation, and river regulation including damming, which disturbs longitudinal, lateral and vertical connectivity. Restoring perturbed riverine systems is costly, and many such restorations are ineffective, with restored systems continuing to degrade. Gravel augmentation, the adding of in-stream gravels, focusses mainly on improving habitat for salmonids, and is one method frequently used to mitigate the impacts of damming. The impact of these augmentations on riverine macroinvertebrates and ecosystem functioning in catchments with altered riparian inputs of leaf litter is, however, still unclear, given the lack of work to date investigating leaf litter combined with macroinvertebrate assemblage structure.
This thesis investigates, for the first time, macroinvertebrate assemblage composition, functional diversity and leaf litter breakdown at macro and meso-scales across two low-order, sediment-starved streams on Dartmoor, UK, subject to gravel augmentation. Investigations used macroinvertebrate survey techniques, leaf litter breakdown experiments and univariate and multivariate analyses to explore potential shifts in ecosystem functioning and impacts to the food web related to augmentation. In total, 5641 individuals from 44 taxa were recorded across both catchments. Evidence was found that augmentation led to small and large-scale differences in assemblage structure and functioning, which has the potential to influence both higher and lower trophic levels. Leaf litter breakdown was found to be higher in augmented reaches, although whether associated differences in macroinvertebrate assemblage, diversity, functionality and leaf pack mass loss were due solely to augmentation or a combination of augmentation and other biological and environmental factors remains unclear and merits further study.
... The construction of impoundments is the most common strategy to increase long-term water security. However, their operation alters the magnitude of downstream river discharge, frequency of flood events, and seasonal patterns of flow (Loneragan and Bunn 1999;Davis and Koop 2006;Richter et al. 2006). The loss of such patterns is to the detriment of flow-dependent riverine biota that have evolved traits that enable them to survive, exploit, and even depend on disturbances resulting from natural flow regimes (Bunn and Arthington 2002;Lytle and Poff 2004). ...
Context
Where water is used to support ecosystem processes under a changing climate, it is vital that it is done efficiently. The Australian bass (Percalates novemaculeata) is a freshwater fish endemic to south-eastern Australia that has been adversely affected by anthropogenic disturbances. This has prompted investigations as to the use of environmental water in support of the species in addition to widespread stocking.
Aims
We investigate whether environmental flows and stocking in isolation support a population of Australian bass more effectively than they do in combination, under various climate-change scenarios. We also determine the cost efficiency of each strategy.
Methods
We used an age-based stochastic population model to determine outcomes of strategies.
Key results
Our model suggested that the application of two or three large environmental flows per year was highly effective in all but the most-extreme climate-change scenarios. Alternatively, the value of stocking increased with an increasing severity of climate change. The cost of delivery of environmental flows far exceeds that of stocking. However, stocking directly benefits only a single species (in this case Australian bass), whereas the provision of environmental water has multi-species benefits, in addition to being vital to maintaining the river ecosystem itself.
Conclusions
Under severe climate-change scenarios, stocking, and the use of environmental water in support of populations, may be successful only to a point.
Implications
Extreme climate change may therefore negate any attempts to halt the decline of populations of some species.
... To date, major efforts have been made to define or calculate ecological streamflow according to the eco-hydrological relationship (Richter et al., 2006;Jiang et al., 2021c). Currently, there are four types of method, including the hydrological, hydraulic rating, habitat simulation, and holistic methods (Tharme 2003). ...
Although various studies have investigated the impacts of climate variability and human activities on drought, researches specifically analysing the impact on ecological drought are still limited. A deep understanding of the climatic and anthropogenic effects on ecological drought processes is crucial for ecological regulation and management in the changing environments. In the present study, an integrated approach for comprehensive understanding and quantification of ecological drought in rivers was proposed which first applied the nonparametric kernel density estimation (KDE) method to calculate the most suitable ecological streamflow (MSES) for a river ecosystem. Then, the variable threshold level method based on the MSES for each month and the run theory method were applied to identify the ecological drought duration and deficit volumes. Finally, a quantification approach based on hydrological model simulation was proposed to attribute the impacts of climate variability and human activities on ecological drought. The proposed approach was applied on two catchments, Xianyang (XY) and Huaxian (HX) within the Weihe River Basin (WRB) in northern China. Comparison results obtained using the two empirical methods revealed that the MSES calculated using the KDE method was reasonable and can be used for ecological drought identification. The identification results showed that both the median and upper quartile values of the drought duration and deficit volumes during the disturbed period (1991–2017) were greater than those during the undisturbed period (1961–1990). Quantification results showed that human activities were the dominant factor aggravating ecological drought in the WRB after 1990. The contribution rates of climate variability and human activities toward ecological drought variations were 25.6% and 74.4%, respectively, for the XY station and 42.7% and 57.3%, respectively, for the HX station. Although the WRB was selected as a case study, the proposed approach can also be applied to other regions to provide scientific guidance for regional ecological management.
... Despite these controversial effects, artificial reservoirs have been constructed widely across many basins of the world, serving a variety of purposes such as hydropower generation, water supply, irrigation, navigation, flood control, and recreation (Belletti et al., 2020;Biemans et al., 2011;Döll et al., 2009;Grill et al., 2019;Boulange et al., 2021). In addition, reservoirs assist water managers in converting natural flow conditions into flow conditions that meet human demands, which is especially important in locations where water resources are restricted due to the hydrologic seasonality or the growing influences of climate change and variability (Richter et al., 2006). The solution to balance the benefits and consequences of reservoirs should not be a simple decision of whether or not to construct them. ...
With rapid population growth and socioeconomic development over the last century, a great number of dams/reservoirs have been constructed globally to meet various needs. China has strong economical and societal demands for constructing dams and reservoirs. The official statistics reported more than 98 000 dams/reservoirs in China, including nearly 40 % of the world's largest dams. Despite the availability of several global-scale dam/reservoir databases (e.g., the Global Reservoir and Dam database (GRanD), the GlObal geOreferenced Database of Dams (GOODD), and the Georeferenced global Dams And Reservoirs (GeoDAR)), these databases have insufficient coverage of the reservoirs in China, especially for small or newly constructed ones. The lack of reservoir information impedes the estimation of water budgets and the evaluation of dam impacts on hydrologic and nutrient fluxes for China and its downstream countries. Therefore, we presented the China Reservoir Dataset (CRD), which contains 97 435 reservoir polygons and fundamental attribute information (e.g., name and storage capacity) based on existing dam/reservoir products, national basic geographic datasets, multi-source open map data, and multi-level governmental yearbooks and databases. The reservoirs compiled in the CRD have a total maximum water inundation area of 50 085.21 km2 and a total storage capacity of about 979.62 km3 (924.96–1060.59 km3). The quantity of reservoirs decreases from the southeast to the northwest, and the density hotspots mainly occur in hilly regions and large plains, with the Yangtze River basin dominating in reservoir count, area, and storage capacity. We found that these spatial accumulations of reservoirs are closely related to China's socioeconomic development and the implementation of major policies. Finally, we presented the comparison of the CRD with GOODD, GeoDAR, and GRanD databases. The CRD has significantly increased the reservoir count, area, and storage capacity in China, especially for reservoirs smaller than 1 km2. The CRD database provides more comprehensive reservoir spatial and attribute information and is expected to benefit water resources managements and the understanding of ecological and environmental impacts of dams across China and its affected transboundary basins. The CRD database is publicly available at 10.5281/zenodo.6984619 (Song et al., 2022).
... Future groundwater issues cannot be overlooked if GWR management is consistent (Dey et al., 2017). Thus, sustainable GWR management depends on precisely evaluating groundwater resources' current and future trend patterns (Richter et al., 2006). This study concentrates on assessing the present and forthcoming trends of GWL in the Joypurhat district of northwest Bangladesh, which covers how decision-makers take the right initiative for combined sustainable GWR management. ...
Groundwater resource plays a crucial role for agricultural crop production and socio-economic development in some parts of the world including Bangladesh. Joypurhat district, the northwest part of Bangladesh, a crop production hub, is entirely dependent on groundwater irrigation. A precise assessment and prediction of groundwater level (GWL) can assist long-term groundwater resources (GWR) management, especially in drought-prone agricultural regions. Therefore, this study was carried out to identify trends and magnitude of GWL fluctuation (1980–2019) using the modified Mann–Kendall test, Pettitt’s test, and Sen slope estimators in the drought-prone Joypurhat district, northwest Bangladesh. Time-series data analysis was performed to forecast GWL from 2020 to 2050 using the Auto-Regressive Integrated Moving Average (ARIMA) model. The findings of the MMK test revealed a significant declining trend of GWL, and the trend turning points were identified in the years 1991, 1993, 1997, and 2004, respectively. Results also indicate that the declining rate of GWL varied from 0.104 to 0.159 m/year and the average rate of GWL declination was 0.136 m/year during 1980–2019. The outcomes of wavelet spectrum analysis depicted two significant periods of the declining trend in Khetlal and Akkelpur upazilas. The results obtained from the optimal identified model ARIMA (2, 1, 0) indicate that GWL will decline at a depth of 13.76 m in 2050, and the average declination rate of GWL will be 0.143 m/year in the study area. The predicted results showed a similar declining tendency of GWL from 2020 to 2050, suggesting a disquieting condition, particularly for Khetlal upazila. This research would provide a practical approach for GWL assessment and prediction that could help decision-makers implement long-term GWR management in the study area.
... This strategy is based on the premise that the hydrological regime is one of the fundamental drivers of the structure and function of riverine and floodplain ecosystems [25,26]. Water used to restore some of the natural river flow conditions necessary to support functioning river and floodplain ecosystems is commonly referred to as environmental water or environmental flow [27]. ...
Globally, wetlands have experienced significant declines in area and condition. Reedbeds are a key attribute of many wetlands and are typically composed of Phragmites australis (common reed), a globally distributed emergent aquatic perennial grass. Environmental water is increasingly used to support functioning river and floodplain ecosystems, including reedbeds, where maintaining wetland vegetation condition is a common objective. Drone-based remote sensing allows for the consistent collection of high-quality data in locations such as wetlands where access is limited. We used unoccupied aerial vehicles (UAVs) and convolutional neural networks (CNNs) to estimate the cover of Phragmites australis and examine the role of reedbed condition and prior environmental watering in the response of reedbeds to flooding. Data were collected from a large inland reedbed in semi-arid western New South Wales, Australia between October 2019 and March 2021 using UAVs and processed using CNNs. Prior to the flood event, sites that had received environmental water had a significantly greater cover of Phragmites australis. The sites that were not managed with environmental water had very low cover (<1%) of reeds prior to the flood event and transitioned from a Critical condition to a Poor or Medium condition following flooding. Using UAVs and CNNs we demonstrated the role environmental water plays in filling the gaps between large flood events and maintaining the condition and resilience of reedbeds.
... A certain volume of water flow is required for improving the river ecosystem and the protection of rivers for supporting riverine ecology and the environment (Richter et al. 2006). Environmental flow also refers to the flow regime that maintains the quality, quantity, and duration of river water flow which are crucial for the protection, and restoration of the degraded ecological condition of a river system (Chen and Wu 2019;Sarkar and Islam 2020;Tharme 2003). ...
Environmental flow is the minimum flow required in a fluvial system to maintain its ecological health and to promote socio-economic sustainability. The present work critically examines the concept of the environmental flow in the context of dams and development using a systematic methodology to find out the previous works published during the last 3 decades (1990–2020) in different search engines and websites. The study reviews that structural interventions in the form of dams, barrages, weirs, etc. impede the natural flow of the rivers. Moreover, other forms of development such as industrialization, urbanization, and expansion of modern agriculture also exacerbate the problems of environmental flow across the world, especially in monsoon Asia. The present case of the environmental flow for the Damodar River portrays that the construction of dams and barrages under the Damodar Valley Project have significantly altered the flow duration, flood frequency, and magnitude (high-frequency low magnitude events in the post-dam period), while urban-industrial growth in the basin has polluted the river water (e.g., lower dissolved oxygen and higher biological oxygen demand). This typical alteration in the flow characteristics and water quality has threatened aquatic organisms, especially fish diversity and community structure. This review will make the readers aware of the long-term result of dam-induced fluvial metamorphosis in the environment through the assessment of environmental flow, species diversity, flow fluctuation, and river pollution. The study may be useful for policy-making for ushering in the sustainable development pattern that will attract future researchers, planners, and stakeholders.
... This orientation is perfectly captured in a comment by one respondent regarding a stalled case: "Too much [of] an outside approach by environmental NGOs trying to provide evidence for the justification of an e-flow approach using studies." Indeed, Richter et al. (2006), in their work on the Sustainable Rivers Project, promoted the ideal of the communicative model because this fosters ownership of the process and a commitment to see e-flows implemented. Based on over 25 years of experience in the e-flows field, O'Keeffe (2018) also identified the need for "local champions" as essential for successful training and implementation of e-flows. ...
The provision of flows for the environment, e-flows, is a means to restore the benefits of naturally flowing rivers. Despite the development of numerous methodologies to determine e-flows and optimize dam releases, actual implementation is relatively limited. Examples of successful e-flows implementation through dam reoperation exist in scientific literature; however, there is a missing narrative on cases where dam reoperation has been attempted but not successfully implemented. This study explores this impasse narrative and presents four hypotheses for further research on this subject: (1) Scientists are important stakeholders in the process of dam reoperation, but should play a supportive role rather than drive the process; (2) In undertaking scientific studies for determination of e-flows, a consensus on the priorities, knowledge gap, and solutions must be reached together with local stakeholders; (3) Local-level legislation and policy on e-flows provide the enabling environment for dam reoperation for e-flows; and (4) Genuine, carefully designed consultations of, and negotiations between, stakeholders can overcome hurdles encountered in the process of dam reoperation for e-flows implementation.
... The starting point and key to success in developing environmental flow measures was the collaboration process, where agreement on a vision and leitbild for rehabilitation was a prerequisite for further actions Richter et al., 2006). Reaching consensus on this was challenging, but without an agreement on the vision being rehabilitating ecosystems to resemble aspects of pristine river ecosystems rather than developing some novel, more lake-like ecosystem in the impoundments and reservoirs, setting objectives for ecosystem rehabilitation would have been difficult, and the process would likely have derailed. ...
To enable prioritization among measures for ecological restoration, knowing the expected benefits and consequences of implementation is imperative, but rarely explicitly quantified. We developed a novel method to prioritize among environmental-flow measures to rehabilitate ecosystems in the Ume River catchment in northern Sweden, a river system heavily regulated for hydropower production. Our strategy was to identify measures with minimal impact on hydropower production while providing substantial environmental benefits. Based on field surveys of remaining natural values and potential for ecological rehabilitation, we quantified the projected gain in habitat area of implementing environmental flows for target organism groups, e.g. lotic fish species and riparian vegetation, along the whole river length. We quantified the consequences for hydropower production by identifying a set of hydropower operational rules reflecting the constraints added by environmental flows. We then used production optimization software to calculate changes in hydropower production and revenues. Implementing restrictions on zero-flow events by mandating minimum discharge at all run-of-river hydropower stations, and allocating 1-12% of mean annual discharge to bypassed reaches in the entire catchment, would result in a 2.1% loss of annual electricity production. Adding flow to fishways would increase the loss to 3.1% per year. With implementation of more natural water-level fluctuations in run-of-river impoundments, the loss increases to 3.8%. These actions would increase the habitat for lotic species like the grayling Thymallus thymallus more than threefold, and increase the area of riparian vegetation by about 66%. Our method forms a basis for ongoing implementation of nation-wide environmental rehabilitation schemes.
The dominant plant species in many African wetlands is Cyperus papyrus . Its adaptation to saturated and low‐oxygen conditions and its dense structure and height provide breeding and feeding grounds for unique flora and fauna. As a keystone species adapted to local hydrology, the flooding regime of papyrus offers the full range of hydrologic conditions and events essential to ecosystem health. However, no study has attempted to link papyrus wetlands' flow regimes to their biologically relevant hydrologic attributes. This study assesses hydrologic alterations of a papyrus wetland's flow regime due to rice irrigation. We develop a conceptual ecological model linking papyrus to hydrologic attributes to determine the consequences of changed environmental flow components (EFCs) on papyrus as a habitat. We find that agricultural water management considerably alters the magnitude, duration, timing and rate of change of EFCs, which could affect productivity (seed dispersal, germination and establishment; rhizome spreading; papyrus distribution across transects; and dispersal of floating mats) in papyrus wetlands. However, the effect on the papyrus wetlands' natural pulsed regime is negligible when the ratio of irrigated area to catchment area is no greater than 1:150. Overall, a better understanding of the threats of water diversion for agriculture is made by linking papyrus' flow regimes to biologically relevant hydrologic attributes. Knowledge of the roles of the various EFCs could provide opportunities for conserving and protecting papyrus wetlands, especially for systems at risk of altered flows.
This study quantifies the degree of hydrological regime alteration in the middle and lower reaches of the Yangtze River (MLYR) by incorporating the indicators of hydrologic alteration (IHA) along with six additional indicators. The ecohydrological risks are analyzed using the eco-surplus and eco-deficit indicators. Furthermore, the ecohydrological satisfaction index (ESI) is proposed to characterize the degree to which hydrological conditions meet the eco-water demand of rivers. The results indicate that the concentration period is delayed, and the complexity of hydrological processes is increased in the MLYR. Regarding the variability of hydrological conditions, except for Datong station with a change degree below 0.5, the other stations have experienced high changes. At the annual scale, the eco-surplus and eco-deficit of the MLYR basin have changed with the alteration degree of 0.41 and 0.37, respectively, and the eco-deficit of the mainstream exceeds the eco-surplus, indicating high ecohydrological risks. The ESI at Yichang station has significantly decreased, with the most pronounced decrease occurring in February (−0.35). The ESI of tributaries in the MLYR remains stable, with periods when the ESI at Huangzhuang station exceeds 0.8 accounting for more than 80% of the period from 2004 to 2021.
Human disturbance and climatic factors alter the hydrological state of rivers in many ways and have a degree of negative impact on the quality of watershed habitats; quantifying the impact of both human disturbance and climatic factors on hydrological change can help improve the quality of watershed habitats. Therefore, in this research, an integrated watershed assessment framework is proposed to analyse the watershed from four perspectives: hydrological situation, environmental flows, drivers, and habitat quality. A meteorological streamflow model based on the Long Short-Term Memory (LSTM) model was employed to analyse the hydrological evolution and quantify the influence of the drivers from the perspective of hydrological and environmental flows. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was then used to evaluate the spatial and temporal evolution of habitat quality in the basin. And, finally, the grey correlation theory was used to reveal the response of habitat quality to hydrological changes. Studies have shown that annual flow and precipitation are increasing in the Xiangjiang River (XJR) basin, while its annual potential evapotranspiration is decreasing significantly. After 1991, the hydrological conditions of the XJR were highly variable, with the combined rate of change of the most Ecologically Relevant Hydrological Indicators, ERHIs-IHA and ERHIs-EFCs, reaching 26.21% and 121.23%, respectively. Climate change and human disturbance are the main drivers of change for both (with contributions of 60% and 71%, respectively). Between 1990 and 2020, the habitat quality in the basin declined over time (from 0.770 to 0.757), with areas of high habitat value located mainly in mountainous areas and habitat degradation being concentrated in urban areas in the middle and lower reaches, gradually evolving towards areas of high habitat value in the periphery. There is a strong correlation between watershed habitat quality and the ERHIs. The results of the study can provide a scientific basis for maintaining regional ecological security and rational allocation of water resources.
Sustainable river management requires the construction and operation of dams that provide environmental flows to support downstream rivers ecosystem. Dam construction in Iran has significantly altered natural flow regimes and caused various environmental issues. The main aim of the present study was to evaluate the hydrologic and environmental alteration of the flow regime in the Jajrud River downstream of the Latian Dam. In this study, a set of long-term flow data (1947-2017) was analyze using the IHA and RVA models. The results show that the degree of alterations for the 24 flow variables is in the range of high to medium, denoting the high hydrological alterations of the Jajrud River. The values of mean, maximum and minimum monthly flows have decreased by 57, 94 and 21 percent, respectively. The overall change is 51%. Magnitude and duration of annual extreme flows have decreased, and in particular, the minimum flows and the base-flow indices have changed the most. The large flood events has been eliminated and small and frequent floods has been damped in the downstream river system. The results indicate that the goals of RVA have not been achieved in the post-construction period of the Latian Dam, and the environmental conditions of the river have been severely damaged. With reference to the eco-hydrological indices, the rehabilitation of the environment status of the Jajrud River requires the dam releases of minimum monthly flows in order of 2.3 to 33.8 m3/s, with an average annual discharge of 6.5 m3/s.
Keywords
Indicator of hydrologic alteration (IHA) Range of variability approach (RVA), Environmental flow, Latian Dam, Jajrud River
Reservoirs are sometimes managed to meet agricultural and other water demands, while also maintaining streamflow for aquatic species and ecosystems. In the Henrys Fork Snake River, Idaho (USA), irrigation‐season management of a headwater reservoir is informed by a flow target in a management reach ~95 km downstream. The target is in place to meet irrigation demand and maintain aquatic habitat within the 11.4 km management reach and has undergone four flow target assignments from 1978 to 2021. Recent changes to irrigation‐season management to maximize reservoir carryover warranted investigation into the flow target assignment. Thus, we created a streamflow‐habitat model using hydraulic measurements, habitat unit mapping, and published habitat suitability criteria for Brown Trout ( Salmo trutta ), Rainbow Trout ( Oncorhynchus mykiss ), and Mountain Whitefish ( Prosopium williamsoni ). We used model output to compare habitat availability across two management regimes (1978–2017 and 2018–2021). We found that efforts to minimize reservoir releases in 2018–2021 did not reduce mean irrigation‐season fish habitat relative to natural flow, but did reduce overall fish habitat variability during the irrigation season compared to streamflow management in 1978–2017. Field observations for this research led to an adjusted flow target in 2020 that moved the target location downstream of intervening irrigation diversions. Using our model output, we demonstrated that moving the location of the target to account for local irrigation diversions will contribute to more consistently suitable fish habitat in the reach. Our study demonstrates the importance of site selection for establishing environmental flow targets.
Riverine ecosystems are dependent in large part on the climate of the region, and climate change is expected to alter climatic factors of interest, such as precipitation, temperature, and evapotranspiration. In central Texas, precipitation is expected to decrease while temperature increases as the climate changes. Drought and flooding events are also expected to increase in the region, which will also effect streamflow and stream temperature in riverine ecosystems. Numerous studies have assessed the potential impacts of climate change on riverine species. This study examines the projected climate changes, determines potential changes in streamflow and stream temperature for river basins in central Texas, and assesses the appropriate uses of climate projections for riverine species impact assessments, using the Texas fatmucket ( Lampsilis bracteata ) as a case study. Previously established regression methods were used to produce projections of streamflow and stream temperature. This study finds that streamflow is projected to decrease and stream temperature is projected to increase. Using thermal tolerance thresholds previously determined for the Lampsilis bracteata , this study also finds that the lethal temperature events for the Lampsilis bracteata will increase. Finally, this study makes several recommendations on the use of downscaled climate projections for impact assessments for riverine species such as the Lampsilis bracteata .
Although previous studies have analyzed ecohydrological changes, external pressure sources on the ecohydrological regime have rarely been clarified, and knowledge about the individual impacts of large reservoir regulation is still insufficient. In this study, we reconstructed the natural flow in the middle reaches of the Yangtze River (MRYR) not regulated by the Three Gorges Reservoir (TGR) based on a long–short-term memory model. We then evaluated the dynamics of ecohydrological regimes using environmental flow components and ecohydrological risk indicators and quantified the impacts of the TGR. The results showed that the hydrological stability has increased after TGR construction, with significant decreases in the frequency and duration of extremely low-flows, large floods, and small floods. In addition, there is a high ecohydrological risk in the MRYR, with a higher ecodeficit and showing a continuous upward trend. The impact of the TGR on environmental flow components decreases along the river, averaging 42.1%, with the strongest impact on small floods, accounting for 56.2%. Overall, reservoir regulation has counteracted the increased eco-risk caused by climate change. Considering only the TGR, the ecosurplus in the spring and winter seasons increased, while the ecodeficit increased in the autumn season, with corresponding contribution rates of 81.4, 82.7, and 53.1%, respectively.
HIGHLIGHTS
Reconstructed the natural flow of the river without the influence of reservoirs.;
Investigated the relationship between environmental flow patterns in response to reservoir construction.;
Assessed the independent influence of reservoirs on daily flow processes throughout the year.;
Separated the impacts of reservoir construction and natural factor changes on river ecohydrological components at long–short time scales.;
The final (peer-reviewed) paper is available at https://doi.org/10.5194/nhess-24-2191-2024,
https://nhess.copernicus.org/articles/24/2191/2024/, or https://www.researchgate.net/publication/381854871_Catchment-scale_assessment_of_drought_impact_on_environmental_flow_in_the_Indus_Basin_Pakistan?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6ImhvbWUiLCJwYWdlIjoicHJvZmlsZSIsInByZXZpb3VzUGFnZSI6InByb2ZpbGUifX0
Protecting freshwater systems to ensure sustainability requires diagnosing threats over a broad range of scales, from local to global. There is growing acceptance that environmental flows must be protected to sustain river channels and floodplain ecosystems downstream of reservoirs. Meeting environmental water requirements has proven difficult because they reduce water yield available for human use – a particular challenge in regions already experiencing declining water availability with climate change. A further challenge is the difficulty of assessing the impact of environmental water requirements on water availability for other purposes. This paper provides a modification of the Gould-Dincer method to assess the yield of carry-over reservoirs subject to environmental water requirements. The method characterizes reservoir inflows using readily available flow characteristics (annual mean and Cv). We develop and test the method using ten examples with well-understood environmental water requirements and a range of annual flow Cv s. We then demonstrate this method at continental scale, to investigate the impact on yield of providing high-reliability supply including environmental water requirements, under a changing climate. According to our results, considering climate change and environmental flow provision simultaneously, the decline in water yield is projected to be about 27% and 18% respectively for Australia and US (based on hypothetical reservoirs capacity of one times mean annual inflow). Adapting environmental flow demands to future hydrological conditions results in a 2% and 3% increase in Australia and US-wide yield for human use respectively. While further testing is needed, the method provides a simple and rapid way to estimate the impact of providing environmental flow on yield, applicable at global scale.
Freshwater ecosystems have been degraded due to intensive freshwater abstraction. Therefore, environmental flow requirements (EFRs) methods have been proposed to maintain healthy rivers and/or restore river flows. In this study, we used the Variable Monthly Flow (VMF) method to calculate the transgression of freshwater planetary boundaries: (1) natural deficits in which flow does not meet EFRs due to climate variability, and (2) anthropogenic deficits caused by water abstractions. The novelty is that we calculated spatially and cumulative monthly water deficits by river types including the frequency, magnitude and causes of environmental flow (EF) deficits (climatic and/or anthropogenic). Water deficit was found to be a regional rather than a global concern (less than 5% of total discharge). The results show that, from 1960 to 2000, perennial rivers with low flow alteration, such as the Amazon, had an EF deficit of 2–12% of the total discharge, and that the climate deficit was responsible for up to 75% of the total deficit. In rivers with high seasonality and high water abstractions such as the Indus, the total deficit represents up to 130% of its total discharge, 85% of which is due to withdrawals. We highlight the need to allocate water to humans and ecosystems sustainably.
This article is part of the Royal Society Science+ meeting issue ‘Drought risk in the Anthropocene’.
Altered flow regimes remain one of the most serious threats to ecological sustainability of estuarine fish populations throughout the world. Estuary Perch (Percalates colonorum) is an estuary-dependent fish native to south-eastern Australia. The species is highly valued by recreational fishers and has greatly declined in abundance in recent decades. Strategies to recover populations include the use of environmental flows. We developed an age-based stochastic matrix population model based on the ecology of the species to explore the likely benefits of present and constructed environmental flow rules on recruitment and population response of the species in the lower Snowy River for 20 years into the future. The model outcomes indicate that the present environmental flow rules produce minimal population response and are of little benefit to recruitment of Estuary Perch. The flow prescription that produced the best modelled outcome, and that was most risk adverse to decline of females, was the annual release of 3 × 15,000 ML/day flow events, spaced 30 days apart in late winter/spring. Our approach highlights the importance of considering the whole life cycle of a species and identifying the key life history traits that can be influenced to achieve the desired conservation outcome. Although the model developed here was used to test management activities at a single site (and for a single species), it provides a novel approach that may be tailored to test and guide management activities aimed at benefiting similar flow-dependent species in estuaries throughout the world.
Managers of protected areas are under increasing pressure to measure their effectiveness in conserving native biological diversity in ways that are scientifically sound, practical, and comparable among protected areas over time. The Nature Conservancy and its partners have developed a "Measures of Success" framework with four core components: (1) identifying a limited number of focal conservation targets, (2) identifying key ecological attributes for these targets, (3) identifying an acceptable range of variation for each attribute as measured by properly selected indicators, and (4) rating target status based on whether or not the target's key attributes are within their acceptable ranges of variation. A target cannot be considered "conserved" if any of its key ecological attributes exceeds its acceptable range of variation. The framework provides a rigorous basis not only for measuring success but for setting conservation objectives, assessing threats to biodiversity, identifying monitoring and research needs, and communicating management information to nonspecialists.
The development of water resources to satisfy urban water needs has had serious impacts on freshwater ecosystem integrity and on valuable ecosystem services, but positive trends are emerging that point the way toward a solution. We demonstrate this through case studies of water resource development in and around five large urban areas: Los Angeles, Phoenix, New York, San Antonio, and Atlanta. Providing freshwater ecosystems with the water flows necessary to sustain their health, while meeting the other challenges of urban water management, will require greatly increased water productivity in conjunction with improvements in the degree to which planning and management take ecosystem needs into account. There is great potential for improvement in both these areas, but ultimately water planners will also need to set limits on human alterations to river flows in many basins in order to spur greater water productivity and protect ecosystem water allocations before water supplies become overtaxed.
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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
"Adaptive management is appraised as a policy implementation approach by examining its conceptual, technical, equity, and practical strengths and limitations. Three conclusions are drawn: (1) Adaptive management has been more influential, so far, as an idea than as a practical means of gaining insight into the behavior of ecosystems utilized and inhabited by humans. (2) Adaptive management should be used only after disputing parties have agreed to an agenda of questions to be answered using the adaptive approach; this is not how the approach has been used. (3) Efficient, effective social learning, of the kind facilitated by adaptive management, is likely to be of strategic importance in governing ecosystems as humanity searches for a sustainable economy."
Real and apparent conflicts between ecosystem and human needs for fresh water are contributing to the emergence of an alternative model for conducting river science around the world. The core of this new paradigm emphasizes the need to forge new partnerships between scientists and other stakeholders where shared ecological goals and river visions are developed, and the need for new experimental approaches to advance scientific understanding at the scales relevant to whole-river management. We identify four key elements required to make this model succeed: existing and planned water projects represent opportunities to conduct ecosystem-scale experiments through controlled river flow manipulations; more cooperative interactions among scientists, managers, and other stakeholders are critical; experimental results must be synthesized across studies to allow broader generalization; and new, innovative funding partnerships are needed to engage scientists and to broadly involve the government, the private sector, and NGOs. Yes Yes
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.
Maintaining natural hydrologic variability is essential in conserving native riverine biota and river ecosystem integrity. Hydrologic variation plays a major role in structuring the biotic diversity within river ecosystems as it controls key habitat conditions within the river channel, the floodplain, and hyporheic (stream-influenced ground water) zones. Alterations in streamflow regimes may modify many of these habitat attributes and impair ecosystem connectivity. We demonstrate use of the ‘Range of Variability Approach’ for assessing hydrologic alteration at available streamgauge sites throughout a river basin. We then illustrate a technique for spatially mapping the degree of hydrologic alteration for river reaches at and between streamgauge sites. Such maps can be used to assess the loss of natural hydrologic variation at a river basin scale, thereby facilitating river restoration planning. © 1998 John Wiley & Sons, Ltd.
Adaptive management is appraised as a policy implementation approach by examining its conceptual, technical, equity, and practical strengths and limitations. Three conclusions are drawn: (1) Adaptive management has been more influential, so far, as an idea than as a practical means of gaining insight into the behavior of ecosystems utilized and inhabited by humans. (2) Adaptive management should be used only after disputing parties have agreed to an agenda of questions to be answered using the adaptive approach; this is not how the approach has been used. (3) Efficient, effective social learning, of the kind facilitated by adaptive management, is likely to be of strategic importance in governing ecosystems as humanity searches for a sustainable economy.
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.
In making resource management decisions, agencies use a variety of approaches that involve different levels of political concern, historical precedence, data analyses, and evaluation. Traditional decision-making approaches have often failed to achieve objectives for complex problems in large systems, such as the Everglades or the Colorado River. I contend that adaptive management is the best approach available to agencies for addressing this type of complex problem, although its success has been limited thus far. Traditional decision-making approaches have been fairly successful at addressing relatively straightforward problems in small, replicated systems, such as management of trout in small streams or pulp production in forests. However, this success may be jeopardized as more users place increasing demands on these systems. Adaptive management has received little attention from agencies for addressing problems in small-scale systems, but I suggest that it may be a useful approach for creating a holistic view of common problems and developing guidelines that can then be used in simpler, more traditional approaches to management. Although adaptive management may be more expensive to initiate than traditional approaches, it may be less expensive in the long run if it leads to more effective management. The overall goal of adaptive management is not to maintain an optimal condition of the resource, but to develop an optimal management capacity. This is accomplished by maintaining ecological resilience that allows the system to react to inevitable stresses, and generating flexibility in institutions and stakeholders that allows managers to react when conditions change. The result is that, rather than managing for a single, optimal state, we manage within a range of acceptable outcomes while avoiding catastrophes and irreversible negative effects.
The free-flowing nature of streams in the U.S. has been dramatically altered over the past century, especially through construction of dams. The Nationwide Rivers Inventory (NRI) estimated a total of 5,200,000 km of streams in the contiguous 48 states, but only 2% (<100,000 km) have sufficient high quality features to be worthy of federal protection status. The future of this dwindling number of high-quality streams is in doubt as proponents of development compete with conservation interests. Hydropower projects are projected to be built well into the future with a large increase in small projects (55% more than in 1988) even though the total generating capacity of the U.S. would increase only 0.3%. On the other hand, conservation efforts have resulted in increasing levels of federal protection of streams since the 1960s. "National River" or "Wild and Scenic River" status now provides protection for almost 16,000 km of streams, but only about 10% are found east of the Mississippi River. Analysis of the NRI database showed that the greatest quantity and density of high-quality streams are found in the south-Atlantic states, where streams have the least protection. The greatest number of NRI streams are found in the Coastal Plain and Central Lowland physiographic provinces. The NRI analysis showed only 42 high-quality, free-flowing (no major dams) rivers >200 km remaining in the 48 contiguous states. With continuing threats of exploitation, major conservation efforts are required to preserve these last free-flowing streams.
Maintaining natural hydrologic variability is essential in conserving native riverine biota and river ecosystem integrity. Hydrologic variation plays a major role in structuring the biotic diversity within river ecosystems as it controls key habitat conditions within the river channel, the floodplain, and hyporheic (stream-influenced ground water) zones. Alterations in streamflow regimes may modify many of these habitat attributes and impair ecosystem connectivity. We demonstrate use of the ‘Range of Variability Approach’ for assessing hydrologic alteration at available streamgauge sites throughout a river basin. We then illustrate a technique for spatially mapping the degree of hydrologic alteration for river reaches at and between streamgauge sites. Such maps can be used to assess the loss of natural hydrologic variation at a river basin scale, thereby facilitating river restoration planning. © 1998 John Wiley & Sons, Ltd.
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.
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.
Using fisheries agency databases and files, we assembled a summary database on the status of anadromous salmon stocks (genus Oncorhynchus) from British Columbia and Yukon streams. We then collected supplementary information by circulating the database among fisheries professionals and interest groups throughout British Columbia and thus identified 9,662 anadromous salmon stocks. These stocks included 866 chinook, 1,625 chum, 2,594 coho, 2,169 pink, 917 sockeye, 867 steelhead and 612 sea-run cutthroat trout stocks. We assessed the status of anadromous stocks by employing a classification scheme similar to that of Nehlsen et al. (1991). Assessments were possible for 5,487 (57%) of all stocks and included all large, commercially important stocks. The assessments found 624 stocks were at high risk, 78 were at moderate risk, 230 were of special concern, and 142 were extirpated in this century. We were unable to classify 4,172 (43%) of the stocks because of an absence of reliable data. Due to their small size, these stocks are not of great commercial importance, although they are important to the maintenance of salmonid diversity. We also identified many potential threats to anadromous salmon stocks. The absence of systematic, high-quality assessments at the biological stock level precluded reliable assignment of the specific causes for many of the stocks apparently at risk. Nevertheless, habitat degradation associated with logging, urbanization, and hydropower development contributed to most of the 142 documented stock extinctions. Furthermore, there is little doubt that overutilization by commercial and recreational fisheries has in many cases resulted in severe stock depressions that, when added to other factors, has put many stocks at risk.
Hydrologic regimes play a major role in determining the biotic composition, structure, and function of aquatic, wetland, and riparian ecosystems. However, human land and water uses are substantially altering hydrologic regimes around the world. Improved quantitative evaluations of human-inducedhydrologic changes,are needed,to advance research on the biotic implications of hydrologic alteration, and to support ecosystem,management,and restoration plans. To facilitate such improved,hydrologic evaluations, we propose a method for assessing the degree of hydrologic alteration attributable to human impacts within an ecosystem. This method, referred to as the Indicators of Hydrologic Alteration(IHA), is based upon an analysis of hydrologic data available either from existing measurement,points within an ecosystem (such as at streamgauges or wells) or model-generated data. We use 32 different parameters, organized into five groups, to statisticallycharacterize hydrologic variation within each year. These 32 parameters provide information on some of the most ecologically significant features of surface and ground water regimes influencing aquatic, wetland, and riparian ecosystems. The hydrologic perturbations associated with activities such as dam operations, flow diversion, ground water pumping, or intensive land use conversion are then assessed,by comparing measures,of central tendency and dispersion for each parameter, between user-defined "pre-impact" and "post-impact" time frames, generating 64 different "Indicators of Hydrologic Alteration." The IHA method,is intended to be used conjunctively with other ecosystem,metrics in inventories 2 of ecosystem integrity, in planning ecosystem management activities, and in setting and
This book is about ways of dealing with uncertainty in the management of renewable resources, such as fisheries and wildlife. The author's basic theme is that management should be viewed as an adaptive process: one learns about the potentials of natural populations to sustain harvesting mainly through experience with management itself, rather than through basic research or the development of general ecological theory. The need for an adaptive view of management has become increasingly obvious over the last two decades, as management has turned more often to quantitative model building as a tool for prediction of responses to alternative harvesting policies. The model building has not been particularly successful, and it keeps drawing attention to key uncertainties that are not being resolved through normal techniques of scientific investigation. The author's major conclusion is that actively adaptive, probing, deliberately experimental policies should indeed be a basic part of renewable resource management.
Large catchment basins may be viewed as ecosystems with interactive natural and cultural attributes. Stream regulation severs ecological connectivity between channels and flood plains by reducing the range of natural flow and temperature variation, reduces the capacity of the ecosystem to sustain native biodiversity and bioproduction and promotes proliferation of non-native biota. However, regulated rivers regain normative attributes, which promote recovery of native biota, as distance from the dam increases and in relation to the mode of regulation. Therefore, reregulation of flow and temperature to normative pattern, coupled with elimination of pollutants and constrainment of nonnative biota, can naturally restore damaged habitats from headwaters to mouth. The expectation is rapid recovery of depressed populations of native species. The protocol requires: restoration of seasonal temperature patterns; restoration of peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilization of base flows to revitalize the shallow water habitats; maximization of dam passage to allow restoration of metapopulation structure; change in the management belief system to rely on natural habitat restoration as opposed to artificial propagation, installation of artificial instream structures (river engineering) and artificial food web control; and, practice of adaptive ecosystem management.
Large catchment basins may be viewed as ecosystems in which natural and cultural attributes interact. Contemporary river ecology emphasizes the four-dimensional nature of the river continuum and the propensity for riverine biodiversity and bioproduction to be largely controlled by habitat maintenance processes, such as cut and fill alluviation mediated by catchment water yield. Stream regulation reduces annual flow amplitude, increases baseflow variation and changes temperature, mass transport and other important biophysical patterns and attributes. As a result, ecological connectivity between upstream and downstream reaches and between channels, ground waters and floodplains may be severed. Native biodiversity and bioproduction usually are reduced or changed and non-native biota proliferate. Regulated rivers regain normative attributes as distance from the dam increases and in relation to the mode of dam operation. Therefore, dam operations can be used to restructure altered temperature and flow regimes which, coupled with pollution abatement and management of non-native biota, enables natural processes to restore damaged habitats along the river’s course. The expectation is recovery of depressed populations of native species. The protocol requires: restoring peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilizing baseflows to revitalize food-webs in shallow water habitats; reconstituting seasonal temperature patterns (e.g. by construction of depth selective withdrawal systems on storage dams); maximizing dam passage to allow recovery of fish metapopulation structure; instituting a management belief system that relies upon natural habitat restoration and maintenance, as opposed to artificial propagation, installation of artificial instream structures (river engineering) and predator control; and, practising adaptive ecosystem management. Our restoration protocol should be viewed as an hypothesis derived from the principles of river ecology. Although restoration to aboriginal state is not expected, nor necessarily desired, recovering some large portion of the lost capacity to sustain native biodiversity and bioproduction is possible by management for processes that maintain normative habitat conditions. The cost may be less than expected because the river can do most of the work. KEY WORDS restoration; general protocol CCC 0886-
The general effects of single dams on the downstream ecology of temperature lotic systems are predictable, although some underlying causal mechanisms remain elusive. Few quantitative data of an ecological nature are available for regulated tropical rivers, however, and it would not be prudent to uncritically apply principles and patterns developed from temperate rivers to fluvial systems of the tropics. New techniques of gradient analysis appear especially suited to examining spatial recovery gradients below dams at any latitude and portend to provide considerable insight into the mechanisms responsible for such patterns. Few studies have specifically examined the influence of regulation on interactions between the river channel and the floodplain and virtually nothing is known of channel-aquifer interactions. A fuller understanding of these interactive pathways is necessary to effectively regulate discharge as part of river restoration strategies. Viewing regulated streams as experimental systems for addressing ecological questions has proved to be useful and should be further exploited. It is concluded that research and expertise in regulated stream ecology will increasingly be needed as the rational basis for flow criteria to conserve, protect and enhance the societal values of regulated rivers world-wide.
Recognition of the escalating hydrological alteration of rivers on a global scale and resultant environmental degradation, has led to the establishment of the science of environmental flow assessment whereby the quantity and quality of water required for ecosystem conservation and resource protection are determined.
A global review of the present status of environmental flow methodologies revealed the existence of some 207 individual methodologies, recorded for 44 countries within six world regions. These could be differentiated into hydrological, hydraulic rating, habitat simulation and holistic methodologies, with a further two categories representing combination‐type and other approaches.
Although historically, the United States has been at the forefront of the development and application of methodologies for prescribing environmental flows, using 37% of the global pool of techniques, parallel initiatives in other parts of the world have increasingly provided the impetus for significant advances in the field.
Application of methodologies is typically at two or more levels. (1) Reconnaissance‐level initiatives relying on hydrological methodologies are the largest group (30% of the global total), applied in all world regions. Commonly, a modified Tennant method or arbitrary low flow indices is adopted, but efforts to enhance the ecological relevance and transferability of techniques across different regions and river types are underway. (2) At more comprehensive scales of assessment, two avenues of application of methodologies exist. In developed countries of the northern hemisphere, particularly, the instream flow incremental methodology (IFIM) or other similarly structured approaches are used. As a group, these methodologies are the second most widely applied worldwide, with emphasis on complex, hydrodynamic habitat modelling. The establishment of holistic methodologies as 8% of the global total within a decade, marks an alternative route by which environmental flow assessment has advanced. Such methodologies, several of which are scenario‐based, address the flow requirements of the entire riverine ecosystem, based on explicit links between changes in flow regime and the consequences for the biophysical environment. Recent advancements include the consideration of ecosystem‐dependent livelihoods and a benchmarking process suitable for evaluating alternative water resource developments at basin scale, in relatively poorly known systems. Although centred in Australia and South Africa, holistic methodologies have stimulated considerable interest elsewhere. They may be especially appropriate in developing world regions, where environmental flow research is in its infancy and water allocations for ecosystems must, for the time being at least, be based on scant data, best professional judgement and risk assessment. Copyright © 2003 John Wiley & Sons, Ltd.
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.
1. In trying to operationalize the notion of sustainable ecosystem health, ecologists have focused on identifying sets of indicators which can be used to assess river condition relative to some normative, undegraded condition. Recognition and description of this normative state has proved elusive, particularly in highly variable semiarid ecosystems. Without an operational definition of the desired system condition that reflects both scientific rigour and broader societal value systems, rivers are unlikely to be managed effectively.
2. Managing river health should not be confused with measuring it. Many monitoring or assessment programs become ends in themselves instead of being the means to achieving specific management goals. The absence of a test of the results of monitoring further introduces the risk of management by observation and ‘pseudo‐fact’. Health ‘endpoints’ provide a scientific description of management goals, while ‘values’ provide a societal perspective. Together they complement the use of indicators and provide the basis for a strategic rather than reactive approach to management.
3. The integration of value systems, endpoints and indicators of ecosystem health or ecosystem integrity forms the cornerstone of a consultative management process for the rivers of the Kruger National Park.
4. An objectives hierarchy has been developed to service management’s institutional hierarchy. ‘Vision’ and objectives serve upper levels of management with value based statements of strategic intent which have been tested against public opinion. Goals provide managers on the ground with specific ecological endpoints termed ‘thresholds of probable concern’ (TPCs). TPCs are described by a range of spatially and temporally bounded indicators of the system’s response to the main potential agents of change.
5. TPCs represent statements or hypotheses of the limits of acceptable change in ecosystem structure, function and composition. They thereby provide an inductive and strategic approach to adaptive management in a data poor situation. Integrated monitoring, research and modelling track criteria relative to TPCs and question whether management action, or recalibration of the TPC, is needed. TPCs thus provide direction for management but their validity and appropriateness are frequently challenged and adaptively modified.
6. The objectives hierarchy gives Kruger Park management a mandate to ‘maintain biodiversity in all its natural facets and fluxes’. Alluviation, as a consequence of increased sediment supply and decreased sediment transport capacity, is a major threat to the biodiversity of the bedrock‐controlled rivers which flow through the park. Thus, for example, TPCs for geomorphic diversity reflect permissible ranges of change in bedrock character of the physical template. They are measured as change in the proportion of different geomorphic units in identified representative reaches. TPCs for riparian vegetation are measured as change in population structure of selected species within the representative reaches. They reflect a likely range of biotic responses to change in the physical template. A specific set of indicators, reflecting response to the major agents of change, therefore provides a parsimonious program for assessing ecosystem condition relative to explicit goals and a clearly defined management process.
Conserving river biota will require innovative approaches that foster and utilize scientific understanding of ecosystem responses to alternative river-management scenarios. We describe ecological and societal issues involved in flow management of a section of the Tallapoosa River (Alabama, U.S.A.) in which a species-rich native fauna is adversely affected by flow alteration by an upstream hydropower dam. We hypothesize that depleted low flows, flow instability, and thermal alteration resulting from pulsed flow releases at the hydropower dam are most responsible for changes in the Tallapoosa River biota. However, existing data are insufficient to prescribe with certainty minimum flow levels or the frequency and duration of stable flow periods that would be necessary or sufficient to protect riverine biotic integrity. Rather than negotiate a specific change in the flow regime, we propose that stakeholders-including management agencies, the power utility, and river advocates-engage in a process of adaptive-flow management. This process would require that stakeholders (1) develop and agree to management objectives; (2) model hypothesized relations between dam operations and management objectives; (3) implement a change in dam operations; and (4) evaluate biological responses and other stakeholder benefits through an externally reviewed monitoring program. Models would be updated with monitoring data and stakeholders would agree to further modify flow regimes as necessary to achieve management objectives. A primary obstacle to adaptive management will be a perceived uncertainty of future costs for the power utility and other stakeholders. However, an adaptive, iterative approach offers the best opportunity for improving flow regimes for native biota while gaining information critical to guiding management decisions in other flow-regulated rivers.
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"Observed declines in the Snake River basin salmon stocks, listed under the U.S. Endangered Species Act (ESA), have been attributed to multiple causes: the hydrosystem, hatcheries, habitat, harvest, and ocean climate. Conflicting and competing analyses by different agencies led the National Marine Fisheries Service (NMFS) in 1995 to create the Plan for Analyzing and Testing Hypotheses (PATH), a collaborative interagency analytical process. PATH included about 30 fisheries scientists from a dozen agencies, as well as independent participating scientists and a technical facilitation team. PATH had some successes and some failures in meeting its objectives. Some key lessons learned from these successes and failures were to: (1) build trust through independent technical facilitation and multiple levels of peer review (agency scientists, independent participating scientists and an external Scientific Review Panel); (2) clarify critical uncertainties by developing common data sets, detailed sensitivity analyses, and thorough retrospective analyses of the weight of evidence for key alternative hypotheses; (3) clarify advice to decision makers by using an integrated life cycle model and decision analysis framework to evaluate the robustness of potential recovery actions under alternative states of nature; (4) involve key senior scientists with access to decision makers; (5) work closely with policy makers to clearly communicate analyses in nontechnical terms and provide input into the creation of management alternatives; and (6) recognize the trade-off between collaboration and timely completion of assignments."
"Many case studies in adaptive-management planning for riparian ecosystems have failed to produce useful models for policy comparison or good experimental management plans for resolving key uncertainties. Modeling efforts have been plagued by difficulties in representation of cross-scale effects (from rapid hydrologic change to long-term ecological response), lack of data on key processes that are difficult to study, and confounding of factor effects in validation data. Experimental policies have been seen as too costly or risky, particularly in relation to monitoring costs and risk to sensitive species. Research and management stakeholders have shown deplorable self-interest, seeing adaptive-policy development as a threat to existing research programs and management regimes, rather than as an opportunity for improvement. Proposals for experimental management regimes have exposed and highlighted some really fundamental conflicts in ecological values, particularly in cases in which endangered species have prospered under historical management and would be threatened by ecosystem restoration efforts. There is much potential for adaptive management in the future, if we can find ways around these barriers."
"An Adaptive Environmental Assessment and Management workshop process was used to assist Grand Canyon scientists and managers in developing conceptual and simulation models for the Colorado ecosystem affected by Glen Canyon Dam. This model examines ecosystem variables and processes at multiple scales in space and time, ranging from feet and hours for benthic algal response to diurnal flow changes, to reaches and decades for sediment storage and dynamics of long-lived native fish species. Its aim is to help screen policy options ranging from changes in hourly variation in flow allowed from Glen Canyon Dam, to major structural changes for restoration of more natural temperature regimes. It appears that we can make fairly accurate predictions about some components of ecosystem response to policy change (e.g., autochthonous primary production, insect communities, riparian vegetation, rainbow trout population), but we are moderately or grossly uncertain about others (e.g., long-term sediment storage, response of native and non-native fishes to physical habitat restoration). Further, we do not believe that existing monitoring programs are adequate to detect responses of native fishes or vegetation to anything short of gross habitat changes. Some experimental manipulations (such as controlled floods for beach/habitat-building) should proceed, but most should await development of better monitoring programs and sound temporal baseline information from those programs."
Incluye índice Incluye bibliografía Recorrido histórico sobre el papel de la escasez de agua y problamas de irrigación en la caída de diversas civilizaciones.
In making resource management decisions, agencies use a variety of approaches that involve different levels of political concern, historical precedence, data analyses, and evaluation. Traditional decision-making approaches have often failed to achieve objectives for complex problems in large systems, such as the Everglades or the Colorado River. I contend that adaptive management is the best approach available to agencies for addressing this type of complex problem, although its success has been limited thus far. Traditional decision-making approaches have been fairly successful at addressing relatively straightforward problems in small, replicated systems, such as management of trout in small streams or pulp production in forests. However, this success may be jeopardized as more users place increasing demands on these systems. Adaptive management has received little attention from agencies for addressing problems in small-scale systems, but I suggest that it may be a useful approach for creating a holistic view of common problems and developing guidelines that can then be used in simpler, more traditional approaches to management. Although adaptive management may be more expensive to initiate than traditional approaches, it may be less expensive in the long run if it leads to more effective management. The overall goal of adaptive management is not to maintain an optimal condition of the resource, but to develop an optimal management capacity. This is accomplished by maintaining ecological resilience that allows the system to react to inevitable stresses, and generating flexibility in institutions and stakeholders that allows managers to react when conditions change. The result is that, rather than managing for a single, optimal state, we manage within a range of acceptable outcomes while avoiding catastrophes and irreversible negative effects.
Instream Flow Assessment Methods: Guidance for Assessing Instream Flow Needs in Hydropower Relicensing
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Anthropogenic Impacts on the Hydrology of Rivers and Lochs. Stage 1 Report: Literature Review and Proposed Methods Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity
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Bragg OM, Black AR. 1999. Anthropogenic Impacts on the Hydrology of Rivers and Lochs. Stage 1 Report: Literature Review and Proposed Methods. University of Dundee: Scotland. Bunn SE, Arthington AH. 2002. Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30: 492–507.
Is lateral chan-nel migration or bar formation important in forming these physical habitats? Instream Flows for Riverine Resource Stewardship. Instream Flow Council: Cheyenne
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Do certain riparian plants or animals depend upon physical habitat conditions that are shaped by river flows? Is lateral chan-nel migration or bar formation important in forming these physical habitats? REFERENCES Annear T, Chisholm I, Beecher H, Locke A, et al. 2002. Instream Flows for Riverine Resource Stewardship. Instream Flow Council: Cheyenne, Wyoming. Arthington AH, Zalucki MJ. 1998. Comparative Evaluation of Environmental Flow Assessment Techniques: Review of Methods. Land and Water Resources Research and Development Corporation: Canberra, Australian Capitol Territory. 316 B. D. RICHTER ET AL. Copyright # 2006 John Wiley & Sons, Ltd. River Res. Applic. 22: 297–318 (2006) Baron JS, Poff NL, Angermeier PL, Dahm CN, Gleick PH, Hairston NG, Jackson RB, Johnston CA, Richter BD, Steinman AD. 2002. Meeting ecological and societal needs for freshwater. Ecological Applications 12: 1247–1260.