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... Several studies have reported declining river flows and changes in the water quantity during the past decades [57,58], but it remains unclear how reducing precipitation is linked with hydrological alterations. This is more prominent in the Mediterranean since river damming and water abstractions are major environmental problems that are responsible for changing flow patterns and reduced water quantity [59][60][61]. For instance, Mentzafou et al. [57] showed significant relationships between precipitation and discharge with similar fluctuation patterns for major Greek rivers but concluded that a more in-depth analysis that considers the water uses will reveal the actual causes of flow regime changes. ...
... Moreover, an improved accuracy of hourly or daily ERA5-Land precipitation data can help to investigate inter-annual changes in the intensity and frequency of extreme precipitation events that often cause flash floods, having critical implications for freshwater ecosystems, the economy, and society [71][72][73][74][75][76][77][78]. It is also interesting that such future work using ERA5-Land data could facilitate applications of the Indicators of Hydrologic Alteration (IHA) methodology in river ecosystems to explore their ecological integrity and functioning [60]. ...
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Precipitation is one of the most variable climatic parameters, as it is determined by many physical processes. The spatiotemporal characteristics of precipitation have been significantly affected by climate change during the past decades. Analysis of precipitation trends is challenging, especially in regions such as Greece, which is characterized by complex topography and includes several ungauged areas. With this study, we aim to shed new light on the climatic characteristics and inter-annual trends of precipitation over Greece. For this purpose, we used ERA5 monthly precipitation data from 1950 to 2020 to estimate annual Theil–Sen trends and Mann–Kendall significance over Greece and surrounding areas. Additionally, in order to analyze and model the nonlinear relationships of monthly precipitation time series, we used generalized additive models (GAMs). The results indicated significant declining inter-annual trends of areal precipitation over the study area. Declining trends were more pronounced in winter over western and eastern Greece, but trends in spring, summer and autumn were mostly not significant. GAMs showcased that the trends were generally characterized by nonlinearity and precipitation over the study area presented high inter-decadal variability. Combining the results, we concluded that precipitation did not linearly change during the past 7 decades, but it first increased from the 1950s to the late 1960s, consequently decreased until the early 1990s and, afterwards, presented an increase until 2020 with a smaller rate than the 1950–1960s.
... As a key variable of the hydrological system, the flow regime can be analyzed using many indicators at daily and monthly scales (Cui et al., 2020;Haghighi et al., 2014;Richter et al., 1996;Stefanidis et al., 2016;L.S. Yang et al., 2017;Y.Y. Zhang et al., 2017). ...
... In this study, analogous to the analysis of monthly runoff regime (Cui et al., 2020;Haghighi et al., 2014;Richter et al., 1996;Stefanidis et al., 2016;L.S. Yang et al., 2017;Y.Y. Zhang et al., 2017), we analyzed the magnitude, variability and duration (timing) of storage regime ( Table 1). ...
Article
Analogous to flow regime, this study proposed a new statistical framework to assess inter-annual and intra-annual terrestrial water storage (TWS) regime and its changes from the aspects of magnitude, variability, duration and components. The framework was applied to two endorheic basins, Inner Basin (IB) and Qaidam Basin (QB), in the Tibetan Plateau and their eight sub-regions. Our major findings are as follows: (1) TWS in the IB (2.09–2.35 mm/a, P < 0.05) and QB (0.05–0.52 mm/a, P > 0.1) increased in all seasons from 1989 to 2019 with regional climate warming and wetting. TWS showed high increase rates (>4.50 mm/a, P < 0.05) in northeastern IB but decrease rates (<−0.90 mm/a) in southern IB. Seasonal total storage in groundwater, lake, permafrost and glacier (GLPIA) also increased in both the IB (2.55–2.68 mm/a, P < 0.05) and QB (0.05–0.43 mm/a). Seasonal soil water storage (SWA) decreased in the IB (−0.39 to −0.26 mm/a) and slightly increased in the QB (0.002–0.08 mm/a); (2) Intra-annual TWS followed approximately a cosine curve. After mutation, monthly TWS showed a higher positive magnitude change (>50 mm), accompanied by a longer duration and higher variability in the IB and its northeastern sub-regions. There was a large reduction in low storage (−18.25 mm) combined with higher variability in southeastern IB; (3) SWA change dominated the storage surplus in summer (82%) and storage deficit in autumn (−78%) and winter (−51%) in the IB, while GLPIA change dominated the storage surplus in spring (57%). In the QB, TWS change was mainly contributed by SWA change in spring (94%) and by GLPIA change in summer (73%), autumn (−62%) and winter (−58%). Component contribution rates showed a significant change in spring and winter but not much change in summer and autumn, indicating that the TWS components were more sensitive to climate change in the cold season.
... The reduction of flows in the South is rather easy to interpret: irrigated crop areas added in the anthropogenic scenario were responsible for large amounts of water abstracted from water bodies and used by crops. The typical irrigation abstraction needed in the dry period of the year for the growth of a typical crop in Southern countries is around 500 mm of water, which is equivalent to 5000 m 3 /ha [46,47]. Water in PCR-GLOBWB was obtained either directly from rivers or from surface reservoirs and groundwater. ...
... Water in PCR-GLOBWB was obtained either directly from rivers or from surface reservoirs and groundwater. The impact of groundwater depletion on river flows is well-known in Southern countries, resulting in poorer contribution to surface water hydrology as, due to the warm climate, this irrigated water becomes almost entirely crop evapotranspiration [47,48]. Given that irrigated agriculture mostly exists in the South, many rivers in the Mediterranean countries have been impacted negatively and this is considered the major factor for noticing significant areas with MAF ratios < 1. ...
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The hydrologic regime of a river is one of the factors determining its ecological status. This paper tries to indicate the present hydrologic stress occurring across European rivers on the basis of model integration. This results in a pan-European assessment at the resolution of the functional elementary catchment (FEC), based on simulated daily time-series of river flows from the model PCR-GLOBWB. To estimate proxies of the present hydrologic stress, two datasets of river flow were simulated under the same climate, one from a hypothetic least disturbed condition scenario and the second from the anthropogenic scenario with the actual water management occurring. Indicators describing the rivers’ hydrologic regime were calculated with the indicators of hydrologic alteration (IHA) software package and the river total mean flow and the relative baseflow magnitude over the total flow were used to express the deviations between the two scenarios as proxy metrics of rivers’ hydrologic alteration or hydrologic stress. The alteration results on Europe’s FEC-level background showed that Southern Europe is more hydrologically stressed than the rest of Europe, with greater potential for hydrology to be clearly associated with river segments of unreached good ecological status and high basin management needs.
... Nutrient pollution, habitat fragmentation and alteration in hydrology are perhaps the most common issues that Mediterranean lotic systems are facing today (Filipe et al., 2013;López-Doval et al., 2013;Stefanidis et al., 2016a;Stefanidis et al., 2018;Vörösmarty et al., 2010). Specifically, changes in riverine hydromorphology along with increased nutrient loadings are known to heavily influence both the ecological integrity and the aquatic biodiversity of these systems (Bonada and Resh, 2013;Filipe et al., 2013;Gasith and Resh, 1999;Hershkovitz and Gasith, 2013;Stefanidis et al., 2016b). ...
... To this end, the main objective of this study was to identify the potential role of anthropogenic stressors in explaining the observed patterns of aquatic plant diversity in Mediterranean streams. We hypothesized that nutrients and hydromorphological modifications would be important explanatory variables because Mediterranean streams are heavily impacted by major drivers such as agricultural activities and narrowing of riparian zone (Stefanidis et al., 2016b). These drivers are the main cause for severe hydromophological alterations and nutrient pollution that negatively affect the aquatic biota . ...
Article
Aquatic and riparian plants play a crucial role in the functioning of riverine ecosystems. Hence, analyzing multiple facets of plant diversity could be extremely useful for assessing the ecological integrity of lotic ecosystems. The main objective of this study was to investigate the response of multiple facets of aquatic plant diversity, such as species richness, taxonomic distinctness and compositional dissimilarity, to environmental factors (i.e. nutrient pollution and hydromorphological alteration) in 72 stream reaches of mainland Greece. We employed Generalized Additive Models to identify the variables with the highest influence and examine the response of species richness and taxonomic distinctness to environmental gradients. The relationship between compositional dissimilarity and the environment was examined with Generalized Dissimilarity Modelling. Our results supported our hypothesis that human disturbances play a considerable role in shaping macrophyte assemblages. In particular, phosphates and hydromorphological modification were significant predictors of species richness, whereas taxonomic distinctness was unaffected by indicators of anthropogenic stress but it was influenced mostly by elevation, water temperature and pH. Concerning the compositional dissimilarity, geographic distance, elevation, temperature and total inorganic nitrogen were the most important environmental parameters. Our findings suggest that human stressors, such as hydromorphological modification and nutrient enrichment, affect the plant species richness at stream reach scale, but when considering community composition or taxonomic distinctness, environmental factors associated with the natural variability (e.g. elevation, temperature and geographic distance) are of higher importance. Overall, our results emphasize the advantage of examining multiple aspects of diversity when designing conservation schemes and management plans for riparian areas.
... In addition, transboundary rivers require a genuine need utilization and regulation of water resources, and this will be more strenuous without considering climate change. In this regard, Indicators of Hydrologic Alterations (IHA) method has been widely used to precisely distinguish the flow regimes with the help of ecological information and its interconnection with respect to hydrological and ecosystem elements (Richter et al. 1998;Brouziyne et al. 2021) including inter and intra annual variability of the streamflow conditions (Stefanidis et al. 2016). ...
... High Range: Values in a set of annual values above 67th percentile • Middle Range: Values between 33rd and 67th percentile in a set of annual flow values • Low Range: Values below 33rd percentile in a set of annual flow valuesThe software then determines the predicted frequency and the frequency at which post impact values of IHA(Stefanidis et al. 2016;Brouziyne et al. 2021) parameters will fall respectively within each of the three categories. ...
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Assessing the impacts of climate change on a transboundary river plays an important role in sustaining water security within as well as beyond the national boundaries. At times, the unilateral decision taken by one country can increase the risk of negative effect on the riparian countries and if the impact is felt strongly by the other country, it can lead to international tension between them. This study examines the impact of climate change on hydrology between a shared river which is Wangchu river in Bhutan and Raidak river in India. The river is mainly used to produce hydropower in the two largest hydropower plants on which the majority of Bhutan's economic development depends and is mainly used for agriculture in India. The Soil and Water Assessment Tool (SWAT) was used for future flow simulation. Future climate was projected for near future (NF) from 2025–2050 and far future (FF) from 2074–2099 using an ensemble of three regional climate models (ACCESS, CNRM-CM5 and MPI-ESM-LR) for two RCPs (Representative Concentration Pathways), RCP 4.5 and RCP 8.5 scenario. The ensemble results indicated that, in future, the study area would become warmer with temperature increase of 1.5 °C under RCP 4.5 and 3.6 °C under RCP 8.5. However, as per RCP 4.5 and RCP 8.5, rainfall over the study area is projected to decrease by 1.90% and 1.38%, respectively. As a consequence of the projected decrease in rainfall, the flow in the river is projected to decrease by 5.77% under RCP 4.5 and 4.73% under RCP 8.5. Overall, the results indicated that the degree of hydrological change is expected to be higher, particularly for low flows in both Wangchu and Raidak River. Since transboundary water is shared for economic growth, climate change adaptation and opportunities should also be considered by both the nations for better water management.
... The impact of land use type, topography, climate change, soil type, agriculture management, and other factors that affect NPS pollutant loads has often been investigated using hydrologic and water quality models (Fereidoon and Koch 2018;Molina-Navarro et al. 2018;Nasab et al. 2017 Pesce et al. 2018;Stefanidis et al. 2016;Wang et al. 2018a;Yu et al. 2018;Zou et al. 2018). These studies indicate that landscape patterns greatly influence NPS pollution (Boongaling et al. 2018). ...
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Landscape patterns have a substantial effect on non-point source (NPS) pollution in watersheds. Facilitating sustainable development of mountain-rural areas is a major priority for China. Knowledge of the impacts of various landscapes on water quality in these areas is critical to meeting environmental goals. This study applied the Soil and Water Assessment Tool (SWAT) to create a hydrologic and water quality model of the study watershed; then, the relationship between water quality and landscape patterns was investigated using multiple linear regression and redundancy analysis. The results show that the western sub-basins had higher nitrogen pollution loads, and the total nitrogen concentration reached a maximum value of 3.91 mg/L; the eastern sub-basins had a higher pollution load of phosphorous featured by maximum total phosphorous concentration of 2.15 mg/L. The water quality of the entire watershed in all scenarios tended to deteriorate over time. Landscape metrics accounted for 81.7% of the total variation in pollutant indicators. The percentage of forest landscape was negatively correlated with NPS pollution, while other types of landscape showed a positive correlation. The patch density, landscape shape index, and largest patch index of urban and agricultural lands were negatively correlated with pollutant concentrations. Upland landscapes contributed more pollutants than paddy fields. Some measures, e.g., returning grassland and farmland to forest in steep regions and replacing upland crops with paddy fields, were recommended for mitigating NPS pollution in the study watershed.
... There are several incidents of coastal eutrophication in Europe, namely, in France, Italy, Spain, Germany, and Poland where case studies were chosen (Seine, Po, Ebro, Oder, and Vistula;. In the recent decades, however, Greece has developed agricultural activities in the alluvial plains of the Pinios, Aliakmon, and Axios rivers, where better management of fertilization is also necessary (Fytianos et al 2002, Stefanidis et al 2016. Despite a significant reduction in P levels in most of these selected rivers, their receiving coastal bays still present some of the episodic eutrophication symptoms mentioned above (northern Adriatic bay for the Po River . ...
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For a number of well-documented watersheds and their adjacent coastal zones, a simplified, but generic approach was developed to explore current nutrient deliveries to their corresponding marine system, characterized by their flushing rate/residence time and morphology. An indicator of eutrophication was defined derived from both the C:N:P:Si stoichiometry of the riverine nutrient delivery and the physical features of the receiving marine bay (B_ICEP). Results show that the morphological and hydrological conditions characterizing coastal zones are the main determinants of the manifestation of eutrophication caused by an imbalance of nitrogen (and/or phosphorus) with respect to silica in the river nutrient loading. Action on the structure of the agro-food system of the upstream watershed, which determines the nitrogen losses to the hydrosystem, is identified as the most efficient control for attenuating coastal eutrophication. A comprehensive and generic concept of the systemic processes responsible for river and coastal water degradation can be achieved with a chain of nested models, describing the terrestrial agro-food system of the watershed, the river network, including the biogeochemical processes responsible for water quality, and the ecological functioning of the receiving marine area, in terms of carbon, nitrogen, phosphorus, and silica cycles. This leads to a land-to-sea continuum view, promoting interdisciplinarity and dialogue among the various scientific communities and their modeling approaches. This would also help the actors in multiple sectors (farming, fisheries, tourism, etc) and policy-makers make harmonized choices for a sustainable environment through an economically and socially viable way of life for all citizens.
... Understanding the stationary/non-stationary behaviour in hydrological regimes in a basin is a thrust area, which greatly influences the ecosystem for sustainable development of river basin. Various studies in the past (Richter et al., 1996;Poff et al., 1997;Pumo et al., 2016;Stefanidis et al., 2016;Alonso et al., 2017, Lin et al., 2017Vigiak et al., 2018;Cervi et al., 2018) showed that the impact of flow alterations greatly influence the hydrologic cycle and ecosystem. The important indicators giving information of the hydrological regimes of hydrologic alterations are flow variables which are investigated for various applications like hydrogeomorphic, environmental responses and river flow management (Olden and Poff, 2003;Poff and Zimmerman, 2010;Yang et al., 2012;Poff and Matthews, 2013;Fanaian et al., 2015;Poff and Schmidt, 2016;Pumo et al., 2016, Poff, 2018. ...
Article
The present study focuses on change detection and attribution analysis for a case study of Allegheny river catchment (at two unregulated sites namely Eldred and Salamanca) in USA. The proposed methodology involves, multiple change-point detection (MCPD) techniques i.e., Binary Segmentation based cumulative sum algorithms with Monte Carlo based threshold (BSCSth) and Bayesian Information Criteria (BIC) based penalty (BSCSBIC) and validating the two techniques using standard performance measures for different hypothetical riverflow time-series. The proposed BSCSth technique was applied to the Allegheny river at two sites for the series of different hydrological alteration indicators to identify the location of change-point in mean, and the hydrological regime shifts. To perform attribution analysis, hydrologic simulations were carried out using Sacramento model for the identified segments. The overall hydrologic alterations of selected annual flow metrics extracted from daily simulated flows and observed flow values were also estimated. The results of MCPD analysis showed that overall three hydrological regimes comprising of three segments i.e., near natural period (NNP, 1940–1955), low impact period (LIP, 1956–1966) and high impact period (HIP, 1967–2014) were identified for both the sites. The results of attribution analysis for the three cases (case-1: NNP & LIP; case-2: LIP & HIP; case-3: NNP & HIP) showed that for the case-1, the changes of flow regimes in Eldred and Salamanca were predominantly affected by climate-induced processes. But, for case-2 and case-3, it was seen that there were magnification of human-induced changes probably due to the landuse change (forest and rangeland increased by 18.31% (19.79%) for Eldred (Salamanca) from 1940 to 1992), construction of Kinzua dam (in the year 1966) and other anthropogenic pressures. Thus, the results of the study can be helpful for quantifying the main drivers of hydrological changes in river basin, and planning suitable water resource management strategies in the basin.
... The range of variability approach (RVA) is an application of IHA, which incorporates the concepts of hydrologic variability and ecosystem integrity intending to set preliminary hydrologic management targets when conclusive and detailed long-term ecosystem data are not available . The IHA software, developed by the Nature Conservancy (based on Richter et al. 1996Richter et al. , 1997, is one of the most popular tools and is used worldwide in many studies to evaluate alterations in the hydrologic regime in a river system (Fernández et al. 2012;Alrajoula et al. 2016;Papadaki et al. 2016;Song et al. 2020;Stefanidis et al. 2016;Gierszewski et al. 2020;Yang et al. 2017). For example, Song et al. (2020) analysed the hydrologic alteration of major rivers in China using IHA and RVA, and the results revealed that the majority of them showed moderate flow regime alteration due to reservoir impoundment. ...
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Hydrologic regime changes of the Roanoke River basin under three different scenarios defined based on different periods of post-impact datasets have been studied. For evaluating the degree of hydrologic alterations, the traditional and improved range of variability approach (RVA) which incorporate periodicity [as an index of periodicity (IP)], trend [as an index of trend (IT)], and symmetry [as an index of symmetry (IS)] of the parameters has been used. Comparative analysis of the results obtained with traditional and improved RVA and that obtained with the histogram matching approach (HMA) has also been performed. The overall degree of hydrologic alteration obtained through traditional RVA for Scenarios-I, II, and III was 0.39, 0.42, and 0.40, respectively. The improved RVA method, when applied to the 32 IHA parameters, indicates that many IHA parameters exhibit a higher IP or IT or IS value compared to the corresponding value of the degree of hydrologic alteration (DR), which underscore the inadequacy of the traditional RVA in assessing the degree of alteration in the flow regime of the Roanoke River. Through principal component analysis, the most ecologically relevant hydrologic indicators for understanding eco-hydrology of Roanoke River have been identified, which include Julian date of maximum flow, monthly flow for July and September, and 90-day maximum flow. Analysis of results further reveals that the combination of improved RVA and HMA can better reveal changes in IHAs and provide a better tool for designing strategies to enhance further the ecosystem services available from a managed river system.
... On the other hand, the ecology has less beneficial and more detrimental effects since that significant increase of magnitude of streamflow and flooding frequent and extreme would damage the new habitat (Stefanidis et al. 2016). Generally, the remarkably increased streamflow may lead to high-flow velocities and shear stresses, which increase the mortality of benthic invertebrates and depth of bed scour (Palmer et al. 1992;TOWNSEND et al. 1997;Poff et al. 2006). ...
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The source region of Yellow river is an alpine river sensitive to climate changes, but the potential effects of climate change on hydrological regime characteristics and ecological implications are less understood. This study aims to assess the response of the alterations in the flow regimes over the source region of Yellow river to climate change using Soil and Water Integrated Model driven by different Global Circulation Models (GFDL-ESM2M, IPSL-CM5A-LR and MIROC-ESM-CHEM) under three Representative Concentration Pathway emission scenarios (RCP2.6, RCP4.5 and RCP8.5). Indicators of hydrological alteration and River impact index are employed to evaluate streamflow regime alterations at multiple temporal scales. Results show that the magnitude of monthly and annual streamflow except May, the magnitude and duration of the annual extreme, and the number of reversals are projected to increase in the near future period (2020–2049) and far future period (2070–2099) compared to the baseline period (1971–2000). The timing of annual maximum flows is expected to shift backwards. The source region of Yellow river is expected to undergo low change degree as per the scenarios RCP2.6 for both two future periods and under the scenarios RCP4.5 for the near future period, whereas high change degree under RCP4.5 and RCP8.5 in the far period on the daily scale. On the monthly scale, climate changes mainly have effects on river flow magnitude and timing. The basin would suffer an incipient impact alteration in the far period under RCP4.5 and RCP8.5, while low impact in other scenarios. These changes in flow regimes could have several positive impacts on aquatic ecosystems in the near period but more detrimental effects in the far period.
... Another major change in the flow regime is the reduction in extreme maximum discharge and the moderate alteration of time series in these parameters. As a result, it is expected that the hydrological connectivity between the river channels and floodplains and the exchange of nutrients and organic matter between the river ecosystems and floodplains will be significantly reduced, resulting in a shortage of food supplies and seriously affecting the growth of aquatic organisms (Stefanidis et al., 2016). ...
Article
The undeniable fact of climate change and dam construction alters the hydrological systems and threatens aquatic ecosystems of rivers around the world. Quantifying the impact of climate change and dam construction on flow regime is essential for water resources management and environmental protection. However, previous studies have rarely separated the effects of two factors on flow regimes, and the individual impact of each remains insufficient to date. Moreover, the existing methods have not fully captured the characteristics and temporal changes of flow regimes. In this study, we propose a new framework that integrates a streamflow reconstruction technique, indicators of hydrologic alteration (IHA), indicators of intra-annual flow variations, a revised range of variability approach to assessing the climate change and dam-induced impacts on the flow regime. The Upper Yellow River Basin (UYRB) was selected as the study area. The results show that climate change significantly reduces the monthly flow, extreme water conditions and the intra-annual indicators, and advances the Julian date of annual maximum flow. Dam construction delays the Julian date of annual maximum flow that opposes climate change impact, reduces the monthly flow in the flood season and the annual maximum flow, but increases the monthly flow in the dry season and annual minimum flow. Changes in flow regimes in the UYRB are found to be mainly due to climate change albeit there exists a cascade of dams. Based on the range of variability approach (RVA), fifteen of forty indicators are moderately changed. While the number increases to thirty-seven when considering the temporal order alteration of flow regime. The case study demonstrates that the developed framework can serve as a useful tool to evaluate the impact of climate change and dam construction on flow regimes.
... Hence, at this moment, the use of models that can estimate the volume of water used in agriculture based on agricultural land use recorded by Integrated Administration and Control System (IACS), meteorological data and annual crop statistics seems to be the most suitable methodology for countries facing data sparseness. Models are widely used in every aspect of planning and management of water resources in agriculture [5,[28][29][30][31][32] as well as in evaluating various economic and environmental impacts of RDP effects [8,17,18,[33][34][35]. ...
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Agriculture is an essential driving force in water resources management and has a central role in the European Union's Rural Development Programme (RDP). In this study, the solution developed addresses countries characterised by relatively small farms, vast spatial and temporal variability and severe data scarcity. The proposed model-based approach is directly relevant to the evaluation of agricultural policies affecting water abstraction based on multisource data. The evaluation process utilises an entirely spatially distributed, continuous hydrological model. The model provides a gridded output of the main hydrological balance components, as well as vegetation water deficit and irrigation water requirements, on a daily temporal step on a country scale. It provides information at the farm level and facilitates the estimation of water abstractions in agriculture, taking into consideration all the pertinent information included in the Integrated Administration and Control System database that is maintained by RDPs in Europe. Remote sensing data also are used to validate crop patterns. The obtained results were analysed to estimate the net effect of the RDP to the reduction of water abstractions in agriculture. This work produces valuable information concerning the evaluation of agricultural policies and the assessment of land use, and climate change adaptation and mitigation strategies.
... Alterations in annual extreme flow conditions Analysis of median values of degree of deviation and degree of hydrological alteration for the annual extreme flow conditions (11 IHAs under Group-2 and 2 IHAs under Group-3) reveal that degree of deviation is highest (16.1%) for a 90-day maximum, followed by 30day maximum (12.9%) (Fig. 5) whereas it decreases in 1-day, 3day, and 90-day minimum extreme flow parameter from pre-to post-impact period. This suggests a possible increase in flood magnitude, which may have been both beneficial as well as harmful effects depending on channel morphology, types of substrate, depth, and other geomorphological characteristics (Stefanidis et al. 2016). Furthermore, increase in 1-day, 3-day, and 7-day maximum flow causes change in the floodplains due to dominant particle size of bed materials inducing ecological implications like low oxygen and prolongation of duration of stressful high temperatures (Graf 2006). ...
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Climate change/variability and subsequent exacerbation of extremes are affecting human and ecological health across the globe. This study aims at unpacking hydro-climatic extremes in a snow-fed Marshyangdi watershed, which has a potential for water infrastructure development, located in Central Nepal. Bias-corrected projected future climate for near (2014–2033) and mid-future (2034–2053) under moderate and pessimistic scenarios were developed based on multiple regional climate models. Historical (1983–2013) and future trends of selected climatic extreme indices were calculated using RClimDex and hydrological extremes using Indicators of Hydrologic Alteration tool. Results show that historical trends in precipitation extremes such as number of heavy and very heavy precipitation days and maximum 1-day precipitation are decreasing while the temperature-related extremes have both increasing and decreasing trends (e.g., warm spell duration index, warm days and summer days are increasing whereas cold spell duration index, cool days and warm nights are decreasing). These results indicate drier and hotter conditions over the historical period. The projected future temperature indices (hot nights, warm days) reveal increasing trend for both the scenarios in contrast with decreasing trends in some of the extreme precipitation indices such as consecutive dry and wet days and maximum 5-day precipitation. Furthermore, the watershed has low mean hydrological alterations (27.9%) in the natural flow regime. These results indicate continuation of wetter and hotter future in the Marshyangdi watershed with likely impacts on future water availability and associated conflicts for water allocation, and therefore affect the river health conditions.
... moderate alteration). Our results proved that the IHA method encasing RVA targets is an easy and useful tool to quantify the hydrologic alteration in the study area as already reported for many rivers worldwide [36][37][38][39][40] . However, these results were preliminary since only three years of data (2011-2013) were used for IHA calculation for the post-weir period. ...
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Our study focused on quantifying the alterations of streamflow at a weir site due to the construction of a mini-hydropower plant in the Gurugoda Oya (Sri Lanka), and evaluating the spatial responses of benthic macroinvertebrates to altered flow regime. The HEC–HMS 3.5 model was applied to the Gurugoda Oya sub-catchment to generate streamflows for the time period 1991–2013. Pre-weir flows were compared to post-weir flows with 32 Indicators of Hydrologic Alteration using the range of variability approach (RVA). Concurrently, six study sites were established upstream and downstream of the weir, and benthic macroinvertebrates were sampled monthly from May to November 2013 (during the wet season). The key water physico-chemical parameters were also determined. RVA analysis showed that environmental flow was not maintained below the weir. The mean rate of non-attainment was ~ 45% suggesting a moderate level of hydrologic alteration. Benthic macroinvertebrate communities significantly differed between the study sites located above and below the weir, with a richness reduction due to water diversion. The spatial distribution of zoobenthic fauna was governed by water depth, dissolved oxygen content and volume flow rate. Our work provides first evidence on the effects of small hydropower on river ecosystem in a largely understudied region. Studies like this are important to setting-up adequate e-flows.
... The results reveal a significant reduction in the natural flow variability due to the construction of a dam, which has been projected to worsen further due to future climate change impacts. The IHA method combined with a semi-distributed hydrological model like Soil and Water Assessment Tool (SWAT) has been used in many studies to evaluate the impact of climate change on the riverine aquatic ecosystem (Bharati et al. 2014;Chatterjee et al. 2018;Jeong et al. 2014;Kim et al.2016;Mittal et al., 2014;Morid et al. 2016;O'Keeffe et al. 2019;Papadaki et al. 2016;Schilling et al. 2015;Siebenmorgen et al. 2010;Stefanidis et al. 2016). Groombridge and Jenkins (1998) identified 30 major river basins worldwide based on their priority level for riverine ecosystem protection, nine of them are in India, and the Godavari is one such river basin. ...
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The present study attempts to assess the impacts of climate change on multi-dimensional flow characteristics of the Godavari River discharge regime. The assessment of the impact of climate change on the river flow regime has been carried out using 32 indicators of hydrologic alteration (IHA) and analysis of flow duration curves (FDCs). A well-calibrated hydrological model (Soil and Water Assessment Tool, SWAT) has been used to simulate near future (NF 2020–2050) and far future (FF 2070–2100) period flows using climate data obtained from four General Circulation Models (GCMs) for two representative concentration pathways (RCPs) scenarios. The projected relative change (%) analysis of IHAs reveals that for the Godavari River basin (GRB), several IHAs showed increasing relative change in their median values higher than the threshold value of ± 30%, indicating significant alteration. The overall flow regime alteration for the GRB has been projected to be of highly altered category for future periods and emission scenarios. The FDC analysis for GRB reveal that the overall water yield is likely to increase for both future periods and emission scenarios, indicating the need for a relook into the future water management perspective in terms of water storage capacity, large area inundation, agricultural water management, cropping intensity, and aquatic ecosystem management. Therefore, the present study results would provide a valuable tool for decision-makers for strategy formulation in the GRB. The methodology adopted in the present study could be utilized for the hydrologic alteration assessment under climate change in the major river basins of India and elsewhere.
... In the Mediterranean, water abstraction for irrigation purposes strongly affected the flow regime in irrigated catchments. The parameters related to the timing of annual extreme flow conditions (group 3), frequency and duration of high and low pulses (group 4), and rate and frequency of hydrologic changes (group 5) were strongly impacted (Stefanidis et al., 2016). In the Geba catchment, Ethiopia, the expansion of agricultural and grazing land at the expense of natural vegetation increased almost all hydrological parameters from 1972 to 2014 (Gebremicael et al., 2019). ...
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Tropical river basins have experienced dramatically increased hydropower development over the last 20 years. These alterations have the potential to cause changes in hydrologic and ecologic systems. One heavily impacted system is the Upper Paraguay River Basin, which feeds the Pantanal wetland. The Pantanal is a Ramsar Heritage site and is one of the world's largest freshwater wetlands. Over the past 20 years, the number of hydropower facilities in the Upper Paraguay River Basin has more than doubled. This paper uses the Indicators of Hydrologic Alteration (IHA) method to assess the impact of 24 of these dams on the hydrologic regime over 20 years (10 years before and 10 years after dam installation) and proposes a method to disentangle the effects of dams from other drivers of hydrologic change using undammed “control” rivers. While most of these dams are small, run-of-the-river systems, each dam significantly altered at least one of the 33 hydrologic indicators assessed. Across all studied dams, 88 of the 256 calculated indicators changed significantly, causing changes of 5–40%, compared to undammed reaches. These changes were most common in indicators that quantify the frequency and duration of high and low pulses, along with those for the rate and frequency of hydrologic changes. Importantly, the flow regime in several undammed reaches also showed significant alterations, likely due to climate and land-use changes, supporting the need for measurements in representative control systems when attributing causes to observed change. Basin-wide hydrologic changes (in both dammed and undammed rivers) have the potential to fundamentally alter the hydrology, sediment patterns, and ecosystem of the Pantanal wetland. The proposed refinement of the IHA methods reveals crucial differences between dam-induced alteration and those assigned to other drivers of change; these need to be better understood for more efficient management of current hydropower plants or the implementation of future dams.
... Zhang (2013) suggested that agricultural pollution significantly increased during a flood event. Moreover, highmagnitude flood events probably cause major damage to fisheries habitat (Stefanidis et al., 2016). ...
... Most river catchments are characterized by intensive agricultural activities (median of agricultural land use 39.7%). Water abstractions for irrigation combined with limited water availability during summer influence the structure of the riparian vegetation and the overall hydromorphological status [40]. ...
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Riparian zones play an important role in the ecological stability of rivers. In particular, the quality of the riparian vegetation is a significant component of the hydromorphological status. In Europe, the QBR index (Qualitat del Bosc de Ribera) and the River Habitat Survey (RHS) are commonly used for the qualitative assessment of the riparian vegetation. In this study, we estimated the QBR index and the Riparian Quality index, which is derived from the RHS method, for 123 river reaches of the National Monitoring Network of Greece. Our field work included the completion of RHS and QBR protocols, as well as the use of Unmanned Aerial Vehicles (UAVs). The aim of this study is to assess the riparian vegetation status and to identify linkages with the dominant land uses within the catchment. Correlation analysis was used to identify the relationships between hydromorphological alterations and the degradation of the riparian vegetation, as well as their connection to land uses in the catchment area. Our results highlighted severe modifications of the riparian vegetation for the majority of the studied reaches. We also showed a differentiation of the QBR with respect to changes in the altitude and the land uses in the catchment area. Overall QBR reflects the variation in the riparian vegetation quality better than RQI. Our findings constitute an assessment of the status of the riparian zones in Greek rivers and set the basis for further research for the development of new and effective tools for a rapid quality assessment of the riparian zones.
... Prolonged periods of low flow or stagnation and high temperatures increase productivity, which in turn leads to the decomposition of the excessive organic material and the depletion of oxygen levels (Marcarelli et al. 2010, Bernhardt et al. 2018). In the Pinios Catchment, water overexploitation for irrigation combined with a dry climate during summer maintains low river flows (Stefanidis et al. 2016b) while future climate scenarios predict more frequent low flow and drought events (Stefanidis et al. 2018). Thus, future climate change is expected to impact DO indirectly through changes in the hydrologic regime and increased nutrient pollution but also directly through warming. ...
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Interactions between stressors in freshwater ecosystems, including those associated with climate change and nutrient enrichment, are currently difficult to detect and manage. Our understanding of the forms and frequency of occurrence of such interactions is limited; assessments using field data have been constrained as a result of varying data forms and quality. To address this issue, we demonstrate a statistical approach capable of assessing multiple stressor interactions using contrasting data forms in 3 European catchments (Loch Leven Catchment, UK: assessment of phytoplankton response in a single lake with time series data; Pinios Catchment, Greece: macroinvertebrate response across multiple rivers using spatial data; and Lepsämänjoki Catchment, Finland: phytoplankton response across multiple rivers using spatiotemporal data). Statistical models were developed to predict the relative and interactive effects of climate change and nutrient enrichment sensitive indicators (stressors) on indicators of ecological quality (ecological responses) within the framework of linear mixed effects models. In all catchments, indicators of nutrient enrichment were identified as the primary stressor, with climate change-sensitive indicators causing secondary effects (Loch Leven: additive, total phosphorus [TP] × precipitation; Pinios: additive, nitrate × dissolved oxygen; Lepsämänjoki: synergistic, TP × summer water temperature), the intensity of which varied between catchments and along the nutrient stressor gradient. Simple stressor change scenarios were constructed for each catchment and used in combination with mechanistic models to explore potential management responses. This approach can be used to explore the need for multiple stressor management in freshwaters, helping practitioners navigate a complex world of environmental change.
... The presented approach provides a robust and simple method to assess changes in hydrology. The results obtained are comparable with other extensive studies in similar climate and river basins using complex hydrological modelling (Hassanzadeh et al., 2012;Guo et al., 2016;Zhang et al., 2016;Zhan et al., 2013), flow regime alteration index (IHA) analysis (Stefanidis et al., 2016;Wang et al., 2014;Wang et al., 2016) or direct analysis of streamflow (Vicente-Serrano et al., 2017;Gao et al., 2012;Batalla et al., 2004). The outcome of previous studies is a disassociation between change in climate and streamflow. ...
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The natural flow regime of rivers has been strongly altered world-wide, resulting in ecosystem degradation and lakes drying up, especially in arid and semi-arid regions. Determining whether this is due mainly to climate change or to water withdrawal for direct human use (e.g. irrigation) is difficult, particularly for saline lake basins where hydrology data are scarce. In this study, we developed an approach for assessing climate and land use change impacts based on river flow records for headwater and lowland reaches of rivers, using the case of Lake Urmia basin, in north-westen Iran. Flow regimes at upstream and downstream stations were studied before and after major dam construction and irrigation projects. Data from 57 stations were used to establish five different time intervals representing 10 different land use development periods (scenarios) for upstream (not impacted) and downstream (impacted) systems. An existing river impact (RI) index was used to assess changes in three main characteristics of flow (magnitude, timing and, intra-annual variability). The results showed that irrigation was by far the main driving force for river flow regime changes in the lake basin. All stations close to the lake and on adjacent plains showed significantly higher impacts of land use change than headwaters. As headwaters are relatively unaffected by agriculture, the non-significant changes observed in headwater flow regimes indicate a minor effect of climate change on river flows in the region. The benefit of the method developed is clear interpretation of results based on river flow records, which is useful in communicating land use and climate change information to decision makers and lake restoration planners.
... In Europe as well, flow estimates using IHA were employed for a variety of water management purposes. The flow alteration in the selected catchments was described by the IHA in the studies of Bizzi et al. [31], De Girolamo et al. [32], Stefanidis et al. [33], Halleraker et al. [34], and Gierszewski et al. [35]. In three catchments from three European ecoregions (Central Plains, Central Highlands, and Alpine), climate change impacts on ecologically relevant hydrological indicators were investigated by Kiesel et al. [36]. ...
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Hydropower remains the most important and largest source of renewable energy. However, besides many additional benefits, such as dams for water supply, irrigation, flood control, recreation, navigation, etc., hydropower generation has a negative impact on the environment. This study aimed to investigate the hydrologic changes in Lithuanian lowland rivers caused by small hydropower plants (HPPs). Thirty-two indicators of hydrologic alteration (IHA) were studied in 11 rivers downstream of hydropower plants in the post-impact and pre-impact periods. The findings showed that HPPs and reservoirs considerably disturbed the primary flow of river ecosystems downstream. The largest changes in mean IHA values were found for low and high pulse characteristics (up to 57%) and the number of reversals (up to 44%). Only small or no deviations of the timing of annual extreme flows were found. The number of reversals, a low pulse count, and a fall rate were the flow characteristics that fell outside their historical ranges of variability most often. Six (out of 11) hydropower plants were identified that provoked hydrologic alterations of a moderate degree.
... Many previous studies have pointed to the hydrologic implications of reservoir construction and land use changes. Similar to the Develi basin, decreases in average and extreme flows are the most documented changes due to hydrologic alterations (Ty et al., 2011;Stefanidis et al., 2016;Xue et al., 2017;Peñas & Barquín, 2019). Reservoir construction followed by land use conversions intensified the extent of alterations (Ty et al., 2011). ...
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en Basins with hydrological modifications pose challenges in hydrological modelling, especially when there are limited data about basin characteristics. Models, however, are vital if we are to identify undisturbed hydrological conditions and evaluate the extent of modifications. In this study, we used SWAT to model the hydrological processes in a semi-arid closed basin, where basin hydrology was heavily modified with reservoirs and irrigation canals and drains. Modelling was also challenging due to limited data about basin characteristics and irrigation management. We modelled the hydrological processes using topographic, land use/cover, soil and climate data. The auto-irrigation tool in SWAT, which determines the timing and amount of irrigation based on the plant water stress factor, was used to represent irrigation. We successfully calibrated/validated the model for streamflow and reservoir storage and confirmed it further by analysing simulated water volumes in wetlands collecting drainage flows. We used the model to simulate the undisturbed hydrologic state and the effects of intensified irrigation. This study showed that SWAT can provide reasonable predictions of hydrological processes in agricultural basins where the natural flow regime is altered by man-made structures. Simulations with the model revealed that the construction of reservoirs followed by land use changes and intensified irrigation have affected streamflows and downstream ecosystems significantly. Résumé fr Les bassins avec des modifications hydrologiques posent des défis dans la modélisation hydrologique, en particulier lorsque les données sur les caractéristiques des bassins sont limitées. Les modèles, cependant, sont essentiels pour identifier les conditions hydrologiques non perturbées et pour évaluer l'étendue des modifications. Dans cette étude, nous avons utilisé SWAT pour modéliser les processus hydrologiques dans un bassin fermé semi-aride, où l'hydrologie du bassin a été fortement modifiée avec des réservoirs, des canaux d'irrigation et des drains. La modélisation était également difficile en raison des données limitées sur les caractéristiques du bassin et la gestion de l'irrigation. Nous avons modélisé les processus hydrologiques à l'aide de données topographiques, d'utilisation/couverture des terres, de sol et de climat. L'outil d'auto-irrigation dans SWAT, qui détermine le moment et la quantité d'irrigation en fonction du facteur de stress hydrique des plantes, a été utilisé pour représenter l'irrigation. Nous avons calibré/validé avec succès le modèle d'écoulement fluvial et de stockage en réservoir et l'avons confirmé davantage en analysant les volumes d'eau simulés dans les zones humides collectant les écoulements de drainage. Nous avons utilisé le modèle pour simuler l'état hydrologique non perturbé et les effets d'une irrigation intensifiée. Cette étude a montré que SWAT peut fournir des prévisions raisonnables pour les processus hydrologiques dans les bassins agricoles où le régime d'écoulement naturel est modifié par des structures artificielles. Des simulations avec le modèle ont révélé que la construction de réservoirs suivie de changements d'utilisation des terres et d'une irrigation intensifiée ont considérablement affecté les débits des cours d'eau et les écosystèmes en aval.
... The native biota is adapted to this variability, but only within certain admissible ranges (de Jal on, del Tánago & de Jal on, 2019). The combined pressures of climate change and increased water abstraction are likely to shift flow and temperature regimes outside of those boundaries, compromising ecological integrity and functioning(Filipe, Lawrence & Bonada, 2013;Stefanidis et al., 2016). In central Spain, a reduction in spring river discharges combined with an increase in peak flow discharges brought about by climate change had detrimental impacts on endemic riverine cyprinid populations(Sánchez-Hernández & Nunn, 2016); and in the Evrotas River in ...
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Freshwater fish are in decline worldwide as a result of introduced non‐native species, impoundment, water quality changes, over‐abstraction, and climate change. The Clanwilliam sandfish Labeo seeberi is an endangered migratory cyprinid endemic to a single river system in South Africa's Cape Fold Ecoregion. It has declined across its range and persists as fragmented populations in the Doring River system. One of the last recruiting populations occurs in the Oorlogskloof River, where three non‐native fish species are present: smallmouth bass Micropterus dolomieu, bluegill sunfish Lepomis macrochirus (both alien and invasive), and banded tilapia Tilapia sparrmanii (extralimital). Impacts of these non‐natives, together with climate change, may pose a serious threat to this important sandfish population and to other cohabiting native fish species. A 6 year data set, collected over 9 years and spanning 25 km of the Oorlogskloof River, was analysed to characterize spatio‐temporal variation in sandfish abundance and size structure and to evaluate the relative impacts of biotic and abiotic factors on population trends. Sandfish experienced a 92.6% decline in relative abundance from 2013 to 2018, driven by a 99.6% decline in young‐of‐the‐year individuals. A combination of extreme rainfall events and drought appear to have played a key role in the decline and subsequently prevented recovery. Small sandfish (≤200 mm) were almost entirely absent from the centrarchid‐invaded section of the Oorlogskloof but were relatively abundant where these centrarchids were absent, suggesting a strong adverse impact of these non‐native species. Banded tilapia co‐occurred with sandfish without any apparent adverse impacts on the relative abundance or size structure of sandfish. Improved water resource management and preventing the further spread of non‐natives must be conservation priorities. Localized eradication of non‐native species must also be considered to reclaim habitat and restore connectivity. Translocations may be required to prevent species extinctions.
... Human activities, especially dam construction, can directly alter the natural flow regime in rivers, causing notable ecological effects [1,2]. Water extraction for irrigation also causes flow regime alteration, especially in semi-arid and Mediterranean regions [3][4][5]. Additionally, variation in precipitation and rising air temperatures due to climate change contribute to changes in the flow regime [6][7][8]. River flow is a major driver of instream ecological health and changes in the flow regime can result in significant impacts on riverine ecological integrity and biodiversity [9,10]. ...
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Changes in the flow regime of the Yangtze River were investigated using an efficient framework that combined the eco-flow metrics (ecosurplus and ecodeficit) and Indicators of Hydrologic Alteration (IHA) metrics. A distributed hydrological model was used to simulate the natural flow regime and quantitatively separate the impacts of reservoir operation and climate variation on flow regime changes. The results showed that the flow regime changed significantly between the pre-dam and post-dam periods in the main channel and major tributaries. Autumn streamflow significantly decreased in the main channel and in the tributaries of the upper Yangtze River, as a result of a precipitation decrease and reservoir water storage. The release of water from reservoirs to support flood regulation resulted in a significant increase in winter streamflow in the main channel and in the Minjiang, Wujiang, and Hanjiang tributaries. Reservoir operation and climate variation caused a significant reduction in low flow pulse duration in the middle reach of the Yangtze River. Reservoir operation also led to an increase in the frequency of low flow pulses, an increase in the frequency of flow variation and a decrease in the rate of rising flow in most of the tributaries. An earlier annual minimum flow date was detected in the middle and lower reaches of the Yangtze River due to reservoir operation. This study provides a methodology that can be implemented to assess flow regime changes caused by dam construction in other large catchments.
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Hydrologic regime plays a vital role in the sustainable ecosystem. However, its alterations due to various climatic and anthropogenic activities cause significant impacts on river health. Hence, in this paper, we have analyzed the degree of hydrologic alterations in a snow-fed Marshyangdi watershed, Nepal, using the Indicators of Hydrologic Alteration tool which is based on the range of variability approaches. Hydrologic alterations in the basin vary among the groups from low to moderate with an overall mean hydrologic alteration of 30% based on 32 hydrologic indices. An increase in the median flow values during the period of March-August and consequent statistically significant increasing trend in the 30-day and 90-day maximum values indicate the possibility of flood in the future. Further, increases in anthropogenic influences could alter the natural flow regime of the Marshyangdi watershed with severe ecological consequences in river health.
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River regulation is challenging when there is diverse upstream and downstream interest, leading to regional and international conflict. However, quantifying the upstream-downstream flow regime changes and their causes are given less consideration in the river basin. In this study, we presented three new ratios for downstream-upstream low flow contribution (DUL), downstream-upstream high flow contribution ratio (DUH), and meteorological-hydrological drought ratio (MHD), for an integrated assessment of flow regime alteration across the river basin. To test the methods, we compared flow regime alteration upstream and downstream in the Ceyhan basin in central Turkey, which was significantly modified by agriculture between 1984 and 2018 (the irrigated area increased 2.8-fold, rainfed farming decreased by 67.6%). Our analysis revealed a clear change in the contribution of low and high flow seasons to annual flow in the last station of the river at Misis after 1984, but no considerable change in upstream tributaries. In the last decade (2005-2014) and the second half (1995-2014) of the study, the frequency of hydrological droughts increased, while meteorological droughts followed a stationary pattern. Evaluation of the impact of anthropogenic activities on river regime (by comparing flow regime characteristics after 1984 with those from 1975-1984 as post- and pre-impact periods) revealed low to incipient impact upstream (Hanköy, Karaahmet, and Kadirli river headwaters), severe impact below the Aslantaş dam in the basin center, and moderate impact at the last station on the Ceyhan river. The new metrics provide supplementary information on the flow regime alteration in the basin and can be introduced as a novel quantitative measure to recognize the driving factor of droughts.
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Surface water abstraction from rivers for irrigated agriculture is one of the largest uses of freshwater resources in the world. Water abstraction has important impacts on the structure of riverine assemblages. However, little work has examined the chronic, season-long impacts on ecosystem functions. Invertebrate drift is an important ecosystem function of river systems influencing nutrient cycling, food webs, and invertebrate population dynamics. We examined the season-long impact of reduced discharge resulting from multiple points of abstraction on drift assemblage composition, concentration, and total drift load. Early in the season, water abstraction had little impact on drift assemblage composition. However, later in the irrigation season, the drift assemblage at sites impacted by water abstraction diverged from upstream, control sites. The degree of change in assemblage composition at impacted sites was related to the amount of water abstracted such that sites with the lowest discharge also had assemblages that differed most strongly from control sites. Drift assemblages at impacted sites became dominated by tolerant microcrustaceans. In addition, water abstraction resulted in an increase in drift concentration (ind./m3). However, despite this increase in concentration at impacted sites, total drift load (# of invertebrates drifting in the river) decreased with decreasing discharge.
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Environmental flows are now an important restoration technique in flow-degraded rivers, and with the increasing public scrutiny of their effectiveness and value, the importance of undertaking scientifically robust monitoring is now even more critical. Many existing environmental flow monitoring programs have poorly defined objectives, nonjustified indicator choices, weak experimental designs, poor statistical strength, and often focus on outcomes from a single event. These negative attributes make them difficult to learn from. We provide practical recommendations that aim to improve the performance, scientific robustness, and defensibility of environmental flow monitoring programs. We draw on the literature and knowledge gained from working with stakeholders and managers to design, implement, and monitor a range of environmental flow types. We recommend that (1) environmental flow monitoring programs should be implemented within an adaptive management framework; (2) objectives of environmental flow programs should be well defined, attainable, and based on an agreed conceptual understanding of the system; (3) program and intervention targets should be attainable, measurable, and inform program objectives; (4) intervention monitoring programs should improve our understanding of flow-ecological responses and related conceptual models; (5) indicator selection should be based on conceptual models, objectives, and prioritization approaches; (6) appropriate monitoring designs and statistical tools should be used to measure and determine ecological response; (7) responses should be measured within timeframes that are relevant to the indicator(s); (8) watering events should be treated as replicates of a larger experiment; (9) environmental flow outcomes should be reported using a standard suite of metadata. Incorporating these attributes into future monitoring programs should ensure their outcomes are transferable and measured with high scientific credibility.
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A future higher risk of severe flooding of streams and rivers has been projected to change riparian plant community composition and species richness, but the extent and direction of the expected change remain uncertain. We conducted a meta-analysis to synthesise globally available experimental evidence and assess the effects of increased flooding on: (1) riparian adult plant and seedling survival; (2) riparian plant biomass and (3) riparian plant species composition and richness. We evaluated which plant traits are of key importance for the response of riparian plant species to flooding. We identified and analysed 53 papers from ISI Web of Knowledge which presented quantitative experimental results on flooding treatments and corresponding control situations. Our meta-analysis demonstrated how longer duration of flooding, greater depth of flooding and, particularly, their combination reduce seedling survival of most riparian species. Plant height above water level, ability to elongate shoots and plasticity in root porosity were decisive for adult plant survival and growth during longer periods of flooding. Both 'quiescence' and 'escape' proved to be successful strategies promoting riparian plant survival, which was reflected in the wide variation in survival (full range between 0-100%) under fully submerged conditions, while plants that protrude above the water level (>20 cm) almost all survive. Our survey confirmed that the projected increase in the duration and depth of flooding periods is sufficient to result in species shifts. These shifts may lead to increased or decreased riparian species richness depending on the nutrient, climatic and hydrological status of the catchment. Species richness was generally reduced at flooded sites in nutrient-rich catchments and sites that previously experienced relatively stable hydrographs (e.g., rain-fed lowland streams). Species richness usually increased at sites in Desert and Semi-arid climate regions (e.g., intermittent streams). This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Human population growth, economic development, climate change, and the need to close the electricity access gap have stimulated the search for new sources of renewable energy. In response to this need, major new initiatives in hydropower development are now under way. At least 3,700 major dams, each with a capacity of more than 1 MW, are either planned or under construction, primarily in countries with emerging economies. These dams are predicted to increase the present global hydroelectricity capacity by 73 % to about 1,700 GW. Even such a dramatic expansion in hydropower capacity will be insufficient to compensate for the increasing electricity demand. Furthermore, it will only partially close the electricity gap, may not substantially reduce greenhouse gas emission (carbon dioxide and methane), and may not erase interdependencies and social conflicts. At the same time, it is certain to reduce the number of our planet’s remaining free-flowing large rivers by about 21 %. Clearly, there is an urgent need to evaluate and to mitigate the social, economic, and ecological ramifications of the current boom in global dam construction.
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1. Frequency and duration of summer droughts are predicted to increase in the near future in many parts of the world, with considerable anticipated effects on riparian plant community composition and species richness. Riparian plant communities along lowland streams are characterised by high species richness due to their system-specific environmental gradients. As these streams and their hydrological gradients are mainly rain-fed, they are sensitive to precipitation changes. 2. We conducted a literature survey and meta-analysis to examine the effects of an increase in summer drought on: (i) riparian plant biomass; (ii) riparian seedling survival and (iii) riparian plant species composition and richness. We also aimed to determine whether hydrological thresholds related to drought tolerance can be distinguished for riparian plant species. 3. ISI Web of Knowledge was searched for relevant peer-reviewed studies, and 23 papers were found that met our criteria and contained quantitative study results. To detect overall responses of biomass and seedling survival, a random-effects model was applied using Comprehensive Meta-analysis™ software. Regression curves were then fitted to response ratio data relating the effects on drought-impacted groups to those on control groups. 4. Our results showed that a drought duration of approximately >30 days strongly reduces riparian plant biomass and that a duration of approximately >30–35 days and high drought intensities (starting from 3 to 4 cm water table decline per day) can be detrimental for riparian seedling survival. Especially Populus and Salix seedlings showed a reduced survival in response to drought, in contrast to Tamarix seedlings, which have the ability to rapidly and expansively elongate their roots. The data also revealed that an increase in drought conditions rapidly leads to a decline of riparian species richness and an increased presence of species adjusted to drier conditions. 5. Riparian groundwater level, surface water permanence and certain plant traits, especially plasticity in rooting depth, were mentioned most frequently as factors determining species responses. Very few studies mentioned hydrological thresholds, such as critical values for ground- and/or surface water levels, and so far these results have proved difficult to generalise. 6. Our meta-analysis has shown that the projected increase in the duration and intensity of drought periods, especially intense droughts lasting more than 30 days, can be expected to narrow the riparian wetland zone with typical hydric species and accelerate riparian wetland species losses in the near future. This may require extra efforts in terms of management and restoration of species-rich riparian areas.
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Climate variability due to the greenhouse effect has important implications on hydrological processes and water resources systems. Indeed, water availability, quality and streamflow are very sensitive to changes in temperature and precipitation regimes whose effects have to be fully considered in current water management and planning. International literature proposes several models, attempting to assess accurately the available water resources under stationary and changing climatic conditions at different spatial and temporal scales. In order to assess the potential impacts of climate change on surface and groundwater resources water availability in a Southern area of Italy, a conceptual hydrologic model, the TOPDM, was applied at daily scale to simulate the hydrological processes in the Belice river basin, located in Sicily and which feeds an artificial lake. The analysis of climatic forcings trend provided the parameters needed in order to generate synthetic climate forcing series through the use of the AWE-GEN, an hourly weather generator, able to reproduce the characteristics of hydro-climatic variables and their statistical properties. . The hydrological model was used to estimate the basin water balance components and the surface and groundwater availability, at annual and monthly scale, in a no trend scenario, representing the current climate conditions, and in three different groups of scenarios, in which a decrease of precipitation, an increase of temperature, and a combination of these effect were reproduced. The application of TOPDM to the test basin provided some important conclusions about the implications of climate change in the Southern part of Italy. Results showed that runoff and evapotranspiration reflect variations in precipitation and in temperature; in particular the negative trend in precipitation determines a decrease in surface and groundwater resources, and this effect is intensified in the scenarios that include an increase in potential evapotraspiration as well. The consequences of changes on water supply system were also analyzed through a simple balance evaluation of the lake water reservoir, in order to assess the possible impacts on the resource managements. Results indicated an exacerbation of the water resources stresses, in which water scarcity is already an important issue for water resource management. The analysis provides useful information about the quantification of the potential effects of climate change in the area of study, in order to develop new strategies to deal with these changes.
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In order to assess the potential impacts of climate change in the hydrologic regime of River Pinios Basin, an area-differentiated model for total run-off (Qt) estimation based on the GROWA model was applied with bias-corrected precipitation and temperature data from four regional climate models (RCMs) for the projected periods 2020–2050 (period A) and 2050–2080 (period B). Bias correction was performed using the linear scaling approach. As a reference basis, monthly precipitation data from 57 meteorological stations and average temperature data from 17 stations were analyzed for the period 1980–2000. Relative assessments were achieved by comparing reference to projected periods values for Qt, after incorporating bias-corrected projected climate data from the four RCMs driven by several general circulation models (GCMs) as input data to the hydrological model. Results showed that all RCM–GCM combinations lead to a considerable decrease in total run-off with variable rates between the examined projected periods; the greatest reduction of Qt (62%) from the reference period was forecasted for period A (2020–2050), and was simulated when GROWA model ran with input data from HIRHAM5 model driven by ARPEGE GCM, which indicated greater decrements in precipitation and increments in temperature. Regarding the estimations of total run-off for the end of the projected periods (2080) with simulated climatic data input from HIRHAM–ARPEGE, RACMO–ECHAM5 and REMO–ECHAM5 RCM–GCM combinations, a significant adverse impact to the overall water budget is forecasted, as the total amount of Qt is decreased from 46 to 66%. On the contrary, when Qt was simulated with climatic data from RCA4 RCM driven by HadCM3, smoother rates were exhibited due to smaller variations of precipitation and temperature from the reference period and the relevant Qt reduction by the end of the projection (2080) is 22%.
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As human water demand is increasing worldwide, pressure on available water resources grows and their sustainable exploitation is at risk. To mimic changes in exploitation intensity and the connecting feedbacks between surface water and groundwater systems, a dynamic attribution of demand to water resources is necessary. However, current global-scale hydrological models lack the ability to do so. This study explores the dynamic attribution of water demand to simulated water availability. It accounts for essential feedbacks, such as return flows of unconsumed water and riverbed infiltration. Results show that abstractions and feedbacks strongly affect water allocation over time, particularly in irrigated areas. Also residence time of water is affected, as shown by changes in low flow magnitude, frequency, and timing. The dynamic representation of abstractions and feedbacks makes the model a suitable tool for assessing spatial and temporal impacts of changing global water demand on hydrology and water resources.
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Streams and rivers in mediterranean-climate regions (med-rivers in med-regions) are ecologically unique, with flow regimes reflecting precipitation patterns. Although timing of drying and flooding is predictable, seasonal and annual intensity of these events is not. Sequential flooding and drying, coupled with anthropogenic influences make these med-rivers among the most stressed riverine habitat worldwide. Med-rivers are hotspots for biodiversity in all med-regions. Species in med-rivers require different, often opposing adaptive mechanisms to survive drought and flood conditions or recover from them. Thus, metacommunities undergo seasonal differences, reflecting cycles of river fragmentation and connectivity, which also affect ecosystem functioning. River conservation and management is challenging, and trade-offs between environmental and human uses are complex, especially under future climate change scenarios. This overview of a Special Issue on med-rivers synthesizes information presented in 21 articles covering the five med-regions worldwide: Mediterranean Basin, coastal California, central Chile, Cape region of South Africa, and southwest and southern Australia. Research programs to increase basic knowledge in less-developed med-regions should be prioritized to achieve increased abilities to better manage med-rivers.
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1. Agriculture affects streams worldwide, and multiple stressors are usually at work. The effects of farming intensification in the catchment are likely to interact with flow reduction due to abstraction for irrigation, but their combined effects on fish communities are unknown. 2. In a low-rainfall, agricultural catchment, we sampled instream physicochemistry and fish populations (non-native brown trout, Salmo trutta, and native upland bullies, Gobiomorphus breviceps, dominated the fish communities) at 36 stream sites chosen to cover wide gradients of % Farming Intensity (%FI) (% catchment in 'high-producing exotic grassland') and % Water Abstraction (%WA) (estimated from a published hydrological model). These landscape variables were not well correlated, allowing us to unravel their individual and combined effects. 3. Presence of trout was best described by an additive multiple-stressor model consisting of a unimodal response to %FI and a negative response to %WA. Trout density only showed a negative response to %FI. Upland bullies were unrelated to either landscape variable. 4. When populations were modelled using instream variables, trout presence was negatively related to fine sediment depth, while density was negatively related to both sediment depth and total nitrogen (themselves closely related to %FI). Upland bully presence and density showed unimodal responses to just total nitrogen. Ammonium concentration was the only measured instream variable related to %WA. 5. The final models for instream stressors explained more of the variation in fish density, whereas the final models for landscape stressors explained more of the variation in fish presence. 6. Overall, farming intensity showed stronger negative relationships with fish populations than water abstraction, and fish were absent from stream reaches whose upstream catchments contained more than 40% high-producing exotic grassland. Resource managers considering intensifying water abstraction or agriculture in low-rainfall river catchments should be aware of the interplay between these two agricultural stressors.
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The effects of drought on stream invertebrates have been reviewed, but the effects of artificially reduced flows have not. We addressed this knowledge gap by reviewing the literature on the effects of natural low flows and artificially reduced flows (without complete cessation of flow). We considered the effects of low water volume on habitat conditions and on invertebrate community structure, behavior, and biotic interactions. Decreases in discharge usually cause decreased water velocity, water depth, and wetted channel width; increased sedimentation; and changes in thermal regime and water chemistry. Invertebrate abundance increases or decreases in response to decreased flow, whereas invertebrate richness commonly decreases because habitat diversity decreases. Invertebrates differ in their environmental tolerances and requirements, and any loss of habitat area or alteration of food resources from decreased flow can influence organism behavior and biotic interactions. Invertebrate drift often increases immediately after flow reduction, although some taxa are more responsive to changes in flow than others. Natural low flows and artificially reduced flows have similar effects on invertebrates, but the severity (duration and magnitude) of the flow decrease can influence invertebrate responses. Certain invertebrate taxa are especially sensitive to flow decreases and might be useful indicators for reduced flows or flow restoration. The effect of low flow on streams is an important issue, but few empirical studies of the impacts of decreased flow on stream ecosystems have been done, and more manipulative experiments are needed to understand the ecological consequences of decreased flow.
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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.
Article
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.
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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
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In Europe, the Water Framework Directive (2000/60/EC) demands the achievement of a good ecological status for water bodies by 2015. However, it also defines exceptions to these objectives, such as a good ecological potential instead of a good ecological status or a more distant temporal horizon than 2015. Those exceptions may only be applied to heavily modified water bodies (HMWBs). This paper presents a method, P-IAHRIS, incorporated into the free software IAHRIS v2.2, that offers objective criteria for the preliminary designation of HMWBs downstream from irrigation dams, flood protection dams or drinking water supply dams. The procedure incorporates two indicators: (i) the P10%–90% indicator, which analyses the alterations in the flow regime associated with the range of natural variability defined by the 10th and 90th percentiles of the annual and monthly discharges; and (ii) the IHA-HMWB indicator, which assesses the changes in the magnitude, seasonality, variability and duration of natural flows. P-IAHRIS was applied to 103 water bodies in Spain. The functionality and versatility of the method have been proven and allow the fast and objective preliminary designation of HMWBs, both in the Mediterranean and Atlantic environments.
Article
1. Many ecosystems are influenced simultaneously by multiple stressors, and the consequences of stressors are often unpredictable on the basis of knowledge of single effects. Agriculture affects streams world-wide via nutrient enrichment, elevated fine sediment and water abstraction for irrigation, but the combined impacts of these stressors are unknown. 2. We manipulated all three stressors simultaneously in an 18-day experiment and determined their individual and pair-wise combined effects on benthic invertebrates, algal biomass and leaf decay. We added nutrients (phosphorus plus nitrogen) and/or fine sediment (grain size 0·2 mm) to 18 experimental stream channels (dimensions 250 × 15 × 15 cm) supplied with water from a nearby stream. Three sediment and three nutrient treatments (high, intermediate, natural) were applied to each of six channels while flow was reduced by 80% in half the channels. Invertebrates (composition, abundance) and algae (chlorophyll a) were assayed using ceramic tile substrata and leaf decay was assayed using bundled leaves of a native shrub. Invertebrates colonizing leaf packs were also sampled. 3. Effects of sediment addition and flow reduction on biological response parameters were twice as common as nutrient enrichment effects. Nutrient enrichment increased total invertebrate abundance on tiles, algal biomass accrual and leaf decay rates, whereas both sediment addition (at the highest level) and flow reduction had mostly negative effects (e.g. reduced algal biomass, invertebrate abundance and/or taxonomic richness). 4. Stressors interacted often, and interactions between sediment and flow were particularly common. The negative impact of added sediment on aquatic biota was stronger at reduced flow, especially on tile substrata that were more exposed to the current than leaf-pack substrata. 5. Synthesis and applications. Our key findings imply that abstracting water from a stream already subjected to high fine sediment inputs may have far worse effects on the invertebrate fauna than abstraction from a similar stream with lower sediment levels. Aquatic resource managers should be aware of this important interaction between multiple stressors.
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1. How big is the difference in the herbaceous layer composition between flooded and unflooded stands? 2. Are there species or species groups which have an affinity to ancient vs. recent forests in stands with different water regimes? 3. Are patterns of life history traits different between flooded and unflooded stands as well as between ancient and recent forests in stands with a different water regime? Floodplain forests in the Middle Elbe region and district of Leipzig, Central Germany. The herbaceous layer was studied in randomly selected quadrats of 9 m(2) in 2000 and 2001. Six ancient (n(plot)=59) and six adjacent recent forests (n(plot=)108) were investigated in flooded stands as well as three ancient (n(plot)=41) and three recent forests (n(plot)=70) in stands that have not been flooded for 50 years. The association of single species, species groups and life history traits were statistically tested for flooded vs. unflooded stands and for ancient vs. recent forests. Interruption of flooding caused a complete species turnover in the herbaceous layer composition. Whereas in the still flooded stands typical alluvial species prevail, species composition in stands without flooding for 50 years showed a closed relation to the Stellario-Carpinetum. Six herbaceous species in the flooded and five in the unflooded stands showed a preference for ancient forests. Only one species in the flooded and six herbaceous species in the unflooded stands are significantly associated with recent forests. Life history traits differ between flooded and unflooded stands but are similar in ancient and recently flooded stands, while unflooded ancient forests have more geophytes and myrmecochorous species than recent forests. The specificity of species composition in floodplain forests can only be maintained by regular flooding. Interruption of inundations lead to differences in the patterns of species composition and life history traits between ancient and recent forests.
Article
Ecological integrity in floodplain rivers is based in part on a diversity of water bodies with differing degrees of connectivity with the main river channel. Collectively, these water bodies occupy a wide range of successional stages, thereby forming a mosaic of habitat patches across the floodplain. This diversity is maintained by a balance between the trend towards terrestrialization and flow disturbances that renew connectivity and reset successional sequences. To counter the influence of river regulation, restoration efforts should focus on re-establishing dynamic connectivity between the channel and floodplain water bodies. -from Authors
Chapter
IntroductionDefinition of DisturbanceDisturbances and ResponsesDisturbance and RefugiaFloodsDroughtsThe Responses to FloodsResponses to DroughtSummaryHydrological Disturbances and Future ChallengesAcknowledgementsReferences
Article
Key Words flooding, drying, human impact s Abstract Streams in mediterranean-climate regions (areas surrounding the Mediterranean Sea, parts of western North America, parts of west and south Australia, southwestern South Africa and parts of central Chile) are physically, chemically, and biologically shaped by sequential, predictable, seasonal events of flooding and drying over an annual cycle. Correspondingly, aquatic communities undergo a yearly cycle whereby abiotic (environmental) controls that dominate during floods are reduced when the discharge declines, which is also a time when biotic controls (e.g. predation, compe-tition) can become important. As the dry season progresses, habitat conditions become harsher; environmental pressures may again become the more important regulators of stream populations and community structure. In contrast to the synchronous input of autumn litterfall in forested temperate streams, riparian input to mediterranean-type streams is more protracted, with fall and possibly spring peaks occurring in streams in the Northern Hemisphere and a summer peak existing in their Southern Hemisphere counterparts. We present 25 testable hypotheses that relate to the influence of the stream hydrograph on faunal richness, abundance, and diversity; species coexistence; seasonal changes in the relative importance of abiotic and biotic controls on the bi-otic structure; riparian inputs and the relative importance of heterotrophy compared to autotrophy; and the impact of human activities on these seasonally water-stressed streams. Population increases in mediterranean-climate regions (particularly in fer-tile regions) result in an intensification of the competition for water among different users; consequently, water abstraction, flow regulation, increased salinity, and pollu-tion severely limit the ability of the streams to survive as sustainable, self-regulated systems.
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