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Droughts and resulting low flows are a threat for society, economy, and ecosystems. Droughts are natural phenomena, but anthropogenic water use can increase the pressure on water resources. To analyze the effects of changing land-use or water management and climate variability/change on water resources, models integrating the most important hydrological processes are needed. These models must account for natural processes and water resources management at different spatial and temporal scales, e.g., reservoir operation, water withdrawals. Low flow indices are analyzed for observed and simulated flows for the highly managed São Francisco river basin in Brazil, showing that during wet, normal, and moderately dry years, the existing reservoir system is able to augment low flows while during strong droughts the system reaches its limits. This effect is also represented in the simulations using the eco-hydrological model SWIM, which was adapted to account for regionspecific characteristics of land-use and water management. While good to very good performance was achieved for calibration and validation for most gauges, for some gauges at tributaries only insufficient quantitative criteria are reached. The reasons for the deviation between observations and simulation results are discussed. Overall, the model is able to represent natural discharges and observed, managed discharges. [ABSTRACT FROM AUTHOR]

Scenarios have become a key tool for supporting sustainability research on regional and global change. In this study we evaluate four regional scenario assessments: first, to explore a number of research challenges related to sustainability science and, second, to contribute to sustainability research in the specific case studies. The four case studies used commonly applied scenario approaches that are (i) a story and simulation approach with stakeholder participation in the Oum Zessar watershed, Tunisia, (ii) a participatory scenario exploration in the Rwenzori region, Uganda, (iii) a model-based prepolicy study in the Inner Niger Delta, Mali and (iv) a model coupling-based scenario analysis in upper Thukela basin, South Africa. The scenario assessments are evaluated against a set of known challenges in sustainability science, with each challenge represented by two indicators, complemented by a survey carried out on the perception of the scenario assessments within the case study regions. The results show that all types of scenario assessments address many sustainability challenges, but that the more complex ones based on story and simulation and model coupling are the most comprehensive. The study highlights the need to investigate abrupt system changes as well as governmental and political factors as important sources of uncertainty. For an in-depth analysis of these issues, the use of qualitative approaches and an active engagement of local stakeholders are suggested. Studying ecological thresholds for the regional scale is recommended to support research on regional sustainability. The evaluation of the scenario processes and outcomes by local researchers indicates the most transparent scenario assessments as the most useful. Focused, straightforward, yet iterative scenario assessments can be very relevant by contributing information to selected sustainability problems. [ABSTRACT FROM AUTHOR]

Conventional water management strategies, that serve solely socio-economic demands and neglect changing natural conditions of the river basins, face significant challenges in governing complex human-hydrological systems, especially in the areas with constrained water availability. In this study we assess the possibility to harmonize the inter-sectoral water allocation scheme within a highly altered human-hydrological system under reduction in water availability, triggered by projected climate change applying scenario-based approach. The Tagus River Basin headwaters, with significant disproportion in the water resources allocation between the environmental and socio-economic targets were taken as a perfect example of such system out of balance. We propose three different water allocation strategies for this region, including two conventional schemes and one imposing shift to sustainable water management and environmental restoration of the river. We combine in one integrated modelling framework the eco-hydrological process-based Soil and Water Integrated Model (SWIM), coupled with the conceptual reservoir and water allocation modules driven by the latest bias-corrected climate projections for the region and investigate possible water allocation scenarios in the region under constrained water availability in the future. Our results show that the socio-economic demands have to be re-considered and lowered under any water allocation strategy, as the climate impacts may significantly reduce water availability in the future. Further, we show that a shift to sustainable water management strategy and river restoration is possible even under reduced water availability. Finally, our results suggest that the adaptation of complex human-hydrological systems to climate change and a shift to a more sustainable water management are likely to be parts of one joint strategy to cope with climate change impacts. [ABSTRACT FROM AUTHOR]

This study assesses future flood risk in the Niger River Basin (NRB), for the first time considering the simultaneous effects of both projected climate change and land use changes. For this purpose, an ecohydrological process-based model (SWIM) was set up and validated for past climate and land use dynamics of the entire NRB. Model runs for future flood risks were conducted with an ensemble of 18 climate models, 13 of them dynamically downscaled from the CORDEX Africa project and five statistically downscaled Earth System Models. Two climate and two land use change scenarios were used to cover a broad range of potential developments in the region. Two flood indicators (annual 90th percentile and the 20-year return flood) were used to assess the future flood risk for the Upper, Middle and Lower Niger as well as the Benue. The modeling results generally show increases of flood magnitudes when comparing a scenario period in the near future (2021–2050) with a base period (1976–2005). Land use effects are more uncertain, but trends and relative changes for the different catchments of the NRB seem robust. The dry areas of the Sahelian and Sudanian regions of the basin show a particularly high sensitivity to climatic and land use changes, with an alarming increase of flood magnitudes in parts. A scenario with continuing transformation of natural vegetation into agricultural land and urbanization intensifies the flood risk in all parts of the NRB, while a “regreening” scenario can reduce flood magnitudes to some extent. Yet, land use change effects were smaller when compared to the effects of climate change. In the face of an already existing adaptation deficit to catastrophic flooding in the region, the authors argue for a mix of adaptation and mitigation efforts in order to reduce the flood risk in the NRB. [ABSTRACT FROM AUTHOR]

Semi-arid regions are known for erratic precipitation patterns with significant effects on the hydrological cycle and water resources availability. High temporal and spatial variation in precipitation causes large variability in runoff over short durations. Due to low soil water storage capacity, base flow is often missing and rivers fall dry for long periods. Because of its climatic characteristics, the semi-arid north-eastern region of Brazil is prone to droughts. To counter these, reservoirs were built to ensure water supply during dry months. This paper describes problems and solutions when calibrating and validating the eco-hydrological model SWIM for semi-arid regions on the example of the Pajeú watershed in north-eastern Brazil. The model was calibrated to river discharge data before the year 1983, with no or little effects of water management, applying a simple and an enhanced approach. Uncertainties result mainly from the meteorological data and observed river discharges. After model calibration water management was included in the simulations. Observed and simulated reservoir volumes and river discharges are compared. The calibrated and validated models were used to simulate the impacts of climate change on hydrological processes and water resources management using data of two representative concentration pathways (RCP) and five earth system models (ESM). The differences in changes in natural and managed mean discharges are negligible (< 5%) under RCP8.5 but notable (> 5%) under RCP2.6 for the ESM ensemble mean. In semi-arid catchments, the enhanced approach should be preferred, because in addition to discharge, a second variable, here evapotranspiration, is considered for model validation. [ABSTRACT FROM AUTHOR]

The regional climate as it is now and in the future will put pressure on investments in sub-Saharan Africa in water resource management, fisheries, and other crop and livestock production systems. Changes in oceanic characteristics across the Atlantic Ocean will result in remarkable vulnerability of coastal ecology, littorals, and mangroves in the middle of the twenty-first century and beyond. In line with the countries' objectives of creating a green economy that allows reduced greenhouse gas emissions, improved resource efficiency, and prevention of biodiversity loss, we identify the most pressing needs for adaptation and the best adaptation choices that are also clean and affordable. According to empirical data from the field and customized model simulation designs, the cost of these adaptation measures will likely decrease and benefit sustainable green growth in agriculture, water resource management, and coastal ecosystems, as hydroclimatic hazards such as pluviometric and thermal extremes become more common in West Africa. Most of these adaptation options are local and need to be scaled up and operationalized for sustainable development. Governmental sovereign wealth funds, investments from the private sector, and funding from global climate funds can be used to operationalize these adaptation measures. Effective legislation, knowledge transfer, and pertinent collaborations are necessary for their success. [ABSTRACT FROM AUTHOR]

The precariousness of the rural population in Africa is often symbolized by the lack of potable and safe drinking water. This study investigates the physico-chemical and bacteriological characteristics of 32 water samples with respect to WHO standards. The water samples were collected from wells, boreholes and small drinking water supply systems (DWS) in and around the township of Bonkoukou (Niger). The Water Quality Index (WQI) tool was used to assess the overall water quality with different physico-chemical parameters. Where the pH of the samples was acceptable, the samples showed higher levels of mineralization and deoxygenation. Overall, the samples were slightly hard, chlorinated and sulfated but much alkaline and contained nitrate and nitrite ions 2-16 times higher than the WHO standards. The use of WQI shows that samples in the DWS are safe for drinking. Samples coming from wells are the most polluted (58.50%) compared to those taken from boreholes (53.00%), while the percentage of samples from boreholes, unfit for drinking, is higher (41.00%) than that of the samples taken from wells (25.00%). Moreover, water in this area was characterized by the presence of total germs indicating bacteriological pollution. Hence, for the supply of safe drinking water to the larger number of people in such a rural area, the capacity of actual DWS must be improved and widespread. [ABSTRACT FROM AUTHOR]

In regional climate impact studies, good performance of regional models under present/historical climate conditions is a prerequisite for reliable future projections. This study aims to investigate the overall performance of 9 hydrological models for 12 large-scale river basins worldwide driven by the reanalysis climate data from the Water and Global Change (WATCH) project. The results serve as the basis of the application of regional hydrological models for climate impact assessment within the second phase of the Inter-Sectoral Impact Model Intercomparison project (ISI-MIP2). The simulated discharges by each individual hydrological model, as well as the ensemble mean and median series were compared against the observed discharges for the period 1971-2001. In addition to a visual comparison, 12 statistical criteria were selected to assess the fidelity of model simulations for monthly hydrograph, seasonal dynamics, flow duration curves, extreme floods and low flows. The results show that most regional hydrological models reproduce monthly discharge and seasonal dynamics successfully in all basins except the Darling in Australia. The moderate flow and high flows (0.02-0.1 flow exceedance probabilities) are also captured satisfactory in many cases according to the performance ratings defined in this study. In contrast, the simulation of low flow is problematic for most basins. Overall, the ensemble discharge statistics exhibited good agreement with the observed ones except for extremes in particular basins that need further scrutiny to improve representation of hydrological processes. The performances of both the conceptual and process-based models are comparable in all basins. [ABSTRACT FROM AUTHOR]

The Soil and Water Integrated Model (SWIM) is a continuous-time semi-distributed ecohydrological model, integrating hydrological processes, vegetation, nutrients and erosion. It was developed for impact assessment at the river basin scale. SWIM is coupled to GIS and has modest data requirements. During the last decade SWIM was extensively tested in mesoscale and large catchments for hydrological processes (discharge, groundwater), nutrients, extreme events (floods and low flows), crop yield and erosion. Several modules were developed further (wetlands and snow dynamics) or introduced (glaciers, reservoirs). After validation, SWIM can be applied for impact assessment. Four exemplary studies are presented here, and several questions important to the impact modelling community are discussed. For which processes and areas can the model be used? Where are the limits in model application? How to apply the model in data-poor situations or in ungauged basins? How to use the model in basins subject to strong anthropogenic pressure? Editor D. Koutsoyiannis; Associate editor C. Perrin [ABSTRACT FROM AUTHOR]

Participatory research has in recent years become a popular approach for problem-oriented scientific research that aims to tackle complex problems in a real management context. Within the European Union project NeWater, stakeholder processes were initiated in seven case studies to develop approaches for adaptive water management. The Uzbek part of the Amudarya River basin was one of the studied river basins. However, given the current political and cultural context in Uzbekistan, which provides little room for stakeholder participation, it was unclear to what extent participation could be realized there. In this paper, we present an evaluation of the participatory research carried out in the Amudarya case study with respect to (i) the choice and application of different participatory methods and their adaptation to the given political, socioeconomic, and cultural environment, (ii) their usefulness in improving system understanding and developing strategies and measures to improve water management and monitoring, and (iii) their acceptance and suitability for enhancing policy-making processes in the Amudarya River basin context. The main lessons learned from the comparison of the different participatory methods were (1) the stakeholder process provided an opportunity for meetings and discussions among stakeholders from different organizational levels and thus promoted communication between different levels and organizations, and (2) in a context where most stakeholders are not generally involved in policy-making, there is a danger of raising expectations that a research project cannot meet, e.g., of transferring local interests to higher levels. Our experience shows that in order to choose participatory methods and adapt them to the Uzbek cultural and political setting (and most likely this applies to other post-Soviet transition countries as well), four aspects should be taken into account: the time required to prepare and apply the method, good information about the participants and the context in which the method will be applied, knowledge of the local language(s), and careful training of local moderators. While these aspects are relevant to any application of participatory methods, they become even more important in a political and socio-cultural setting such as that found in Uzbekistan. One added value of the activities and a crucial aspect of a participatory research processes was the capacity building of local scientists and practitioners, which facilitates the further application of the methods. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of the FLUMAGIS project, in which we developed a spatial decision support system (SDSS) to support the implementation of the European Water Framework Directive (WFD). The modelling approach is based on the integration of ecological and socio-economic assessment methods, scale-specific and GIS-based data and knowledge modelling and visualization techniques. The project study area is the intensively cropped Upper Ems River Basin in north-western Germany. A method was developed that enables the transfer of scale-specific data and information. Analyses were performed for baseline conditions and specific management and planning scenarios to improve water quantity and quality at micro-, meso- and macro-scale. The results of the study indicate that substantial, expensive water and land management changes at different scales would be necessary to achieve the WFD water quality targets in this basin. Ecological-economic analysis of cost-effectiveness reveals that the costs of achieving certain goals of the WFD can vary more than tenfold depending on which measure is chosen out of the pool of management alternatives. Moreover, the study shows that the differentiation between landscapes and other regional characteristics although considered essential to the successful implementation of WFD measures is very data intensive. [Copyright &y& Elsevier]

A correction is presented to the article "Evaluation of an ensemble of regional hydrological models in 12 large-scale river basins worldwide" that was published online on January 6, 2017.