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The planform rotation of river basins has been used as a marker of crustal strain and been used to assess the style and rates of on‐fault deformation. We use the geometry of river basins to evaluate horizontal deformation associated with the South China–North China relative block motion in the east Qinling mountains. The long‐time average slip rates of the Luonan fault and Shangdan fault are constrained as 0.31 mm/year and 0.3–0.6 mm/year, respectively. According to the latest GPS, we believe that a minor portion of the crustal strain of relative block motion between North China and South China was partitioned into the east Qinling strike‐slip fault system, leaving a major portion of deformation to be accommodated by southern North China (SNC). We conclude that the eastward extrusion of South China cannot explain the present deformation of the entire eastern China, and more attention should be paid into the SNC. [ABSTRACT FROM AUTHOR]

Structural control on drainage patterns has long been suggested to play an important role in the development of fluvial systems, including their map pattern. Along the western Taiwan orogenic wedge, a prominent drainage pattern change is present, from predominantly orogen parallel drainages in the south to river systems that flow perpendicular to the long axis of the mountain belt in the north. Such change likely reflects the temporal evolutionary process as the Taiwan orogen propagates southward. We propose that the flow direction change of river systems is produced by the development of the fold‐and‐thrust belt on the pro‐wedge side of the mountain belt and is facilitated by drainage reorganization that includes abrupt drainage captures and more gradual divide movements, permitting drainage basins to attain a geometrically stable configuration with time. Our observations in Taiwan demonstrate not only how tectonic uplift is effective at modifying river patterns in the early stages of orogenic development but also how time and increased stream power encourage river networks to adjust to more effective patterns in mature mountain belts. [ABSTRACT FROM AUTHOR]

India witness floods during the summer monsoon (June–September) that disproportionately affect the socioeconomic well‐being of millions of people. Nonstructural measures such as flood early warning systems play a crucial role in mitigating the impacts; however, these require a proper understanding of flood drivers. The drivers of floods in the Indian river basins have not been examined for the observed and projected future climate. Here using a novel framework, we examine antecedent moisture conditions and precipitation characteristics before high flow events. We estimate the probability of occurrence of flood drivers and their association with peak flood magnitude under the observed and projected future climate in Indian river basins. Multiday precipitation, a proxy to heavy precipitation on wet soil conditions, was found as the predominant flood driver in the observed and projected future climate. We show that multiday precipitation is more prominent driver than extreme soil moisture conditions in larger rivers basins while extreme precipitation drives floods in smaller river basins. The frequency of major drivers of floods is projected to rise in the future, which may pose a greater risk to agriculture and infrastructure under the warming climate. Key Points: Multiday precipitation is the prominent driver of high flows in Indian River basins in the observed and projected future climateMore than 70% of the time when extreme precipitation (EP) precedes high flow events, EP occurs on wet antecedent conditionsA significant increase in the frequency of high flow days, extreme precipitation, and multiday precipitation is projected [ABSTRACT FROM AUTHOR]

When assessing the socio‐economic impacts of climate change, it is sensible to make targeted climate projections for regions of high population density and economy activity. Much of human activity is concentrated at river basins, yet it has been difficult to resolve the complex boundaries of these basins in coarse resolution global climate models. The latest high‐resolution observation and climate projection datasets enable such basin‐based evaluations now, and this study assesses the historical and projected climate changes over three major river basins in China—the Yellow, Yangtze and Pearl River basins. Based on CN05.1 dataset, the Yellow River basin has significantly warmed by about 1.8°C over the past five decades, far more than the other two basins. The change in temperature extremes has been as severe, with the annual maxima of daily maximum temperatures (TXx) increasing by 1.5°C, and the annual minima of daily minimum temperatures (TNn) increasing by 2.5°C. Precipitation over the Yangtze River has significantly increased by about 0.2 mm·day−1, while changes over the other two basins were not statistically significant. The uncertainty in the change of precipitation was greater than that of temperature. A selection of simulations from the Fifth and Sixth Coupled Model Intercomparison Projects (CMIP5 and CMIP6) were validated against the CN05.1 dataset for the historical period of 1961–2018. Changes in temperature indices were well‐reproduced, but changes in precipitation indices poorly so. CMIP6 models performed better than the CMIP5 models. Both CMIP5 and CMIP6 multi‐model ensembles (MMEs) projected about 1.0–2.0°C warming over China and the three river basins by 2015–2050. Both MMEs projected wetting trends over most parts of China and the three river basins. Both warming and wetting were projected to accelerate with time, particularly warming over the Yellow River basin, and wetting over the Pearl River basin. [ABSTRACT FROM AUTHOR]

Amphibians show a high amount of species richness and endemism. Such diversity can be attributed to their microenvironment as amphibians display fine‐scale heterogeneity depending on the microhabitats they inhabit. Tadpoles are considered as good indicators for understanding microhabitat–species association as they reflect the breeding sites and signify species survival potential. In this study, we assessed the microhabitat factors influencing the distribution of tadpoles of three endemic frogs of the genus Nyctibatrachus namely N. jog, N. kempholeyensis, and N. kumbara from central Western Ghats, India. Forty‐three streams were sampled from three river basins, and stream characteristics were analyzed using generalized linear models. The results indicate that the tadpoles show specific microhabitat preferences and spatial niche partitioning. Among microhabitat variables, the slope significantly influenced the distribution of tadpoles of N. jog and N. kempholeyensis. The tadpoles of N. jog preferred steep slopes, while N. kempholeyensis tadpoles were found in gradual slopes with low water depth. For N. kumbara tadpoles, water temperature significantly influenced their distribution in the streams. Such spatial heterogeneity promotes the coexistence of these species supporting the niche theory. The study advances the understanding of how amphibian diversity from the Western Ghats is shaped at the microhabitat scale. The perennial streams that the Nyctibatrachus tadpoles inhabit are at risk due to anthropogenic activities. The findings of this study provide important baseline data that could be useful for the conservation of the endemic anurans in the Western Ghats, India. [ABSTRACT FROM AUTHOR]

Reservoirs are mostly managed at local scales as spatially independent units. A basin‐scale perspective may increase awareness at a broader scope and generate insight not evident at local scales. We examined the array of reservoir attributes and fisheries in the Mississippi Basin to identify management opportunities. The basin is the third largest in the world and includes over 1,700 reservoirs >100 ha, the most of any river basin. Our bird's‐eye view shows a piecemeal approach where reservoirs are mostly administered at the local level. Basin‐wide or catchment coordination to holistically address problems that recur across the basin is mostly lacking. A basin‐wide coordination arrangement could facilitate various facets of reservoir management. We reviewed governance arrangements in major river basins across the globe and concluded that the basin‐wide administrative layer we encourage for the Mississippi Basin may already exist in some basins but may not be directly applicable everywhere. [ABSTRACT FROM AUTHOR]

This study investigates possible impacts of four global warming levels (GWLs: GWL1.5, GWL2.0, GWL2.5, and GWL3.0) on drought characteristics over Niger River basin (NRB) and Volta River basin (VRB). Two drought indices—Standardized Precipitation Index (SPI) and Standardized Precipitation‐Evapotranspiration Index (SPEI)—were employed in characterizing droughts in 20 multi‐model simulation outputs from the Coordinated Regional Climate Downscaling Experiment (CORDEX). The performance of the simulation in reproducing basic hydro‐climatological features and severe drought characteristics (i.e., magnitude and frequency) in the basins were evaluated. The projected changes in the future drought frequency were quantified and compared under the four GWLs for two climate forcing scenarios (RCP8.5 and RCP4.5). The regional climate model (RCM) ensemble gives a realistic simulation of historical hydro‐climatological variables needed to calculate the drought indices. With SPEI, the simulation ensemble projects an increase in the magnitude and frequency of severe droughts over both basins (NRB and VRB) at all GWLs, but the increase, which grows with the GWLs, is higher over NRB than over VRB. More than 75% of the simulations agree on the projected increase at GWL1.5 and all simulations agree on the increase at higher GWLs. With SPI, the projected changes in severe drought is weaker and the magnitude remains the same at all GWLs, suggesting that SPI projection may underestimate impacts of the GWLs on the intensity and severity of future drought. The results of this study have application in mitigating impact of global warming on future drought risk over the regional water systems. [ABSTRACT FROM AUTHOR]

Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water‐energy‐food‐environmental (WEFE) "nexus" sectors. A range of views on the extent to which such natural‐human systems should be developed typically exists. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimized) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade‐offs. We apply the approach to Tanzania's Rufiji river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritize energy production adversely affect environmental performance; however, part of the negative impacts can be minimized through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental‐oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade‐offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin‐scale interdependencies. Benefits and limitations of the approach and its application are discussed. Plain Language Summary: Infrastructure in water‐energy‐food‐environment systems such as dams can play a beneficial role in supporting hydropower production and regulating the variability of river flow. However, these benefits often come with negative environmental impacts on wildlife, affect income from other economic sectors, and can damage river‐linked ecosystems (e.g., wetlands, floodplains, riverine forests, and mangroves). System‐scale option assessment approaches that consider the different relevant issues simultaneously help identify infrastructure and operating policy designs with acceptable balances of potential benefits and impacts. While optimized model‐based assessments can balance outcomes across performance metrics, this is contingent on the need for effective coordination between sectors and between upstream‐downstream developments. One way to help design future systems is to compare the energy, agricultural, and environmental conservation trade‐offs implied by different extents of development (i.e., realization of various reservoirs and irrigation schemes). We apply such a multisector spatial computer‐aided design approach to the Rufiji river basin in Tanzania and consider linkages across the water‐energy‐food‐environment sectors. Results show considerable potential for infrastructure development in the basin but highlight important trade‐offs between the sectors, particularly how downstream performance indicators are affected by upstream cumulative effects of informal irrigation expansion, something that may be difficult to regulate in the future. Key Points: System wide multi‐sector assessments reveal the benefits of coordinated interventions and help identify sectoral trade‐offsTrade‐offs between water, energy, food and environment can be optimised under different scenarios of river basin developmentMulti‐criteria decision‐making methods can inform collaborative water‐energy‐food‐environment system planning in Tanzania [ABSTRACT FROM AUTHOR]

Environmental Flows (EFlows) are defined as the quantity, timing and quality of the flow of water, sediment and biota necessary to sustain freshwater and estuarine ecosystems, and the human livelihoods and well‐being that depend on these ecosystems. As such they are a vital component of Integrated Water Resource Management (IWRM). A recent survey found that, in general, Africa lags behind schedule with respect to the global SDG Target 6.5 to implement IWRM at all levels, including through transboundary cooperation as appropriate. This web‐based review explores progress made in EFlows Assessments and implementing their outcomes in southern Africa. It outlines the apparent impetus to the uptake of EFlows provided by legislation, common funding mechanisms for EFlows assessment and evolving trends in EFlows assessment. It also highlights instances of implementation of EFlows in both in‐country and transboundary settings. [ABSTRACT FROM AUTHOR]

Freshwater is one of the most critical elements for sustainable development of ecosystems and societies. River basins, concomitant with administrative zones, form a common unit for freshwater management. So far, no comprehensive, global analysis exists that would link the ecological challenges of the planet's river basins to the capacity of the societies to cope with them. We address this gap by performing a geospatial resilience analysis for a global set of 541 river basins. We use the social‐ecological systems approach by relating three ecological vulnerability factors (human footprint, natural hazards, and water scarcity) with three adaptive capacity factors (governance, economy, and human development), based on temporal trajectories from 1990 to 2015. Additionally, we examine resilience by subtracting ecological vulnerability from adaptive capacity. The most striking result is the fundamentally different patterns of controlling factors of the resilience in different developing regions, particularly those of Africa and Asia. Their root causes are particularly low adaptive capacity in Africa and high ecological vulnerability in Asia. Alarmingly, the difference between those continents grew within the study period. Finally, this study highlights the rapid dynamics of adaptive capacity in comparison to ecological vulnerability, the latter having more inertia. Their fragile balance is of our interest; they can either support or counteract each other depending on the geographic location. Plain language summary: The ongoing global environmental change highlights the critical role of freshwater for sustainable development of ecosystems and human societies. Resilience is the capacity to absorb disturbance and reorganize while undergoing changes. In this study, we perform a spatial analysis for 541 watersheds to identify the drivers of this resilience. We define resilience of each basin by first examining their adaptive capacity, which is a combination of governance, economy, and human development. We then define ecological vulnerability by combining human footprint, natural hazards, and water scarcity into one index. To conclude, resilience indicates the strength of community's adaptive capacity in the presence of ecological vulnerability. Our results indicate the different patterns resilience across the globe, pointing out how the similarly low resilience in Africa and Asia is caused by low adaptive capacity and high ecological vulnerability, respectively. Our temporal analysis 1990–2015 shows how this difference has been increasing over time. Interestingly, adaptive capacity was more dynamic over time, compared to more constant ecological vulnerability. The examined balance between adaptability and vulnerability provides a useful tool for managing the resilience of freshwater resources. Key Points: We quantify resilience of the world's river basins using geospatial social‐ecological systems approachThe approach uses composite indicators of both adaptive capacity and ecological vulnerabilityAfrica and Asia show the lowest resilience, which is due to low adaptive capacity in Africa and high ecological vulnerability in Asia [ABSTRACT FROM AUTHOR]

Based on recent water quality data collected from 763 monitoring sections nationwide, this study examined the concentration of major pollutants in China's major rivers. A spatial autocorrelation analysis confirmed that river pollution was spatially uneven and clustered. While pollution of surface water was a nationwide concern, most serious water pollution happened in the Huai, Hai, Yellow, and Liao river Basins in Northern China. The results of the spatial regression analysis showed that GDP per capita, surface water stock, population, and economic structure were all significantly correlated with surface water pollution, with population having strongest impact, followed by level of economic development. By investigating the common characteristics shared by the "hotspot" cities where serious water pollution occurred, this study recommended a regional or basin approach to assessing water quality and controlling river pollution that cuts across jurisdiction boundaries. While China has made considerable progress in improving water productivity, there is still enormous potential in water conservation. It is also imperative to restructure local economy and develop water‐efficient, less polluting industries and services. Practitioner points: River pollution in China was spatially uneven and clustered.Most serious water pollution happened in the Huai, Hai, Yellow, and Liao river basins in Northern China.GDP per capita, surface water stock, population, and economic structure correlated with surface water pollution, with population having strongest impact.A regional or basin approach was recommended to assess water quality and controlling river pollution across jurisdiction boundaries.It is also imperative to restructure local economy and develop water‐efficient, less polluting industries and services. [ABSTRACT FROM AUTHOR]

Many pharmaceuticals inevitably end up in surface waters, exerting unwanted biological activity in nontarget organisms. This effect is confined by the compound's environmental persistence. Regulatory laboratory simulation tests are used in persistence assessment and exposure modeling. While doubt has been expressed about the usefulness of laboratory‐derived persistence indicators under field conditions, these remain the only inputs for chemical fate models due to difficulties of measuring persistence in situ, especially at large scales. To improve understanding about relationships between laboratory experiments and the environmental fate in streams, we developed a mathematical model of biodegradation in stream networks and combined it with in‐stream monitoring data to (i) test if persistence could be evaluated from field data, (ii) check if persistence extracted from laboratory tests applied in the field, and (iii) locate hot spots of biodegradation in a large river basin. The model describes partitioning, and particle settling and resuspension, and is structurally compatible with those applied for evaluating laboratory simulation tests. Application to the Rhine river basin suggests that biotransformation rate constants extracted from laboratory tests underestimate those in the field, yet the percentage of biotransformation in the Rhine basin is less than in the laboratory tests due effective biotransformation being limited to small‐ and medium‐sized streams. In conclusion, our data show that biotransformation rates can accurately be predicted if (i) monitoring is performed across a wide range in stream order and (ii) precise estimates for consumption and removal rates at wastewater treatment plants are known. Key Points: Biotransformation of pharmaceuticals takes place in small to medium streamsOECD 308 tests underestimate pharmaceutical biotransformation rates yet overestimate total degradation in the Rhine basinAssessment of pharmaceutical persistence from measured river fluxes is conditional on precise emission and removal data [ABSTRACT FROM AUTHOR]

Abstract: River networks play a key role in the spatial organization of human settlements. Both river networks and human settlements have been found to exhibit regular self‐similar patterns, but little is known about the generalized spatial patterns of human settlements embedded within river networks. Here based on night light data, we find a universal fractal structure at the global scale, with both robust Hortonian scaling relationships with the extent of human settlements and statistically significant power law scaling of the power spectra of human area functions. Globally, we find consistent patterns of power law preferential downstream clustering of human settlements across all six populated continents, typically up to 40% of the maximum flow length. This downstream clustering suggests an optimum distribution of humans in large river basins for trade, transport, and natural resource utilization but with attendant implications for human impacts on rivers. Recognition of such spatial patterns helps generalize assessments of human impacts on rivers, with direct implications for management of water quality and biological diversity in river networks. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the nonlinearity of runoff response to global mean temperature (GMT) change in the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models at the river basin scale globally. Results show that changes in long‐term mean annual runoff are nonlinear with GMT rise over most extended subtropical basins, suggesting that estimation of future runoff change derived from the linear scaling relations would be biased. As for the interannual variability, nonlinearities are apparent mainly in central and western Asia, southern and western Africa, most of Europe, and Australia when GMT increases beyond 1.5°C. This suggests that impacts of climate change under 1.5°C GMT rise on runoff variability should not be simply scaled from that under a 2°C warming world. Our results highlight the contrasting response of areal runoff to GMT rise across global major river basins and reveal the threshold of GMT increment at which the nonlinear runoff response is projected to emerge. [ABSTRACT FROM AUTHOR]

Much of our understanding of competition comes from observations in sessile systems, such as rainforests and marine invertebrate communities. In terrestrial systems, sessile species often compete for multiple limiting resources (i.e., space, light, and nutrients), but in marine systems, space is viewed as the primary or sole limiting resource. Competition theory, on the other hand, suggests that competition for a single limiting resource is unlikely to maintain high species diversity, but manipulative tests of competition for other resources in marine benthic systems are exceedingly rare. Here, we manipulate the availability of food for a classic system, marine sessile invertebrate communities, and investigate the effects on species diversity, abundance, and composition during early succession as well as on the growth of bryozoan populations in the field. We found the number of species to be greater, available space to be lower, and the community composition to be different in assemblages subjected to increased food availability compared to controls. Similarly, laboratory-settled bryozoans deployed into the field grew more in the presence of enhanced food. Our results suggest that food can act as a limiting resource, affecting both diversity and abundance, even when bare space is still available in hard-substratum communities. Consequently, broadening the view of resource limitation beyond solely space may increase our understanding and predictability of marine sessile systems. [ABSTRACT FROM AUTHOR]

Biotic communities are shaped by adaptations from generations of exposure to selective pressures by recurrent and often infrequent events. In large rivers, floods can act as significant agents of change, causing considerable physical and biotic disturbance while often enhancing productivity and diversity. We show that the relative balance between these seemingly divergent outcomes can be explained by the rhythmicity, or predictability of the timing and magnitude, of flood events. By analyzing biological data for large rivers that span a gradient of rhythmicity in the Neotropics and tropical Australia, we find that systems with rhythmic annual floods have higher fish species richness, more stable avian populations, and elevated rates of riparian forest production compared with those with arrhythmic flood pulses. Intensification of the hydrological cycle driven by climate change, coupled with reductions in runoff due to water extractions for human use and altered discharge from impoundments, is expected to alter the hydrologic rhythmicity of floodplain rivers with significant consequences for both biodiversity and productivity. [ABSTRACT FROM AUTHOR]

ABSTRACT Contemporary patterns in river basin sediment dynamics have been widely investigated but the timescales associated with current sediment delivery processes have received much less attention. Furthermore, no studies have quantified the effect of recent land use change on the residence or travel times of sediment transported through river basins. Such information is crucial for understanding contemporary river basin function and responses to natural and anthropogenic disturbances or management interventions. To address this need, we adopt a process-based modelling approach to quantify changes in spatial patterns and residence times of suspended sediment in response to recent agricultural land cover change. The sediment budget model SedNet was coupled with a mass balance model of particle residence times based on atmospheric and fluvial fluxes of three fallout radionuclide tracers (7Be, excess 210Pb and 137Cs). Mean annual fluxes of suspended sediment were simulated in seven river basins (38-920 km2) in south-west England for three land cover surveys (1990, 2000 and 2007). Suspended sediment flux increased across the basins from 0.5-15 to 1.4-37 kt y-1 in response to increasing arable land area between consecutive surveys. The residence time model divided basins into slow (upper surface soil) and rapid (river channel and connected hillslope sediment source area) transport compartments. Estimated theoretical residence times in the slow compartment decreased from 13-48 to 5.6-14 ky with the increase in basin sediment exports. In contrast, the short residence times for the rapid compartment increased from 185-256 to 260-368 d as the modelled connected source area expanded with increasing sediment supply from more arable land. The increase in sediment residence time was considered to correspond to longer sediment travel distances linked to larger connected source areas. This novel coupled modelling approach provides unique insight into river basin responses to recent environmental change not otherwise available from conventional measurement techniques. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Wildfire can cause substantial changes to runoff, erosion and downstream sediment delivery processes. In response to these disturbance effects, the main sources of sediment transported within burned catchments may also change. Sediment tracing offers an approach to determine the proportional contributions of fine sediment (typically <63 µm) from burned catchment sources. In this paper, we review the application of various sediment tracers to discriminate fine sediment sources following wildfire. Fallout radionuclides provide the most effective tracers for discriminating hillslope surface and sub-surface (usually channel bank) sources. Previous tracer studies quantifying contributions from these sources after wildfire are based exclusively on radionuclides. The potential for fallout radionuclides to discriminate spatial sources defined according to burned and unburned areas depends on burn-related changes in surface soil concentrations. Tracing of burned and unburned source areas will be problematic where most radionuclides in surface material are bound to ash rather than soil. Geochemical properties of surface soils are probably too susceptible to natural and burn-related variability to consistently discriminate burn-defined spatial sources. Mineral magnetic properties have shown potential for discriminating soil burned at different severities as well as unburned areas. More research is needed to assess the use of soil organic compounds as tracers of burned source areas. Linking fallout radionuclide-based hillslope and channel source discrimination with process measurements and monitoring after fire can provide enhanced insight into fine sediment transfer and related water quality impacts. Adopting such integrated and multi-scale approaches would contribute to improved understanding of hydrological and geomorphological responses to wildfire. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Following the 2000 European Water Framework Directive and recent insights into sediment management on a river basin scale, we discuss in this paper an exposure model aiming to support a risk assessment for chemicals on a basin-wide scale. It establishes spatial relations between causes (pollution sources) and effects (ecological risk), taking into account the geometry, hydrology, and fine sediment dynamics of European river basins. The model, called EXPOBASIN, explicitly takes into account the interaction of chemicals with fine sediment particles, which is important for many policy-relevant chemicals, such as trace metals and polycyclic aromatic hydrocarbons, and it addresses the potential release of historically polluted sediments as a result of extreme floods, which is a major concern in different European river basins. Bioavailability and bioaccumulation are included in the assessment. As a result, the exposure can be quantified not only in terms of water concentrations, but also in terms of sediment concentrations and concentrations in biota. The primary question to be answered by EXPOBASIN is how chemicals, pollution sources, or both rank quantitatively and objectively on a basin-wide scale. Near the end of 2009, the tool will become available to all European water managers and their technical advisors, as a result of the European Union 6th Framework Programme project MODELKEY The calibration and validation of EXPOBASIN has only just started and will be completed in 2008/2009. Applications to 3 case study areas are planned in this respect. This paper presents the key building blocks of EXPOBASIN and shows some sample results illustrating the raking of pollution sources and chemicals. At the end of the paper, some perspectives for future developments are outlined. [ABSTRACT FROM AUTHOR]

This paper seeks to identify some promising policy options which could be part of a strategic and holistic effort to address India's future water challenges. Significant increases in agricultural water productivity would be a major factor in reducing the need for developing new water sources. Crop diversification, appropriately targeted to account for the present agricultural systems and available water resources, will increase productivity. Furthermore, much more emphasis needs to be placed on effective management of the groundwater resources through renewed efforts to enhance artificial recharge and conservation. Also, efforts should be revived to improve the existing surface irrigation systems. In particular, systems could be reconfigured to provide a more reliable water supply and allow effective community level management, where appropriate. Finally, while some of the increasing demands from domestic and industrial users will be met by the development of groundwater and reallocation of water from the agricultural sector, this will not be sufficient. Given that such conditions are emerging in states with high economic growth and relatively water scarce basins, this will require the further development of water resources. In some cases, these conditions along with the demand for reliable water for high value crops, will be part of the justification for inter-basin transfers. [ABSTRACT FROM AUTHOR]

Aim To deconstruct the biodiversity pattern of the 152 waterbird species breeding in Europe to better understand its multiple causal processes. Location Continental Europe, Iceland and the British Isles. Methods We considered the orders that are typically comprised by swimming, diving or wading birds, which inhabit marshes, fens, peatlands and fresh, brackish or salt waters, including coastal waters. We used the 55 main river basins of Europe as geographical units, and searched for either chorotypes (groups of similar species distributions) or gradual replacement of species throughout the river basins. Chorotypes were recognized by applying a probabilistic classification method to the distributions. Then we used GLM to characterize the extent and the species richness of each chorotype according to energy availability (higher levels of environmental energy favouring the presence of species), climatic stress due to an excess of energy, availability of water, productivity, seasonality and surface area. Results One hundred and forty species significantly aggregate into nine chorotypes. The other 12 species, most of them marine, are centred on Great Britain, dropping away progressively on coasts further away from there. Differences in either the availability of energy or climatic stress significantly characterized the distribution of seven chorotypes comprising 90.8% of the species. Main conclusions Chorotypes are meaningful and useful to deconstruct biodiversity patterns. Our results suggest that energy is the main factor related to the biogeographical patterns of breeding waterbirds in Europe, and provide an insight into regional trends of species richness previously analysed with a habitat-scale perspective. [ABSTRACT FROM AUTHOR]

Outlet point positions taken from hydrometric stations commonly do not coincide with stream locations extracted from digital elevation models (DEMs). This is a serious problem for accurate watershed delineation of data sets containing numerous outlets, which is critical in regional-scale studies that relate catchment characteristics to basin responses. The advanced outlet repositioning approach (AORA), presented here, replicates the processes involved in manual outlet placement while reducing inefficiency and potential for blunders. The technique uses water body names to identify locations for outlet repositioning that are consistent with nearby outlets. The AORA performance was compared against two existing automated techniques using 993 stations in seven basins in northwest England. The AORA had the fewest repositioning errors in each basin and nearly halved the overall number of errors in the data set, compared with the second-best method. This work highlights the potential errors that may be present in studies that have employed existing automated watershed mapping methods. [ABSTRACT FROM AUTHOR]

Computer models of flow and transport processes in critical or vulnerable reaches of rivers have become essential tools in assessing the long-term sustainable management of river basins. A generic long-standing source of uncertainty in the output from these models arises from the difficulty in estimating flow rates at the upstream boundary of the reach. When the process being modeled relies on an accurate description of the autocorrelation in the flow, such as in sediment transport, and predictions are required for future changed climatic conditions, this difficulty becomes acute. One currently popular solution is to combine stochastic weather generators with catchment hydrology models to simulate hydrographs. This paper offers an alternative solution, which bypasses the complexities of this approach and the extra uncertainties that arise from imposing restrictive predefined model structures. The proposed method uses an autoregressive multinomial logit model to link temperature and precipitation catchment data to flow data of the River Tees in the northeast United Kingdom. This model accounts for temporal autocorrelation by using the previous day's observation and other variables as explanatory variables. Incorporating basin area average temperature and precipitation allows climate change predictions from regional climate models to be used when predicting flows. The successful application of the method is demonstrated for the River Tees in northeast United Kingdom. [ABSTRACT FROM AUTHOR]

Using radiative reflectance as the discriminatory functional trait, we find scale-free signatures of local functional diversity density of vegetation in river basins, implying a high likelihood of locations with very high diversity relative to the overall diversity of the riparian systems (i.e., riparian diversity hot spots). The spatial series of average local functional diversity exhibits correlation structures that indicate long-range communication of diversity information along river networks. The riparian area of a randomly selected streamlink is found to be exponentially distributed. Our findings suggest that landscape structure and dispersal directionality play crucial roles in determining biodiversity patterns, and thus should be addressed in comprehensive biodiversity theories and fieldwork and conservation campaigns. Finally, the connection between the spectral-group-based functional diversity signatures and those associated with the actual species richness is yet to be verified and quantified; such connection will significantly enhance the importance of the already meaningful signatures reported here. [ABSTRACT FROM AUTHOR]

Quantifying P losses to surface waters at different scales and partitioning of the loads into P losses from point sources and diffuse sources are significant future challenges for river basin managers. The agricultural share of P losses to surface waters is, in many river basins, increasing and therefore becoming more important to quantify and analyse. The importance of phosphorus losses from agricultural land was analysed using monitoring data and two different models for 35 micro-catchments (<30 km2) in the Nordic–Baltic region of Europe, 17 European macro-catchments (250–11 000 km2) and 10 large European river basins (>50 000 km2). Average annual phosphorus loss from agricultural land in the micro-catchments varied from 0.1 to 4.7 kg P ha−1 and showed no relationship with the short-term P surplus on agricultural land. The average annual total P loss from agricultural land showed equally large variation in the 17 macro-catchments (0.1–6.0 kg P ha−1), but the range was less for the 10 larger river basins (0.09–2.0 kg P ha−1). The annual P loss from the 35 micro-catchments was greatest in the micro-catchments characterized by soil erosion and a high proportion of surface run-off as in the Norwegian catchments. The same pattern was true for the 17 macro-catchments where the model-simulated total P loss from agricultural land was greatest in the catchments in northern and southern parts of Europe. The main diffuse pathways for total P loads in the 17 macro-catchments were simulated with the MONERIS model. On average, soil erosion and surface run-off was estimated to have contributed 53% (4.1–81%), groundwater 14% (0.2–41.7%) and tile drainage water 3% (0–14.0%). [ABSTRACT FROM AUTHOR]

This paper investigates the multiscale statistical structure of the area and width functions of simulated and real river networks via state-of-the-art wavelet-based multifractal (MF) formalisms. First, several intricacies in performing MF analysis of these signals are discussed, and a robust framework for accurate estimation of the MF spectrum is presented. Second, it considers the following three questions: (1) Does the topology of river networks leave a unique signature on the MF spectrum of area and width functions? (2) How different are the MF properties of commonly used simulated trees and those of real river networks? and (3) Are there differences between the MF properties of width and area functions, and what can these tell us about the topology of hillslope versus channelized drainage patterns in a river basin? The results indicate discrepancies between the statistical scaling of the area functions of real networks (found to be multifractal with a considerable spread of local singularities and the most prevailing singularity ranging from 0.4 to 0.8) and that of several commonly used stochastic self-similar networks (found to be monofractal with a single singularity exponent H in the range of 0.5-0.65). Moreover, differences are found between the MF properties of width and area functions of the same basin. These differences may be the result of distinctly different branching topologies in the hillslope versus channelized drainage paths and need to be further investigated. [ABSTRACT FROM AUTHOR]

Freshwater finfish species richness and level of endemism in East, and South and South-East Asia that included 17 nations were studied using available databases, and included nation-wise distribution, habitat types, and conservation status. The number of endemic finfish species in the region was 559, belonging to 47 families. Families Cyprinidae and Balitoridae accounted for 43.5% and 16.2% of the total number of endemic species in the region, respectively, followed by Sisoridae (25), Gobiidae (20), Melanotaeniidae (19), and Bagridae (16), and the other 41 families had at least one endemic species. Nation-wise the most number of endemic freshwater finfish species occur in India (191), followed by China (88), Indonesia (84), and Myanmar (60). In India, the endemic species accounted for 26.4% of the native freshwater fish fauna, followed by South Korea (16.9%), the Philippines, (16.3%) and Myanmar (15.7%). Statistically significant relationships discerned between the number of indigenous and endemic species richness to land area (Xla in 103 km2) of the nations in the region were, Yin = 218.961 Ln(Xla) – 843.1 ( R2 = 0.735; P < 0.001) and Ye = 28.445 Ln Xla−134.47 ( R2 = 0.534; P < 0.01), respectively, and between indigenous and endemic species richness was Ye = 0.079Xn− 1.558 ( R2 = 0.235; P < 0.05). The overall conservation status of endemic finfish in Asia was satisfactory in that only 92 species were in some state of vulnerability, of which 37 species (6.6%) are endangered or critically endangered. However, the bulk of these species (83.7%) were cave- and or lake-dwelling fish. However, nation-wise, the endemic freshwater finfish fauna of the Philippines and Sri Lanka, based on the imperilment index, were found to be in a highly vulnerable state. Among river basins, the Mekong Basin had the highest number of endemic species (31.3%). The discrepancies between databases are highlighted and the need to consolidate information among databases is discussed. It is suggested that the Mekong Basin be considered as a biodiversity hotspot, and appropriate management strategies be introduced in this regard. [ABSTRACT FROM AUTHOR]

The upper Cheat River network departs from scaling laws describing a large number of river networks in North America. This departure is traced to its corrugated terrain. The more typical random terrain of the lower Cheat River network obeys the standard scaling laws. We modify the random network model of Scheidegger to include the effects of topography, reproducing the behavior observed in the Cheat River basin. [ABSTRACT FROM AUTHOR]