A model for water sharing in the Ganges River Basin

This study investigates water resources sharing and in particular the impact of the Farakka Barrage in the Ganges River Basin management which has led to conflict between the Ganges states since 1951. A deadlock prevailed between Bangladesh and India during the dry seasons. The 1996 water sharing treaty adopted and the results suggest that availability of flows is crucial during the period 1 March to 31 May. Moreover, the average flow availability at Farakka dam has been gradually declining during the period 1997 to 2007. For 2005 and 2006, it was found that the average flow availability declined by 12 and 25%, respectively. A Stackelberg leader–follower model is described for optimal water allocation in the Ganges River Basin between Bangladesh and India both with and without additional water transfers from Nepal. It is recommended that a market‐based water transfer arrangement from Nepal is implemented for both Bangladesh and India.     

Can sediment data be used to predict alkalinity and base cation chemistry of surface waters?

We hypothesise that stream sediment elemental composition can predict mean and minimum concentrations of alkalinity, Ca and Mg in the river water throughout a river network. We tested this hypothesis for the River Derwent catchment in North Yorkshire, England, by using 6 years of water chemistry data from the Environment Agency and a digital elevation model to flow path-weight British Geological Survey (BGS) sediment element concentration data. The predictive models for mean concentrations were excellent for Ca and alkalinity, but less good for Mg, and did not require land use data inputs as stream water sediment composition seems to reflect all aspects of the riparian zone soil system. Predictive model forms were linear. Attempts to predict minimum values for Ca and alkalinity also were less satisfactory. This probably is due to variations in hydrological response times to individual precipitation events across the catchment.     

Management of stream compensation for a large conjunctive use scheme,Shropshire, UK

The Shropshire Groundwater Scheme (SGS) is the largest conjunctive use scheme in the United Kingdom. The SGS operates in drought periods, pumping water from the Permo‐Triassic Sandstone aquifer in Shropshire, England to regulate flows in the River Severn, alongside releases from conventional surface water reservoirs. This regulation protects the environment and increases the security of supply of major public water supply abstractions downstream. An important operational consideration is the impact SGS groundwater abstraction has on small streams that rise on the Shropshire Permo‐Triassic Sandstone. Compensation boreholes have been installed to maintain flows during and after the operation of the SGS. This paper shows how a groundwater model of the East Shropshire Permo‐Triassic Sandstone has been used to estimate the required level of compensation flows for recent climatic conditions to optimise the use of the SGS. The catchment wide conditions are included in this analysis by using the results of a large‐scale surface water model of the River Severn.     

A Semi-Empirical Investigation of the Influence of Flood-Plain Storage on Flood Flow

A simple model is used to assess the effect of flood-plain storage on flood flows, with a view to developing methods for general use in flood-frequency estimation. Recent floods on the River Severn at Montford are 'unrouted' in order to determine the shape and magnitude of the hydrographs, provided that there had been no overtopping and all flows had been contained within the banks. The model used to unroute the hydrographs has, at its core, a relationship between water depth and flooded area derived from a coarse (50 m) digital terrain model developed from Ordnance Survey 1:50 000 maps. The implications for flood-frequency curves at sites downstream from significant flood-plain storage are discussed.     

Modeling the effects of population growth on water resources: a CGE analysis of the South Platte River Basin in Colorado

This research examines the general equilibrium implications of economic and population growth on a fixed (or exogenously determined) total supply of available water in the South Platte River Basin in Colorado. Instead of looking at the effects of increased demand for water on a fixed allocation regime, we allow for transfers of water between agricultural and municipal water users based on the respective factor demand for water across the economy. The study utilizes an 18-sector computable general equilibrium (CGE) model, where water is incorporated as a primary factor of production for agricultural operations and for a municipal water supply sector, but as an intermediate input for all other sectors. It is determined that, by allowing for water transfers with a fixed supply of water, the projected 50% increase in population from 2002 to 2030 will result in a 5.7% shift in water allocation from agriculture to other sectors. However, the total real value of agricultural sales is expected to increase slightly over this same period. The price of municipal water is expected to increase by 8.4% and the price of agricultural water is expected to increase by 10.4%. This result is contrasted to a scenario where significant barriers to water transfers are enacted. In this case the price of municipal water increases by 25% and agricultural water prices remain constant.     

Defining the sources of low-flow phosphorus transfers in complex catchments

Nutrient transfers from the land to rivers have the potential to cause persistent eutrophic impacts at low flows even though the transfers may constitute a minor percentage of total annual fluxes. In rural catchments, the contribution from agricultural soils during storm events can be particularly large and untangling the relative contributions from multiple sources that vary in time and space is especially problematic. In this study, the potential for domestic septic tank system pollution during low flows was investigated in 3 small catchments (3 to 5 km(2)) using an integrated series of methods. These included septic system surveys, continuous (10 min) total phosphorus (TP) monitoring at the outlet of each catchment, repeated low-flow water quality surveys in sub-catchments upstream of the catchment outlets and single day river-walk water quality surveys. A series of faecal matter and grey-water fingerprinting techniques were also employed. These included determining sterol ratios in stream sediments, monitoring the presence of proteins, E. coli and enterococci bacterial signatures and boron. The total density and density of poorly maintained septic systems mirrored the magnitude of frequent TP concentrations in the catchments although this relationship was less apparent in the nested sub-catchments. The exception was possibly related to the simple hydraulics in one particular catchment and indicated temporary effluent attenuation in the other catchments. Repeated low-flow and river-walk water quality surveys highlighted discrete areas and reaches where stepped changes in nutrient concentration occurred. Bio-chemical fingerprinting showed that between 7% and 27% of sediments were contaminated with human faecal material and correlation matrices indicated that, at least during low flows, P fractions were positively correlated with some markers of faecal and grey-water contamination.     

The assimilative capacity of Qiantang River watershed,China

The Qiantang River, located in Zhejiang Province, China, is a major water supplier to a highly populated region for multiple uses. With economic development, the received pollutants exceeded its assimilative capacity, leading to algal blooms or fish kills. This study was an up‐to‐date evaluation of the assimilative capacity of the Qiantang River, investigating the influence of stream flow. A confidence of 75 and 90% of instream flows were selected as the design flows, while the traditional one‐dimensional point discharge model and QUAL2K model were used to analyse biochemical oxygen demand (BOD) assimilative capacity. The results showed that the assimilative capacity of 75% confidence instream flow was larger than that of 90% confidence. The assimilative capacity based on QUAL2K model considered almost all rates of BOD gain and loss, which were larger than that of one‐dimensional point discharge model. The total amount of BOD discharged into Qiantang River was 17 1283 t·a^?1 in 2004. Under 75 and 90% confidence river flow conditions, the calculated total BOD reduction percentage of the whole river was 38.2 and 55.9%, respectively. Furthermore, the results were used as criteria for developing a BOD total maximum daily load (TMDL) in order to achieve the sustainable use of water resources derived from Qiantang River watershed.     

Density currents in the Chicago River: characterization, effects on water quality, and potential sources

Bidirectional flows in a river system can occur under stratified flow conditions and in addition to creating significant errors in discharge estimates, the upstream propagating currents are capable of transporting contaminants and affecting water quality. Detailed field observations of bidirectional flows were made in the Chicago River in Chicago, Illinois in the winter of 2005-06. Using multiple acoustic Doppler current profilers simultaneously with a water-quality profiler, the formation of upstream propagating density currents within the Chicago River both as an underflow and an overflow was observed on three occasions. Density differences driving the flow primarily arise from salinity differences between intersecting branches of the Chicago River, whereas water temperature is secondary in the creation of these currents. Deicing salts appear to be the primary source of salinity in the North Branch of the Chicago River, entering the waterway through direct runoff and effluent from a wastewater-treatment plant in a large metropolitan area primarily served by combined sewers. Water-quality assessments of the Chicago River may underestimate (or overestimate) the impairment of the river because standard water-quality monitoring practices do not account for density-driven underflows (or overflows). Chloride concentrations near the riverbed can significantly exceed concentrations at the river surface during underflows indicating that full-depth parameter profiles are necessary for accurate water-quality assessments in urban environments where application of deicing salt is common.     

Spatial and temporal trends in nitrate concentrations in the River Derwent, North Yorkshire, and its need for NVZ status

Long-term spatial and temporal variations in nitrate-N concentrations along the River Derwent have been examined using Environment Agency data to investigate the relative importance of impacts of atmospheric N deposition, land use, and changes in management. Where moorland and rough grazing dominate upstream of Forge Valley and Malton, over the 20 years since 1988 mean nitrate-N concentrations were initially increasing significantly, but are now levelling off, with peaks at ca. 4.5 mg N l⁻¹. As expected in a catchment in a nitrate vulnerable zone (NVZ), more agricultural land use increases mean nitrate concentrations and the occurrence of distinct winter maxima, though the latter have become markedly less pronounced since 2001. It is suggested that this improvement is a combined effect of imposition of NVZ designation in the lower reaches in 2002, animal number declines associated with the Foot & Mouth outbreak in the region in 2001, and the impact of farmers' responses to increasing fertilizer prices and to beneficial pollutant mineral N inputs from the atmosphere. Minima in nitrate-N concentrations in summer have become much less pronounced over the past decade and are typically ca. 60% higher in concentration than a decade earlier. This probably is attributable to the effects of pollutant-N leaching to depths in soil below the rooting zone when near surface biotic uptake is low in winter. The resultant N mineralization in summer enhances summer nitrate leaching. The Derwent is a relatively clean river; however, its entire catchment was designated justifiably as a NVZ in January 2009, apparently based upon a projected 95 percentile nitrate-N concentration > 11.29 mg l^− 1 for 2010 based upon forward projection of data from 1990 to 2004 for Derwent Bridge. A survey of water quality in March 2009 showed that some agricultural areas are still making a significant contribution to the total nitrate level well downstream, at the point responsible for implementation of NVZ status. At 3 of the 29 sites sampled, nitrate concentration exceeded 60 mg l^− 1.     

基于神经网络的蔷薇河水质综合评价

基于BP神经网络的改进算法,提出了以Matlab7．0为平台的算法程序的人工神经网络水质评价模型。参照《地表水环境质量标准》（GB3838-2002）,确定了神经网络学习和训练的样本以及模型的相应参数,并以流经连云港市蔷薇河的六个断面的水质数据为样本,进行水质综合评价分析。     

Features of tropical cyclone-induced flood peaks on Grande Terre, New Caledonia

New Caledonia, an archipelago of islands in the South Pacific, is periodically affected in the wet season by tropical cyclones that can deliver intense rainfall and cause severe river flooding. On the mountainous island of Grande Terre, the majority of the largest historical flows in the Tontouta River were caused by tropical cyclones and 75% of cyclone-induced floods were overbank events. Discharge data for the Tontouta River over the period 1969–2003 were used to construct partial duration series (PDS) of daily mean and instantaneous flows. The log Pearson Type III distribution provided a good fit to the PDS. Instantaneous flows are much higher than daily flows, reflecting the flashiness of tropical cyclone hydrographs. This highlights the need to use instantaneous flow data, where available, to investigate flood hazards in steep tropical basins impacted by tropical cyclones.     

Drivers of water quality in a large water storage reservoir during a period of extreme drawdown

This study examined the drivers of water quality in a large water storage reservoir (Lake Hume) during a period of extreme drawdown (to less than 3% of capacity). During the period of extreme drawdown, the reservoir can be thought of as consisting of three separate but inter-related parcels of water. The warm surface mixed layer was about 6m deep. Cold water inflows from the Mitta Mitta River undershot the surface mixed layer in the Mitta Mitta arm of the reservoir and flowed along the bottom of the reservoir to the Dam Wall without substantial interaction with the surface mixed layer. When inflows from the Murray River occurred, the temperature of these inflows was similar to that of the surface mixed layer within the dam and the flows appeared to move within the surface mixed layer towards the Dam Wall. These Murray River inflows were insufficient to promote total mixing of the surface and bottom waters. The Murray River arm of the reservoir became a 'hot spot' for nutrient production. Stratification and subsequent anoxic conditions promoted the release of nutrients - ammonium, organic N and total P - from the sediments into the overlying hypolimnion. Because the depth of the lake was relatively shallow due to the extreme drawdown, wind driven events lead to a substantial deepening (turnover) of the thermocline allowing periodic pulses of nutrients into the warm surface layer. These nutrient pulses appeared to stimulate cyanobacterial growth. Warm inflows from the Murray River then served to push the blooms formed in the Murray arm into the main body of the lake.     

Factors influencing development of management strategies for the Abou Ali River in Lebanon I: spatial variation and land use

Surface water bodies are progressively subject to increasing stress as a result of environmentally degrading processes primarily related to anthropogenic activities. This study assesses and examines the impact of land use and land-based activities on the spatial variation in water quality of the Abou Ali River in North Lebanon. It is the first detailed study of its kind in Lebanon and adds to the existing knowledge by shedding light on a relatively small Mediterranean river in a developing country where there is a paucity of such studies. The assessment was conducted at the end of the dry season in 2002 and 2003 and the end of the wet season in 2003 and 2004. The study has demonstrated the importance of anthropogenic influences on the water quality of the Abou Ali River Basin, as concentrations of most contaminants were higher at locations with greatest human activity. The most adversely affected area was the section of the river that flows through an entirely urbanized and highly populated region, the Tripoli conurbation. Upstream rural sites were enriched by contaminants primarily from non-point sources such as agricultural runoff and poultry litter whereas contaminant concentrations at the urban sites were enriched by a combination of sewage discharge and flow of contaminants from upstream. If the Abou Ali River is to be utilized as a managed water resource and its water quality sustained, point source discharges will require treatment and land use management must be planned to minimize the impact of diffuse source pollution on the river. A high priority should be given to the implementation and enforcement of the precautionary and polluter pays principles. Moreover, an effective legal, economic and institutional framework is required to encourage investment in waste reduction and control and to introduce environmentally sound practices.     

Impacts of climate change on in-stream nitrogen in a lowland chalk stream: an appraisal of adaptation strategies

The impacts of climate change on nitrogen (N) in a lowland chalk stream are investigated using a dynamic modelling approach. The INCA-N model is used to simulate transient daily hydrology and water quality in the River Kennet using temperature and precipitation scenarios downscaled from the General Circulation Model (GCM) output for the period 1961-2100. The three GCMs (CGCM2, CSIRO and HadCM3) yield very different river flow regimes with the latter projecting significant periods of drought in the second half of the 21st century. Stream-water N concentrations increase over time as higher temperatures enhance N release from the soil, and lower river flows reduce the dilution capacity of the river. Particular problems are shown to occur following severe droughts when N mineralization is high and the subsequent breaking of the drought releases high nitrate loads into the river system. Possible strategies for reducing climate-driven N loads are explored using INCA-N. The measures include land use change or fertiliser reduction, reduction in atmospheric nitrate and ammonium deposition, and the introduction of water meadows or connected wetlands adjacent to the river. The most effective strategy is to change land use or reduce fertiliser use, followed by water meadow creation, and atmospheric pollution controls. Finally, a combined approach involving all three strategies is investigated and shown to reduce in-stream nitrate concentrations to those pre-1950s even under climate change.     

Possible Environmental Impact of the Closure of Two Collieries in County Durham

In County Durham the forthcoming closure of two coastal collieries is, in effect, the final closure of a large hydraulically interconnected coalfield which has been progressively dewatered over three centuries. Groundwater will gradually rise through the previously worked strata after the cessation of coalfield dewatering. Past experience shows that the rising groundwater will develop high acidity and heavy metal loadings as oxidized pyrite remnants are dissolved. Conceptual modelling suggests that this acidic groundwater will ultimately discharge into the River Wear and its tributaries, with serious consequences for the aquatic ecology and human use of the River Wear system. Further environmental impacts may include (a) groundwater pollution in the adjacent Basal Permian Sands aquifer, (b) leaching from landfills intersected by the rising water table, (c) compromised integrity of foundations, (d) increased flows in old sewers below the new rest water level (leading to problems at sewagetreatment works and combined sewer overflows), (e) corrosion of other buried services, (f) surface gas emissions, and (g) long-term subsidence risk from old workings. The prevention of these impacts would involve long-term maintenance of regional dewatering, although local mitigation of most effects could be arranged – albeit at considerable cost. Current legislation fails to place responsibility for the prevention of such environmental impacts in the hands of any one organization; this 'vacuum of responsibility'needs to be addressed urgently if a pragmatic, consensual approach to environmental protection in abandoned coalfields is to be pursued.     

Integrated Catchment Modelling as a Water Resources Management Tool

Groundwater models are becoming increasingly important in water resources management. Most aquifers in the UK are closely linked with river systems, to which they contribute baseflow from seepages and springs. As a result, major groundwater abstractions almost inevitably affect river flows. To assess with confidence the effect of utilizing ground-water resources, an aquifer and river system has to be linked within an integrated model which can simulate varying hydrogeological conditions throughout the catchment.
The main features of an integrated catchment management model, which links aquifer and river systems, are described in this paper. The model has been applied to a number of catchments in southern England including the River Darent in Kent, which is probably the most well-known and worst-affected of all rivers identified nationally as suffering from over-abstraction.
The process of model preparation and calibration is illustrated with reference to the River Darent. Twenty years of river flow and groundwater hydrograph records were used in producing a close simulation of modelled and actual hydrological conditions. The model was then operated to assess a large number of possible options for restoring flows to the river. Examples of various management strategy simulations are given, leading to formulation of a water resources management plan for the Darent. This involved (a) reductions in selected abstractions, (b) flow augmentation using river support boreholes, and (c) meeting peak groundwater supply demands in drought periods.     

Use of watershed factors to predict consumer surfactant risk, water quality, and habitat quality in the upper Trinity River, Texas

Surfactants are high production volume chemicals that are used in a wide assortment of “down-the-drain” consumer products. Wastewater treatment plants (WWTPs) generally remove 85 to more than 99% of all surfactants from influents, but residual concentrations are discharged into receiving waters via wastewater treatment plant effluents. The Trinity River that flows through the Dallas-Fort Worth metropolitan area, Texas, is an ideal study site for surfactants due to the high ratio of wastewater treatment plant effluent to river flow (> 95%) during late summer months, providing an interesting scenario for surfactant loading into the environment. The objective of this project was to determine whether surfactant concentrations, expressed as toxic units, in-stream water quality, and aquatic habitat in the upper Trinity River could be predicted based on easily accessible watershed characteristics. Surface water and pore water samples were collected in late summer 2005 at 11 sites on the Trinity River in and around the Dallas-Fort Worth metropolitan area. Effluents of 4 major waste water treatment plants that discharge effluents into the Trinity River were also sampled. General chemistries and individual surfactant concentrations were determined, and total surfactant toxic units were calculated. GIS models of geospatial, anthropogenic factors (e.g., population density) and natural factors (e.g., soil organic matter) were collected and analyzed according to subwatersheds. Multiple regression analyses using the stepwise maximum R² improvement method were performed to develop prediction models of surfactant risk, water quality, and aquatic habitat (dependent variables) using the geospatial parameters (independent variables) that characterized the upper Trinity River watershed. We show that GIS modeling has the potential to be a reliable and inexpensive method of predicting water and habitat quality in the upper Trinity River watershed and perhaps other highly urbanized watersheds in semi-arid regions.     

圆明三园进出水口探析

圆明三园作为京西海淀山水御园,河网密布,水系勾连,引玉泉山水、万泉河水入园,辅以自有泉水,遂有河湖溪渠,山泉瀑布之胜景。三园周边环绕护园河,外围河水通过水闸、涵洞、暗沟等流入三园,主水自藻园门东进水闸而入,自长春园东墙出水闸闸、七孔闸、绮春园东墙二孔闸、五孔闸出,合“西北为首,东南为尾”之势。由样式雷图及文献可见,三园进出水口数量约30处,起到进水、出水、沟通水系、连接园区的作用,三园进水、出水呈现出相似而又不同的规律。     

Seeking a compromise between pharmaceutical pollution and phosphorus load: Management strategies for Lake Tegel, Berlin

Lake Tegel (Berlin, Germany) is controlled by two main inflows: inflow #1 (River Havel) is heavily phosphorus-laden, whereas inflow #2 is an artificial confluence that includes discharge from a municipal wastewater treatment plant distinguished by high levels of phosphorus and pharmaceuticals. To reduce the phosphorus load on the lake, a phosphorus elimination plant (PEP) is situated at inflow #2. Moreover, the two inflows are short-circuited by a pipeline that transfers part of the inflow #1 water to the PEP and finally releases it into inflow #2. The pipeline and the PEP have contributed to a continuous reduction in the total phosphorus concentration of Lake Tegel in the past 25 years. We investigate the question of whether the existing lake pipeline can also be used to reduce the amount of pharmaceuticals in Lake Tegel originating from inflow #2 by dilution with water from River Havel, by diverting part of inflow #2 around the lake, or by a combination of both strategies. The circulation pattern of Lake Tegel is complicated by complex bathymetry and numerous islands and is therefore highly sensitive to winds. We tested seven different management scenarios by hydrodynamic modeling for a period of 16 years with the two-dimensional version of the Princeton Ocean Model (POM). None of the scenarios provided a strategy optimal for both pharmaceuticals and phosphorus. Nonetheless, compound regimes, such as alternating the pipe flow direction or adding another pipeline, allowed the most abundant pharmaceutical (carbamazepine) to be reduced while maintaining the current phosphorus level. This study demonstrates the ability of immediate lake regulation measures to maintain water quality. In the case of Lake Tegel, the pipeline can be fully effective with regard to pharmaceuticals only in combination with additional efforts such as advanced pharmaceutical treatment of wastewater and/or phosphorus reduction in the River Havel catchment.     

Rate and pathways of phosphorus assimilation in the Nepean River at Camden, New South Wales

The Nepean River receives effluent containing phosphorus from a sewage treatment plant at Camden, N.S.W. Phosphorus concentration, suspended solids, sediments and aquatic plants downstream of the outfall, were examined to determine the rate and pathways of phosphorus loss from the waterway.The phosphorus added was found to follow first order kinetics in its removal from the waterway. Two reaction pathways were discernible with over 90% of the added phosphorus being removed from the water column in 11 days, and the remainder in a further 70 days. The process remained constant from summer to winter and could be modelled for dry weather flows representing 68% of river flows.Soluble phosphorus was first incorporated into particles before being removed from the water column. Evidence is presented to show that the particles were predominantly phytoplankton and they were largely removed from the water column by littoral zone filtration. The second pathway appears to be sedimentation of nutrient laden particles.