Catchment‐scale controls on groundwater–surface water interactions in the hyporheic zone: implications for salmon embryo survival

The spatial and temporal variability of groundwater–surface water (GW–SW) interactions in the hyporheic zone were investigated in a semi‐pristine upland salmon spawning catchment (Girnock Burn) in the Cairngorm Mountains, northeast Scotland. Stream and hyporheic water quality (200–300 mm depth) were monitored fortnightly at 16 spawning locations distributed throughout the catchment. Hydrochemical tracers were used to assess local GW–SW interactions. Stratified streambed incubators (50–300 mm) provided information on salmon embryo mortality at a sub‐set of ten locations. Hyporheic water quality varied both temporally and spatially according to local GW–SW interactions. It was possible to categorize sites into three broad typologies reflecting local stream–aquifer interactions: (1) groundwater‐dominated; (2) surface water‐dominated; and (3) sites exhibiting transient water table features. Groundwater upwelling occurred in areas where low permeability glacial moraine features caused substantive valley constriction. These locations were also conducive to accumulation of spawning grade gravels and consequently were utilized heavily by spawning salmon. Long residence groundwater was typically characterized by low dissolved oxygen (DO), of sufficiently low quality to be detrimental to salmon embryo survival. At sites dominated by surface water, hyporheic DO remained high throughout and rates of embryo survival were correspondingly high. Survival rates were also high at sites where hydrochemical characteristics indicated a transient water table. This is probably attributable to the hydrological conditions which resulted in increasing DO concentrations towards hatch time when embryo oxygen demand is at its maximum. The degree to which the findings of this study are directly applicable to other catchments is currently unknown. However, similar effects have been observed elsewhere, and based on the information presented here, there are clear implications for fisheries managers who may wish to consider the use of surface incubation facilities to negate the effects of low DO groundwater upwelling where it dominates available spawning habitat. It is suggested that future research should aim to integrate across spatial scales and disciplines to obtain a better understanding of the ways in which hillslope and riparian zone hydrology affect GW–SW interactions, hyporheic zone processes and stream ecology. © Crown copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Water quality before and after dam building on a heavily polluted river in semi‐arid Algeria

The impact of the construction and management of a reservoir on a polluted stream in a semi‐arid region has been highlighted using physico‐chemical indicators. The Tafna river (Algeria) collects heavily polluted wastewater from the town of Maghnia and from several factories. Organic pollution comes from domestic sewage and from food industries. Ore treatment industries discharge very acidic wastewater. Temperature, pH, conductivity, chloride, dissolved oxygen, biological oxygen demand (BOD), and nitrogen compounds have been surveyed between 1996 and 2001, before and after the construction of the dam. The change in each parameter is compared between sites located upstream and downstream from the dam. The spatio‐temporal evolution of the organic pollution indicators was highlighted by ANOVA and principal component analysis. By enhancing sedimentation of the organic matter, the reservoir makes possible a significant decline in the BOD downstream of the dam, but increases NH₄ concentration at the downstream sites. The pollution is diluted during high flows and dam releases. Conversely, during low flow periods, mineralization of organic matter is higher in the lower Tafna. Copyright © 2004 John Wiley & Sons, Ltd.     

Survival of salmonid eggs in a degraded gravel‐bed stream: effects of groundwater–surface water interactions

The effect of hyporheic water quality on developing salmonids was assessed between spawning and hatch. Results from a low‐lying degraded agricultural catchment (Newmills Burn) were compared with those from a near‐pristine upland spawning stream (Girnock Burn), providing a set of comparisons beyond the range of hyporheic conditions present in the Newmills Burn. It was demonstrated that hyporheic water quality in the Newmills Burn varied temporally and spatially as a consequence of variable fluxes of chemically reduced groundwater through heterogeneous drift deposits. Mortality rates from samplers located within artificial redds ranged from 0 to 100% and showed a clear negative relationship with mean dissolved oxygen (DO) concentrations (r² = 0.85, P < 0.01). Where embryo mortality was less than 100%, low DO appeared to affect rates of embryo development. Embryos exposed to lower DO concentrations were observed to have a higher percentage mass of yolk sac than those developing in more favourable conditions. The chemical characteristics of hyporheic water in the stream were indicative of the mixing of longer residence regional groundwater with local surface water at shallow depths. The hyporheic water of the Girnock Burn approximated closely to that of surface water suggesting a local origin. Hyporheic water quality affects egg survival and may limit recruitment when egg deposition is marginal or inadequate. A consideration of hyporheic dynamics and groundwater–stream interactions should form part of channel modification or restoration works in salmonid spawning streams. Copyright © 2003 John Wiley & Sons, Ltd.     

Stream regulation and nitrogen dynamics in sediment interstices: comparison of natural and straightened sectors of a third‐order stream

Nitrogen dynamics were studied in the interstitial environment (i.e. hyporheic zone) of a sandy‐bottom stream in a rural landscape. A third‐order stream in Brittany (France) was studied at 11 stations (riffles) to evaluate spatial patterns of water exchange between surface and interstitial habitats. More intensive sampling was conducted in three riffles selected according to their hydrological characteristics. Chemical characteristics (especially nitrogen) and microbial denitrification were studied at 12.5 and 25 cm depth upstream, and 25 cm depth downstream of each riffle. This study confirms that the interstitial habitat of a N‐rich stream acts as a sink for the nitrate‐nitrogen. Experimental manipulation of sediment cores indicates that denitrification is limited by carbon in surface (i.e. benthic) and by nitrate in hyporheic sediments. River regulation increases inputs of fine sediments, modifies river channel location, and generates changes in the spatial patterns of biogeochemical processes, water origins, and hydrologic exchanges. Copyright © 2004 John Wiley & Sons, Ltd.     

渭河下游垂向潜流通量动态特征研究

潜流交换控制着潜流带内水量的变化及各种物质(氧气、有机质)的滞留时间,对地下水的水量和水质变化具有重要的影响。精确计算潜流带内的潜流通量及其动态变化特征,对河流的综合治理及生态恢复具有十分重要的意义。采用热量运移解析模型求解潜流通量,利用温度示踪技术,重点研究潜流交换过程的空间非均质特征和动态变化特征;以渭河下游草滩段为研究区,进行河床浅层沉积物潜流通量的计算。结果表明:监测时段内研究区地下水流为河水补给地下水,河道内不同位置的浅层潜流带内呈现出不同的潜流通量动态特征,其变化范围在0.873～8.900 μm/s之间,潜流带厚度约为0.75 m,呈现比较复杂的动态变化特征。监测时段内各深度间潜流通量总体变化趋势为上升趋势,在垂向分布上存在差异,而且这种差异随时间变化。温度示踪方法简单易行,在潜流通量的计算中具有较好的准确性,适用于潜流带内水动力交换量的精确计算。     

Near Real-Time Optimization of Multi-Reservoir during Flood Season in the Fengman Basin of China

This study aims to develop a multi-objective optimization model in a multi-reservoir system during flood season using Numerical Weather Predictions (NWPs) outputs (short forecast). The optimization model was coupled with the Water and Energy Budget-based Distributed Hydrological Model that was used to forecast the reservoir inflows. The model was forced by 8-day lead time global deterministic NWPs by Japan Meteorological Agency. The reservoir objective function was established by considering the reservoir and upstream safety, downstream safety and future water use. The model was applied to the Baishan-Fengman multi-reservoir system of Northeast China. The results have demonstrated the model with high efficiency in optimizing reservoir objectives for all of the reservoirs. The sensitivity of the system to lead time and decision time were investigated. With the decreasing of lead time, the dam release peaks decrease and the end water levels increase. This is mainly due to the fact that the model with longer lead time needs to keep storage capacity for detected floods during long lead time period. The variation amplitude of dam releases and water levels decrease with the increasing of decision time due to the smoothing of floods and dam releases during long decision period. The model is easy to operate and is able to be coupled with other hydrological models or earth system models.     

Hyporheic invertebrate community composition in streams of varying salinity in south‐western Australia: diversity peaks at intermediate thresholds

Many streams of southwestern Australia have become secondarily saline through land clearance and other human activities in their catchments. Elevated salinities impact on aquatic biota and ecological processes of surface streams but little is known of the effects on the diversity and community composition of hyporheic (subsurface) invertebrates occupying the saturated sediments where surface and groundwaters exchange. We hypothesized that biodiversity of hyporheic invertebrates would decline with increasing salinity, especially where saline groundwater upwelled into the surface stream. We also predicted changes in community composition associated with salinity and direction of vertical hydrological exchange. Water and hyporheic invertebrates were sampled from downwelling and upwelling zones of 13 streams in southwestern Australia ranging in median surface water salinity from 0.27 to 17.86 g L⁻¹. Overall, taxa richness of hyporheic invertebrates was uncorrelated with salinity but, surprisingly, correlated positively with the salinity of upwelling water. However, when the sites were divided into ‘fresh’ (<3 g L⁻¹) and ‘mesosaline’ (>3 g L⁻¹) groups, this relationship became non‐significant. Instead, taxa richness and total abundance were correlated positively with salinity of downwelling water in fresh sites and negatively in mesosaline sites, resulting in a peak in richness at intermediate salinities. Community composition was unrelated to direction of hydrological exchange but was strongly associated with hyporheic salinity. Hyporheic assemblages of ‘fresh’ rivers were typified by harpacticoid copepods and candoniid ostracods, whereas the amphipod Austrochiltonia and several dipteran groups were more common below ‘mesosaline’ rivers. Although many hyporheic taxa collected in this study apparently have broad tolerances to salinity, secondary salinization due to human activities potentially changed community composition, possibly altering rates of ecological processes such as organic matter breakdown occurring within the sediments of streams undergoing salinization. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of bed geometric characteristics on hyporheic exchange

As an active ecotone between the surface stream and groundwater, hyporheic zone (HZ) plays a crucial role in hydrological and ecological processes. Previous numerical simulation and experimental studies have shown that hyporheic exchange can be affected not only by current but also by geometric characteristics of the streambed. However, the geometric characteristics that affect hyporheic exchange remain unclear. In this study, a one-way sequential coupling method was established to connect the river water flow and pore-water flow in the streambed. The change of flux at the interface, mass flux, depth, and area of hyporheic zone were investigated by altering the bed geometric characteristics, i.e. the depth, crest position, and shapes of bedforms. The results clearly demonstrate the following conclusions: (a) the hyporheic exchange flux, depth and area with wave-like bedform is greater than the triangular bedform. (b) The increase of the bed height accelerates the hyporheic exchange processes at the sediment–water interface. (c) A good linear relationship was found between the depth and area of the hyporheic zone. These results provide necessary theoretical understandings of hyporheic exchange, broadening the knowledge of mechanism of stream-streambed exchange processes.     

Groundwater-surface water interactions and agricultural nutrient transport in a Great Lakes clay plain system

Nutrient export from agricultural land to surface waters is a significant environmental concern within the Great Lakes Basin (GLB). A field-based watershed-scale study was completed to investigate spatial and temporal variations of phosphorus and nitrate to assess nutrient transport pathways and groundwater-surface water interactions in an agriculturally dominated clay plain system. This was conducted in the 127 km² Upper Parkhill Watershed, near Lake Huron in southwestern Ontario, Canada. Data collection occurred from June 2018 to May 2019 via continuous sensor deployment and discrete sampling of stream water, groundwater, hyporheic zone, and tile drainage water. Samples were analyzed for various nutrient species (total, total dissolved, soluble reactive, and particulate phosphorus, and nitrate-N) to examine the hydrological dynamics of principal transport pathways of agriculturally-derived nutrients. Total phosphorus and nitrate concentrations in stream water ranged from 0.007 to 0.324 mg/L and 0.32 to 13.13 mg NO₃^?-N/L, respectively. Tile drainage water total phosphorous concentrations varied from 0.006 to 0.066 mg/L. Groundwater total dissolved phosphorus concentrations ranged from <0.003 to 0.085 mg/L. Transport of phosphorus through tile drainage was observed to be greater than through groundwater over the study period. No distinct relationship was observed between nutrient concentrations in the hyporheic zone and the vertical hydraulic gradient within this zone in the studied stream reach. Preliminary correlations were discerned between water quality observations and recognized land management practices. Given the elevated stream nutrient concentrations, these results are consequential for the continual improvement of strategies and programs devised to conserve water resources within the GLB.     

Water quality changes in hyporheic flow paths between a large gravel bed river and off‐channel alcoves in Oregon,USA

Changes in water quality that occur as water flows along hyporheic flow paths may have important effects on surface water quality and aquatic habitat, yet very few studies have examined these hyporheic processes along large gravel bed rivers. To determine water quality changes associated with hyporheic flow along the Willamette River, Oregon, we studied hyporheic flow at six‐bar deposit sites positioned between the main river channel and connected lentic alcoves. We installed piezometers and wells at each site and measured water levels and water quality in river, hyporheic and alcove water. Piezometric surfaces along with substrate characteristics were used to determine hyporheic flow path direction and hyporheic flow rate. At all sites, hyporheic flow moved from the river through bar deposits into alcove surface water. Stable isotope analysis showed little influence of upwelling groundwater. At a majority of sites, hyporheic dissolved oxygen and ammonium decreased relative to river water, and hyporheic specific conductance, nitrate and soluble reactive phosphorous increased relative to river water. At three sites, hyporheic temperature decreased 3–7°C relative to river water; there was less temperature change at the other three sites. At the two sites with the highest hyporheic flow rates, hyporheic cooling was propagated into the alcove surface water. Hyporheic changes had the greatest effect on alcove water quality at sites with highly permeable substrates and high‐hyporheic flow rates. The best approach to enhancing hyporheic flows and associated water quality functions is through restoring fluviogeomorphic channel processes that create and maintain high‐permeability gravel deposits conducive to hyporheic flow. Copyright © 2006 John Wiley & Sons, Ltd.     

Influence of dams on river water‐quality signatures at event and seasonal scales: The Sélune River (France) case study

Dams and reservoirs are known to disturb river‐water composition, among other impacts, with potential implications for downstream river ecosystems and water uses. Existing studies have emphasized the variable influence of dams on water composition according to the element, its speciation (dissolved vs. particulate), reservoir properties (residence times), reservoir functions (e.g., hydropower, irrigation), and management (water releases). A now common approach to analyzing hydrological, geochemical, and biological controls on element export from unregulated rivers is to study hydrochemical signatures such as concentration‐flow relationships. We investigated a case study to analyze hydrochemical signatures of a regulated river (Sélune River, western France) upstream and downstream of a chain of two hydropower dams, assuming that the dams disturbed the river's signatures, and that those disturbances would provide information about processes occurring in the reservoirs. Both seasonal and event‐scale signatures were analyzed over two contrasting hydrological years and a range of storm events. The dams induced a chemostatic downstream response to storm events whenever elements were diluted or concentrated upstream. Dams did not disturb the seasonality of major anions but did modify silica and phosphorus concentration‐flow relationships, especially during low flow. Such changes in dynamics of river‐water composition may affect downstream biological communities. This study presents an initial state of the hydrochemical signature of the downstream river, before the removal of the two dams.     

水库运行对下游河岸潜流带水位-温度影响研究

选取浙江省新安江大坝下游尾水至富春江水库某一河段作为试验场地,实时监测同一河流剖面的河道水位、温度以及河岸水位与温度分布。通过分析侧向潜流交换流量,定量描述侧向潜流交换的空间非均质性和动态特征,刻画河岸潜流带与河道水体水位、温度之间的响应关系。结果表明:本次试验剖面上的侧向潜流交换流量变化范围为-8.36~3.87 m2/s,监测时间段内单位长度上的潜流交换量可达2.49 m2;河岸带侧向潜流区同一剖面不同观测井处的潜流流量呈线性相关,且离河道越远,潜流区水位波动振幅消减越多,响应越滞后,潜流交换流量越小;受水库下泄水流影响,河道水温日波幅很小,河岸含水层具有显著的垂向温度分层。在垂直方向上,冬季浅层河岸温度较低,深层河岸温度较高,夏季则相反,同时浅层温度梯度较大,尤以地面以下0.8~1.7 m范围内温度梯度最大,深层温度梯度小;在水平方向上,离河道越远,受河道入渗水影响越小,温度越高。揭示了水库运行对下游河岸潜流带的影响规律,为河流潜流带生态影响评估提供参考。     

Unclogging improvement based on interdate and interreach comparison of water release monitoring (Durance,France)

Large‐scale flow release experiments are becoming common for improving aquatic habitat quality downstream of dams. Because of the naturally high fine sediment load in the Durance River, France due to inputs from torrential tributaries draining badlands, unpredictable high flow events with dam overspill are not always sufficient to prevent clogging, which can lead to habitat degradation (especially spawning habitats) in bypassed reaches. Therefore, large‐scale flow experiments were conducted on four reaches to test the efficacy of clear‐water releases to improve aquatic habitat conditions. Continuous measurements of water depth, suspended sediment concentrations, and turbidity were conducted during twelve releases and compared on nine. Before and after each release, superficial clogging was measured. The study shows that there is a link between the volume of suspended sediments carried by water releases and the initial clogging. The volumes carried were low compared with the river's annual transport. The effect on clogging can vary significantly from one release to another. In particular, the hydrological context surrounding the releases has a significant influence on clogging. Comparisons of monitoring showed that releases are more effective on reaches that are more severely regulated (high hydrological control) than on those that are less well‐controlled. The areas with the highest initial clogging tend to unclog more than those with lower initial clogging; however, the latter zones are most impacted by ineffective releases. Performing a release on environments with low initial clogging can therefore be environmentally damaging. To ensure that releases are successful and that intervention is warranted, initial clogging should be measured in the field and releases should only be performed if the clogging is judged to be unfavourable.     

河流潜流带渗透系数变化研究进展

介绍了河流潜流带的含义,即是河水与地下水发生物质能量交换的区域,其水力联系和交换水量大小受河床沉积物渗透系数的影响。对近年来国内外学者对河床潜流带渗透系数变化进行了大量研究。由于特殊的环境与水文地质条件,潜流带渗透系数的大小不仅取决于沉积物孔隙大小和孔隙的连通性,而且与生物扰动、河流流水等作用紧密相关:洪水带来的细小颗粒引起河床表面沉积物孔隙淤塞,致使渗透系数减小,但在洪水退后,潜流带的水文交换和生物扰动能破坏淤塞层,从而引起反淤塞作用,造成河床渗透系数增大。因此,淤塞-反淤塞作用改变着河床的渗透性能。最后,指出存在的问题今后的研究方向。     

Modelling Scenarios to Estimate the Potential Impact of Hydrological Standards on Nutrient Retention in the Tobacco Creek Watershed,Manitoba, Canada

Nutrient loading from agricultural drainage systems into downstream aquatic ecosystems, like Lake Winnipeg in the prairie province of Manitoba, Canada, represents a major challenge for water quality management. In order to improve water quality in downstream waterbodies, the Manitoba government is currently investigating the relationship between hydrological standard of agricultural drainage network and nutrient retention in the drainage systems. Briefly, oversized drains have more capacity to transport nutrients, which can increase nutrient loading to downstream waterbodies, especially during rainfall events. Currently, the hydrological standards of agricultural drainage design in Manitoba were mainly developed according to cost-benefit analysis without considering nutrient retention. The purpose of this study was to use computer modelling techniques to simulate the impact of drain size (based on different hydrological standards) on nutrient retention within an agricultural drainage network. The site chosen was the Tobacco Creek Watershed, an agricultural area which drains into the Red River, and thence into Lake Winnipeg. Suspended sediment, nutrient and flow data, from several locations along the Brown drain within this watershed, were used to calibrate a water quality model. Scenarios were then simulated with the model to estimate how different drain sizes affect nutrient transport and retention. Sampling took place during the spring and summer of 2013 starting with freshet and ending when the drains dried up near mid-summer. Study results indicated that the amount of nutrients transported was generally greater during freshet and summer rain storms. Occasionally, however, nutrients in summer discharge exceeded those transported during freshet. The water quality model was applied to the Brown drain to investigate the effects of different drain sizes for rainfall amounts under 2, 5, 10, 15, and 20 year return periods. Generally the results indicate that as the return periods became larger (in larger channels) lower nutrients concentrations were predicted downstream (higher decay rates). On average, the model predicted a 15%–20% decline in nutrient concentration with a 20-year return channel design compared to a 2-year return. The research from this study may provide an impetus to the policy-making process of drainage design.     

Economic analysis of water temperature reduction practices in a large river floodplain: an exploratory study of the Willamette River,Oregon

This paper examines ecosystem restoration practices that focus on water temperature reductions in the upper mainstem Willamette River, Oregon, for the benefit of endangered salmonids and other native cold‐water species. The analysis integrates hydrologic, natural science and economic models to determine the cost‐effectiveness of alternative water temperature reduction strategies. A temperature model is used to simulate the effects of combinations of upstream riparian shading and flow augmentations on downstream water temperatures. Costs associated with these strategies are estimated and consist of the opportunity costs of lost agricultural production and recreation opportunities due to flow releases from an up‐stream reservoir. Temperature reductions from another strategy, hyporheic flow enhancement, are also examined. Restoration strategies associated with enhanced hyporheic cooling consist of removal/reconnection of current obstacles to the creation of dynamic river channel complexity. The observed reduction of summer water temperatures associated with enhanced channel complexity indicates that restoring hyporheic flow processes is more likely to achieve cost‐effective temperature reductions and meet the total maximum daily load (TMDL) target than conventional approaches that rely on increased riparian shading or/and combinations of flow augmentation. Although the costs associated with the hyporheic flow enhancement approach are substantial, the effects of such a long‐term ecological improvement of the floodplain are expected to assist the recovery of salmonid populations and provide ancillary benefits to society. Copyright © 2008 John Wiley & Sons, Ltd.     

黄河小浪底水利枢纽工程建设期库区及下游水环境状况分

为监控污染 ,保护环境 ,减轻工程对环境的影响 ,1997年 3月开始对小浪底工程库区及下游影响区水质进行监测。 5年的监测表明 ,小浪底库区及下游影响区水质主要受耗氧有机物污染 ,干流污染重于支流 ,非汛期污染重于汛期 ,水质主要受上游来水水质、库区污染源、工程施工以及水量变化的影响。随着工程施工结束以及库区开发活动的开始 ,上游来水水质和开发活动可能产生的污染将成为影响小浪底库区及其下游影响区水质的主要因素     

Influence of extreme drawdown on water quality downstream of a large water storage reservoir

The Serial Discontinuity Concept (SDC) proposes that dams have the potential to affect the downstream ecological condition of rivers. While the SDC was developed principally around changes to physical habitat or temperature, reservoirs also have the potential to impact on downstream water quality, including algal community structure. In the current study we examined the impacts of an extreme drawdown event on nutrient loads and algal community structure downstream of a large water storage reservoir in south‐eastern Australia—Lake Hume. The lake was a net exporter of carbon, nitrogen, phosphorus and iron during the study period and was a net sink for manganese. Most of the carbon, nitrogen and phosphorus exported from the lake was in the form of algal biomass. Processes in the lake also influenced the downstream algal community structure. Upstream of the reservoir green algae were the most dominant species; within and downstream of the reservoir cyanobacteria dominated. Much of the algal biomass found at the downstream sites appeared to originate in Lake Hume and was physically transported downstream. Copyright © 2009 John Wiley & Sons, Ltd.     

城市重度污染内河水质断面追踪监测与污染成因分析

针对某条流经城市人口密集区域河流的重度污染现状,在多个断面布点,对干流和支流水质进行了全面监测,以追踪分析水质变化趋势和污染成因.结果显示,该河流从上游到下游水质有所好转,COD从321 mg/L下降至100～135 mg/L,BOD5从226 mg/L下降至27～36 mg/L,悬浮物从159 mg/L下降至15～30 mg/L,总磷从8.91 mg/L下降至3～4 mg/L.位于河流上游的污水处理厂在水质改善中发挥了重要作用,COD整体去除率达到77.6％,但不能根本改善河流的污染现状.4条支流污染严重,是造成干流水质污染的主要原因,COD均在230 mg/L以上,最高达到512mg/L,BOD5最高达295 mg/L.对支流D实行重点监测,发现氨氮和总氮规律性升高,镍、锰、铜、锌、铬等重金属多次检出,铅的检出率高达77.1％.针对污染现状提出了治理建议.     

The effect of hydrodynamic flow regimes on the algal bloom in a monomictic reservoir

The effectiveness of a proposed curtain weir to be installed in the transitional zone of a eutrophic reservoir located in monsoon areas on the control of algal blooms in the lacustrine zone where drinking water withdrawals occur was assessed with various hydrodynamic flow regimes. A two-dimensional hydrodynamic and eutrophication model that can accommodate vertical displacement of the weir following the water surface changes was developed and validated using field data obtained from two distinctive hydrological years; drought (2001) and wet (2004). The model adequately reproduced the temporal and spatial variations of temperature, nutrients and phytoplankton concentrations in the reservoir. The efficacy of the curtain weir method found to be diverse for different hydrological conditions and dependent on the inflow densimetric Froude number (Fr(i)). Algal blooming was considerably mitigated by curtailing the transport of nutrients and algae from riverine zone to lacustrine epilimnion zone during the drought year as long as Fr(i) < 1.0. However, some flood events with Fr(i) > 1.0 transported nutrients and algae built upstream of the weir into the downstream euphotic zone by strong entrainments in 2004. Numerical experiments revealed that the efficiency of the weir on the control of algal blooming becomes marginal if the Fr(i) > 3.0.