Climate change uncertainty in environmental flows for the Mekong River

Abstract

A MIKE SHE model of the Mekong, calibrated and validated for 12 gauging stations, is used to simulate climate change scenarios associated with a 2°C increase in global mean temperature projected by seven general circulation models (GCMs). Impacts of each scenario on the river ecosystem and, hence, uncertainty associated with different GCMs are assessed through an environmental flow method based on the range of variability approach. Ecologically relevant hydrological indicators are evaluated for the baseline and each scenario. Baseline-to-scenario change is assessed against thresholds that define likely risk of ecological impact. They are aggregated into single scores for high and low flows. The results demonstrate considerable inter-GCM differences in risk of change. Uncertainty is larger for low flows, with some GCMs projecting high and medium risk at the majority of locations, and others suggesting widespread no or low risk. Inter-GCM differences occur along the main Mekong, as well as within major tributaries.

Editor Z.W. Kundzewicz

Citation Thompson, J.R., Laizé, C.L.R., Green, A.J., Acreman, M.C., and Kingston, D.G., 2014. Climate change uncertainty in environmental flows for the Mekong River. Hydrological Sciences Journal, 59 (3–4), 935–954.     

Restoring environmental flows through adaptive reservoir management: planning,science, and implementation through the Sustainable Rivers Project

Abstract

River managers worldwide are increasingly addressing flow needs for ecosystem processes and services in their management plans for dams and reservoirs. However, while planning and scientific assessments have advanced substantially, successful re-operation of infrastructure to achieve environmental benefits has been more limited. The Sustainable Rivers Project (SRP) was formalized in 2002, as a national partnership between the United States Army Corps of Engineers and The Nature Conservancy to define and implement environmental flows through adaptive reservoir management. The project has focused on eight demonstration basins containing 36 Corps dams, but is designed to direct the collective experience from these sites to help guide agency-wide operational changes for as many as 600 dams to benefit up to 80 000 river kilometres and tens of thousands of hectares of related floodplain and estuarine habitat. This article summarizes the progress to date on defining and implementing environmental flows through the SRP, and evaluates the technical, social, legal, and institutional factors that act as dominant enabling conditions and constraints to implementation.

Editor Z.W. Kundzewicz; Guest editor M. Acreman     

A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River,South Africa

Abstract

Environmental flow provisions are a legal obligation under South Africa’s National Water Act (1998) where they are known as the “ecological reserve”, which is now being realized in river operations. This article presents a semi-quantitative method, based on flow–duration curve (FDC) analysis, used to assess the compliance of the Crocodile (East) River with the reserve in an historical context. Using both monthly and daily average flow data, we determine the extent and magnitude of non-compliant flows against environmental water requirements (EWRs) for three periods (1960–1983, 1983–2000, and 2000–2010). The results suggest a high degree of non-compliance, with the reserve increasing with each of these periods (14%, 35%, and 39% of the time), respectively, where effects were most pronounced in the low-flow season. The results also suggest that, whilst the magnitudes of reserve infringements for the latter period are relatively high, there appears to have been some improvement since the implementation of the river’s operating rules.

Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Riddell, E., Pollard, S., Mallory, S., and Sawunyama, T., 2014. A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River, South Africa. Hydrological Sciences Journal, 59 (3–4), 831–843.     

Ecological and environmental instream flow requirements for the Wei River—the largest tributary of the Yellow River

Instream flows are essential determinants of channel morphology, riparian and aquatic flora and fauna, water quality estuarine inflow and stream load transport. The ecological and environmental instream flow requirements (EEIFR) should be estimated to make the exploitation and utilization of water resources in a highly efficient and sustainable way and maintain the river ecosystem good health. As the largest tributary of the Yellow River, the Wei River is the ‘Mother River’ of Guanzhong region in Shaanxi province. It plays a great role in the development of West China and the health of the ecosystem of the Yellow River. The objective of this study is to estimate the EEIFR for improving the Wei River's ecological and environmental condition and develop the river healthily. Concerning the main ecological and environmental functions of the Wei River in Shaanxi Province, the EEIFR for each section of the Wei River including minimum instream flow requirements (IFR) for aquicolous biotopes maintenance, IFR for channel seepage, channel evaporation, stream self‐purification and sediment transportation were estimated in this paper. The methods to estimate the instream flow requirements for stream self‐purification and instream flow requirements for sediment transportation were proposed. The temporal scale of typical years include the year with the probability 25% of occurrence (high‐flow year), the year with the probability 50% (normal‐flow year) and the year with the probability 75% (low‐flow year). The results show that the EEIFR for the Wei River mainly include instream flow requirements for self‐purification and sediment transportation in each typical year. From high‐flow year to low‐flow year, the annual EEIFR for each reach decrease, except those for the reach from Linjiacun to Weijiabao, and from Linjiacun at the upper reaches to Huaxian at the lower reaches, and the annual reach EEIFR decrease in a sequence. Copyright © 2007 John Wiley & Sons, Ltd.     

Identification of appropriate lags and temporal resolutions for low flow indicators in the River Rhine to forecast low flows with different lead times

The aim of this paper is to assess the relative importance of low flow indicators for the River Rhine and to identify their appropriate temporal lag and resolution. This is done in the context of low flow forecasting with lead times of 14 and 90 days. First, the Rhine basin is subdivided into seven sub‐basins. By considering the dominant processes in the sub‐basins, five low flow indicators were selected: precipitation, potential evapotranspiration, groundwater storage, snow storage and lake storage. Correlation analysis was then carried out to determine the relationship between observed low flows and preselected indicators with varying lags (days) and temporal resolutions (from 1 day to 7 months). The results show that the most important low flow indicators in the Alpine sub‐basins for forecasts with a lead time of 14 days are potential evapotranspiration with a large lag and temporal resolution, and lake levels with a small lag and temporal resolution. In the other sub‐basins groundwater levels with a small lag and temporal resolution are important in addition to potential evapotranspiration with a large lag and temporal resolution. The picture is slightly different for forecasts with a lead time of 90 days. The snow storage in the Alpine sub‐basins and the precipitation in the other sub‐basins also become relevant for low flows. Consequently, the most important low flow indicators in the Alpine sub‐basins for forecasts with a lead time of 90 days are potential evapotranspiration with a large lag and temporal resolution, lake levels with a small lag and temporal resolution and snow storage with a small lag and large temporal resolution. The resultant correlation maps provide appropriate lags and temporal resolutions for indicators to forecast low flows in the River Rhine with different lead times. Copyright © 2012 John Wiley & Sons, Ltd.     

Regionalization approaches for the periodic parameters of monthly flows: a case study of Ceyhan and Seyhan River basins

Five alternative regionalization approaches in two broad categories, named function‐free and functional approaches, have been proposed to predict periodic behaviours in the basic parameters of monthly stream flows throughout homogeneous regions defined. Function‐free and functional approaches rely on the standardized (or normalized) forms of raw and fitted values of the monthly periodic parameters considered. Homogeneous regions are identified based on these standardized/normalized parameters by means of the hierarchical clustering analysis. The proposed models are tested for two major river basins in south Turkey. It is concluded that the proposed regional models are very effective to estimate periodic behaviour of monthly flows. The functional approaches are quite plausible, and the function‐free approach needs much more parameters. Both types of regionalization approaches can be reliably used to get regional monthly flow estimates for the flow sections where monthly records are not available or too short. Copyright © 2010 John Wiley & Sons, Ltd.     

生态最相关水文指标的优选及其在洞庭湖环境流量估算中的应用

水文改变指标(IHA)能够较为全面地描述水文状况,在评估水文情势改变及其生态系统影响方面具有广泛的应用.尽管该指标体系较为完善,但是数量众多的水文变量仍然存在信息冗余问题.根据洞庭湖城陵矶水文站1955-2014年的径流量数据,采用主成分分析(PCA)筛选了生态最相关水文指标(ERHIs),结合ERHIs改进了用于估算环境流量的变化范围法(RVA),并将其应用在洞庭湖出口的环境流量估算中.基于PCA选取了年最大90日流量、年最小3日流量、年最小流量出现时间、3月流量、6月流量、流量逆转次数和低流量年内平均历时7个变量作为洞庭湖出口的ERHIs.纵向和横向的对比分析都表明选取的ERHIs是合理的.ERHIs不仅有效缓解了IHA的冗余性问题,还有利于抓住最关键的生态水文变量.根据ERHIs改进的RVA方法在设定洞庭湖出口环境流量时,极大地简化原来的众多管理目标,对生态水文研究、水资源管理和生态保护都具有重要的参考价值和借鉴意义.     

Integrating water management,habitat modelling and water quality at the basin scale and environmental flow assessment: case study of the Tormes River,Spain

Abstract

Multidisciplinary models are useful for integrating different disciplines when addressing water planning and management problems. We combine water resources management, water quality and habitat analysis tools that were developed with the decision support system AQUATOOL at the basin scale. The water management model solves the allocation problem through network flow optimization and considers the environmental flows in some river stretches. Once volumes and flows are estimated, the water quality model is applied. Furthermore, the flows are evaluated from an ecological perspective using time series of aquatic species habitat indicators. This approach was applied in the Tormes River Water System, where agricultural demands jeopardize the environmental needs of the river ecosystem. Additionally, water quality problems in the lower part of the river result from wastewater loading and agricultural pollution. Our methodological framework can be used to define water management rules that maintain water supply, aquatic ecosystem and legal standards of water quality. The integration of ecological and water management criteria in a software platform with objective criteria and heuristic optimization procedures allows realistic assessment and application of environmental flows to be made. Here, we improve the general methodological framework by assessing the hydrological alteration of selected environmental flow regime scenarios.

Editor D. Koutsoyiannis; Guest editor M. Acreman

Citation Paredes-Arquiola, J., Solera, A., Martinez-Capel, F., Momblanch, A., and Andreu, J., 2014. Integrating water management, habitat modelling and water quality at the basin scale and environmental flow assessment: case study of the Tormes River, Spain. Hydrological Sciences Journal, 59 (3–4), 878–889.     

Introducing environmental thresholds into water withdrawal management of mountain streams in the Kura River basin,Azerbaijan

Abstract

The study aims to set and implement environmentally relevant limits for the exploitation of mountain streams in the Kura River basin of Azerbaijan. Such streams represent the preferred spawning grounds for valuable sturgeon of the Caspian Sea, but experience continuously increasing exploitation in the form of water withdrawals for industry and irrigation. Since no detailed environmental flow assessments have been conducted on any of the Kura basin streams, an interim approach is suggested based on minimum flow, referred to as “base environmental minimum”. The latter may be estimated from the unregulated parts of observed or simulated daily flow records. Environmental flow requirements for individual months of an individual year may be calculated using correction factors related to monthly rainfall. Simple relationships are suggested for base environmental flow estimation at ungauged sites, and the implications of river pollution for monthly environmental requirements are examined. Further, definition of environmentally critical periods in a stream is proposed based on a ratio of observed to “environmental” flow as an indicator of environmental stress. It is illustrated that the conjunctive use of several closely located streams for water supply may significantly reduce the duration of, or completely eliminate, environmentally critical periods. The idea of environmentally acceptable areal water withdrawal is formulated, so that the overall approach may be applied for environmentally sustainable water withdrawal management in other small streams.     

Low and high flow analyses and wavelet application for characterization of the Blue Nile River system

The low and high flow characteristic of the Blue Nile River (BNR) basin is presented. The study discusses low and high flow, flow duration curve (FDC) and trend analysis of the BNR and its major tributaries. Different probability density functions were fitted to better describe the low and high flows of the BNR and major tributaries in the basin. Wavelet analysis was used in understanding the variance and frequency‐time localization and detection of dominant oscillations in rainfall and flow. FDCs were developed, and low flow (below 50% exceedance) and high flow (over 75% exceedance) of the curves were analysed and compared. The Gravity Recovery and Climate Experiment (GRACE) satellite‐based maps of monthly changes in gravity converted to water equivalents from 2003 to 2006 for February, May and September showed an increase in the moisture influx in the BNR basin for the month of September, and loss of moisture in February and May. It was also shown that 2004 and 2005 were drier with less moisture influx compared to 2003 and 2006. On the basis of the Kolmogorov‐Smirnov, Anderson‐Darling and Chi‐square tests, Gen. Pareto, Frechet 3P, Log‐normal, Log‐logistics, Fatigue Life and Phased Bi‐Weibull distributions best describe the low and high flows within the BNR basin. This will be beneficial in developing flow hydrographs for similar ungauged watersheds within the BNR basin. The below 50% and above 75% exceedance on the FDC for five major rivers in addition to the BNR showed different characteristics depending on size, land cover, topography and other factors. The low flow frequency analysis of the BNR at Bahir Dar showed 0·55 m³/s as the monthly low flow with recurrence interval of 10 years. The wavelet analysis of the rainfall (at Bahir Dar and basin‐wide) and flows at three selected stations shows inter‐ and intra‐annual variability of rainfall and flows at various scales. Copyright © 2009 John Wiley & Sons, Ltd.     

Potential of the LASH model for water resources management in data-scarce basins: a case study of the Fragata River basin,southern Brazil

ABSTRACT

The objective of this study was to evaluate, based on a data-scarce basin in southern Brazil, the potential of the Lavras Simulation of Hydrology (LASH) model for estimating daily streamflows, annual streamflow indicators and the flow–duration curve. It was also used to simulate the different runoff components and their consistency with the basin physiographical characteristics. The statistical measures indicated that LASH can be considered suitable according to widely used classifications and when compared with other studies involving hydrological models. LASH also showed satisfactory results for annual indicators, especially for maximum and average annual streamflows, as well as for the flow–duration curve. It was found that the model was consistent with the basin characteristics when simulating runoff components. The results obtained in this study allowed us to conclude that the LASH model has the potential to aid practitioners in water resources management of basins with scarce data and similar soil and land-use conditions.

Editor A. Castellarin; Associate editor Y. Gyasi-Agyei     

A spatial assessment of hydrologic alteration caused by dam construction in the middle and lower Yellow River,China

The ‘range of variability approach’ (RVA) and mapping technique are used to investigate the spatial variability of hydrologic alterations (HA) due to dam construction along the middle and lower Yellow River, China, over the past five decades. The impacts of climate variability on hydrological process have been removed during wet and dry periods and the focus is on the impacts of human activities, such as dam construction, on hydrological processes. Results indicate the following: (1) The impacts of the Sanmenxia reservoir on the hydrologic alteration are relatively slight with a mean HA value of 0·48, ranking in the last place among the four large reservoirs. (2) Xiaolangdi reservoir has significantly changed the natural flow regime downstream with mean HA value of 0·56, ranking it in first place among the large reservoirs. (3) The results of ranked median degrees of 33 hydrologic alteration indicators for 10 stations in the Yellow River show that the hydrologic alteration of Huayuankou ranks the highest among 10 stream gauges. (4) Impacts of reservoirs on hydrological processes downstream of the dams are closely associated with the regulating activities of the reservoirs. At the same time, alterations of streamflow regimes resulting from climatic changes (e.g. precipitation variability) make the situation more complicated and more hydrological observations will be necessary for further analysis. The results of the current study will be greatly beneficial to the regional water resources management and restoration of eco‐environmental systems in the middle and lower Yellow River characterized by intensified dam construction under a changing environment. Copyright © 2008 John Wiley & Sons, Ltd.     

Cost of environmental flow during water scarcity in the arid Huasco River basin,northern Chile

Abstract

This investigation presents a new approach to estimate the costs resulting from the introduction of environmental flows in the arid Huasco River basin, located in the Atacama Region of Chile, one of the most sophisticated private water markets worldwide. The aim is to provide information to the water users, who hold the right to decide on water use, and thereby support the inclusion of environmental flows into decision-making. Costs are estimated by calculating the loss of agricultural productivity resulting from a trade-off between users and environmental flow requirements in times of water scarcity. Based on environmental flow requirements calculated by International Union for Conservation of Nature (IUCN), and hydrological supply-and-demand modelling using the Water Evaluation and Planning (WEAP) model, economic parameters of water productivity are calculated for the main economic sectors and then included in hydrological analysis. The study presents concrete costs that might be imposed on the water users during times of water scarcity, and confirms that there are significant variations in water productivity between different sectors.

Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Wagnitz, P., Núñez, J., and Ribbe, L., 2014. Cost of environmental flow during water scarcity in the arid Huasco River basin, northern Chile. Hydrological Sciences Journal, 59 (3–4), 700–712.     

A 130 year record of pollution in the Suances estuary (southern Bay of Biscay): implications for environmental management

Geochemical composition (Al, Zn, Pb, Cd, Cu, Ni, Cr and As) and foraminiferal assemblages in surface and core sediments were determined to assess the current situation and the recent environmental transformation of the Suances estuary (southern Bay of Biscay, Spain). Dating of the historical record has been achieved using isotopic analysis (²¹⁰Pb, ¹³⁷Cs) and two benchmark events such as the beginning of the mineral exploitation in the Reocín Pb-Zn deposits and the evolution of the chlor-alkali industry (inputs of Hg). Concentrations of Zn, Pb and Cd in both surface and core samples are remarkably higher than background values, reflecting the existence of significant amounts of polluted materials. The dramatic environmental impact of this pollution is clearly recorded by the change of the foraminiferal assemblages that even reach an afaunal stage during recent decades. Application of two different sets of Sediment Quality Guidelines confirm that they exert potential risk to the environment, and therefore if dredged they should need specific management measures.The results provide a reference database to monitor future environmental changes in the Suances estuary, particularly as regards the contaminated sediment storage and the re-colonization by autochtonous meiofauna.