Impacts of dam construction on streamflows during drought periods in the Upper Colorado River Basin,Texas

The purpose of this study was to assess the impacts of dam construction on streamflow during a severe drought in the upper Colorado River basin (TX), upstream of Lake Buchanan reservoir. The region has experienced severe, prolonged droughts over the past century. To ameliorate the effects of drought, and increase water storage for use during dry periods, several dams were constructed on the mainstem and tributaries of the Colorado River upstream of Lake Buchanan since the late‐1940s. Analysis of flow at the gauge above Lake Buchanan indicated streamflow was significantly reduced during the recent drought (2009–2014), compared with streamflows during the ‘drought of record’ (1950–1957). The construction of these upstream dams reduced streamflow by intercepting and storing water. It is concluded that building reservoirs in the western portion of the basin, largely in response to past droughts, although increasing water supplies for local uses, exacerbated the downstream effects of the hydrological drought, essentially making it the worst in recorded history.     

Temporal Hydrologic Alterations Coupled with Climate Variability and Drought for Transboundary River Basins

Climate change (CC) and drought episode impacts linked with anthropogenic pressure have become an increasing concern for policy makers and water resources managers. The current research presents a comprehensive methodology but simple approach for predicting the annual streamflow alteration based on drought indices and hydrological alteration indicators. This has been achieved depending on the evaluation of drought severity and CC impacts during the human intervention periods to separate the influence of climatic abnormality and measure the hydrologic deviations as a result of streamflow regulation configurations. As a representative case study, the Lesser Zab River Basin in northern Iraq has been chosen. In order to analyse the natural flow regime, 34 hydrological years of streamflow (1931–1965) prior to the main dam construction were assessed. The Indicators of Hydrologic Alteration (IHA) method has been applied to quantify the hydrological alterations of various flow characteristics. In addition, an easy approach for hydrological drought prediction in relatively small basins grounded on meteorological parameters during the early months of the hydrological year has been presented. The prediction was accomplished by implementing the one-dimensional drought examination and the reconnaissance drought index (RDI) for evaluating the severity of meteorological drought. The proposed methodology is founded on linear regression relations connecting the RDI of 3, 6, and 12 months and the streamflow drought index (SDI). The results are critical for circumstances where an early exploration of meteorological drought is obtainable. Outcomes assist water resources managers, engineers, policy makers and decision-makers responsible for mitigating the effects of CC.     

基于GRACE卫星数据的汉江流域旱情反演及影响因素定量分析

气候变化和人类活动对汉江流域旱情有重要影响。利用卫星时变重力场反演地面水储量可以弥补传统流域水储量监测的缺陷。以GRACE卫星数据为基础,采用水储量亏损方法建立模型反演汉江流域2004—2014年间干旱事件,结合多源卫星数据和居民用水量数据,定量分析了气候变化和人类活动对汉江流域干旱事件的影响。结果表明,汉江流域2006、2007、2011、2013年分别发生了干旱事件,降雨、蒸发、人类活动(水库蓄水和居民用水量)等变量与陆地水储量变化显著相关,气候变化对4场干旱事件发生的贡献率分别为0.41、0.43、0.36、0.36,人类活动对4场干旱事件发生的贡献率分别为0.59、0.57、0.65、0.64,贡献度的趋势表明人类活动对汉江流域干旱事件的影响在不断增强。     

基于SWAT的北江流域蓝绿水评估及其干旱响应

为探究北江流域的水资源状况及其在不同程度干旱下的变化特征,利用SWAT模型模拟北江流域径流过程,并在此基础上评估北江流域的蓝绿水资源时空变化及其对干旱的响应特征。研究表明:北江流域水资源以蓝水为主,多年平均蓝水量为1 149.08 mm,绿水量为981.08 mm,绿水系数为0.48; 1966—2010年间,北江流域蓝绿水无显著变化趋势,空间分布上蓝水表现为南多北少,而绿水则与之相反;蓝水对干旱的响应更敏感,重度干旱下,北江流域的蓝水量较多年平均值分别减少16.94%,流域内的水资源分配模式由以蓝水为主转变为以绿水为主,绿水系数达0.53。从蓝水和绿水的角度研究北江流域的水资源状况及其干旱响应特征,可以为流域水资源管理提供依据,增强应对干旱风险、保障流域水安全的能力。     

Assessment of Hydrological Drought Revisited

A variety of indices for characterising hydrological drought have been devised which, in general, are data demanding and computationally intensive. On the contrary, for meteorological droughts very simple and effective indices such as the Standardised Precipitation Index (SPI) have been used. A methodology for characterising the severity of hydrological droughts is proposed which uses an index analogous to SPI, the Streamflow Drought Index (SDI). Cumulative streamflow is used for overlapping periods of 3, 6, 9 and 12 months within each hydrological year. Drought states are defined which form a non-stationary Markov chain. Prediction of hydrological drought based on precipitation is also investigated. The methodology is validated using reliable data from the Evinos river basin (Greece). It can be easily applied within a Drought Watch System in river basins with significant storage works and can cope with the lack of streamflow data.     

Methodology for Drought Risk Assessment in Within-year Regulated Reservoir Systems. Application to the Orbigo River System (Spain)

Drought occurrence and its related impacts are a major concern in many river basins throughout the world. In the last years, drought management procedures have moved from a crisis approach towards a more sensitive preparedness approach. Drought plans development has arisen as an effective way of providing measures and actions to manage drought situations. However, due to each river basin has different operation characteristics, drought management requires a different approach in order to be efficient. Decision support tools are a great ally of water managers, especially in situations of high water stress and hydrologic uncertainty, allowing them to in-deep analyze the system and finding the best measures to minimize the risk of a system failure. This paper studies the difficulties of only using an indicator system based in current and past data to assess the drought risk in within-year regulated reservoir systems. It proposes the complementary use of a general risk assessment methodology to anticipate the future probable status of the system and defining the current drought scenario. It shows how the complementary use of a monitoring system and a risk assessment decision support system may improve the drought detection process allowing water managers optimizing the selection of mitigation measures and minimizing the probability of overreaction during a drought situation.     

Development of a Demand Driven Hydro-climatic Model for Drought Planning

In recent years, droughts with increasing severity and frequency have been experienced around the world due to climate change effects. Water planning and management during droughts needs to deal with water demand variability, uncertainties in streamflow prediction, conflicts over water resources allocation, and the absence of necessary emergency schemes in drought situations. Reservoirs could play an important role in drought mitigation; therefore, development of an algorithm for operation of reservoirs in drought periods could help to mitigate the drought impacts by reducing the expected water shortages. For this purpose, the probable drought’s characteristics and their variations in response to factors such as climate change should be incorporated. This study aims at developing a contingency planning scheme for operation of reservoirs in drought periods using hedging rules with the objective of decreasing the maximum water deficit. The case study for evaluation of the performance of the proposed algorithm is the Sattarkhan reservoir in the Aharchay watershed, located in the northwestern part of Iran. The trend evaluations of the hydro-climatic variables show that the climate change has already affected streamflow in the region and has increased water scarcity and drought severity. To incorporate the climate change study in reservoir planning; streamflow should be simulated under climate change impacts. For this purpose, the climatic variables including temperature and precipitation in the future under climate change impacts are simulated using downscaled GCM (General Circulation Model) outputs to derive scenarios for possible future drought events. Then a hydrological model is developed to simulate the river streamflow, based on the downscaled data. The results show that the proposed methodology leads to less water deficit and decreases the drought damages in the study area.     

Trend Analysis of Streamflow Drought Events in Nebraska

A streamflow drought event, defined by applying the threshold level approach on streamflow time series, is composed of three parameters: duration, severity and magnitude. This study reveals statistical characteristics on streamflow drought event parameters and detects spatial and temporal trends in the streamflow drought in terms of frequency, duration and severity in Nebraska. The studies are conducted on three time periods: 1970–2001 (60 stations), 1950–2001 (43 stations), and 1932–2001 (9 stations). The statistical tests performed on the drought event parameters include correlation between event parameters tests, Hurst coefficients and lag-one coefficients, and trend-free pre-whitening Mann–Kendall (TFPW-MK) tests. The analysis shows that there is no uniform trend on the streamflow drought in the whole state. However, some trends are evident for specific regions. Specifically, it is most likely that droughts in the Republican watershed have become more intense; whereas the drought has become slightly alleviated in the Missouri and nearby watersheds.     

龙羊峡水库旱限水位优化控制研究

龙羊峡水库是黄河上游具有供水、发电等多目标运用方式的多年调节水库。在分析多年调节水库功能的基础上,辨析提出多年调节水库旱限水位的概念、内涵。研究多年调节水库旱限水位控制的理论与方法,基于最优控制理论和自适应技术,建立由多年调节水库跨年度补水收益最大化和出库过程最优化的控制模型,并探讨人工鱼群智能算法的求解实现。以黄河流域1990年代连续干旱枯水时段为例,研究了龙羊峡水库最优旱限水位控制策略,结果表明通过龙羊峡水库旱限水位最优控制实施跨年度补水、蓄丰补枯可增加干旱枯水年份的可供水量,在一定程度上减轻黄河流域旱灾损失。     

Diagnosing Causes of Water Scarcity in Complex Water Resources Systems and Identifying Risk Management Actions

From the water management perspective, water scarcity is an unacceptable risk of facing water shortages to serve water demands in the near future. Water scarcity may be temporary and related to drought conditions or other accidental situation, or may be permanent and due to deeper causes such as excessive demand growth, lack of infrastructure for water storage or transport, or constraints in water management. Diagnosing the causes of water scarcity in complex water resources systems is a precondition to adopt effective drought risk management actions. In this paper we present four indices which have been developed to evaluate water scarcity. We propose a methodology for interpretation of index values that can lead to conclusions about the reliability and vulnerability of systems to water scarcity, as well as to diagnose their possible causes and to propose solutions. The described methodology was applied to the Ebro river basin, identifying existing and expected problems and possible solutions. System diagnostics, based exclusively on the analysis of index values, were compared with the known reality as perceived by system managers, validating the conclusions in all cases.     

尽快制订抗旱条例的建议

我国是一个干旱及旱灾频繁发生的国家.面对日趋严峻的抗旱形势,急需加强法制建设,制订<中华人民共和国抗旱条例>,使抗旱工作有法可依.制订这一条例应遵循针对性强、涵盖性强等原则,突出抗旱工作中基本关系,在制订<抗旱条例>时,应明确抗旱责任制度,旱情预测、监测、发布制度,旱前检查制度,抗旱预案工作制度等,确立抗旱责任制等九项基本抗旱工作制度.     

多年调节水库旱限水位优化控制研究

在分析多年调节水库功能的基础上,辨析提出多年调节水库旱限水位的概念和内涵。基于最优控制理论和自适应技术,以干旱年份流域供水总收益最大为目标建立具有在线辨识、自动寻优的多年调节水库旱限水位最优控制模型,并引入人工鱼群智能求解算法,实现多年调节水库跨年度补水收益最大化和出库过程最优化。以黄河流域20世纪90年代连续干旱枯水时段为例,优化提出龙羊峡水库旱限水位控制方案,集成多年调节水库旱限水位控制策略。结果表明,通过龙羊峡水库旱限水位最优控制实施跨年度补水和蓄丰补枯,可增加干旱枯水年份的供水量,在一定程度上减轻流域旱灾损失。     

Climate Change and Resource Management in the Columbia River Basin

Abstract

Scenarios of global climate change were examined to see what impacts they might have on transboundary water management in the Columbia River basin. Scenario changes in natural streamflow were estimated using a basin hydrology model. These scenarios tended to show earlier seasonal peaks, with possible reductions in total annual flow and lower minimum flows. Impacts and adaptation responses to the natural streamflow scenarios were determined through two exercises: (a) estimations of system reliability using a reservoir model with performance measures and (b) interviews with water managers and other stakeholders in the Canadian portion of the basin. Results from the two exercises were similar, suggesting a tendency towards reduced reliability to meet objectives for power production, fisheries, and agriculture. Reliability to meet flood control objectives would be relatively unchanged in some scenarios but reduced in others. This exercise suggests that despite the high level of development and management in the Columbia, vulnerabilities would still exist, and impacts could still occur in scenarios of natural streamflow changes caused by global climate change. Many of these would be indirect, reflecting the complex relationship between the region and its climate.     

The evolution of water management in Alberta,Canada: the influence of global management paradigms and path dependency

This study examines the evolution of Alberta's water management framework in response to changing demands, national policy and global paradigms. The South Saskatchewan River basin is presented as the crucible for Albertan water policy, given the severity of droughts, over-allocation, and environmental degradation. The analysis finds a distinct trend in the past two decades towards integration and sustainable management, as affirmed by the globally dominant integrated water resource management paradigm. The concept of path dependency offers valuable insight into the barriers posed by past policy frameworks to water management systems, particularly in relation to the prior-allocation system of water rights.     

Drought Analysis in the Awash River Basin,Ethiopia

This study analyzes drought characteristics in the Awash River Basin of Ethiopia based on meteorological and hydrological variables. Standardized precipitation index is used for temporal and spatial analyses of meteorological drought and the theory of runs is used to define hydrological drought by considering streamflow as the drought indicator. Drought severity maps are generated using Arc View/GIS by summarizing the percentage of occurrence of droughts in areas within the study basin. Extreme drought category on 12-month time scale indicated that extreme events occur most frequently in the Upper and Middle Awash Basin. However, while considering the overall categories of drought, the most frequent droughts occurred in the Middle and Lower Awash Basin during the period of analysis. Similarly, results based on hydrological drought analysis shows that the severest drought events occurred in the Middle Awash Basin during May 1988 to June 1988 and April 1998 to May 1998. Analysis of the relationship between meteorological and hydrological drought indices in the basin shows that occurrence of hydrological drought event at Melka Sedi stream gauging station lags meteorological drought event in the Upper Awash on average by 7 months with a variation of 3 to 13 months.     

海河流域区域干旱特征的分析与研究

海河流域素有“十年九旱”的说法,是我国水资源短缺问题非常严重的地区.根据海河流域1951～2001年的逐月降雨资料和历史的灾情文献记载,采用游程理论识别拟定了适合海河流域干旱状况的干旱指标,并用该指标分析了海河流域典型干旱年份的旱情区域分布特征,给出了各等级干旱的区间分布.结果表明干旱现象具有明显的地区差异,不同地区在干旱规划管理中应采取相应不同的措施.     

基于SWAT的沁河流域水资源生态足迹计算及承载程度分析

水资源生态足迹能够反映人类发展对自然界水资源的压力,明确流域水资源承载状况可为生态环境保护、经济社会发展和水资源科学管理提供决策依据,对推动流域生态文明建设和高质量发展具有重要意义。以沁河流域为例,借助水资源生态足迹模型,利用SWAT模型输出结果计算各子流域水资源生态足迹,并评估沁河流域水资源承载状况。结果表明：2010—2016年沁河流域水资源量多年平均值为6.17×10⁸ m³,主要受到降水量影响;各子流域水资源生态压力指数均大于1,说明沁河流域水资源处于不可承载状态,供需矛盾突出;2010—2016年水资源承载状况虽有所改善,但仍处于不可持续利用状态。研究结果可为沁河流域水资源科学管理提供参考依据,同时为其他流域尺度上的水资源生态足迹计算提供新思路。     

Streamflow Forecast and Reservoir Operation Performance Assessment Under Climate Change

This study attempts to investigate potential impacts of future climate change on streamflow and reservoir operation performance in a Northern American Prairie watershed. System Dynamics is employed as an effective methodology to organize and integrate existing information available on climate change scenarios, watershed hydrologic processes, reservoir operation and water resource assessment system. The second version of the Canadian Centre for Climate Modelling and Analysis Coupled Global Climate Model is selected to generate the climate change scenarios with daily climatic data series for hydrologic modeling. Watershed-based hydrologic and reservoir water dynamics modeling focuses on dynamic processes of both streamflow generation driven by climatic conditions, and the reservoir water dynamics based on reservoir operation rules. The reliability measure describes the effectiveness of present reservoir operation rules to meet various demands which are assumed to remain constant for the next 100 years in order to focus the study on the understanding of the structure and the behaviour of the water supply. Simulation results demonstrate that future climate variation and change may bring more high-peak-streamflow occurrences and more abundant water resources. Current reservoir operation rules can provide a high reliability in drought protection and flood control.     

三峡水库抗旱调度问题的探讨

基于三峡水库现有调度方案,分析了三峡水库防洪、抗旱、发电和航运等调度的运行条件和控制因素;根据长江经济社会发展需求和近年来出现的干旱缺水问题,分析长江中下游干旱情况及对三峡水库调度的需求;初步论述了三峡水库承担抗旱调度的能力和存在的问题,并对三峡水库抗旱调度和长江抗旱综合措施提出一些建议。研究表明：三峡水库增加抗旱调度是必要的,但需要设定适当的调度条件,建立调度效果评价体系。