Impact of Human Intervention and Climate Change on Natural Flow Regime

According to the ‘natural flow paradigm’, any departure from the natural flow condition will alter the river ecosystem. River flow regimes have been modified by anthropogenic interventions and climate change is further expected to affect the biotic interactions and the distribution of stream biota by altering streamflow. This study aims to evaluate the hydrologic alteration caused by dam construction and climatic changes in a mesoscale river basin, which is prone to both droughts and monsoonal floods. To analyse the natural flow regime, 15 years of observed streamflow (1950–1965) prior to dam construction is used. Future flow regime is simulated by a calibrated hydrological model Soil and Water Assessment Tool (SWAT), using ensemble of four high resolution (~25 km) Regional Climate Model (RCM) simulations for the near future (2021–2050) based on the SRES A1B scenario. Finally, to quantify the hydrological alterations of different flow characteristics, the Indicators of Hydrological Alteration (IHA) program based on the Range of Variability Approach (RVA) is used. This approach enables the assessment of ecologically sensitive streamflow parameters for the pre- and post-impact periods in the regions where availability of long-term ecological data is a limiting factor. Results indicate that flow variability has been significantly reduced due to dam construction with high flows being absorbed and pre-monsoon low flows being enhanced by the reservoir. Climate change alone may reduce high peak flows while a combination of dam and climate change may significantly reduce variability by affecting both high and low flows, thereby further disrupting the functioning of riverine ecosystems. We find that, in the Kangsabati River basin, influence of dam is greater than that of the climate change, thereby emphasizing the significance of direct human intervention.     

气候变化和人类活动对开都河上游径流量的影响评价

开都河是新疆焉耆盆地内的重要河流,对维持焉耆盆地水土生态平衡具有极其重要的作用。近年来,开都河流域的水资源问题已经引发了较为严重的生态环境问题。根据流域内1960—2011年水文气象数据,采用小波分析法、累积距平法、累积量斜率变化率法,对开都河上游径流量和气候变化特征及趋势进行了分析,并定量评估了气候变化和人类活动对径流量变化的影响。结果表明:年降水量、蒸散发量和径流量总体均呈增加趋势;径流量的增加变幅为1.93亿m3/(10 a),具有16 a和28 a的准周期变化,且在1995年前后发生了突变;气候变化对开都河上游径流增加的贡献率达100%,人类活动对径流基本无扰动。     

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.     

The Transboundary Impacts of Trade Liberalization and Climate Change on the Nile Basin Economies and Water Resource Availability

A multi-country, multi-sector computable general equilibrium (CGE) model is used for the first time to evaluate the economic and water resource availability effects of trade liberalization (removal of import tariffs) and facilitation (reducing non-tariff barriers) under climate change in the Nile Basin. The analysis uses the GTAP 9 Database and the GTAP-W model that distinguishes between rainfed and irrigated agriculture and implements water as a factor of production directly substitutable in the production process of irrigated agriculture. A full trade liberalization and improved trade facilitation scenario is considered with and without climate change. The study reveals that trade liberalization and facilitation generates substantial economic benefits and enhances economic growth and welfare in the Nile basin. The effect of instituting a free trade policy on water savings is found to be limited, while climate change improves water supply and hence irrigation water use, enhancing economic growth and welfare in the basin.     

Transboundary Impact Assessment in the Sesan River Basin: The Case of the Yali Falls Dam

This case study of the Yali Falls Hydropower Dam in the Vietnamese portion of the Sesan River Basin demonstrates a range of institutional and political challenges encountered in the assessment of large-scale infrastructure projects with transboundary impacts. These challenges include the failure to implement standard international planning processes and the failure to follow due process in dam planning, construction and operation, despite having received funding for international expertise that could have enabled Vietnam to implement such standards. Weak technical and financial capacity on the part of the downstream country, Cambodia, has allowed the politically dominant upstream country, Vietnam, to impose its national interests on downstream communities in Vietnam and Cambodia. A transboundary impact assessment has only been implemented many years after construction was completed.     

WatBal: An Integrated Water Balance Model for Climate Impact Assessment of River Basin Runoff

A water balance model combined with the Priestley-Taylor m ethod for computing potential evapotranspiration has been developed as an integrated tool for modelling the response of river basins to potential climate change. The system was designed in the EXCEL 5.0 spreadsheet environment making use of the Visual Basic programming language. The model is sim ple to use and takes advantage of IIASA's mean monthly hydrologic data base (Leemans & Cramer, 1991). The model environment and two case studies are described.     

The Impact of Climate Change on Crop Production in West Africa: An Assessment for the Oueme River Basin in Benin

Climate change studies for West Africa tend to predict a reduced potential for farming that will affect the food security situation of an already impoverished population. However, these studies largely ignore farmers’ adaptations and market adjustments that mitigate predicted negative effects. The paper attempts to fill some of this gap through a spatially explicit evaluation of the impact of climate change on farm income in the Oueme River Basin (ORB), Benin. The ORB is in many respects representative for the middle belt of West Africa where the predominantly sparse occupation leaves potential for migration from more densely populated areas. We apply a number of structural, spatially explicit relationships estimated for the whole territory of Benin to simulate conditions in the ORB proper that are similar to those currently prevailing in the drier North, and the more humid South. Our scenario results factor out for the main crops cultivated the constituent effects on yields, area, and revenue per ton. We find that under average climate change conditions the current low yields are not reduced, provided that cropping patterns are adjusted, while price increases partly compensate for the remaining adverse effects on farmer income. Consequently, without any policy intervention, farm incomes remain relatively stable, albeit at low levels and with increased occurrence of crop failures after extreme droughts. Scenario simulations show that there are also beneficial aspects that can, with adequate interventions, even turn losses into gains. Main channel for improvement would be the reduction of fallow, which is particularly promising because it requires few adjustments in prevailing farming practices, exploits the potential of uncultivated land and improves the water use efficiency. It also enables the Basin's capacity to absorb future migrant flows from more severely affected neighboring Sahelian areas.     

气候变化对喷赤河径流过程的影响研究

为更好地应对气候变化对塔吉克斯坦积雪冰川流域水文水资源的影响,以塔吉克斯坦的喷赤河流域为研究区,采用假设情景法设定气候变化情景,基于融雪型新安江模型对该流域1981—1990年的径流进行模拟,以期定量分析流域径流对气候变化的响应程度。结果表明:1仅气温升高时,该流域多年平均径流随之增大,且1990年增幅最大;仅降水增大或减小20%时,年径流也相应地增大或减小,且1982年的径流受降水影响最明显,1986年受影响较小。2仅气温上升时,各月月均流量相应增大,增幅最大的月份为5月,增幅最小的为1月;仅降水变化时,径流的变化与它完全呈正相关关系,3月径流变化率最大,6月和10月最小。     

Impact of Climate Change on Water Resources in the Tarim River Basin

The plausible association between climate change and the variability of water resources in the Tarim River basin, west China is investigated in this study. The long-term trend of the hydrological time series including temperature, precipitation, and streamflow are detected by using both parametric and nonparametric techniques. The possible association between the El Niño/Southern Oscillation (ENSO) and these three kinds of time series are tested. This study enhances the knowledge of the climate change impact on water resources in the Tarim River basin. The conclusion obtained in this investigation shows that the temperature experienced a significant monotonic increase at the 5% level of significance during the past 50 yr, and precipitation also exhibited an upward tendency during the past several decades. A significant jump is also detected for both time series around 1986. This may be resulted from the possible impact of climate change, although the interior climate mechanism needs further investigation. Although precipitation and the streamflow from the headwater of the Tarim River exhibited significant increase, decreasing trend has been detected in the streamflow along the mainstream of the river. It implies that anthropogenic activities instead of the climate change dominated the streamflow cessation and the drying-up of the river. Results also showed that no significant association exists between the ENSO and the temperature, precipitation and streamflow in the study area. This conclusion shows that the water curtailment, river desiccation, and ecosystem deterioration in the Tarim River basin may be mainly resulted from the impact of human activities.     

气候变化对塔里木河流域作物需水量的影响

对塔里木河流域26个气象站1961-2005年的常规气象观测资料进行统计分析,结果表明流域内灌区平均气温近45 a来显著上升,其中2000年以后气温较45 a平均气温升高0.75℃,平均每10 a上升0.28℃,升幅达13.75％.采用FAO-布莱尼-克雷多方法,结合作物系数,计算了流域内主要作物的需水量和农田灌溉需水量,结果表明:流域灌区内现状气温上升的情景下,作物参考蒸散量增加量为24.49 mm,增加幅度为2.83％;灌区小麦、果树、棉花、瓜菜和牧草等作物需水量将分别增加3.39％(70.62 mm)、7.30％(152.35 mm)、3.66％ (76.30 mrn)、2.98％ (62.22 mm)、4.49％(93.58 mm);农田灌溉需水量共增加8.44亿m3.     

Impact of Climate Change on the Hydrological Regime and Water Resources in the Basin of Siatista

This paper examines an assessment of the impact of climate change on hydrological regimes and water resources in the basin of Siatista, a sub-basin of the Aliakmon river basin, located in Northern Greece. Initially all acquired hydrometeorological data of the study area, as well as the hydrometric data at the outlet of the basin, were analyzed and processed. A monthly conceptual water balance model was then calibrated using historical hydrometeorological data for determining changes in streamflow runoff under two different equilibrium scenarios (UKHI, CCC) referring to the years 2020, 2050 and 2100. It was found that by applying the two scenarios there will be a reduction of the mean winter runoff values, a serious reduction of summer runoff, an increase of maximum annual runoff and a decrease of minimum annual runoff values, an increase of potential and actual evapotranspiration, leading to a decrease of soil moisture, a reduction of snow accumulation and melting due to temperature increases, resulting in a decrease of spring runoff values and a shifting of the wet period towards December, resulting in severe prolongation of the dry period.     

气候变化对流域水资源影响评价中的不确定性问题

<正>确评价气候变化背景下的流域水资源是实现其可持续性开发利用的基础,气候变化对流域水资源影响的评价一般采取气候情景驱动水文循环模型的方法。由于气候系统和水文循环过程的复杂性,该方法在气候情景、水文循环模拟及评价过程中存在很大的不确定性。提高流域气候情景预测精度和完善影响评价模型是降低气候变化影响评价结果不确定性的主要方式。本文介绍了气候变化对流域水资源影响的一般评价方法,分析了影响评价结果不确定性的因素,并讨论了降低评价结果不确定性的方式。     

Uncertainty Analysis of Climate Change Impact on River Flow Extremes Based on a Large Multi-Model Ensemble

Water managers are faced with a changing climate in the decision-making process while adaptation and mitigation strategies need to be developed. The climate change impact towards the end of the century, however, is highly uncertain and coping with this is a great challenge for decision makers. Over the recent years, combined efforts of hydrologists and climatologists have led to many climate change impact studies on water resources. However, most studies only use a limited ensemble size and/or focus on only one contributing source and hence possibly underestimate the total uncertainty.

For two Belgian catchments, we simulated daily flow with five different lumped conceptual hydrological models and ten different parameter sets each, forced by the output of 24 global climate models covering four different emission scenarios, combined with 9 different downscaling methods over reference (1961–1990) and future (2071–2100) periods, resulting in a large multi-model ensemble with 41,850 members. Results show that both low and peak flows would become more extreme in the future, and these changes are stronger with increased radiative forcing. The most important uncertainty sources in low-flow projections are the global climate models (explaining 27–36% of the total variance) and the hydrological model structure (34–42%). For peak flow projections, these are global climate models (32–39%) and statistical downscaling methods (21–26%). Also, interaction effects account for a significant part of the uncertainty (24–38%). The results of this study illustrate that one might end up with biased results and overly confident conclusions when only focusing on some of the uncertainty sources in multi-model ensembles.

     

气候变化和人类活动对渭河流域径流量的影响

采用M-K趋势检验法、有序聚类变点分析法以及径流变化归因分离评判方法,分析渭河流域近50 a的气温、降水、径流的演变特征和径流量变化的影响因素。结果表明:流域气温升高趋势显著,通过95%的置信度水平检验,其中1994年是气温突变的节点;流域降水量呈缓慢减少的态势,变化节点发生在1969年;流域径流量减少趋势极显著,通过95%的置信度水平检验,突变节点发生在1969年,与降水突变节点一致。由VIC模型计算得出:流域径流量的变化主要由气候波动和人类活动改变流域下垫面共同作用引起的,其中气候变化的影响较大。     

气候变化和人类活动对永定河流域径流的影响

利用线性回归法和Mann-Kendall趋势检验法对永定河1957—2000年的降水量、潜在蒸发能力和径流量进行了趋势分析,利用降雨—径流双累积曲线以及Pettitt变点检验找出了径流突变年份。在此基础上,运用水文敏感性分析方法计算了人类活动和气候变化对永定河径流变化的贡献程度。结果表明:1957年以来,永定河流域径流深呈显著下降趋势,其变化倾向率为-0.8 mm/a,径流突变点发生在1982年;与基准期相比,1982年之后的年平均径流深减少了20.0mm,其中人类活动使径流深减少了14.0 mm,占总减少量的70.0%。     

气候变化对嘉陵江流域降水变化影响分析

以长江上游支流嘉陵江为研究对象。利用嘉陵江流域的11个国家气象站1961年-2001年的实测降水数据和NCEP再分析数据,建立了嘉陵江流域降水的统计降尺度模型。在A2和B2排放情景下应用HadCM3的输出数据,预测嘉陵江流域未来三个时期（2010年-2039年、2040年-2069年、2070年-2099年）降水变化情况。分析结果表明相对于基准期的模拟降水量,在HadCM3的A2和B2排放情景下．模拟得到嘉陵江流域大部分区域的降水量有明显上升趋势。     

Impact of Climate Change on the Hydrology of Upper Tiber River Basin Using Bias Corrected Regional Climate Model

The use of regional climate model (RCM) outputs has been getting due attention in most European River basins because of the availability of large number of the models and modelling institutes in the continent; and the relative robustness the models to represent local climate. This paper presents the hydrological responses to climate change in the Upper Tiber River basin (Central Italy) using bias corrected daily regional climate model outputs. The hydrological analysis include both control (1961–1990) and future (2071–2100) climate scenarios. Three RCMs (RegCM, RCAO, and PROMES) that were forced by the same lateral boundary condition under A2 and B2 emission scenarios were used in this study. The projected climate variables from bias corrected models have shown that the precipitation and temperature tends to decrease and increase in summer season, respectively. The impact of climate change on the hydrology of the river basin was predicted using physically based Soil and Water Assessment Tool (SWAT). The SWAT model was first calibrated and validated using observed datasets at the sub-basin outlet. A total of six simulations were performed under each scenario and RCM combinations. The simulated result indicated that there is a significant annual and seasonal change in the hydrological water balance components. The annual water balance of the study area showed a decrease in surface runoff, aquifer recharge and total basin water yield under A2 scenario for RegCM and RCAO RCMs and an increase in PROMES RCM under B2 scenario. The overall hydrological behaviour of the basin indicated that there will be a reduction of water yield in the basin due to projected changes in temperature and precipitation. The changes in all other hydrological components are in agreement with the change in projected precipitation and temperature.     

气候变化和人类活动对黄河重点区间径流的影响

科学分析径流变化归因是流域治理的一项基础工作,对水资源管理具有重要意义。采用水文模拟途径定量评估了气候要素变化和人类活动对黄河重点水文站华县、河津、■头、龙门水文站河川径流变化的影响。结果表明:受人类活动影响,实测径流量出现明显的阶段性变化,突变之后的径流量较突变前减少了30%以上;可变下渗容量模型对黄河流域天然径流量具有较好的模拟效果,能够用于天然径流量的模拟;人类活动是黄河径流量减少的主要原因,人类活动的影响占径流量减少的70%以上;进入21世纪以来,由于降水增加,因此气候要素对径流量减少的贡献率有减小趋势。     

Evidence of Climate Change in the Senegal River Basin

International development policy makers are recognizing climate change and desertification as fundamental obstacles to the social and economic development of the Third World. Sub-Saharan Africa, particularly the Sahel region, has been severely impacted by the compounding effects of drought, deforestation and desertification. The Senegal River Basin in the West Africa is a prime example of a region where development objectives are seriously undermined by the drought-induced desertification process. The basic hydrologic constraint on development is revealed in a time series decompositionof Senegal River annual flow volumes, which strongly suggests that water resources availability has been substantially curtailed since 1960. Two alternative time series mechanisms are hypothesized to account for the decreased flow volumes in recent decades. The first time series model suggests the presence of a long-term periodicity, while the second model hypothesizes an ARMA(1,1,) process. The second hypothesis provides a superior model fit. The stationary ARMA(1,1) model can be fitted successfully, however, only after explicitly removing a non-stationary component by linearly detrending after 1960. The implication of non-stationarity in Senegal River hydrology provides additional analytic evidence that the landscape degradation and desertification processes observed in Sahelian Africa can be in part attributed to climate change effects. Efforts to redress desertification should be at once conscious of complex socioeconomic forces exacerbating the desertification process and fundamental hydrologic constraints to river basin development.     

气候变化对黄河水资源的影响及其适应性管理

气候变化将直接影响降水、蒸散发和径流等水文要素,并在一定程度上改变水资源量及其时空分布,进一步影响水资源利用格局及水安全形势。气候变化对水资源安全的影响是国际上普遍关心的全球性问题,也是我国可持续发展面临的重大战略问题。黄河作为中华民族的母亲河,在全球气候变化的条件下,水资源的供需矛盾日益尖锐。结合黄河的水资源特点,研究和评价了气候变化情景下黄河水资源的脆弱性,并从配置、利用、调度、管理方面系统地提出了适应性对策:探讨有序适应的黄河流域水资源优化配置方案;完善水沙调控体系,探讨高效输沙模式;合理开发非常规水资源;优化调整梯级水库运用方式;实施最严格的水资源管理制度;积极实施外流域调水。