变化环境下“中华水塔”水资源及产流规律变化分析研究

受全球气候变暖的影响,“中华水塔”地区正面临着以“变暖变湿”为主的气候变化。受气候及下垫面条件的综合影响,区域水资源显著增加,各流域产流机理在空间上呈现出明显的地区差异特征。基于“中华水塔”区域1956—2020年水文气象资料,通过趋势、突变、距平等分析方法,分析其水文要素和产流规律的变化趋势、特征及相互之间影响关系。结果表明：近年来“中华水塔”区域气温显著升高,蒸发能力总体增强,区域进入丰水期,降水、径流显著增加,在同等降水径流尺度下,黄河源区产流能力有所降低,长江、澜沧江源区产流能力明显增强;气温升高、降水量持续偏丰以及流域前期影响雨量（蓄水量）增加、枯季径流比例提高、下垫面生态持水能力增强是引起区域产流规律变化、水资源量增加的主要原因。     

Effects of Land-Use and Climate Change on Hydrological Processes in the Upstream of Huai River, China

Land use/land cover and climate change can significantly alter water cycle at local and regional scales. Xixian Watershed, an important agricultural area in the upper reach of the Huaihe River, has undergone a dramatic change of cultivation style, and consequently substantial land use change, during the past three decades. A marked increase in temperature was also observed. A significant monotonic increasing trend of annual temperature was observed, while annual rainfall did not change significantly. To better support decision making and policy analysis relevant to land management under climate change, it is important to separate and quantify the effect of each factor on water availability. We used the Soil and Water Assessment Tool (SWAT), a physically based distributed hydrologic model, to assess the impact of Land use and climate changes separately. The SWAT model was calibrated and validated for monthly streamflow. Nash-Sutcliff efficiency (NSE), percentage bias (PBIAS), and coefficient of determination (R ²) were 0.90, 6.3 %, and 0.91 for calibration period and 0.91, 6.9 %, and 0.911 for validation period, respectively. To assess the separate effect of land use and climate change, we simulated streamflow under four scenarios with different combinations of two-period climate data and land use maps. The joint effect of land use and climate change increased surface flow, evapotranspiration, and streamflow. Climate variability increased the surface water and stream-flow and decreased actual evapotranspiration; and land use change played a counteractive role. Climate variability played a dominant role in this watershed. The differentiated impacts of land-use/climate variabilities on hydrological processes revealed that the unapparent change in stream-flow is implicitly because the effects of climate variability on hydrological processes were offset by the effects of land use change.     

泾河流域土地利用/覆被变化对径流情势的影响

通过建立泾河流域SWAT分布式水文模型,重点模拟分析了河流径流情势对土地利用/覆被变化的响应,对比了不同气候条件及人类活动综合影响下研究区水文过程的变化。结果表明:1996年以前土地利用/覆被变化是影响水文过程的主要人类活动影响源,径流量年际变化平稳,属有小幅增加的正偏;年内影响以枯水季节为主,年内分配更趋均匀,径流集中度降低,集中期略有滞后,且趋于平稳;土地利用/覆被变化导致流域蒸散发量、冠层和落叶层截留量减小,入渗量增加,河川基流量和地表径流量相应增大,并在时域上耦合形成了水文过程的新变化;1996年以后,气候条件驱动下泾河年径流量呈现明显的增大趋势,人类活动亦从以土地利用/覆被变化为主转变为以人类水事活动为主的综合影响模式,且人类水事活动超过气候变化和土地利用/覆被变化成为影响水文过程变化的主因。     

Hydrological Responses to Climate Change in Nenjiang River Basin,Northeastern China

Under the background of global climate change, hydrological responses to climate change were investigated in Northeastern China. This study analyses the trends of annual and seasonal temperature, precipitation and streamflow series in Nenjiang River Basin. Correlations between streamflow and meteorological variables were investigated, while parametric method and nonparametric tests were applied to determine the trends and correlations. Data collected from a series of monitoring stations showed significant increasing trends of annual and seasonal mean temperature versus time, whereas during the whole period the annual and seasonal precipitation in the basin did not exhibit similar trends although temporal and spatial variations were detected. Affected by the precipitation and temperature changes, significant trends of decreasing annual, spring and autumn streamflow were demonstrated; the decrease concentrating mainly on the mainstream and tributaries of the left bank. Correlation analyses revealed strong relationships between the streamflow and meteorological variables in Nenjiang River Basin, and the impacts of climate change on streamflow were complicated. Results from this study will help water resource managers for decision makings that address the consequences of climate change.     

Precipitation Trends and Variability in River Basins in Urban Expansion Areas

River basins are important territorial units for geographical analysis, and are crucial for environmental planning, especially in metropolitan settings. The aim of this article was to evaluate rainfall trends and variability in the Guapimirim-Macacu basin, located in an urban development area in the Rio de Janeiro Metropolitan Region. Annual, monthly and daily records were collected from twenty rain gauge stations, for the period of 1967 to 2015. Analyses conducted using the RClimDex software revealed an increase in rainfall volume and number of wet days. The remaining indicators and patterns observed across stations also suggested that changes in precipitation trends occurred mostly on the day scale, and were likely attributable to global climate change. After controlling for seasonality and normalizing the series, a linear tendency between the mean monthly precipitation in the Guapimirim-Macau basin and sea surface temperature (SST), obtained from the National Centers for Environmental Prediction, revealed that rainfall in the region is strongly correlated with Pacific and Atlantic SST, revealing the importance of the South Atlantic Convergence Zone for rainfall variability in the area of study, especially in summer. These data are important for development planning and the management of water resources and supply in the Rio de Janeiro Metropolitan Region.

     

A Novel Spatiotemporal Statistical Downscaling Method for Hourly Rainfall

Finer spatiotemporal resolution rainfall data is essential for assessing hydrological impacts of climate change on medium and small basins. However, existing methods pay less attention to the inter-day correlation and diurnal cycle, which can strongly influence the hydrological cycle. To address this problem, we present a spatiotemporal downscaling method that is capable of reproducing the inter-day correlation, the diurnal cycle, and rainfall statistics on daily and hourly scales. The large-scale datasets, which we obtained from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset (NNR) and general circulation model (GCM) outputs, and local rainfall data are analyzed to assess the impacts of climate change on rainfall. Our proposed method consists of two steps: spatial downscaling and temporal downscaling. We apply spatial downscaling first to obtain the relationship between large-scale datasets and daily rainfall at a site scale using a k-nearest neighbor method (KNN). Then, we conduct an hourly downscaling of daily rainfall in the second step using a genetic algorithm-based KNN (GAKNN) with the inter-day correlation and the diurnal cycle. Furthermore, we analyzed changes in rainfall statistics for the periods 2046–2065 and 2081–2100 under the A2, A1B, and B1 scenarios of the third generation Coupled Global Climate Model (CGCM3.1) and Bergen Climate Model version 2 (BCM2.0). An application of our proposed method to the Shihmen Reservoir basin (Taiwan) has shown that it could accurately reproduce local rainfall and its statistics on daily and hourly scales. Overall, the results demonstrated that the proposed spatiotemporal method is a powerful tool for downscaling hourly rainfall data from a large-scale dataset. The understanding of future changes of rainfall characteristics through our proposed method is also expected to assist the planning and management of water resources systems.     

Scenario-based Impact Assessment of Land Use/Cover and Climate Changes on Water Resources and Demand: A Case Study in the Srepok River Basin,Vietnam—Cambodia

This study investigates an interdisciplinary scenario analysis to assess the potential impacts of climate, land use/cover and population changes on future water availability and demand in the Srepok River basin, a trans-boundary basin. Based on the output from a high-resolution Regional Climate Model (ECHAM 4, Scenarios A2 and B2) developed by the Southeast Asia—System for Analysis, Research and Training (SEA-START) Regional Center, future rainfall was downscaled to the study area and bias correction was carried out to generate the daily rainfall series. Land use/cover change was quantified using a GIS-based logistic regression approach and future population was projected from the historical data. These changes, individually or in combination, were then input into the calibrated hydrological model (HEC-HMS) to project future hydrological variables. The results reveal that surface runoff will be increased with increased future rainfall. Land use/cover change is found to have the largest impact on increased water demand, and thus reduced future water availability. The combined scenario shows an increasing level of water stress at both the basin and sub-basin levels, especially in the dry season.     

基于SWAT模型的秦淮河流域气候变化水文响应研究

为了解气候变化对水文水资源的影响机理,以秦淮河流域为研究区构建SWAT模型,使用SWAT-CUP对模型进行参数敏感性分析、率定及验证,并采用任意假设法设计未来气候情景,分析温度及降雨变化对流域径流及实际蒸散发量的影响。结果表明:模型在月径流模拟中具有较高的精度,适用于秦淮河流域气候变化下的水文响应研究;气温降低或降雨量上升都会引起流域径流量增加,反之则减少;实际蒸散发量与降雨量正相关,而实际蒸散发量对气温变化的响应不明显;平水年径流量对降雨量变化的响应较强,枯水年径流量对温度变化的响应较强;枯水年实际蒸散发量对降雨量变化的响应较强。     

1960—2013年昭通市极端降雨时空演变规律研究

气候变化引起的极端降雨量级和频次变化已经引起了广泛的关注,极端降雨演变规律的研究对于区域防洪减灾和水资源管理具有重要意义。基于昭通市及其周边的16个气象站点1960—2013年共54 a的降雨数据,选取世界气象组织推荐的6个极端降雨指数,采用线性趋势分析、Mann-Kendll法和滑动T检验等方法分析了昭通市的极端降雨时间演变规律,并基于ArcGIS10.2采用反距离插值法(IDW)分析了昭通市极端降雨指数的空间分布格局。结果表明:在趋势演变方面,昭通市的总降雨量PRCPTOT有下降趋势;而反映极端降雨量级的3项指数SDII,RX5day,R95p均呈上升趋势,其中RX5day上升趋势显著;而R10mm和CWD这2项反映极端降雨频率的指数均呈下降趋势,其中R10mm下降趋势显著。在空间分布方面,昭通市6项极端降雨指数具有较高的空间异质性,东北部降雨量级和频率较高,中部趋缓,而西南部总体上相对较低。相关分析的结果表明昭通地区极端降雨指数与高程呈现负相关关系,极端降雨主要发生在低海拔地区。研究成果有助于加深对该区域极端降雨发生规律的认识,为区域防洪减灾和水资源管理提供参考。     

黄河流域降雨-径流关系时空演变研究

由于气候变化和人类活动的影响,黄河流域的降雨-径流关系发生了显著性变化,严重影响流域水资源的规划和管理。为了揭示黄河流域降雨-径流关系的变化特征、趋势及主要驱动因素,研究采用Mann-Kendall检验、双累积曲线法、Copula函数、累积量斜率变化率法分析1960-2010年黄河流域的径流系数时空变化规律、7个主要区间降雨-径流关系的突变年份、降雨径流组合概率变化,以及气候变化和人类活动对降雨-径流关系变化的贡献率。结果表明:黄河全流域降雨-径流关系有明显的趋势性变化,其中除黄河源区的径流系数没有明显变化及少数地区的径流系数有增大的趋势外,绝大部分地区的径流系数有明显减小的趋势;黄河流域7个主要区间,即唐乃亥以上、唐乃亥—兰州、兰州—头道拐、头道拐—龙门、龙门—三门峡、三门峡—花园口及花园口—利津的降雨-径流关系突变年份依次为1989、1984、1997、1979、1992、1987和1970年,年份差异主要受到人类活动时间的影响,流域内大规模水土保持措施开展的年份、水利工程的兴建时间都是造成降雨-径流关系发生转折的重要因素;黄河流域主要区间降雨-径流关系发生转折后,同等降雨条件下其产流能力降低;人类活动是降雨-径流关系变化的主要驱动因素,贡献率均在50%以上,且越往下游,影响越大。     

基于Mann-Kendall的嘉陵江流域降水量时空分布规律研究

了解流域尺度降水的变化,对于研究气候变化对水资源和水文过程的影响具有重要意义。本文对嘉陵江流域9个气象站点的1961—2018年58年间的实测降雨资料,进行Mann-Kendall非参数检验,并结合GIS空间分析技术,探讨了嘉陵江流域降水强弱时间周期及降水分布特征。结果表明:流域多年平均降水量为954.1mm, 1984年发生明显突变之后开始明显减少;流域降水呈梯度变化,由东南至西北方向逐步下降。研究表明,流域降水区域性明显,东南部整体偏涝;从时间上看1984年后整体偏旱。     

气候变化对滇中引水工程取水影响分析

气候变化正在逐渐改变全球的水循环现状,并对水文水资源及其应用产生重大影响。在联合国政府间气候变化专门委员会(IPCC)对气候变化趋势进行分析的基础上,优选近期、远期气候变化情景,并模拟在未来气候变化情景下金沙江流域干流主要断面的逐日流量过程,用以分析气候变化对金沙江干流石鼓断面水文干旱以及对滇中引水工程取水的影响。研究结果表明:受未来可能的气候变化影响,金沙江干流石鼓断面的水文干旱发生强度和发生频率都将有所增加,远期较近期具有高的不确定性;滇中引水工程不可取水天数和可调水量将会增加,但总体而言对工程的不利影响较小。     

Response of Hydrodynamics and Water-quality Conditions to Climate Change in a Shallow Lake

Lake water resources operation and water quality management come up with higher challenges due to climate change. The frequency and intensity of extreme hydrological events are increasing under global warming, which may directly lead to more uncertainty and complexity for hydrodynamic and water-quality conditions in large shallow lake. However, studies about effects of climate change on lake hydrodynamic and water-quality conditions are not enough. Thus, a coupled model is es-tablished to investigate the potential responses of lake water level, flow field and pollutant migra-tion to the changing climatic factors. The results imply that water flow capacity and self-purification in the Hongze Lake can be improved by west, northwest, north, south and southeast winds indi-cating wind filed change has a great effect on the hydrodynamic and water-quality conditions in large shallow lake. It is further observed that both hydrodynamics and water quality are more sensitive to rainfall change than to temperature change; compared to the effect from temperature and rainfall, the effect from wind field appear to be more pronounced. Moreover, the results verify the feasibility of coupling basin hydrological model with lake hydrodynamic and water quality model. To the best of knowledge, the coupled model should not be used until independent calibra-tions and verifications for hydrodynamics and water quality modeling, the hydrological model and the coupled model.

     

海河流域径流变化趋势及其归因分析

在气候变化和人类活动共同影响下,流域径流发生了很大变化。尤其是海河流域,水资源匮乏的现象更为严重,分析水资源变化趋势对实现水资源的可持续开发利用具有重要意义。根据海河流域实际地形地貌特征及水文站分布情况,选取观台、响水堡、张家坟、下会和桃林口等5个水文站所在的区域,采用Mann-Kendall秩次相关检验法及线性回归方法,分析检验各典型区域年径流量的历史变化趋势。基于半分布式流域水文模型——TOPMODEL,采用水文模拟的途径,定量评估了典型区域气候变化和人类活动对径流变化的影响。归因结果表明:除桃林口外的其他4个水文站的年径流量均呈显著减小趋势,海河典型区域年径流减小主要跟人类活动有关,其占比都在65%以上。人类活动对观台、张家坟和响水堡站径流量减小的影响占比为65%~70%,对桃林口站径流量减小的影响占比为75.4%,对下会站径流量减小的影响占比高达81.7%,主要原因是海河流域自20世纪60年代中后期以来进行大规模水利建设所产生的水文效应。     

1956-2019年乌江水文情势变化及其对鱼类的影响研究

水量变化导致河流生态水文情势发生改变,进而影响河流生态系统健康。为深入明晰乌江干流水文变异前后水文情势变化对鱼类生境的影响,选取武隆水文站1956-2019年逐日流量数据及2009-2015年12种漂流性鱼类产卵量资料,采用曼-肯德尔 (M-K)检验法、累积距平法研究乌江干流变异节点,分析突变前、后逐日流量的变化趋势,通过生态水文指标变化范围法(IHA-RVA)综合评价乌江32组水文指标特征及改变度,基于水文情势变化下研究鱼类数量变化过程。结果表明：乌江流量突变年份为2009年,与彭水水电站的运行时间相同,变异后,多年平均日流量峰值波动于15 000 m³/s,而变异前流量峰值接近18 000 m³/s。乌江32组水文指标整体改变度为38.7%,处于中度变化范围;属于高度改变的低流量历时和次数改变度分别为74.64%、75.29％,发生时间推迟4 d;高流量历时和次数改变度分别为29.79%、37.83％,发生时间提前21 d。降雨与流量呈极强正相关,降雨量的逐年减少对流量有重要影响。此外,水文情势的变化易受彭水水电站的影响。流量减少和变化下的水文情势对鱼类的影响是一个累积的过程,2009年后12种漂流性卵鱼类的产卵总量大幅减少,尤以2011年最为突出,仅为1 541.69×10⁴粒。本研究可为研判乌江水文情势变化过程及制定水生态修复措施提供参考。     

灞河流域气候因子对水沙变化的影响

利用灞河流域蓝田气象站和马渡王水文站1960—2012年的气象、水文实测资料,分析灞河流域气候及水沙变化规律,同时运用相关性分析、灰色关联分析、多元线性回归模型等多种方法探讨了该流域水沙变化与气候变化的关系。结果表明:灞河流域降雨量、蒸发量、径流量和输沙量皆呈显著下降趋势,而气温呈上升趋势;降雨量与水沙都有重要的相关关系,1960—1990年影响径流量的气候因子敏感度由大至小依次为降雨量、气温、蒸发量,而1991—2012年则为降雨量、蒸发量、气温,当气温和蒸发量不变时,降雨量每增加1 mm,两阶段的年径流量分别增加0.14亿m3和0.08亿m3;1960—2012年影响输沙量的气候因子敏感度由大至小依次为降雨量、气温、蒸发量,当气温和蒸发量不变时,降雨量每增加1 mm,年输沙量增加0.668万t。     

Spatio-Temporal Variation of Water Availability in a River Basin under CORDEX Simulated Future Projections

In the present study, spatio-temporal variability of hydrological components under climate change is analysed over Wainganga River basin, India. In order to address the climate change projection, hydrological modelling is carried out using a macro scale, semi-distributed three (3)-Layer Variable Infiltration Capacity (VIC-3 L) model. The high-resolution (0.5^o?×?0.5^o) meteorological variables are divided into multiple periods to calibrate and validate the VIC-3 L model. The future projections (2020–2094) of the water balance components are achieved using the high resolution hydrological variables from the COordinated Regional Downscaling EXperiment (CORDEX) dataset under Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. The uncertainty associated with the multi-model projections are evaluated using Reliability Ensemble Averaging (REA) and the bias correction is accomplished with non-parametric quantile mapping. A probabilistic based areal drought index is also computed for different scenarios using Standardized Precipitation Evapotranspiration Index (SPEI). From the results, it is observed that amount of rainfall, evapotranspiration, and runoff has increased over the basin with no change in the spatial pattern. However, temporal variability is noticed with an increasing trend for rainfall and runoff in the non-monsoon season than the monsoon. Streamflow is expected to increase significantly, especially for medium to low flows (those occurring between 0.2 and 0.9 probability of exceedance in a Flow Duration Curve). In addition, the area under the drought condition has decreased under the projected climate scenarios.     

统计降尺度方法及其评价指标比较研究

针对目前气候变化对水资源影响研究中关注的问题,以汉江白河上游为研究对象,比较研究统计降尺度方法及其评价指标。以美国环境预报中心/美国国家大气研究中心全球再分析资料、CGCM3和HadCM3的A2情景为大尺度气候背景资料,应用SSVM和SDSM统计降尺度方法对大尺度气候因子进行尺度降解,得到降水情景序列后作为水文模型的输入,通过模拟径流比较分析统计降尺度方法的优劣。研究结果表明,由不同统计降尺度方法得到的降水作为水文模型输入,模拟径流的结果相差很大;对广泛应用于统计降尺度方法的降水模拟评价指标和径流模拟结果进行比较,发现所采用的降水评价指标侧重于考虑降水的统计分布特征,不能完整地描述降水过程特性。分析认为,径流模拟结果应该作为气候变化对径流影响研究中统计降尺度方法评价的重要参考。     

Effects of climate and land use changes on stream flow of Chitral river basin of northern highland Hindu-Kush region of Pakistan

Adverse impacts of climate change on the ecosystem have been a significant concern in the last decades. However, the studies related to the impacts of climate change on water resources, especially in northern Pakistan are of great importance as this region is the main supplier of freshwater to the downstream areas. So, the present study was carried out in Chitral River Basin (CRB) to investigate the long term climatic and topographic changes. Spatiotemporal datasets from MODIS Land Cover Type product (MCD12Q1) from 2001 to 2018, ground-based observational climatic and hydrological data were used. Moreover, the Mann-Kendall trend test, linear regression analysis, correlation, and Sen’s slope values for the mean annual and seasonal flows were assessed. The acquired results show that land use changes are the key non-natural factors in transforming the ecological and hydrological processes of CRB. The mixed and evergreen forest, shrubland, savannas, and barren land respectively decreased from 0.07 to 0.03%, 0.07 to 0.05%, 3.64 to 3.25%, and 70.10 to 67.17%, from 2001 to 2018. In addition, a considerable increment in snow cover from 8.79% to 10.71%, and slight increment in grasslands, wetlands, and croplands were also found between the period of observation. In addition, total annual precipitation and mean annual stream flow showed slight upward trends. Annual increment in total rainfall and snow covered area could be the possible reasons for the observed increased river flow.     

A Semi-Distributed Monthly Water Balance Model and its Application in a Climate Change Impact Study in the Middle and Lower Yellow River Basin

Abstract

Human activities and climatic change have greatly impacted hydrological cycles and water resources planning in the Yellow River basin. In order to assess these impacts, a semi-distributed monthly water balance model was proposed and developed to simulate and predict the hydrological processes in the middle and lower Yellow River basin. GIS techniques were used as a tool to analyze topography, river networks, land-use, human activities, vegetation, and soil characteristics. The model parameters were calibrated in 35 gauged sub-basins in the middle Yellow River, and then the relationships between the model parameters and the basin physical characteristics were established. A parameterization scheme was developed in which the model parameters were estimated for each grid element by regression and optimization methods. Based on the different outputs of general circulation models (GCMs) and regional climate models (RCMs), the sensitivities to global warming of hydrology and water resources for the Yellow River basin were studied. The proposed models are capable of producing both the magnitude and timing of runoff and water resources conditions. The runoffs are found to be very sensitive to temperature increases and rainfall decreases. Results of the study also indicated that runoff is more sensitive to variation in precipitation than to increase in temperature. The additional uncertainty of climate change has posed a challenge to the existing water resources management practices, and the integration of water resources management will be necessary to enhance the water use efficiency in the Yellow River basin.