基于GIS/RS的流域水文过程分布式模拟——Ⅰ模型的原理与结构

面向流域水资源管理,提出了一个基于GIS/RS的流域分布式水文模型,模型主要包括单元水文模型与河网汇流模型两大部分。单元水文模型涉及到冠层截留、融雪、蒸散发、坡面流、非饱和土壤水运动和地下水出流等水文物理过程。产流计算考虑到地形坡度的影响采用基于地形指数的计算方法。汇流演算基于河网结构采用分段马斯京根方法。模型的大部分参数与输入信息可以利用GIS和RS技术获取,能够对气候变化和人类活动对下垫面的改变,做出快速的模拟与响应。     

干旱区资料稀缺流域日径流过程模拟

选取具有物理基础的分布式水文模型MIKE SHE来模拟大尺度资料稀缺地区水文过程。以塔里木河主要源区之一开都河流域为研究区域,将流域内气象水文站点观测数据与遥感数据相结合,运用GIS空间分析方法修正数据输入。利用气象、土壤类型、土地利用和地表覆盖、数字高程和降雨等资料,研究大气、陆面、地表水和地下水的相互作用机理,通过模型敏感性分析确定了5个"自由"参数,并依据出山口水文站数据对模型进行率定和验证。结果表明,MIKE SHE能在水文、气象站点稀少,土壤及水文地质数据缺乏的条件下,模拟开都河流域的日径流过程,模型效率系数达到0.7以上,率定期与验证期水量平衡误差均小于3%,模拟径流与实测径流高度相关。     

干旱区资料稀缺法流域日径流过程模拟

选取具有物理基础的分布式水文模型MIKE SHE来模拟大尺度资料稀缺地区水文过程.以塔里木河主要源区之一开都河流域为研究区域,将流域内气象水文站点观测数据与遥感数据相结合,运用GIS空间分析方法修正数据输入.利用气象、土壤类型、土地利用和地表覆盖、数字高程和降雨等资料,研究大气、陆面、地表水和地下水的相互作用机理,通过模型敏感性分析确定了5个"自由"参数,并依据出山口水文站数据对模型进行率定和验证.结果表明,MIKE SHE能在水文、气象站点稀少,土壤及水文地质数据缺乏的条件下,模拟开都河流域的日径流过程,模型效率系数达到0.7以上,率定期与验证期水量平衡误差均小于3%,模拟径流与实测径流高度相关.     

气候变化对黄河源区水资源的影响

利用气候模型结果和大尺度分布式水文模型评估黄河源区未来的水资源.根据IPCC DDC的13个系列的GCMs成果,结合黄河源区的实测气象资料,分析了该地区气候在未来100 a内的可能变化;建立了考虑融雪和冻土影响的分布式水文模型,经验证该模型能够适用于黄河源区.计算出了相应的径流情景,分析了黄河源区水量尤其是水资源特性(径流的年内、年际分布)的可能变化;对南水北调西线工程的需水量进行了简单评估.     

数字高程模型分辨率对流域地形特征参数的影响

地形特征(如高程和坡度)和水文特征(如河流长度和河流坡度)是分布式流域水文水质模型的基础输入参数,用于量化描述模型模拟流域的自然特征。这些特征参数的准确性直接影响水文水质过程模拟的准确性。应用数字高程模型(Digital Elevation Model,DEM)在4个不同地形的子流域研究了10种不同分辨率DEM对平均高程、流域面积、坡度、河流坡度、最长河长等参数的影响。结果表明,随着DEM分辨率降低,流域地形变缓,流域平均坡度逐渐减小;随着DEM网格分辨率的变化,子流域划分范围和河道位置也都可能发生变化,且该变化在地形起伏较小的丘陵平原地区较明显,子流域集水面积和河长进一步随之改变;河流坡度随DEM分辨率降低则呈无规则变化。从地形和水文参数两方面揭示了DEM 分辨率在分布式流域模型中的不确定性影响。     

辽河流域径流过程模拟的空间尺度效应分析

针对分布式水文模型的尺度问题,在辽河流域,采用SWAT模型,研究不同DEM分辨率及不同子流域大小导致模拟结果的不确定性。研究结果表明:①DEM分辨率对流域平均高程、流域面积和子流域数量影响较小,而对流域平均坡度有显著的影响,因此径流模拟时需要进行坡度订正。对于河网提取,DEM分辨率为500m时提取的河网与基准河网吻合程度较高。②子流域面积过大,数量过少时,模拟结果与基准结果偏差较大,而在划分一定阈值波动范围内径流对子流域数量敏感性较低。     

气候变化下雅鲁藏布江拉孜以上流域径流过程模拟与预测

西部高寒河源区因冰川积雪冻土等特殊的地理环境,其径流过程的模拟与预测一直是水文学研究的难点和热点问题之一,全球气候变暖为这一地区的水文模拟提出了新的挑战。以雅鲁藏布江拉孜以上流域为研究区域,基于可考虑冰川积雪融水的SWAT分布式水文模型对拉孜站径流过程进行模拟,评估SWAT模型在高寒河源区的适用性。基于未来气候变化情景,统计分析了未来研究区降水、气温的变化趋势,预估了气候变化对区域径流过程的影响。结果表明:SWAT模型在拉孜以上流域径流过程模拟中具有较好的适用性,模型在率定期和验证期月尺度NS系数分别达到了0.78和0.84;未来研究区降水、气温均呈现出增加趋势,且随着排放情景的上升,气温、降水增加幅度有变大趋势;未来研究区不同时段径流量也呈现出不同的增加趋势,在2020～2049年的RCP2.6、RCP4.5和RCP8.5情景下,相较于基准期径流分别增加了约11.8%、14.0%、16.5%,为下游水资源可持续开发利用带来了更大的挑战。     

喜马拉雅山珠峰绒布冰川流域径流模拟

基于2009年5-10月喜马拉雅山北坡珠峰绒布冰川流域实测水文气象数据、 50 m分辨率DEM和中国第一次冰川编目资料, 在HYCYMODEL水文模型中加入冰川消融子模块, 模拟了绒布冰川流域径流过程.冰川消融子模块以海拔5 180 m基站的实测日气温、 日降水作为模型输入, 把气温、 降水插值到该流域40个高程带中, 分别计算各高程带的冰川消融和裸地蒸发, 并考虑液态降水对冰面的加热作用.野外气象观测表明: 2009年5-10月流域海拔5 180~5 750 m内, 月气温递减率在0.63~0.73 ℃·(100m)^-1之间, 均值为0.70 ℃·(100m)^-1; 同期降水观测显示, 海拔5 180 m以下降水梯度为-7.3 mm·(100m)^-1, 该高度之上降水梯度为22 mm·(100m)^-1. HYCYMODEL水文模型的敏感性检验表明, 该流域径流变化主要受气温影响, 降水变化引起的径流变化较小, 气温和降水变化对流域径流的影响是非线性的.     

子流域划分和DEM分辨率对SWAT径流模拟的影响研究

应用SWAT分布式水文模型,选择秦淮河流域为研究区,在不同的子流域划分水平和DEM分辨率条件下,进行流域径流的模拟,进一步分析子流域划分和DEM分辨率对流域径流模拟结果的影响.研究结果表明:产流量随着子流域划分数目的增加几乎没有变化,最大相对偏差不超过5%;DEM分辨率的变化对径流的模拟影响也不大,尤其在DIM格网单元低于100m时,各种DEM格网单元模拟结果的相对偏差最大约为1%.     

浅层地温场中热对流数值模拟

温度示踪的研究区域大多在地表浅层,浅层地温场主要受气象和水文影响。气温波动可用傅立叶级数精确表示,由此建立了在表层气温和垂向水流共同影响下的浅层地温场瞬态分析模型,用Laplace变换的方法得到其解析解,并用有限元模拟了垂向水流对浅层地温的影响。模拟结果表明：浅层地温有季节波动,在地下水补给区,气温波动振幅衰减速率明显减缓,表现为表层气温波动可以影响到更深的深度;在排泄区,温度波振幅衰减很快。另外,还模拟了水平集中渗漏带附近的瞬态温度场,发现由于热对流的传热能力远大于热传导,强渗漏带温度迅速与补给源温度相一致,温深剖面出现异常,温度异常带形成后,继而通过热传导改变较大范围内地质体热量分布。离低温补给源越近,地质体降温越快,温度改变越多;反之则越慢,温度改变越少。因此,由温深剖面的温度异常,可精确探查渗漏带位置。     

Effect of watershed partitioning on hydrologic parameters and estimation of hydrograph of an ungauged basin: a case study in Gokirmak and Kocanaz,Turkey

The main goal of this study is to investigate the effect of the size of the subbasins of a watershed on the hydrologic parameters and their spatial variability in an estimation of the hydrologic parameters and hydrograph of a neighbouring ungauged basin. In this paper, Hydrologic Engineering Center-Hydrologic Modelling System (HEC-HMS), a semi-distributed hydrologic model, is used to calibrate and cross-validate two flood events occurred in 1998 and then validate four other flood events occurred in 1991, 1994, 2002, and 2009 in Gokirmak Basin in Western Black Sea Region, Turkey. The basin is divided into seven different subbasins to investigate the effect of watershed partitioning on calibrated hydrologic parameters of each subbasin using the peak-weighted root mean square error method as an objective function and the hydrograph at the outlet of the whole basin. It is found out that as the geometric magnitudes of the subbasins changed, the calibrated values of the hydrologic parameters of those subbasins changed as well. Then, a neighbouring basin, Kocanaz, is considered as an assumed neighbouring ungauged basin to investigate the effect of watershed partitioning of a gauged basin on the estimation of hydrograph of a neighbouring ungauged basin. Hydrologic parameters and direct runoff hydrograph of assumed ungauged neighbouring basin are estimated from the hydrologic parameters of the HEC-HMS calibration results of Gokirmak. Statistical indicators of the simulation results for each basin partitioning were graded with respect to the boundary values of the simulation outputs to find the best alternative. The grading results show that the simulation results with a single basin gave better representation among all other partitioning except two flood events.     

山区太阳辐射对水热过程影响的敏感性分析

山区短波辐射的空间异质性非常强, 地形的遮蔽影响在山区能水循环模拟研究中不容忽视. 改进了SHAW模型和SHAWDHM模型的辐射模块, 使之能考虑地形的遮蔽作用对山区辐射平衡及其空间分布的影响, 并在单点和流域尺度进行数值模拟实验, 对比分析山区辐射过程对流域能水循环和径流的影响. 结果表明, 因地形的遮蔽作用, 地表接收的太阳直射辐射可减少25%左右, 模型模拟的土壤温度和蒸散发量分别降低约0.5 ℃和20%. 考虑山区辐射过程后, 模型模拟的春季融雪和夏季蒸散发均有所减缓, 导致春季融雪径流降低和夏季径流增加. 与观测径流对比发现, 考虑山区辐射过程后, 模型对径流量的模拟精度有所提高, 逐时径流量的纳什效率系数由0.677提高到0.711, 径流量的观测值与模拟值间的相关系数由0.835提高到0.851.     

Hydrologic modelling of the effect of snowmelt and temperature on a mountainous watershed

Snowmelt-runoff modelling in a mountainous basin is perceived as difficult due to the complexity of simulation. Theoretically, the snowmelt process should be influenced by temperature changes. It is still controversial as how to incorporate the temperature changes into the snowmelt-runoff model in a mountainous basin. This paper presents the results of a study in the North Fork American River basin where the snowmelt-runoff mechanism is modelled by relating the temperature changes to the elevation band in the basin. In this study, a distributed hydrologic model is used to explore the orographic effects on the snowmelt-runoff using the snowfall-snowmelt routine in Soil and Water Assessment Tool (SWAT). Three parameters, namely maximum snowmelt factor, minimum snowmelt factor, and snowpack temperature lag were analysed during the simulation. The model was validated using streamflow data from October 1, 1991 to September 30, 1994 with and without considering the elevation band. The result of this study suggests that the snowmelt-runoff model associated with the elevation band better represents the snowmelt-runoff mechanism in terms of Nash–Sutcliffe coefficient (E _NS ), R ², and Root Mean Square Error (RMSE).     

The simulation of snowmelt runoff in the ungauged Kaidu River Basin of TianShan Mountains,China

Snowmelt runoff is an important source of water resources in the arid mountain area. Modelling snowmelt runoff for cold regions remains a problematic aspect because of the lack of data by gauges in large basins. In order to overcome the shortage of measured data in the snowmelt runoff modelling, the temperature interpolation method would greatly help in improving the simulation accuracy and describing the snow-hydrological behaviours of the study catchments. In this study, the temperature is the principal variable used to estimate the importance of the melting of snow cover using the snowmelt runoff model. Five different temperature interpolation attempts were performed over the Kaidu River Basin for the snowmelt season of the year 2000. Three temperature inputs were taken directly from the individual weather stations in or near the study area, and the other two temperature inputs were interpolated from the three weather stations. The results indicated that the temperature estimated from different methods could result in quite a difference in runoffs in comparison with the observed ones. The simulation results using average temperature from the three stations showed good results; the simulation run with the weighted average temperature generated a lower R ² than the average temperature of three stations and using temperature directly adopted from three individual stations gave various results. The weather stations used to perform the snowmelt runoff simulation should be located in the place which is most representative of the mountain weather conditions, and the land cover and topography that those stations represented also play an important role in the snowmelt runoff simulation.     

Assessing distributed groundwater recharge rate using integrated surface water-groundwater modelling: application to Mihocheon watershed, South Korea

A method of estimating groundwater recharge, based on water-balance components using the SWAT-MODFLOW model (an integrated surface water-groundwater model), is described. A multi-reservoir storage routing module is suggested instead of a single storage routing module in SWAT; this represents a more realistic delay in the travel of water through the vadose zone. By using this module, the parameter related to the delay time can be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater levels as well as the simulated watershed stream flow with the observed groundwater levels and watershed stream flow. This method is applied to the Mihocheon watershed in South Korea to estimate spatio-temporal groundwater recharge distribution. The computed annual recharge rate is compared with the independently estimated recharge rate using BFLOW. The hydrologic modelling results show that the annual average recharge rate should be estimated by a long-term continuous simulation with a distributed hydrologic modelling technique.     

黄河源区气候对径流的影响分析

根据对降水响应速度的快慢,径流又可分为直接径流和基流。基流一般定义为河川径流中来自于地下蓄水或者其他延迟水源的成分,代表地下水出流;直接径流表示对降水事件的直接响应。从这一思路出发,文中在分析降水到总径流、直接径流和基流的转化率的基础上分析了气候变化对径流的影响。研究发现,黄河源区的径流系数随降水量的增加而增大,随气温升高而降低;径流随着降水的增加而增加。20世纪90年代降水减少和气温的大幅度升高是黄河源区径流减少的重要原因。区间子流域分析表明,不同的子流域气温和降水对径流的影响不同,在吉迈以上区间,年气温比较低,气温是影响径流系数的主要因子,径流随着气温的升高而降低,降水对径流的影响比较小;在吉迈—玛曲区间,直接径流量/降水量主要受降水的影响,总径流量/降水量、基流量/降水量随降水增加而升高,随气温升高而降低。总径流和基流随降水的增加而增大,随气温的升高而减少;在玛曲—唐乃亥区间,径流系数随着降水量的增加而增加,直接径流量/降水量随气温的升高而降低,降水是径流的主要影响因素。     

Prediction of snowmelt floods with a distributed hydrological model using a physical snow mass and energy balance approach

Modeling snowmelt is important for water resources management and the assessment of spring snowmelt flood risk. The objective of this study was to develop a physically based module for the WetSpa model to improve the simulation of snowmelt processes. The improved model is applied, calibrated, and verified on the Hornad watershed, upstream of Margecany, Western Carpathians, Slovakia, with 10 years of observed daily precipitation and air temperature, and estimated daily potential evaporation. Daily discharge data of the gauging station at Margecany is used for model calibration and verification. The model proves to predict accurately snow accumulation and snowmelt floods, although the parameters of the snow simulation module are preset and not adjusted by model calibration. In order to show the performance of the model, two particular snow accumulation and melt periods are discussed in detail. The relevant terms of the snowpack mass and energy balances as well as the related heat and mass transport processes are discussed. The study demonstrates that accurate snowmelt prediction based on a physically energy budget approach is possible with controlling parameters that do not need any calibration.     

基于FEFLOW的地下水热源渗流温度研究

为研究地下水"热"源对于渗流场的影响,选取某水库水源地辐射取水区及部分扩张区为研究范围,使用地下水通用软件FEFLOW对单一地下水热源作用下的Y型河道的渗流场和温度场进行研究,得出地下水热源对渗流场和温度场的影响规律,结果显示:地下水位受水源的影响,在不同位置水位不同,含水层内随着到水源点距离的增加,水位逐渐降低,到达某个位置时会保持稳定不变;靠近地表的地下水温会随着到水源点距离的增加逐渐降低,在垂向上,含水层内地下水温随着高程的降低逐渐降低,而在库水区,受库水的影响垂向水温变化规律则刚好相反,研究结论可为实际工程提供理论指导。     

Assessing the impacts of sea-level rise and precipitation change on the surficial aquifer in the low-lying coastal alluvial plains and barrier islands,east-central Florida (USA)

A three-dimensional variable-density groundwater flow and salinity transport model is implemented using the SEAWAT code to quantify the spatial variation of water-table depth and salinity of the surficial aquifer in Merritt Island and Cape Canaveral Island in east-central Florida (USA) under steady-state 2010 hydrologic and hydrogeologic conditions. The developed model is referred to as the ‘reference’ model and calibrated against field-measured groundwater levels and a map of land use and land cover. Then, five prediction/projection models are developed based on modification of the boundary conditions of the calibrated ‘reference’ model to quantify climate change impacts under various scenarios of sea-level rise and precipitation change projected to 2050. Model results indicate that west Merritt Island will encounter lowland inundation and saltwater intrusion due to its low elevation and flat topography, while climate change impacts on Cape Canaveral Island and east Merritt Island are not significant. The SEAWAT models developed for this study are useful and effective tools for water resources management, land use planning, and climate-change adaptation decision-making in these and other low-lying coastal alluvial plains and barrier island systems.