Retrieving Groundwater Depletion and Drought in the Tigris‐Euphrates Basin Between 2003 and 2015

Quantitative estimates of the groundwater depletion and droughts in the Tigris‐Euphrates Basin (TEB) can be useful for sustainably managing its water resources. Here, data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are used to infer the monthly changes in the total water storage of the TEB from January 2003 to December 2015. Additionally, the data of altimetry and output from land surface models are used to remove the contributions from lake water changes and other hydrological factors to obtain the total groundwater depletion (TGWD), human‐driven groundwater depletion (HGWD), and climate‐driven groundwater depletion. We conclude that an alarming rate of decrease in the total water storage and the loss of TGWD have an “accelerating” trend, as the trend during 2007 to 2015 was 3.6 times that during 2003 to 2006. Moreover, the HGWD is 116.09 Gt, which accounts for 98% of the TGWD. Finally, the total storage deficit index (TSDI) is derived from the GRACE data to characterize the drought of the TEB. The results show that TSDI agrees well with the actual drought rather than the Palmer drought severity index (PDSI) and that the TEB has been undergoing a severe drought since September 2007 according to both the TSDI and PDSI. The research in this study provides an effective and unique method for understanding the hydrological processes and sustainable use of water resources in regions or countries with little data, which is essential for more efficient, sustainable, and cross‐boundary cooperative water resource management.     

Hydrologic model-based Palmer indices for drought characterization in the Yellow River basin,China

The Palmer indices (PIs) that have been most widely used for drought monitoring and assessment are criticized for two main drawbacks: coarse hydrological accounting processes with a simplified two-stage bucket soil water balance model and arbitrary rules for defining drought properties and standardizing index values through limited calibration and comparison. In this study, we introduce a new proposal of the VIC hydrologic model-based Palmer drought scheme, where traditional PIs (e.g. PDSI) can readily be calculated on the basis of distributed finescale hydrologic simulations. Moreover, recent variants of PI (i.e., SPDI and SPDI-JDI) also provide a preferable standardization strategy that allows probabilistic invariability and better spatio-temporal comparability of computed drought indices. Using gridded meteorological forcing, soil and vegetation data to drive the three-layer VIC model, both non-VIC and VIC-based PIs are investigated to examine their performances for drought characterization and detection. Results indicate that VIC hydrologic model would allow for adjustments in statistical properties of computed PDSI and VIC-based SPDI is also preferable to PDSI for better statistical robustness and spatio-temporal consistency/comparability. Moreover, the joint SPDI-JDI has the strength of integrating multi-scale probabilistic properties and drought information released by individual SPDI, providing overall drought conditions that take into account the onset, persistence and termination of droughts. At proposed 0.25° grid scale, the VIC-based SPDI-JDI indicates high frequency and long total time of drought condition in the Yellow River basin (YRB), China. Although no significant temporal trends are found in identified drought duration and severity, both the seasonal and annual drought index values demonstrate a downward trend (higher drought intensity) for considerable proportions of the YRB. These findings imply high drought risk and potential drying stress for this region. The new framework of hydrologic model-based PIs can help to strengthen our knowledge and/or practices in regional drought monitoring and assessment.     

Assessment of the WATCLASS hydrological model result of the Mackenzie River basin using the GRACE satellite total water storage measurement

Earlier efforts have been geared towards modelling the hydrological water balance of the Mackenzie River basin and its sub‐basins using a coupled land surface–hydrological model for the Canadian cold region known as WATCLASS. The goal of this current study is to effectively inter‐compare the resulting total water storage anomalies estimated from the gravity recovery and climate experiment (GRACE) satellite analysis with those estimated from the atmospheric‐based water balance approach as well as the model output from WATCLASS over the 1 · 8 × 10⁶ km² Mackenzie River basin in Canada. Since the success of the parameter estimation stage of the coupled land surface–hydrological model, WATCLASS over this large catchment, was entirely based on a goodness of fit between the simulated and observed flows, it is often desirable to assess the reliability of the generated state variables prior to concluding on the overall efficiency of this model in reproducing the relevant hydrological processes over this region. A major challenge here lies in finding suitable dataset with which this comparison can be made to further assess the ability of the model in accurately reproducing other mass fluxes. The outcome of this inter‐comparison reveals the potential application of the GRACE‐based approach as a veritable tool required for the closure of the hydrological water balance of the Mackenzie River basin as well as serving as a dependable source of data for the calibration of traditional hydrological models. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of water resources in the Mahanadi River Basin,India under projected climate conditions

The paper presents the outcomes of a study conducted to analyse water resources availability and demand in the Mahanadi River Basin in India under climate change conditions. Climate change impact analysis was carried out for the years 2000, 2025, 2050, 2075 and 2100, for the months of September and April (representing wet and dry months), at a sub‐catchment level. A physically based distributed hydrologic model (DHM) was used for estimation of the present water availability. For future scenarios under climate change conditions, precipitation output of Canadian Centre for Climate Modelling and Analysis General Circulation Model (CGCM2) was used as the input data for the DHM. The model results show that the highest increase in peak runoff (38%) in the Mahanadi River outlet will occur during September, for the period 2075–2100 and the maximum decrease in average runoff (32·5%) will be in April, for the period 2050–2075. The outcomes indicate that the Mahanadi River Basin is expected to experience progressively increasing intensities of flood in September and drought in April over the considered years. The sectors of domestic, irrigation and industry were considered for water demand estimation. The outcomes of the analysis on present water use indicated a high water abstraction by the irrigation sector. Future water demand shows an increasing trend until 2050, beyond which the demand will decrease owing to the assumed regulation of population explosion. From the simulated future water availability and projected water demand, water stress was computed. Among the six sub‐catchments, the sub‐catchment six shows the peak water demand. This study hence emphasizes on the need for re‐defining water management policies, by incorporating hydrological response of the basin to the long‐term climate change, which will help in developing appropriate flood and drought mitigation measures at the basin level. Copyright © 2008 John Wiley & Sons, Ltd.     

基于多源数据分析维多利亚湖流域水储量变化

本文利用CSR发布的GRACE RL06时变重力场模型,结合两种水文模式、卫星测高、降雨和蒸散等多源数据,从多个角度综合系统地分析维多利亚湖流域2003-01—2017-06的陆地水储量变化.比较了正向建模方法和单一尺度因子对泄漏误差的改正效果,经对比采用正向建模方法在此流域效果更好.基于多源数据得出以下三点与此前研究不同的结论:(1)GRACE RL06版本数据探测到流域内的水储量在2003-01—2017-06呈增加趋势,球谐位系数和Mascon产品得到的变化速率分别为14.9 mm·a^-1和16.7 mm·a^-1,观测误差小于RL05版本的结果,RL05版本低估了流域水储量的变化速率;(2)2013-01—2016-02期间GRACE和测高探测到湖泊水量增长,而水文模式探测到流域内水储量减少,推测这一现象由大坝蓄水造成;(3)受El Ni1o事件影响,2016-03—2017-06流域降雨减少,流域水储量减少,GRACE球谐位系数和Mascon探测到的变化速率分别为-100.3 mm·a^-1和-129.7 mm·a...     

基于Forward-Modeling方法的黑河流域水储量变化特征研究

黑河流域陆地水储量变化对流域下游等周边区域水资源的合理利用以及经济和社会发展等有着重要的意义.本文利用2003年1月至2013年12月的GRACE RL05数据反演了黑河流域陆地水储量长时间序列的变化,并针对重力场模型和数据处理中产生的信号泄漏问题,采用Forward-Modeling方法进行了改正并恢复泄漏信号;将GRACE获得的泄漏信号恢复前后的黑河流域水储量变化结果与全球水文模型GLDAS和CPC进行比较分析,结果表明泄漏信号改正后的结果与水文模型结果的时间序列相关性均有明显提高,从其空间分布结果可以看出Forward-Modeling方法有效地恢复初始信号、增强被湮没的信号,泄漏信号误差减小;通过分析黑河流域水储量变化的长时间序列结果,发现其具有明显的阶段性变化特征,即2003—2006年呈明显下降趋势,约为-0.86cm·a-1,在2007—2010年趋于平衡状态,而2011—2013年则呈现缓慢上升趋势约为0.14cm·a-1;联合GRACE数据和GLDAS数据反演了黑河流域地下水储量变化,并与全球降雨数据GPCC进行了比较分析,两者相关性可达到0.88以上.     

1960—2019年鄱阳湖五河流域陆地水储量变化及其对主湖区水量的影响

流域内地表水、土壤水和地下水等水储量组分相互作用和影响,共同构成了陆地水储量(TWS)的动态变化格局。本文以GRACE卫星数据为基准,利用GLDAS数据解析1960-2019年鄱阳湖“五河”流域TWS的时空变化特征及各组分对其变化的贡献,采用相关分析方法分析TWS对降水的滞后响应关系,并进一步采用多元线性回归分析方法探究了“五河”流域TWS及各组分对鄱阳湖主湖区水量的影响。结果表明:“五河”流域年TWS在1960-2011年(P1)以-0.07 mm/a的下降,而在2012-2019年(P2)以3.37 mm/a的速率上升。相较于P1阶段,P2阶段春、夏季TWS盈余增强,秋、冬季TWS亏损减弱。春、夏季流域西部TWS变化逐渐由地表水转变为地下水储量主导,流域东部TWS变化主要由地下水储量主导;秋、冬季流域TWS变化主要为地下水储量主导,且地表水对TWS变化的贡献减弱。流域TWS对降水变化的响应滞时呈现夏、秋季短(1个月)而冬、春季长(3~6个月)的季节模式。地下水储量和土壤水对TWS变化的贡献增加会延长TWS对降水的响应滞时,而地表水对响应滞时起相反的作用。“五河”流域TWS与鄱阳湖主湖区水量具有显著的正相关性,地表水和地下水储量增加对湖区水体的增长具有正向作用,而土壤水增加对湖区水体的增长具有反向作用。本研究解析了近六十年鄱阳湖“五河”流域陆地水储量的变化及其对主湖区水量的影响,可为流域水安全管理提供参考。     

Wavelet and Gaussian Approaches for Estimation of Groundwater Variations Using GRACE Data

In this study, a scheme is presented to estimate groundwater storage variations in Iran. The variations are estimated using 11 years of Gravity Recovery and Climate Experiments (GRACE) observations from period of 2003 to April 2014 in combination with the outputs of Global Land Data Assimilation Systems (GLDAS) model including soil moisture, snow water equivalent, and total canopy water storage. To do so, the sums of GLDAS outputs are subtracted from terrestrial water storage variations determined by GRACE observations. Because of stripping errors in the GRACE data, two methodologies based on wavelet analysis and Gaussian filtering are applied to refine the GRACE data. It is shown that the wavelet approach could better localize the desired signal and increase the signal‐to‐noise ratio and thus results in more accurate estimation of groundwater storage variations. To validate the results of our procedure in estimation of ground water storage variations, they are compared with the measurements of pisometric wells data near the Urmia Lake which shows favorable agreements with our results.     

Large-Scale Total Water Storage and Water Flux Changes over the Arid and Semiarid Parts of the Middle East from GRACE and Reanalysis Products

Previous studies indicate that water storage over a large part of the Middle East has been decreased over the last decade. Variability in the total (hydrological) water flux (TWF, i.e., precipitation minus evapotranspiration minus runoff) and water storage changes of the Tigris–Euphrates river basin and Iran’s six major basins (Khazar, Persian, Urmia, Markazi, Hamun, and Sarakhs) over 2003–2013 is assessed in this study. Our investigation is performed based on the TWF that are estimated as temporal derivatives of terrestrial water storage (TWS) changes from the Gravity Recovery and Climate Experiment (GRACE) products and those from the reanalysis products of ERA-Interim and MERRA-Land. An inversion approach is applied to consistently estimate the spatio-temporal changes of soil moisture and groundwater storage compartments of the seven basins during the study period from GRACE TWS, altimetry, and land surface model products. The influence of TWF trends on separated water storage compartments is then explored. Our results, estimated as basin averages, indicate negative trends in the maximums of TWF peaks that reach up to ?5.2 and ?2.6 (mm/month/year) over 2003–2013, respectively, for the Urmia and Tigris–Euphrates basins, which are most likely due to the reported meteorological drought. Maximum amplitudes of the soil moisture compartment exhibit negative trends of ?11.1, ?6.6, ?6.1, ?4.8, ?4.7, ?3.8, and ?1.2 (mm/year) for Urmia, Tigris–Euphrates, Khazar, Persian, Markazi, Sarakhs, and Hamun basins, respectively. Strong groundwater storage decrease is found, respectively, within the Khazar ?8.6 (mm/year) and Sarakhs ?7.0 (mm/year) basins. The magnitude of water storage decline in the Urmia and Tigris–Euphrates basins is found to be bigger than the decrease in the monthly accumulated TWF indicating a contribution of human water use, as well as surface and groundwater flow to the storage decline over the study area.     

Application of GRACE to the estimation of groundwater storage change in a data-poor region: A case study of Ngadda catchment in the Lake Chad Basin

The present study is to explore the feasibility of GRACE-based estimation of a groundwater storage change in a data-poor region using a case study of the Ngadda catchment in the Lake Chad Basin. Although the Ngadda catchment has only one set of in situ time series data of groundwater from 2006 to 2009 and a limited number of groundwater measurements in 2005 and 2009, GRACE-based groundwater storage change can be evaluated against the in situ groundwater measurements combined with specific yield data. The cross-correlation analysis in the Ngadda catchment shows that maximum rainfall reached in July and August, whereas both the maximum total water storage anomaly and the maximum groundwater storage anomaly occurred 2months later. Whereas the mean annual amplitude of total water storage anomaly is about 17cm from both the average total water storage anomaly from three mascon products and the one from three spherical harmonic products, the mean annual amplitude of soil moisture storage anomaly is substantially varied from 5.58cm for CLM to about 14cm for NOAH and Mosaic. The goodness-of-fit tests show that CLM soil moisture produces the closest estimation of groundwater storage anomaly to the in situ groundwater measurements. The present study shows that GRACE-based estimation for groundwater storage anomaly can be a cost-effective and alternative tool to observe how groundwater changes in a basin scale under the limitation of modelling and in situ data availability.     

An insight into the Palmer drought mechanism based indices: comprehensive comparison of their strengths and limitations

Considering the drawbacks of the original Palmer drought severity index (PDSI) in terms of its simplified hydrologic algorithm and spatio-temporal inconsistency, we compare six variants of PDSI derived from different combinations of two hydrologic algorithms and three standard processes so as to provide deep insights into the individual impacts of hydrological processing and standardization on final PDSI values as well as their combined effects. Investigations are conducted in whole Yellow River basin. On basis of 52 years’ (1961–2012) hydro-meteorological data, comprehensive analysis on multiple drought characteristics are carried out for each PDSI variant, combined with comparison of three crucial intermediate variables of PDSI. Results show that variable infiltration capacity (VIC) model based modification in the hydrologic accounting section significantly improve drought trends with more reasonable spatial distributions presented. For the statistical characteristics of drought areas and frequency, comparable performance is found between VIC-based modification and self-calibrating standard procedure-based modification, though they are derived from different mechanisms. However, in case of the coupling of these two modifications, indices derived from combined modifications perform poorly than single modification-based indices with unexpected high frequency of extreme events detected in certain regions. This reflects the complicated mechanism of PDSI and it is essential to propose an appropriate standardization to match the hydrological algorithm and further improve the performance of relevant drought index. With the crucial findings mentioned above, this study is promising to provide some theoretical supports and serve as a competent reference for future PDSI based researches.     

利用重力卫星GRACE监测亚马逊流域2002-2010年的陆地水变化

本文利用GRACE (Gravity Recovery and Climate Experiment) 卫星重力资料研究了亚马逊流域2002-2010年的陆地水变化,并与水文模式和降雨资料进行了比较分析.在年际尺度上,GRACE结果表明:2002-2003年和2005年,亚马逊流域发生明显的干旱现象;2007年至2009年,陆地水呈逐年增加的趋势,并在2009年6月变化值达到最大,为772±181 km³;自2009年6月至2010年12月,陆地水总量又急剧减少了1139±262 km³,这相当于全球海平面上升3.2±0.7 mm所需的水量.水文模式得到的亚马逊流域陆地水在2010年也表现出明显的减少.降雨资料与GRACE观测资料有很好的一致性.在2005年和2010年的干旱期,亚马逊流域的降雨显著减少,说明降雨是亚马逊流域陆地水变化的重要因素.此外,本文采用的尺度因子的方法有效地降低了GRACE后处理误差的影响.     

基于双源蒸散和混合产流的分布式水文模型构建及应用--以辽河老哈河流域为例

以北方半干旱地区的辽河老哈河流域为研究对象,采用网格离散化方法进行水文模拟单元划分,利用具有物理基础的双源蒸散发能力估算模型,计算每个栅格单元的截留蒸发、植被蒸腾能力和土壤蒸发能力,并取代蒸发皿资料作为混合产流模型的蒸散发能力输入,从而构建摹于双源蒸散与混合产流的分布式水文模型,并对老哈河流域1970-1979年的日径...     

基于随机森林模型的GRACE数据3种空间降尺度对比

陆地水储量是赋存在陆地上各种形式水的综合体现,研究其时空变化对认识区域水循环过程和水资源调控等具有重要意义。然而现有陆地水储量变化数据实际分辨率较低,限制了其在中小流域或地区中的应用。针对这一问题,本文基于GRACE重力卫星和其后续卫星GRACE-FO反演的陆地水储量变化数据,首先采用随机森林模型,分别基于格点、区域(流域)和区域(全国)3种空间降尺度思路将GRACE数据降尺度至0.25°×0.25°,后结合GLDAS模型数据,基于水量平衡原理计算得到地下水储量变化数据,最后基于降尺度模型模拟效果和实测地下水位数据评估3种降尺度思路在全国的适用性。结果表明:随机森林模型能够较好地模拟驱动数据(降水、气温、植被条件指数和土壤水储量)与GRACE数据的统计关系,验证期格点降尺度思路的平均相关系数总体在0.6左右,区域降尺度思路的平均纳什效率系数、相关系数和均方根误差分别>0.5、>0.75和<6.6 cm,3种空间降尺度思路的模拟精度均满足基本要求;2003—2021年间,GRACE数据、格点降尺度、区域降尺度(流域)和区域降尺度(全国)得到的我国陆地水储量亏缺量分别约为...     

Terrestrial hydrological responses to precipitation variability in Southwest China with emphasis on drought

Abstract

This study investigates the terrestrial hydrological processes during a dry climate period in Southwest China by analysing the frequency-dependent runoff and soil moisture responses to precipitation variability. Two headwater sub-basins, the Nanpan and Guihe basins of the West River (Xijiang), are studied to compare and contrast the terrestrial responses. The variable infiltration capacity (VIC) model is used to simulate the hydrological processes. Using wavelets, the relationships between observed precipitation and simulated runoff/soil moisture are expressed quantitatively. The results indicate that: (a) the Guihe basin shows a greater degree of high-frequency runoff variability in response to regional precipitation; and (b) the Nanpan basin exhibits less capability in accommodating/smoothing extreme precipitation deficits, reflected in terms of both higher scale-averaged (for 3–6 months) and time-averaged (for the year 1963) wavelet power of soil moisture.

Editor Z.W. Kundzewicz; Associate editor C.-Y. Xu

Citation Niu, J. and Chen, J., 2013. Terrestrial hydrological responses to precipitation variability in Southwest China with emphasis on drought. Hydrological Sciences Journal, 59 (2), 325–335.     

Macroscale hydrological modelling approach for study of large scale hydrologic impacts under climate change in Indian river basins

In climate‐change studies, a macroscale hydrologic model (MHM) operating over large scales can be an important tool in developing consistent hydrological variability estimates over large basins. MHMs, which can operate at coarse grid resolutions of about 1° latitude by longitude, have been used previously to study climate change impacts on the hydrology of continental scale or global river basins. They can provide a connection between global atmospheric models and water resource systems on large spatial scales and long timescales. In this study, the variable infiltration capacity (VIC) MHM is used to study large scale hydrologic impacts of climate change for Indian river basins. Large‐scale changes in runoff, evapotranspiration and soil moisture for India, as well as station‐scale changes in discharges for three major river basins with distinct climatic and geographic characteristics are examined in this study. Climate model projections for meteorological variables (precipitation, temperature and wind speed) from three general circulation models (GCMs) and three emissions scenarios are used to drive the VIC MHM. GCM projections are first interpolated to a 1° by 1° hydrologic model grid and then bias‐corrected using a quantile–quantile mapping. The VIC model is able to reproduce observed statistics for discharges in the Ganga, Narmada and Krishna basins reasonably well, even at the coarse grid resolution employed using a calibration period for years 1965–1970 and testing period from 1971–1973/1974. An increasing trend is projected for summer monsoon surface runoff, evapotranspiration and soil moisture in most central Indian river basins, whereas a decrease in runoff and soil moisture is projected for some regions in southern India, with important differences arising from GCM and scenario variability. Discharge statistics show increases in mid‐flow and low flow at Farakka station on Ganga River, increased high flows at Jamtara station upstream of Narmada, and increased high, mid‐flow and low flow for Vijayawada station on Krishna River in the future. Copyright © 2013 John Wiley & Sons, Ltd.     

2005—2017年两次强ENSO事件对中国区域陆地水储量变化影响的卫星重力观测

近年来极端气候事件的频发对全球和区域性水循环产生了重大影响,特别是2005—2017年间两次强ENSO(El Nino-Southern Oscillation)事件使得全球陆地水储量出现了较大的年际波动.GRACE(Gravity Recovery and Climate Experiment)重力卫星随着数据质量的提高、后处理方法的完善和超过十年的连续观测,捕捉陆地水储量异常的能力明显提高,这为研究2005—2017年间两次强ENSO事件对中国区域陆地水储量变化的影响提供了观测基础.本文综合利用GRACE卫星重力数据、GLDAS水文模型和实测降水资料分析了中国区域陆地水储量年际变化和与ENSO的关系.研究发现:长江流域中、下游地区和东南诸河流域与ENSO存在较高的相关性,与ENSO的相关系数最大值分别为0.55、0.78、0.70,较ENSO分别滞后约7个月、5个月和5个月.其中长江流域下游地区与ENSO的相关性最强,2010/11 La Nina和2015/16 El Nino两次强ENSO事件使得陆地水储量分别发生了约-24.1亿吨和27.9亿吨的波动.在2010/11 La Nina期间,长江流域下游地区和东南诸河流域陆地水储量异常约在2011年4—5月达到谷值,而长江流域中游地区晚1~2月达到谷值.在2015/16 El Nino期间,长江流域中、下游地区和东南诸河流域陆地水储量从2015年9月到2016年7月持续出现正异常信号.其中,2015年秋冬季(2015年9月至2016年1月)陆地水储量异常明显是受此次El Nino同期影响的结果;2016年春季(4—5月)陆地水异常是受到此次厄尔尼诺峰值的滞后影响所致;2016年7月的陆地水储量异常则与西北太平洋存在的异常反气旋环流有关.     

A method for estimating soil moisture storage in regions under water stress and storage depletion: a case study of Hai River Basin,North China

Soil moisture is a consideration for soil conservation, agricultural production and climate modelling. This article presents a simple method for estimating soil moisture storage under water stress and storage depletion conditions. The method is driven by the common agro‐hydrologic variables of precipitation (PPT), irrigation (IRR) and evapotranspiration (ET). The proposed method is successfully tested for the 152 000 km² floodplain region of Hai River Basin using 48 consecutive months (2003–2006) of data. Soil moisture data from global land data assimilation system/Noah land surface model are validated with ground‐truth data from 102 soil moisture monitoring sites. The validated soil moisture is used in combination with in situ groundwater data to quantify total water storage change (TWSC) in the region. The estimated storage change is in turn compared with gravity recovery and climate experiment‐derived TWSC for the study area. The soil moisture and TWSC terms show favourable agreements, with discrepancies of < 10% on the average. While there is no consistent seasonal trend in soil moisture, TWSC shows a strong seasonality. It is low in spring and high in summer. This trend corresponds with the IRR–PPT season in the study area. Change in groundwater and total water storage indicates storage depletion in the basin. Storage depletion in the region is driven mainly by groundwater IRR and ET loss. Despite the low PPT and high ET, there is narrowing seasonal trend in soil moisture. This is achieved at the expense of groundwater storage. IRR pumping has induced extensive groundwater depletion in the basin. It is therefore vital to develop cultivation strategies that aim at limiting IRR pumping and ET loss. Water management practices that not only reduce waste but also ensure high productivity and ecological sustainability could also mitigate storage depletion in the region. These measures could reduce further not only the seasonal trend in soil moisture but also that in groundwater storage. Copyright © 2011 John Wiley & Sons, Ltd.     

Responses of hydrological processes to climate change in the Yarlung Zangbo River basin

ABSTRACT

Climate change alters hydrological processes and results in more extreme hydrological events, e.g. flooding and drought, which threaten human livelihoods. In this study, the large-scale distributed variable infiltration capacity (VIC) model was used to simulate future hydrological processes in the Yarlung Zangbo River basin (YZRB), China, with a combination of the CMIP5 (Coupled Model Intercomparison Project, fifth phase) and MIROC5 (Model for Interdisciplinary Research on Climate, fifth version) datasets. The results indicate that the performance of the VIC model is suitable for the case study, and the variation in runoff is remarkably consistent with that of precipitation, which exhibits a decreasing trend for the period 2046–2060 and an increasing trend for 2086–2100. The seasonality of runoff is evident, and substantial increases are projected for spring runoff, which might result from the increase in precipitation as well as the increase in the warming-induced melting of snow, glaciers and frozen soil. Moreover, evapotranspiration exhibits an increase between 2006–2020 and 2046–2060 over the entire basin, and soil moisture decreases in upstream areas and increases in midstream and downstream areas. For 2086–2100, both evapotranspiration and soil moisture increase slightly in the upstream and midstream areas and decrease slightly in the downstream area. The findings of this study could provide references for runoff forecasting and ecological protection for similar studies in the future.     

Modelling surface‐water depression storage in a Prairie Pothole Region

In this study, the Precipitation‐Runoff Modelling System (PRMS) was used to simulate changes in surface‐water depression storage in the 1,126‐km² Upper Pipestem Creek basin located within the Prairie Pothole Region of North Dakota, USA. The Prairie Pothole Region is characterized by millions of small water bodies (or surface‐water depressions) that provide numerous ecosystem services and are considered an important contribution to the hydrologic cycle. The Upper Pipestem PRMS model was extracted from the U.S. Geological Survey's (USGS) National Hydrologic Model (NHM), developed to support consistent hydrologic modelling across the conterminous United States. The Geospatial Fabric database, created for the USGS NHM, contains hydrologic model parameter values derived from datasets that characterize the physical features of the entire conterminous United States for 109,951 hydrologic response units. Each hydrologic response unit in the Geospatial Fabric was parameterized using aggregated surface‐water depression area derived from the National Hydrography Dataset Plus, an integrated suite of application‐ready geospatial datasets. This paper presents a calibration strategy for the Upper Pipestem PRMS model that uses normalized lake elevation measurements to calibrate the parameters influencing simulated fractional surface‐water depression storage. Results indicate that inclusion of measurements that give an indication of the change in surface‐water depression storage in the calibration procedure resulted in accurate changes in surface‐water depression storage in the water balance. Regionalized parameterization of the USGS NHM will require a proxy for change in surface‐storage to accurately parameterize surface‐water depression storage within the USGS NHM.