School of Natural Resources, University of Nebraska-Lincoln, 3310 Holdrege Street HH625, Lincoln, NE 68583.Department of Hydraulic and Water Resources Engineering, Budapest University of Technology and Economics, Muegyetem Rakpart 3-9, H-1111 Budapest, Hungary.
Ground Water. 2013 Sep-Oct;51(5):735-44. doi: 10.1111/j.1745-6584.2012.01019.x. Epub 2012 Dec 5.
Monthly evapotranspiration (ET) rates (2000 to 2009) across Nebraska at about 1-km resolution were obtained by linear transformations of the MODIS (MODerate resolution Imaging Spectroradiometer) daytime surface temperature values with the help of the Priestley-Taylor equation and the complementary relationship of evaporation. For positive values of the mean annual precipitation and ET differences, the mean annual net recharge was found by an additional multiplication of the power-function-transformed groundwater vulnerability DRASTIC-code values. Statewide mean annual net recharge became about 29 mm (i.e., 5% of mean annual precipitation) with the largest recharge rates (in excess of 100 mm/year) found in the eastern Sand Hills and eastern Nebraska. Areas with the largest negative net recharge rates caused by declining groundwater levels due to large-scale irrigation are found in the south-western region of the state. Error bounds of the estimated values are within 10% to 15% of the corresponding precipitation rates and the estimated net recharge rates are sensitive to errors in the precipitation and ET values. This study largely confirms earlier base-flow analysis-based statewide groundwater recharge estimates when considerations are made for differences in the recharge definitions. The current approach not only provides better spatial resolution than available earlier studies for the region but also quantifies negative net recharge rates that become especially important in numerical modeling of shallow groundwater systems.
本研究利用普里斯特利-泰勒（Priestley-Taylor）方程和蒸发互补关系，通过对 MODIS（中分辨率成像光谱仪）白天地表温度值的线性变换，获取了内布拉斯加州约 1 公里分辨率的逐月蒸散（ET）率（2000 年至 2009 年）。对于年平均降水和 ET 差异为正值的情况，通过对地下水脆弱性 DRASTIC 代码值进行幂函数变换的乘积，进一步得到年平均净补给量。全州年平均净补给量约为 29 毫米（即年平均降水的 5%），最大补给率（超过 100 毫米/年）出现在东部沙丘区和内布拉斯加州东部。由于大规模灌溉导致地下水位下降，该州西南部地区的负净补给率最大。估计值的误差边界在相应降水率的 10%到 15%之间，并且估计的净补给率对降水和 ET 值的误差很敏感。本研究在考虑补给定义差异的情况下，在很大程度上证实了早期基于基流分析的全州地下水资源补给估计值。当前的方法不仅为该地区提供了比以往研究更好的空间分辨率，而且量化了负净补给率，这在浅层地下水系统的数值模拟中尤为重要。
