Recharge and Nitrate Transport Through the Deep Vadose Zone of the Loess Plateau: A Regional‐Scale Model Investigation
Recharge and Nitrate Transport Through the Deep Vadose Zone of the Loess Plateau: A Regional‐Scale Model Investigation
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DOI：
10.1029/2017wr022190
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发表时间：
2018-07
影响因子：
5.4
通讯作者：
T. Turkeltaub;X. Jia;Yuanjun Zhu;M. Shao;A. Binley
中科院分区：
文献类型：
--
作者：
T. Turkeltaub;X. Jia;Yuanjun Zhu;M. Shao;A. Binley
黄土高原地区地下水超采严重，地下水位下降。这与最近大规模的土地利用转变有关，这可能会影响地下水的补给，并威胁到未来大量施用氮肥的水质。了解区域非饱和水流量和硝酸盐在深包气带的旅行时间是至关重要的LPC地下水系统的可持续管理。我们在这里开发了一个区域尺度模型，该模型利用了一个广泛的土壤特性数据库，该数据库来自LPC上最近密集的土壤剖面采样，以及气候、包气带厚度和土地利用数据。该模型解决了理查兹方程和保守的溶质运移模型，使用多个一维列的方法。在五个站点的模型模拟和观测之间的比较显示出良好的模型性能。LPC的应用表明，密集灌溉农业用地的地区，地下水补给贡献显着。通过使用1975年至2008年的土地利用/覆盖信息，模拟显示，从农业到森林和草地的过渡占年总补给量的小幅减少（6.1%）。模拟的硝酸盐通过深层非饱和带的时间在几十年到几百年之间;然而，最近人为硝酸盐的负荷预计将在不久的将来到达灌溉区或包气带相对较薄的含水层。模型模拟提供了宝贵的信息，评估未来的脆弱性，地下水资源在区域范围内。
The Loess Plateau of China (LPC) is suffering from the impacts of overexploitation of groundwater, leading to a decline in the regional water table. This is compounded by relatively recent large‐scale transformation of land use, which may impact groundwater recharge and threaten future water quality from intensive nitrogen fertilizer application. Understanding the regional unsaturated water flow and nitrate travel time in the deep vadose zone is crucial for the sustainable management of the LPC groundwater system. We develop here a regional‐scale model that exploits an extensive database of soil properties derived from recent intensive soil profile sampling over the LPC, together with climate, vadose zone thickness, and land use data. The model solves the Richards equation and a conservative solute transport model using a multiple 1D column approach. A comparison between model simulations and observations at five sites reveals good model performance. Application over the LPC indicates that areas with dense irrigated agricultural land use contribute significantly to groundwater recharge. By using land use cover information from 1975 to 2008, simulations reveal that the transition from agriculture to forest and grassland accounts for a small reduction of the total annual recharge (6.1%). Modeled nitrate travel times through the deep unsaturated zone range between decades and centuries; however, recent loading of anthropogenic nitrate is expected to reach the aquifer in the near future under irrigated areas or where the vadose zone is relatively thin. The model simulations provide valuable information for assessing future vulnerability of groundwater resources over a regional scale.