ISSN 1000-3665 CN 11-2202/P

    土地利用变化对榆溪河流域地下水文过程影响

    Effect of land use change on groundwater hydrological process in Yuxi River Basin

    • 摘要: 土地利用变化会改变干旱和半干旱地区的水资源分配与地下水文过程,导致区域地下水水位下降、土地荒漠化等水与生态问题。同时干旱和半干旱地区的地表水资源有限,地下水资源是其生产、生活的重要水源。以黄河流域的无定河一级支流榆溪河流域为研究区,利用2005、2010、2015、2020年4期土地利用数据,采用改进的二级土地利用动态度作为标定指数,基于WetSpass-Modflow耦合模型,预测小流域内长时间尺度土地利用变化对地下水水文要素的影响。结果表明:2020—2035年在城市化进程的影响下,由草地、未利用地转化的建设用地增加247.02 km2,引起研究区降雨入渗补给减少6.8 mm/a,地下水水位变化在±3m的范围内,蒸散发量基本保持不变。土地利用变化主要通过降低下垫面入渗性能、降低植被截流能力等途径降低降雨入渗补给量。利用降雨入渗补给量减蒸散发量得到净补给量,发现未利用地>耕地>林地>草地>建设用地。根据净补给量可以推断耕地、未利用地对地下水储量贡献大于草地。结果证明,改进的WetSpass-Modflow耦合模型可以从土地利用变化方面,对小流域地下水水文变量估算和预测有较好的适用性。未来应考虑更高效的农业节水方案,严格限制农业面积增加,促进区域地下水资源可持续利用。

       

      Abstract: Land use change alters water resources allocation and groundwater hydrological processes in arid and semi-arid areas, leading to water and ecological problems such as regional groundwater level decline and land desertification. In these areas, where surface water resources are scarce, groundwater serves as the primary source for domestic and agricultural use. This study focused on the Yuxi River Basin, a primary tributary of Wuding River in the Yellow River Basin. By employing the land use data of four periods in 2005, 2010, 2015, and 2020, and using the improved dynamic attitude of secondary land use as the calibration index, this study analyzed the effects of long time scale land use change on groundwater hydrological elements in small catchment based on the coupled WetSpass-Modflow model. The results show that under the influence of urbanization from 2020 to 2035, the construction land converted from grassland and unused land will increase by 247.02 km2, resulting in a decrease of 6.8 mm/a in rainfall infiltration recharge in the study area; the change of groundwater level will be within the range of ±3m, while the evapotranspiration will basically remain unchanged. Land use change mainly reduces rainfall infiltration by reducing the infiltration performance of underlying surface and the interception ability of vegetation. Analysis of net recharge (rainfall infiltration minus evapotranspiration) reveals the following order: unused land > cultivated land > forest land > grassland > construction land. This indicates that the contribution of cultivated land and unused land to groundwater reserves is greater than that of grassland. The results show that the improved WetSpass-Modflow coupling model can be used to estimate and predict groundwater hydrological variables in small watershed from the perspective of land use change. In the future, more efficient agricultural water-saving schemes should be considered, and the increase of agricultural area should be strictly limited to promote the gradual improvement of the sustainability of regional groundwater resources.

       

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