潮河上游土地利用/覆被变化对年径流影响模拟

该文以北京潮河密云水库上游流域为研究对象,分析了1961—2000年期间降雨、径流以及土地利用和覆被变化情况,利用一个集总式的水文模型(IHACRES模型)模拟土地利用和覆被变化对年径流的影响。结果表明,40年来,潮河上游流域降雨--径流的演变过程可划分为3个阶段:1961—1978年(第一阶段)、1979—1993年(第二阶段)、1994—2000年(第三阶段)。相对第1阶段而言,第2和第3阶段流域降雨的产流能力总体上呈减少趋势。20世纪80年代末以来,流域内土地利用和覆被变化比较明显,主要变化趋势是林地面积持续增加,耕地、草地及未利用土地向林地的转换构成了土地覆被变化的主导过程,成为影响流域年径流的主要因子。第2阶段,耕地和林地的面积分别增长了7.47%和7.78%,流域内水库和塘坝等水利设施的修建及大规模利用也发生在这一阶段;第3阶段,土地利用和覆被变化主要表现为林地面积的大幅度增加(11.81%)。利用IHACRES模型模拟了第2和第3阶段的"基准年径流",通过对比实测年径流和基准年径流的差异,得出了土地利用和覆被变化减少了流域年径流的结论。其中第2阶段土地利用和覆被变化的影响程度为27.76%,第3阶段为26.15%。

Simulation of impacts of changes in land use and cover on annual streamflow in the upper reach of Chaohe River Basin

This study investigated the precipitation,streamflow,land use and land cover changes during the period 1961-2000 in the upper Chaohe River Basin,one of the key water sources for Beijing,and simulated the impacts of land use and land cover changes on the annual streamflow.Results show that rainfall-streamflow evolution in the upper Chaohe watershed during the past 40 years can be divided into three periods:1961-1978(period Ⅰ),1979-1993(period Ⅱ)and 1994-2000(period Ⅲ).An analysis of land cover data of the three periods suggests that since the late 1980s obvious changes of land cover types occurred in the watershed:area of cultivated land increased by 7.47% from the period Ⅰ to Ⅱ and 0.35% from the period Ⅱ to Ⅲ;forestland area increased by 7.78% and 11.81% respectively.Dominant changes in land cover types are conversion from cultivated land to forestland and grassland;conversion from grassland to forestland or from forestland to grassland.Construction and use of many water conservancy and irrigation works also took place in period Ⅱ.During period Ⅲ,the change of land use and cover is largely characterized by a rapid increase of forestland area by 11.81%.Using period Ⅰ as the reference period,annual streamflow during the period Ⅱ and Ⅲ was simulated by a lumped rainfall-runoff IHACRES model.By calculating the difference between the reference and gauged annual streamflow,a conclusion was reached that land cover changes in this watershed reduced annual streamflow;the impact degrees of land cover changes are 27.76% for period Ⅱ and 26.15% for period Ⅲ.