变化环境下沈乌灌域土地利用/覆盖时空变化分析

为了研究变化环境下内蒙古河套灌区沈乌灌域土地利用/覆盖时空变化,并对今后节水改造和节水规划提供指导依据,以沈乌灌域1995、2005年及2015年Landsat影像为数据源,采用基于CART算法的决策树分类对灌域20 a来5种土地利用/覆盖类型进行了分类,并计算了各土地利用/覆盖类型的单一动态度、双向动态度、变化趋势和状态指数,研究了引黄水量等环境变化因子作用下灌域土地利用/覆盖的时空变化。结果表明,(1)1995—2015年沈乌灌域内沙地和盐碱地分别减少了43.77%和62.54%,植被和荒地分别增加了75.10%和92.32%。(2)沙地、盐碱地和荒地向植被的转化是植被面积增加的主要原因;荒地频繁与沙地、盐碱地发生相互转化,相互转化的位置主要出现在沙地和渠道的周边。(3)引水量和地下水埋深是盐碱地、水体的变化主要因子,工程建设是沙地和植被覆盖区变化的主要因子。为缓解灌域的用水矛盾,今后在制定节水规划时应统筹考虑土地利用类型/覆盖与节水改造的关系。

Spatio-temporal Variation of Land Use under Changing Environments in Shenwu Irrigation District

This paper investigated the spatio-temporal variation of land use in Shenwu within Hetao Irrigation District with a view to providing guidance to water-saving planning. Using the Landsat images in 1995, 2005 and 2015 and the CART algorithm, the land use over the past two decades was classified into five types. The temporal change of each type, binary-types, land use index, as well as the impact of the water transferred from Yellow Riv-er into this region for irrigation were calculated. The result showed that over the past two decades, the desertified and salinized land in Shenwu had reduced by 43.77%and 62.54%respectively, while cropped and fallow land in-creased by 75.10%and 92.32%respectively. The increase in cropped land was due to the remediation of deserti-fied and salinized land as well as conversion of fallow land into cropping land. We also found that the desertified, salinized and fallow land can change from one to another, occurring primarily at the desert proximal to canals. Secondary soil salinization was mainly caused by surface-water irrigation, which led to shallow groundwater ta-ble rising;the desertification was caused by engineering structures. Land use should be taken into account in plan-ning solutions for resolving the water resource dilemma faced by this region.