南水北调中线工程水源区水土保持治理成效

Effectiveness of Soil and Water Conservation in the Water Source Area of Middle Route of South-North Water Diversion Project

为评估南水北调中线工程水源区的水土保持治理成效,从而为现阶段制定水土保护措施提供科学依据,利用遥感数据分析了水源区39个区县2010~2015年的生态系统变化,基于InVEST模型研究了水源区的土壤保持功能及时空分布。结果表明,通过实施水土保持林草措施、小流域综合治理等方式,2010~2015年水源区的自然生态空间面积、格局得到了提升优化,水土保持治理成效明显,主要表现在:(1)水源区湿地、灌丛、森林等减缓泥沙流失的"汇"景观类型的面积增幅分别为11.49%、0.29%、0.11%,同时连通性升高,破碎化降低;农田、裸地等促进泥沙流失的"源"景观类型面积减幅分别为2.24%、2.39%,同时连通性下降,破碎化增强;(2)整体上植被恢复显著,植被覆盖度均值从63.06%提高到72.33%;(3)单位面积生态系统土壤保持能力增加了2.74 t/hm2,增幅为0.73%,总体上79.34%的区域土壤保持能力提升。值得重视的是,在人口分布较密集汉中盆地、丹江口库周、淅川中部和南部等农田平原地区,还需加强土壤保持治理,可通过在农业景观区域实施植物篱、栽植经济果林等措施,降低耕地、裸地的空间连接度,从而增强土壤保持能力。

In order to evaluate the effectiveness of soil and water conservation in the water source area of Middle Route of South-North Water Diversion Project, as well as provide scientific basis for formulating soil and water conservation measures at the present stage, the remote sensing data were used to study the changes in ecosystems in the water source area from 2010 to 2015, including 39 districts and counties, and the spatio-temporal distribution in soil retention capacity was also assessed using the InVEST model. The results show that, through implementing forest-grass measures, comprehensive management of small watershed and other ways, the areas and landscape patterns of natural ecological lands in water source area have been improved and optimized from 2010 to 2015, and the effects of soil and water conservation control were achieved, which mainly seen in three aspects:(1)The area of "sink" landscape types, such as wetlands, shrubs and forests that alleviate sediment loss, increased by 11.49%, 0.29% and 0.11% respectively, while their connectivity increased and fragmentation decreased. The areas of "source" landscape types, such as farmland and bare land that promote sediment loss, decreased by 2.24% and 2.39%, respectively, while their connectivity decreased and fragmentation increased.(2)The restoration effect of vegetation was quite good, and the average vegetation coverage in the water source area increased from 63.06% to 72.33%.(3)The average soil retention capacity per unit area of ecosystem enhanced by 2.74 t/hm2, with an increase of 0.73%, and the areas with improved soil retention capacity accounted for 79.34%. More attention should be paid to the management of the soil retention capacity in the agricultural plain areas with highly dense population distribution such as Hanzhong Basin, Danjiangkou reservoir area, central and southern Xichuan, where the spatial connectivity of cultivated lands and bare lands can be reduced by implementing hedgerows and planting fruit forests having economic benefits, thus to enhance the soil retention capacity.