水土流失综合治理优先小流域识别的空间尺度效应

Scale Effect on Identifying Priority Watershed for Comprehensive Control of Soil and Water Loss

[目的]探讨水土流失综合治理优先小流域识别的空间尺度效应,为小流域水土流失综合治理规划与实施提供科学依据。[方法]以重庆市合川区为例,利用小流域水土流失面积比例,不同土地利用类型比例和流域平均坡度计算了综合指标,用以识别5种流域空间尺度[Ⅰ(流域面积范围50~300 km^2),Ⅱ(10~50 km^2),Ⅲ(1~10 km^2),Ⅳ(0.1~1 km^2)和Ⅴ级(0.01~0.1 km^2)]的水土流失综合治理优先小流域。[结果]流域空间尺度对优先小流域的识别有显著影响。基于Ⅳ和Ⅴ级流域确定的优先小流域在空间分布上与基于栅格土壤侵蚀强度图得到的区域水土流失面积空间分布更为吻合。[结论]综合考虑优先小流域的条数,基于Ⅳ级流域得到的优先小流域条数更少,更便于进行水土保持综合治理规划和管理,是识别优先小流域的最优流域尺度。

[Objective]Identifying priority watershed for soil and water conservation is a premise for the watershed planning.The purpose of this study was to determine the scale effect of identifying the priority watershed.[Methods]Taking Hechuan District,Chongqing Ciyt as an example,the comprehensive indexes was calculated by using the proportion of soil and water loss area,the proportion of land use and the average slope of the basin for identifying the priority watershed.The scale changes from levelⅠ(with watershed area ranged from 50 to 300 km ^2),levelⅡ(10~50 km^ 2),levelⅢ(1~10 km^ 2),levelⅣ(0.1~1 km 2)and levelⅤ(0.01~0.1 km^ 2).[Results]The watershed scale had obvious effect on the identification of priority watershed.The distribution of priority watershed derived from levelⅣandⅤwas more similar to that of soil erosion area derived from soil erosion map in the Hechuan District.The average percentage area of soil loss,the mean proportion of cropland and mining land,and average slope gradient of the priority watersheds from the levelⅣandⅤwere clearly greater than those from the other levels.[Conclusion]The number of the priority watershed from the levelⅣwas less than that from the levelⅤ.The levelⅣwas the best watershed scale for identifying the priority watersheds.It will aid in the management and planning of the priority watershed based on the levelⅣwatershed.