A system framework for spatial allocation of soil management practices (SMPs) in river basins

Abstract

Soil management practices (SMPs) have been widely applied all over the world due to their enhancement of soil water storage capacity (WSC), thus improving the effective utilization of local precipitation. Relevant studies have focused on the mechanisms by which SMPs influence key water cycle processes but tend to ignore the spatial allocation of SMPs across river basins. This paper attempts to provide a system framework for such a spatial allocation of SMPs. A series of empirical equations for evaluating the WSC of different types of SMPs were established based on the assumptions of the SCS-CN model and the geometric parameters of terraces and contour ridges. Using spatial information constraints such as land use, effective soil depth and slope, allocation schemes for SMPs were optimized by comparing the WSCs of various SMPs on evaluation units. Using the Sihe River Basin as a study model, this framework was used to quantify the existing WSCs of various SMPs and determine alternative SMPs for each evaluation unit. Two recommended spatial schemes for SMPs basing on single-object spatial optimization were designed and their corresponding WSCs were calculated. The results show that the WSC of SMPs in the Sihe River Basin was 61.8 million m3 in 2015. This value can be effectively improved with spatial optimization of SMPs. The total WSC of SMPs in Scheme I, taking the maximum WSC as a target function, was 198.36 million m3, and the average WSC per unit area increased by 27 % compared with 2015. Scheme II, with a goal of achieving a minimum ratio of implementation cost to WSC, had a total WSC of 183.61 million m3, and the average WSC per unit area was 17 % higher than that of 2015. These results provide adaptation-strategies for the allocation of SMPs across the river basin and a technical means for integrated soil water management.