Mapping soil pollution risk from riparian land-cover changes in the headwater area of an inter-basin water diversion project

Abstract

A novel scheme was proposed for mapping precise land-cover change in riparian zones and the resulted soil pollution risk of non-point source (NPS) from an inter-basin water diversion project on its headwater area. The scheme held three key points: 1) digital visualization of the riparian land-cover’s cyclical features was done using remote sensing data fusion of NDWI at high water level and NDVI and MNDWI at lower water level; 2) riparian zones were identified through color clustering on optimized RGB-fusion image that was picked out by applying Modified Vector-Angular Distance (MVAD) formula to measure difference between riparian and non-riparian zones in RGB space; 3) combining Export Coefficient Model (ECM) and the derived data on riparian land-cover change around Danjiangkou Reservoir in China, time-series loads of the soil NPS pollutants were estimated before and after the Middle Route of South-to-North Water Diversion Project (SNWDP) started running in 2014. The results indicated that risk of the potential soil pollution from land-cover change in the new riparian zones enlarged. Growth rates (GR) of total nitrogen (TN) and total phosphorus (TP) not only had significant spatial variation, but also were higher during initial running period of the SNWDP’s Middle Route.