The transport characteristics of phosphorus in soil and the assessment of its environmental risk have become hot topics in the environmental and agricultural fields. The Sanjiang Plain is an important grain production base in China, and it is characterised by serious land use change caused by large-scale agricultural exploitation. Agricultural inputs and tillage management have destroyed the soil nutrient balance formed over long-term conditions. There are few studies on non-point source phosphorus pollution in the Sanjiang Plain, which is the largest swampy low plain in a mid-high-latitude region in China. Most studies have focused on the water quality of rivers in marsh areas, or the export mechanism of phosphorus from specific land uses. They were conducted using experimental methods or empirical models, and need further development towards mechanism models and the macro-scale. The question is how to find a way to couple processes in phosphorus cycling and a distributed hydrological model considering local hydrological features. In this study, we report an attempt to use a distributed phosphorus transport model to analyse non-point source total phosphorus pollution from different land uses and soil types on the Sanjiang Plain. The total phosphorus concentration generally shows an annually increasing trend in the study area. The total phosphorus load intensity is heterogeneous in different land use types and different soil types. The average total phosphorus load intensity of different land use types can be ranked in descending order from paddy field, dry land, wetlands, grassland, and forestland. The average total phosphorus load intensity of different soil types can be ranked in descending order: paddy soil, bog soil, planosol, meadow soil, black soil, and dark brown earth. The dry land and paddy fields account for the majority of total phosphorus load in the study area. This is mainly caused by extensive use of phosphate fertilizer on the cultivated land. This has important implications for future agricultural management and non-point source control in this agricultural area of the mid-high latitude region.

Vegetation deterioration and soil loss are the main causes of more precipitation leakages and surface water shortages in degraded karst areas. In order to improve the utilization of water resources in such regions, water storage engineering has been considered; however, site selection and cost associated with the special karstic geological structure have made this difficult. According to the principle of the Soil Plant Atmosphere Continuum, increasing both vegetation cover and soil thickness would change water cycle process, resulting in a transformation from leaked blue water (liquid form) into green water (gas or saturated water form) for terrestrial plant ecosystems, thereby improving the utilization of water resources. Using the Soil Vegetation Atmosphere Transfer model and the geographical distributed approach, this study simulated the conversion from leaked blue water (leakage) into green water in the environs of Guiyang, a typical degraded karst area. The primary results were as follows: (1) Green water in the area accounted for normal year > rainy year. Thus, increased soil thickness was shown effective in improving the utilization ratio of water resources and in raising the amount of plant ecological water use; (4) The transformation of blue water into green water, which avoids constructions of hydraulic engineering, could provide an alternative solution for the improvement of the utilization of water resources in degraded karst area. Although there are inevitable uncertainties in simulation process, it has important significance for overcoming similar problems.

The contradiction between ecological environment protection and economic development in the Yangtze River Basin has become increasingly prominent in recent years, which seriously limits the sustainable development of the basin. Research on water environment changes of the main tributaries of the Yangtze River helps explore measures to improve the ecological environment of the Yangtze River Basin. In this study, based on the theory of behavioral science in modern management, water quality data in the field were collected, and the farmers’ garbage stacking behavior was also investigated in the water source area of the Dabie Mountains. The results showed that ammonia nitrogen (AN), chemical oxygen demand (COD), total organic carbon (TOC), and total dissolved solids (TDS) in the water bodies showed an overall negative correlation with the distance of water quality collection sites from the garbage stacking point. AN was the most important pollution element affecting the rural water quality in the water source area of the Dabie Mountains. The unsuitable garbage stacking locations and the farmers’ behavior of dumping garbage along the riverbanks were the important causes of water pollution. The garbage stacking locations were optimized and designed by using a GIS spatial analysis tool and a developed suitability evaluation model for the garbage stacking points. The optimized garbage stacking locations were more suitable for improving the local water environment, and their average suitability values increased to 2.01 times and 2.94 times that of the original stacking locations in Kanxiawan and Lengshuigou, respectively. This study can be used as a scientific and methodological reference for improving the rural water environment in the water source area of the Dabie Mountains and in other similar regions in the world.