How to control nitrogen and phosphorus loss during runoff process? – A case study at Fushi Reservoir in Anji County (China)

Water pollution is becoming a global issue, and process controls are the key steps for controlling non-point source pollution (NPSP). Runoff ditches collect rainfall and often act as channels for nitrogen (N) and phosphorus (P) pollutants to enter water source areas such as the reservoir, which are important parts of process controls. Therefore, performing in situ analyses to clarify the mechanism of process control are vital for reducing the migration of N and P pollutants into reservoirs. In view of this, the Fushi Reservoir in Taihu lake basin was taken as the test plot and the characteristics of process controls were approached through field investigations to determine the impact of runoff ditch landscape factors on water quality. The results indicated that various landscape factors had different effects on the N and P concentrations in the runoff ditch. Some landscapes that were influenced by human activities, including residential and white tea gardens, could increase N but had relatively little impact on P levels in the runoff ditch. Compared with the white tea (WT3), forested wetlands (FW2) decreased the average total nitrogen (TN) (-29.53%), average dissolved nitrogen (DN) (-40.29%), and average nitrate-nitrogen (-45.32%) in the runoff ditch. Obviously, the novel research suggests constructing rationally landscape factors for runoff ditches is helpful to mitigate NPSP in catchment areas of drinking water and to improve water quality. It is expected that the initial research can push up landscape planning of runoff ditches and promote the improvement of water quality in water source areas.