(GIS and Remote Sensing in Hydrology, Water Resources and Environment – Proceedings of ICGRHWE held at the Three Gorges Dam, China, September 2003 – IAHS Publication 289, 2004, pp. 336–342).
The sources and magnitude of agricultural nutrient export from a catchment are not identical. Nitrogen and phosphorus export patterns and their Critical Source Areas (CSAs) were identified in a 1.74 km2 mountainous agricultural catchment. During baseflow the concentration of nitrate nitrogen (NO3N) increased downstream, but dissolved reactive phosphate (DRP) concentration decreased downstream from the uppermost site to the outlet. The upstream area – segment 1 is a CSA for DRP export, but the outlet areas – segments 6, 7 are CSAs for NO3-N loss during baseflow. Two precipitation events with a similar precipitation magnitude but different duration were used to test the Agricultural Non-Point Source (AGNPS) model. During stormflow, CSAs for both NO3-N and DRP, defined through the AGNPS model tested, are side-slope areas where citrus has been planted.
Agricultural non-point source model, Critical source area, Flow regimes, Nutrient export, Wuchuan catchment
