Water and matter dynamic balance in the rite field and its overflow estimate model

The rice field is the main Iand use type in the watershed of Chaohu Lake．Because of the water dryness alternative farming applied there，the paddy soil has a unique quality regarding soil profile as well as special water and nutrient dynamms．Through the analysis of water and matter dynamics in rice fields．the field water level(H)and the concentrations of total nitrogen(TN)and total phosphorus(TP)in flood water layers of the fields were chosen to estimate the nonpoint pollution from rice fields．A simple model was built and used to calculate the quantRy of N and P pollutants from rice field overflow．it shows the po．tential effects of rice fields on Chaohu Lake eutrophication．