Assessment of the ecosystem service value of river network in irrigation district

River networks (including rivers and drainages) ecosystems in many irrigation districts are getting worse as the development of farmland irrigation. Ecosystem service values can reflect the deteriorating situation of river networks ecosystems. In this paper, a classification of river network ecosystem service values of irrigation district is presented and suitable estimate methods are recommended. According to the basic data of Yanyun Irrigation District in Jiangsu Province from year 2003 to 2007, the assessment of ecosystem services value have been completed on market prices method, replacement cost method and opportunity cost method. The result shows that the annual average service value is 136,313,600 Yuan RMB, and the annual average service value per hectare is 4,150 Yuan RMB. Because of agricultural non-point sources pollution, the service value of water supply is quite small, and only accounts for 2.2% of the total. The service value of aquatic products supply is also decreases gradually.