Abstract:

Based on the complex variation of land cover in plain area, Beisan River of Tianjin area is classified into the water surface, farm land and urban construction land, runoff models are adopted according to different land cover. The land for farming is mainly dry land, in which exist plough pan, so the unsaturated zone is plotted out plough layer, plough pan and basic layer, which adopts respectively the excess storage, excess infiltration and excess storage runoff mode, and the influence of macropore in plough pan on runoff is considered. Hydrologic data of 1966,1971,1974,1975 and 1976 in the 9th area of Beisan River are used to establish the runoff model, which is checked by data of 1977 and 1982, resulting in a comprehensive qualified data up to 85.7%. Application of the model has proved that the model conforms to the actual situation and may truly reflect the characteristics of the Beisan River, and may serve as a reference for hydrologic analysis of plain area.

Key words: vertically-mixed model, runoff, plough pan, macropore, land cover, Tianjin