Influence of Wetland and Farmland Changes on Runoff Depth in Naolihe River Basin

The wetland area decrease and farmland area increase are typical changes of landscape of the Naolihe River basin since 1950s.By adopting linearity,logarithm,exponential,and cubic function to simulate the correlation between the wetland area,farmland area and area precipitation and runoff depth in the basin,respectively,the results show:(1) The simulation correlation of cubic function is best;(2) The correlation between the wetland area decrease and farmland area increase and runoff depth is less than that between the precipitation and the runoff depth.By analyzing the mechanism of contribution from the wetland area decrease and farmland increase to the runoff depth decline,it is believed that the wetland area decrease reduce the cold-wet effect of wetland,and enhance the terrestrial evaporation potential;the conversion from wetland to farmland changes the redistribution processes of precipitation in soils;the farmland area increase enhances the evaporation potential of soils;the conversation from dry farmland to paddy field increase the water utilization quantities of the surface water and groundwater,which result in reducing the runoff depth.The research conclusions show that the wetland area decrease and farmland area increase makes a more obvious contribution to the runoff depth reduction.The runoff depth reduction is an indicator of a basin appearing in a drought tendency.It is supposed to strengthen the wetland conversation and restoration,especially restore the water connection relation between river and marsh wetland,control the area of paddy filed,and enhance the reservoirs' regulating wetland ecological water supply.