Determination of Preferential Flow in Precipitation Infiltration Recharge

Preferential flow is one of main forms of infiltration recharge from rainfall and irrigation to groundwater.It has the characteristics of rapid flow rate, complicated flow path and being very difficult to be quantified.To quantify the preferential flow in the infiltration recharge process and its percentage in total infiltration recharge, a new method has been developed based on the measured infiltration recharge of lysimeters in Zhengzhou Groundwater Balance Test Field.The numerical simulation model that can describe the piston flow in lysimeters by rechards equation was constructed and calibrated according to the soil hydraulic parameters, weather data and so on.The surplus part in the calculated flux can be regarded as the preferential flow because the preferential flow flows faster than piston flow and reaches groundwater earlier.By comparing the measured recharge flux and calculated recharge flux, the quantity of preferential flow and its percentage in total precipitation infiltration recharge can be determined.The preferential flow makes up 10%-80% in total precipitation infiltration recharge.The percentage is higher when the soil contains more clay, and the percentage is lower when the groundwater level is deeper.