Abstract:
Soil Water Infiltration Model (SWIM) has been applied for computation of groundwater recharge from an irrigated paddy field in PAU Campus. Total precipitation and applied irrigation has been about 2460 mm. The model out put consisted of actual evaporation of 1798 mm and with a runoff of 82 mm. The unavailable water in soil zone is 569 mm, with available water at the end of simulation as 499 mm and the groundwater recharge worked out to be 441 mm for 3 m sandy loam profile. The natural recharge estimated by tracer measurements made in Punjab state during 1988 was only about 55 mm/yr. The actual irrigation return flow works out to be 396 mm. The groundwater recharge at the end of one year has been worked out as 149 mm for 6 m sandy loam profile.
Two scenarios of SWIM model results indicate that reduction in potential recharge to the deep water table in the canal irrigated areas may be due to deep water table condition with a large thickness of vadose zone, which in turn may be holding irrigation return flows as available moisture in that zone above the water table, but not contributing actually to the water table. The study warrants imperative need for reduction in the overexploitation of groundwater resources in the area. As overexploitation of groundwater has been resulting in reduction of potential recharge through applied irrigation return flows as well as monsoon rainfall to the groundwater table in various parts of Punjab. It is suggested that farmers may switch over to low water intensive irrigated crops to reduce stress on the groundwater resources, which may keep groundwater table low for faster replenishment of aquifers through natural recharge as well as applied irrigation return flows.
