Agricultural Water Management and Groundwater Recharging Using Vadose Zone Modelling

Abstract

Temporal and spatial soil moisture status in variable-saturated zone plays a vital role in agricultural water management, groundwater recharge and solute transport of that region, and it is fundamentally regulated by plant growth and its water extraction rate along with soil properties and weather conditions. The soil moisture distribution pattern at soil element scale is regulated by Richard’s equation integrated with a sink term representing water uptake rate by plants. For obtaining soil moisture dynamic across the root zone of a site-specific area, Richards equation-based model coupled with sink term is numerically solved using finite-difference method. The developed model is tested for simplified case(s) and applied over a wheat-cropped site in Patna region of Bihar, India, with pedotransfer functions obtained from soil sample analysis. Stimulation results for a period of 120 days show that out of 24 cm irrigation applied and 10.61 cm rainfall occurred, 47.2% has been lost as evapotranspiration, 28.9% of the water has been stored in the soil column as soil moisture, and 23.9% of the water has recharged to groundwater table. Based on these results, an irrigation schedule is recommended for an optimal utilization of both rainwater and irrigation water for a better management of available water resources.