Effective Rainfall, Water Yield, and Groundwater Recharge Under Different Crops Across the Brazos Watershed, TX.

Increase demand for water resources across the Brazos watershed, Texas requires an evaluation of the impact of the impact of some of the major crops grown on this watershed. This study is evaluating the potential effect of four major row crops on the effective rainfall, the portion of gross rainfall that infiltrates into the crop rootzone across the growing season, runoff, and groundwater recharge.  Five locations in five different counties across the Brazos watershed (upper, middle and lower parts) were selected. Historical daily weather data (rainfall and evapotranspiration, ET,), soil physical properties, and crop water parameters were used as input for the Irrigation Management System (IManSys) model (Fares, 2012). Daily water budget components were calculated by the model. From the upper to the lower parts of the watershed rainfall increase by as much as 300% while ET decrease by 30%.  Water yield and groundwater recharge increase with increase in rainfall across the watershed irrespective of the crop. Among the crops growing during similar growing season Sorghum had the highest recharge rates and water yield and consequently the lowest effective rainfall.  Wheat and sorghum crops seem to more conducive to higher water yield and groundwater recharge than Corn.  Further analyses are needed for more conclusive conclusions and recommendations.