Site-Specific and Regional On-Farm Rice Water Conservation Analyzer (RiceWCA): Development and Evaluation of the Water Balance Model.

Rice farming in the Lower Colorado River basin of Texas, United States, is a major economic engine and a major water consumer. This research focuses on the development of a web-based rice water conservation analyzer (RiceWCA) to evaluate field- and regional-level costs, water savings, and yield benefit associated with implementing on-farm conservation measures in the irrigation districts, which include precision leveling, multiple inlets, conservation tillage, lateral improvement, tailwater recovery, and a production system based on growing high-yielding water efficient cultivars. RiceWCA uses a phenology model to time water management events, including flushing and flush drainage for the main crop, and permanent flood, flood maintenance, and drainage before harvest for the main and ratoon crops. RiceWCA simulates daily water balance for each rice field within the Lower Colorado River basin, as affected by the degree of implementing different conservation measures. The water balance model includes site-specific estimation of soil saturation deficit, evapotranspiration, percolation, seepage, rainfall, irrigation, and tailwater. The water balance model was verified and calibrated using 2000 and 2002 weekly irrigation records for the Lakeside and Gulf Coast irrigation districts, and validated using 2001, 2003, and 2004 weekly irrigation records. Conservation improvement that offers most water saving is tailwater recovery, followed by adoption of high-yielding cultivars, multiple inlet, precision leveling, and conservation tillage. Water saving for lateral improvement varies depending on the extent of existing laterals.