Abstract
Water shortages in arid regions present challenges in administering water and requires robust water accounting. In southeast Idaho, the Eastern Snake Plain Aquifer (ESPA) supports an important agricultural sector. Due to connectivity between surface and groundwater in the ESPA, quantifying aquifer recharge is also important. Historically, leaching from excess surface irrigation supported incidental recharge to the ESPA, but more efficient irrigation techniques reduced incidental recharge. This paper outlines a deep infiltration (DI) model developed to evaluate infiltration losses from different irrigation practices and soil types. Twelve scenarios were created to simulate an alfalfa growing season under varying climatic and soil conditions. Under some scenarios, modeled infiltration losses increased by 10%–20% coincident with increased application efficiency. The concept of consumptive use efficiency (CUE) is introduced to quantify the proportion of irrigation beneficially used by crops. The model results show that CUE decreased with increasing application efficiency and suggest CUE could be improved 8%–10% for well-drained loamy soils; clay loam soils showed little opportunity for improvement. The results indicate that more efficient irrigation application techniques may increase DI loss if irrigation schedules do not explicitly include soil water storage for the entire rooting zone. These results indicate that in conditions where losses from DI can be reduced, improving water use efficiency depends on precision irrigation scheduling linked to infiltration rates. This model provides a practical method by which infiltration losses from irrigated lands can be estimated. Considering site-specific infiltration would facilitate and prioritize investments meant to improve water use efficiency.