Sensor-Based Cutoff Strategy for Border Check–Irrigated Fields

Abstract

Inflow cutoff, or turning off water inflow to an irrigated field based on water advance location downfield, is commonly used by irrigators as a means of reducing tail discharge (runoff) during surface irrigation of forage and range crops. To apply a scientifically sound cutoff strategy using a calculated inflow cutoff time or cutoff advance location, multiple field parameters (e.g., water inflow rate, rate of water advancement) need to be measured using multiple (potentially expensive) sensors and instrumentation. In this study, a sensor-based irrigation inflow cutoff strategy for surface irrigation was developed that deploys simple wireless contact-type sensors to measure wetting-front arrival time and surface water depth along a border check during the advance phase. These data were coupled with a multi-irrigation volume balance model (i.e., separate model parts for initial and subsequent irrigations of growing season) to determine appropriate cutoff times and/or locations, based on user-defined runoff and approximations of inflow rates and infiltrated depths. The model was verified using the field data collected during irrigation of a border-irrigated alfalfa field near Davis, California. The inflow rate corresponding to the initial (i.e., first of a growing season) irrigation event was within a 95% confidence interval of the measured inflow rates for all subsequent irrigations, in which identical irrigation setups were maintained. Moreover, a correlation between model approximated and reference infiltration depths was found with a coefficient of determination value (