Early cascade rice irrigation shutoff (ECIS) conserves water: implications for cascade flood automation

Cascade rice flood distribution (CASC), the predominate method used for rice irrigation in the lower Mississippi River basin (LMRB), is inherently water intensive owing to the need to overfill rice paddies to move irrigation water from one paddy to the next. The objectives of this research were to devise practices that make CASC more water efficient, assessing how early cascade rice irrigation shutoff (ECIS) impacts applied irrigation, run-off, and flood depth under LMRB rainfall conditions. This research used a conservation-of-mass model to show that using flood depth in the penultimate rice paddy to trigger irrigation shutoff in a 16-ha simulated rice field results in nominal irrigation water savings of 23% relative to CASC. This savings was reduced to 15% when supplemental irrigation was added to the last paddy at two critical stages of rice production. Field run-off estimates for ECIS were reduced by up to 78% relative to a CASC for both clay and silt loam soils, demonstrating how with ECIS the last paddy of a rice field acts as a 'catch basin' for excess up-field irrigation and uncaptured rainfall. Flood depth estimates for the last paddy resulting from ECIS resembled those of alternate wetting and drying flood management (AWD), suggesting that the agronomics developed for AWD could be used to help address production issues arising in the catch basin from ECIS. Success in coupling ECIS with irrigation automation technologies could reduce aquifer withdrawals across the rice producing areas of the LMRB.

Automated summary

This research aims to make the Cascade rice flood distribution (CASC) method more water efficient by devising practices that reduce irrigation water use. By using flood depth to trigger irrigation shutoff, the early cascade rice irrigation shutoff (ECIS) can significantly save irrigation water, reduce field run-off, and manage flood depth. The results suggest the potential application of ECIS coupled with irrigation automation technologies to reduce aquifer withdrawals in the lower Mississippi River basin (LMRB) rice producing areas.