4C: Irrigation optimization and agriculture’s future in the Colorado River Basin

Agriculture annually consumes about half of the total water share in the upper and lower basins of the Colorado River. This water supports over 360 thousand acres of irrigated cropland. The predominant crops include alfalfa and grass hay, accompanied by a significant portion of pastureland. These crops are well adapted to the high elevation, variable terrain, and frequent droughts that are common in the eastern half of Utah. Sprinkler (wheel-lines and pivots) irrigation is the dominant irrigation method, followed by surface irrigation. Water optimization is possible through water conveyance systems and on-farm improvements.

There are over 1,000 miles of open channel canals in this basin where water losses could be reduced. However, quantifying the opportunity for reduced water consumption is difficult due to high variability and high uncertainty in water losses and return flow in these delivery systems. On-farm improvements through advanced irrigation systems could reduce annual water consumption by up to approximately 10% or 36,000 acre-feet per year if all systems were converted to more-efficient sprinklers or drip irrigation. Changing crop types and ensuring they could be successfully marketed could save up to about one acre-foot per acre of consumption. These improvements would result in long-term investments in water reductions that would not reduce food production.

Deficit irrigation and fallowing provide the largest opportunities to reduce water consumption, with savings of up to two acre-feet per acre. These are short-term but sometimes necessary solutions that reduce crop production. Thus, combinations of optimization in off- and on-farm water use (long-term reductions), and deficit irrigation and fallowing, when necessary, will ensure that agriculture thrives and downstream demands are met.