2B: Balancing Agricultural Water Efficiency With Healthy Groundwater and Streamflows

In Utah’s agricultural systems, some of the water delivered through earthen canals or applied via flood irrigation seeps into the ground. In recent decades farmers have been encouraged to replace these traditional techniques with lined canals and center-pivot sprinklers to conserve water—but this practice can have unintended consequences for both water users and aquatic life. Water that seeps into the ground through less-efficient irrigation systems increases the amount of water stored in underground aquifers and flows back to the river via underground pathways. These “return flows” contribute water to the river system during seasons when river flow is low (Figure 2.B.1). Return flows increase the water available for human use and provide a source for cool water needed by coldwater trout.

In Henry’s Fork of the Snake River, located in Idaho, traditional water conveyance and flood irrigation techniques have contributed large quantities of return flow to the river for over a century. Most farmers transitioned from flood to sprinkler irrigation between 1978–2000. The large-scale change in irrigation practices decreased annual streamflow diversions by 250,000 acre-ft (23%), but also decreased annual groundwater return flow by 240,000 acre-feet. In other words, more efficient irrigation techniques contributed to more water being depleted—or consumed—in the basin, rather than conserving water for other uses.

Farmers in the Teton River Basin have begun using flood irrigation early in the growing season when spring runoff is more abundant and are preserving sprinkler irrigation for use later in the year when surface water is less available. This dual irrigation practice will help agricultural growers recharge groundwater and aquifers and conserve water.