Grand Valley Irrigation Return Flow Case Study

Irrigation water supply is furnished annually to about 71,500 acres (28,932 ha) of land in the Grand Valley of western Colorado. Return flows from that irrigation contribute about 780,000 tons (708 x 10⁶ kg) of salt to the Colorado River each year, causing an increase of 77 mg/L in the salinity concentration at Imperial Dam. This case study for the ASCE Task Committee on Water Quality Programs Affecting Agricultural Return Flows in Arid Areas is centered around three areas: (1)Physical and water quality data for irrigation and return flows in the valley; (2)identification of regulations that affect this irrigation and its return flows; and (3)the proposed program for controlling salinity contributions from the valley to the Colorado River. With water quality standards that have been established for the Colorado River and the continued development of water resources in the basin, a salinity control program for Grand Valley is needed.