Arkansas River Compact
Client: State of Kansas
Water Resources Engineering - Interstate Compact Evaluation
SWE has assisted the State of Kansas since 1984 with matters related to administration of the Arkansas River Compact and the completion of the case, Kansas v. Colorado. SWE provided consulting services related to the evaluation of water use in both the States of Colorado and Kansas and compliance with the compact. The case continued for approximately 25 years to completion of a decree of the United States Supreme Court. SWE continues to assist the State of Kansas with implementation of the decree provisions and ongoing issues with administration of the Compact.
The technical work involved detailed evaluation of irrigation water use in the Arkansas River Basin in Colorado. Ground water pumping in Colorado was determined to result in violations of the compact, resulting in the development and implementation of administrative rules in Colorado to control pumping. SWE was responsible for data collection, analyses of irrigation water use in Colorado and assisted in the development of a surface water model of the basin. The investigations culminated in presenting evidence to the Special Master assigned by the U.S. Supreme Court to take evidence in the case.
Engineering support included evaluation of water rights use in the Arkansas Basin, hydrology, canal and reservoir operations, irrigation and stream aquifer interaction. Specific assignments included: mapping irrigated area; consumptive use analysis for irrigated crops; development of water budgets for irrigation with surface and ground water; analysis of water rights administration on the Arkansas River; development and calibration of a basin simulation model to be used to determine effects of irrigation use at the Stateline; and quantification of historical well pumping by analysis of power records. The consumptive use analysis was performed for twenty-four ditches that irrigate a combined total of 315,000 acres of land and divert a combined average annual amount of approximately 810,000 acre-feet of water. The total average annual consumptive use of the twenty-four ditches was estimated to be approximately 766,000 acre-feet.
After the liability phase of the case, an administrative remedy to control pumping and provide offsets for pumping effects was developed, analyzed and presented to the Special Master. The basin model has been incorporated into the remedy, requiring annual updates. The model is used to assess compact compliance. SWE provides ongoing consulting to the State of Kansas related to the compliance modeling and other matters related to administration of the Compact.