Projects by Discipline / Water Resources Planning and Management

Kansas v. Colorado
Interstate Compact Litigation

In 1985, Kansas filed suit in the U.S. Supreme Court against Colorado over Arkansas River water deliveries across the state line. Kansas alleged that reservoir operations and groundwater development in Colorado had violated the terms of a 1948 compact between the states defining how the flows of the river were to be shared. The trial, which began in 1990, was divided into three phases: liability, damages and future compliance. In 2001, Hydrosphere was retained by the Colorado Division of Water Resources to assist in defending Colorado's interests in the third phase.

In response to decisions made in the first phase of the trial, Colorado had, in 1996, implemented Use Rules that required groundwater users with post-Compact wells to provide replacement water to the Arkansas River to offset the depletive effects of their pumping on useable state line flows. In the third phase of the trial, Kansas alleged that Colorado's Use Rules were not sufficient to prevent future Compact violations. In making these allegations, Kansas relied heavily on results from a computer model of the Colorado portion of the river basin. Both states had used this model in earlier phases of the trial, but Kansas introduced a modified version of it in making its third phase allegations.

Hydrosphere obtained and reviewed the model and data used by Kansas in support of its future compliance allegations. This review included detailed examination and testing of model code, statistical analysis of model input and output data, and advice to other Colorado experts regarding improved calibration of the model. Hydrosphere's evaluation revealed significant shortcomings in Kansas' calibration of the model and inappropriate use of statistics in characterizing model results.

Hydrosphere provided this evidence to the Court in the form of deposition and expert testimony at trial. In October of 2003, the Special Master recommended that the modified Kansas model was not sufficiently accurate to be used to determine Compact violations on anything less than a decadal basis and that Colorado's Use Rules were sufficient to insure future Compact compliance.