Toward Optimal Water Management in Colorado's Lower Arkansas River Valley: Monitoring and Modeling to Enhance Agriculture and Environment: CSU

The agricultural, lower portion of the Arkansas River basin has three adverse conditions due to its irrigation infrastructure built over the past 100 years that required solutions. According to the findings of this report, water policy makers need to find strategies which "(1) maximize the net economic benefits to agricultural production via reduction in salinity and waterlogging; (2) minimize salt and Se[selenium] concentrations in the river at key locations, including the Colorado-Kansas state line; and (3) maximize 'liberated' water via reduction in nonbeneficial consumptive use from high water tables under fallow alluvial land and from invasive phreatophyte vegetation (Tamarisks) along the river corridor" (p. xi). The authors compared the lower Arkansas Basin to "an interlocking web of scale-dependent components, in which local changes ripple upstream and downstream via irrigation-stream-aquifer interactions and water right issues" (p. 3).

Colorado State University has collected data since 1999 at two sites, one upstream and the other downstream of the John Martin Reservoir in the following areas to amass empirical data to address the problems of the lower Arkansas River basin: "river flow and salinity, reservoir storage and releases, irrigation diversions and efficiencies, canal flow and salinity, drain and tributary flow and salinity, canal seepage, physical properties of soils, aquifer characteristics, water table depth and salinity, irrigation methods, soil salinity, crops and crop yield, climate and crop water use, return flows and salt loads to the river and tributaries, and Se and iron (Fe) concentrations in ground water and surface waters" (p. xi).

To ameliorate the problems of the basin, the study recommended the following categories of intervention: "reduction of recharge from field irrigation, seepage reduction from canals, improved drainage options, lowering the water surface elevation along the river, and phreatophyte removal along the river corridor" (p. xii). Support for the rehabilitation of aging infrastructure, new drainage systems, and the adoption of salt-tolerant crops would be required from citizens. From these high level solutions, the University identified 38 specific actions.

From the data gathered, the models developed, and findings published, the Institute aimed to create tools that would assist water managers, farmers, and other stakeholders make wise decisions, "based on calibrated model predictions, refined also by field assessments and demonstrations of their feasibility and potential" (p. xiv). This would lay the foundation for a pilot project for further evaluation of the solutions. The research group would assess the need for incentives, engage in a cost/benefit analysis, consider the organizational issues to implementation, detail financial constraints, and document current legal issues inherent in Colorado water rights, river administration, and Colorado and Kansas compact agreements.


To have a comprehensive view of the basin, policy makers must attend to a variety of sometimes conflicting factors: the integrity of the basin, the ecology of the regions within the basin, storage requirements resulting from decreases in diversions, the effects of water banking on salinity and waterlogging, changes in irrigation and return flows, junior water rights, and compact and legal agreements with the State of Kansas, the new projects--the Southern Delivery Project and the Preferred Storage Options Project--the increase water volume from phreatophyte removal, and the long-term sustainability of the basin.


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Toward Optimal Water Management in Colorado’s Lower Arkansas River Valley:
Monitoring and Modeling to Enhance Agriculture and Environment.
Timothy K. Gates, Luis A. Garcia, and John W. Labadie. Colorado Water Resources Research Institute Completion Report No. 205. Colorado State University