Development of technologies for water budgeting and analyzing effects of water management practices on downstream water supplies and water quality in the South Platte and Arkansas Basins
To best serve the long term interests of Eastern Colofado River basins, should water use efficiency be defined in terms of multiple re-use of water, or in terms of maximizing "first use" opportunities?
Need and Benefit
The South Platte and Arkansas Basins in Eastern Colorado are highly complex systems from a water management perspective. Since the latter 1800's the modest floww in these streams have been over appropriated as water sources, leading to construction of numerous storage reservoirs, miltiple transbasin diversion projects and development of groundwater wells as supplemental supply sources. Today these basins include rapidly growing population centers along the Colorado Front Range whose explosively expanding water demands are largely being met by pulling supplies away from agricultural use.
Remaining irrigated agriculture has become increasingly dependent on groundwater usage, which since the late 1960's has been subject to regulation in accordance with Colorado's Prior Appropriations Doctrine that governs surface diversions. Additionial restrictions have been placed on wells in the Arkansas Basin as a result of a US Supreme Court ruling in a dispute between Colorado and Kansas. To continue pumping, well owners are required to augment streamflow to offset \out-of-priority stream depletions. In efforts to meet these requirements, the practice of artificial groundwater recharge has become popular, particularly in the South Platte Basin.
Much of the land in these basins overlays thick layers of coarse sands and gravels with high hydraulic conductivity. As a result, deep percolation from irrigation, canal and reservoir seepage, and artificial recharge waters complement groundwater from natural sources and re-emerge as surface flow fairly rapidly. This in turn leads to an apparent "natural efficiency". In the South Platte basin it is estimated that water is re-used five or more times between Greeley and the Colorado-Nebraska border.