RIVERSIDE IRRIGATION DISTRICT VANCIL RECHARGE PROJECT The South Platte River in Northeastern Colorado is characterized by high flows during the spring snowmelt runoff and relatively lower flows during the irrigation season. This has created a need for additional storage to regulate these high surplus flows for later release to supplement direct flow diversion demands during the irrigation season. Riverside Irrigation District and W. W. Wheeler and Associates, Inc. developed the Vancil Recharge Project to utilize storage in the alluvial aquifer of the South Platte River to regulate these seasonal fluctuations of flow.

The fundamental concept of the Vancil Project is to divert high rates of flow (up to 1,000 cfs) from the South Platte River during periods of surplus flow, using the existing diversion facilities of the Riverside Irrigation District. The water is delivered to the new downstream, off-channel Vancil Reservoir, where it can be released during the late summer months to provide supplemental irrigation supplies at the lower end of the Riverside system. Significant seepage losses occur from the Riverside Canal during these diversions, recharging the alluvial aquifer of the South Platte River. The accretions to the river attributable to these seepage losses (recharge) are delayed in time, with significant portions accruing to the river during the late summer months of the irrigation season.

Working with the Riverside Irrigation District, Wheeler developed the concepts of the Vancil recharge plan, outlined procedures to estimate the amount of seepage loss (recharge) from the various reaches of the Riverside Canal and Vancil Reservoir, and modeled the timing of the recharge accretions back to the South Platte River using line source recharge formulas developed by Glover. Wheeler also assisted the District with the adjudication of the water rights for the recharge project in the Division 1 Water Court.

Wheeler is currently assisting the Riverside Irrigation District in the development of a comprehensive augmentation plan in which the recharge "credits" from the Vancil Reservoir and Recharge Project are used to offset or replace the stream depletions caused by the pumping of approximately 125 irrigation wells under the Riverside System, as well as providing supplemental water supplies for other existing uses in the basin.