Kelly DiNatale, Arista Hickman and Srijita Jana

Abstract: RiverWare is being used to develop a comprehensive operations and planning model for the East Cherry Creek Valley Water and Sanitation District (ECCV), United Water and Sanitation District (United) and the Arapahoe County Water and Wastewater Authority (ACWWA). These three entities will be managing a new water supply project that covers over 100 miles of the South Platte River in Colorado for an initial delivery of over 10,000 acre-feet of water. This water supply project includes senior agricultural surface water rights to be transferred to municipal use from over 20 irrigation companies and junior direct flow, storage and recharge rights. The model incorporates the operations of four surface reservoirs with multiple physical inflows, outflows, and water user accounts. The objective of the model is to offset alluvial well pumping depletions and delayed historical return flow obligations from changed water rights with lagged accretions from groundwater recharge and direct flow and storage releases and exchanges. Well pumping depletions and groundwater recharge accretions are calculated from unit response functions (URFs) based on Modflow groundwater model results. Exchanges in designated accounting reaches of the South Platte River and the outcomes of several water court decrees for water rights in the area, including water rights accounting, are simulated in the intricate operating policy.