Intentional Groundwater Recharge Through Canal Seepage in the Upper Platte River Basin of Nebraska

In the Upper Platte River Basin of Nebraska, due to the over-appropriation of hydrologically connected surface water and groundwater, state statutes require the Department of Natural Resources (NDNR) and the local Natural Resources Districts (NRDs) to offset streamflow depletions caused by surface water or groundwater uses initiated after 1997, and prevent depletions that would cause noncompliance with the Platte River Recovery Implementation Program interstate cooperative agreement. While some of these stream depletions can be made up through the retirement of surface water and groundwater irrigation, other offset schemes allow beneficial uses like irrigation to be maintained. Some such offset schemes involve the utilization of excess surface water flows, flows above what is already appropriated for surface water irrigation and other uses, through conjunctive water management. Conjunctive water management strategies take advantage of the connection between surface water and groundwater to increase the availability and reliability of the water supply as a whole within a region.

Conventional diversion of streamflow into unlined canals during the irrigation season typically results in seepage of water through the canal bottom during transit from the stream to the field. This water percolates into the unsaturated zone, making its way to the local aquifer. Excess streamflows during the non-irrigation season provide opportunities to divert flow into existing canals to recharge groundwater, increasing long-term water supply and availability within the basin. In 2011, flooding in the Upper Platte created an initial opportunity to test the viability of such a conjunctive water management project. Since then, the coordinated efforts of NDNR, NRDs, and irrigation districts have resulted in several diversions of excess flows into irrigation canals, recharge pits, and surface water reservoirs. Initial analytical evaluations show positive impacts to streamflows continuing well into the future. These recharge events can also be analyzed using numerical groundwater models.