Plains rivers seldom escape consequences of upstream water diversion and depletion, yet they bear responsibility for supplying downstream users. Jon Altenhofen of Northern Colorado Water Conservancy District described how return-flow hydrology drives water development and management of the South Platte. Altenhofen described differences between surface and subsurface water use, and how irrigators drilled wells to access water that had previously recharged the Ogalalla aquifer and South Platte River. This usage eventually diminished return flows to the river and caused consternation from downstream folks dependent on those flows. Since 1970, augmentation plans have been required to replace water withdrawn by wells to satisfy senior, downstream water rights holders.
Augmentation replaces the water extracted by irrigation wells.
Restoration of natural flow regimes was expanded upon by Colorado State University's LeRoy Poff. If we change the environmental template of which natural flow regimes are part, he said, we can expect direct biological responses from changes in ecological processes. We must approximate natural flows to maintain numerous species rather than optimizing flows for only one or two. A partial restoration of the natural flow regime can benefit ecological integrity and biodiversity. Instrumental in all this was 35-year Brush resident Steve Treadway.