TWO STREAM FLOW SCENARIOS IN THE REPUBLICAN RIVER BASIN: SOCIAL DECISION-MAKING AND STREAM FLOW RESULTS

Water resource managers and their actions have subsumed some hydrological systems to the extent that those systems’ functionality as independent actors could be questioned. Such a situation appears to exist in the rainwater-fed Republican River basin that is managed primarily for agricultural irrigation in Colorado, Nebraska, and Kansas. 100 years of local weather data with a water budget and USGS stream gage data are used to examine stream flow and assess management impacts for two scenarios. The first scenario explores how the river might behave given ‘natural’ conditions in the basin without management, while the second examines its behavior based on stream gauge data with management decisions. Management infrastructure consists of several dams and reservoirs, which are used for irrigation water storage, recreation, and flood control, along with stream augmentation projects from groundwater pumping and pipeline delivery. Shaping management decisions are both climatic conditions and political forces, principally the 1943 Republican River Compact, a federal statute that governs the waters of the basin. Initial analysis suggests that physical and political management of the Republican River has had an impact on stream flow patterns and rhythms, which, if left unmanaged, may have been adequate for meeting Compact requirements and limiting costly inter- and intra-state litigation. However, groundwater irrigation pumping in the basin has hydrological connections to the stream, rendering the USGS data doubly impacted after certain dates, thereby making the scenario comparisons hypothetical. The Republican River’s hydrological system cannot be examined nor fully understood without including and considering its socio-hydrology—the how and why of human activity and management that impacts the river’s current and future viability.