STREAMFLOW ALTERATION IN KANSAS: ASSESSMENT, CAUSES AND HABITAT IMPLICATIONS

An understanding of streamflow alteration, in response to various disturbances, is requisite for the effective management of stream habitat for various fish species. Using a random forest modeling approach, streamflow alteration was assessed for 129 selected U.S. Geological Survey streamgages in Kansas. The assessment involved a comparison of the observed (O) condition (1980 to 2015) with the predicted expected (E) reference condition for 29 streamflow metrics. The metrics, computed from mean daily flow data, represent key aspects of the flow regime including average flow (annual, monthly), low and high flow (frequency, duration, magnitude), flow variability, and baseflow.

In Kansas, streamflow alteration was indicated locally, regionally, and statewide. Locally, a flashier flow regime was indicated for three streamgages with urbanized basins. Together, localized reservoir effects and regional groundwater pumping (mostly for irrigated agriculture) likely were responsible, in part, for decreased flow conditions in western and central Kansas. Statewide, the use of agricultural land-management practices to reduce runoff may have been partly responsible for a decreased magnitude and duration of high flows. In central and eastern Kansas, agricultural land-management practices may have been partly responsible for an increased magnitude of low flows at several sites.

The Arkansas darter (Etheostoma cragini) is listed as a threatened fish species by the State of Kansas. Survival of the darter is threatened by habitat loss caused by altered streamflow conditions, in particular flow depletion. Future management of darter populations and habitats requires an understanding of streamflow conditions and how those conditions have responded to natural and anthropogenic factors. In Kansas, streamflow alteration was examined at nine U.S. Geological Survey streamgages located in six priority basins within the historical range of the darter. The O/E results indicated a likely or possible decreased flow condition in two basins the primary cause of which is groundwater-level declines resulting from groundwater pumping. In these two basins, important habitat characteristics adversely affected by flow depletion may include stream connectivity, pools, and water temperature.