Seasonal fish use of Missouri River reservoir deltas

William J. Schreck

Graduate Research Proposal

Master’s of Science

ABSTRACT

Modified rivers are common components of modern landscapes.  Dams and associated reservoirs generate valuable services to society (e.g., hydroelectricity and recreation), but also can disrupt hydrology and alter ecosystem function.  Upon impoundment sediment transport is hindered, sediments settle and deposition commences.  As reservoirs age these sediments aggrade creating novel “delta” habitats with characteristics (e.g., braided, dynamic channels, and backwater habitat) similar to pre-regulated rivers.  This aging process is evident in the lower reservoirs of the Missouri River where expansive deltas have become established in Lake Francis Case and Lewis and Clark Lake.  I propose to examine the ecological significance of deltas in aging reservoir ecosystems to fishes.  Specifically, I propose to quantify spatial growth of the White River delta and siltation of embayments in Lake Francis Case, quantify the limnological contributions of both deltas and associated tributary rivers, and assess the seasonal use of the White and Niobrara deltas by fishes.  During 2008 and 2009 water samples will be collected and analyzed for Nitrogen, Phosphorus, Total Suspended Solids, and fishes will be sampled with a suite of gears during multiple seasons.  Currently there are proposals to remove the Niobrara River delta—as operational capacity of the reservoir will diminish over time—but little information exists regarding the biological contribution of such areas to reservoirs.  This study enables managers to better predict consequences of management actions, and will contribute to the foundation of aging reservoir ecology.