Pre-restoration assessment, Big Sunflower River, Mississippi: Where to Begin?

The Big Sunflower River in northwestern Mississippi drains about 8,000 km 2 , is a low-gradient slowly-moving stream, and has historically provided a valuable ecological, navigational and recreational resource. However, present conditions are characterized by depauperate physical habitat, depressed baseflows linked to falling groundwater levels, elevated turbidity, and chronically low dissolved oxygen levels. Eight 200-m long reaches were sampled biannually (spring and fall) for three years. Two reaches were located downstream from major weirs; three reaches were located in a channelized reach with a trapezoidal cross-section; and three reaches were in a reach with natural morphology. Fish were collected with boat-mounted electroshockers, and bed material types, water depths, and current velocities were sampled using an acoustic Doppler current profiler. Limited water quality data were collected for comparison with data provided by others. Fish populations appear to be primarily limited by degraded water quality. Low-head weirs support relatively dense and diverse fish assemblages and thus provide local habitat enhancement, but may create stagnant zones upstream due to backwater effects that exacerbate low dissolved oxygen problems.