M.S. Flannery et al. Management approach for unimpounded rivers A PERCENT-OF-FLOW APPROACH FOR MANAGING REDUCTIONS OF FRESHWATER INFLOWS FROM UNIMPOUNDED RIVERS TO SOUTHWEST FLORIDA ESTUARIES Michael S. Flannery1 Southwest Florida Water Management District 2379 Broad St. Brooksville, Florida 34604 Tel: 352-796-7211 Fax: 352-797-5806 email:
[email protected] Ernst B. Peebles, Ph.D. University of South Florida, College of Marine Science 140 Seventh Ave. S. St. Petersburg, Florida 33701 Tel: 727-553-3983 Fax: 727-553-1189 email:
[email protected] Ralph T. Montgomery, Ph.D. PBS&J, Inc. 5300 West Cypress St., Suite 300 Tampa, Florida 33606 Tel: 813-282- 7275 Fax: 813-287-1745 email:
[email protected] 1 Corresponding author Flannery, Peebles, and Montgomery; Page 1 ABSTRACT: Based on a series of studies of the freshwater inflow relationships of estuaries in the region, the Southwest Florida Water Management District has implemented a management approach for unimpounded rivers that limits withdrawals to a percentage of streamflow at the time of withdrawal. The natural flow regime of the contributing river is considered to be the baseline for assessing the effects of withdrawals. Development of the percent-of-flow approach has emphasized the interaction of freshwater inflow with the overlap of stationary and dynamic habitat components in tidal river zones of larger estuarine systems. Since the responses of key estuarine characteristics (e.g., isohaline locations, residence times) to freshwater inflow are frequently nonlinear, the approach is designed to prevent impacts to estuarine resources during sensitive low-inflow periods and to allow water supplies to become gradually more available as inflows increase.