Surface-water hydrology and salinity of the Anclote River estuary, Florida

Direct measurements of streamflow, tides, and salinity in the Anclote River Estuary, Florida were made during the period January 1984 through May 1986; historical streamflow was compared to that measured during the study; the influence of well-field pumpage on streamflow was evaluated; and regression relations between salinity, tide, and average daily streamflow were developed. Mean monthly streamflows during the study period generally were lower than the corresponding long-term monthly averages yet representative of flows that typically enter the estuary. The influence of pumpage from individual well fields in or near the basin on streamflow was not statistically significant; the influence of total well-field pumpage, however, was significant at the 5% level. The upstream daily location of 0.44-, 5.0-, 10-, and 18-parts-per-thousand (ppt) salinity was quantified using multiple regression techniques. Streamflow used in the analysis ranged from 2.3 to 263 cu ft/sec, and high tides ranged from 0.25 ft below to 2.76 ft above sea level. Vertical salinity profiles indicated partially to well-mixed conditions throughout the estuary during the study period. Results of the regression analyses show that streamflow has a large effect on the location of the saltwater- freshwater interface (defined as 0.44 ppt salinity) as well as water having a salinity of 5.0 ppt. The location of water having salinities greater than 5.0 ppt is affected increasingly by tide, with a corresponding decrease in effect by streamflow. (USGS)