STREAMFLOW AND WATER-QUALITY DATA FOR LAKE PURDY AND ITS TRIBUTARIES, JEFFERSON AND SHELBY COUNTIES, ALABAMA, WATER YEARS 1987-91 By V.E. Stricklin U.S. GEOLOGICAL SURVEY Open-File Report 93-498 Prepared in cooperation with the WATER WORKS AND SEWER BOARD OF THE CITY OF BIRMINGHAM Tuscaloosa, Alabama 1994 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY ROBERT M. HIRSCH, Acting Director For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Earth Science Information Center 520 19th Avenue Open-File Reports Section Tuscaloosa, Alabama 35401 Box 25286, MS 517, Federal Center Denver, Colorado 80225 CONTENTS Page Abstract.................................................................................................................................. 1 Introduction............................................................................................................................ 2 Purpose and scope......................................................................................................... 2 Data-collection methods............................................................................................... 2 Description of the study area................................................................................................. 5 Streamflow............................................................................................................................. 5 Water quality.......................................................................................................................... 7 References.............................................................................................................................. 20 ILLUSTRATIONS Figure l.Map showing location of study area........................................................................ 3 2. Map showing location of data-collection sites....................................................... 4 3. Diagram showing generalized surface geology of the study area.......................... 6 4-13.Box plots showing: 4. Specific conductance at selected sites in Lake Purdy drainage basin................. 8 5. pH at selected sites in Lake Purdy drainage area................................................ 9 6. Alkalinity at selected sites in Lake Purdy drainage area..................................... 10 7. Dissolved oxygen at selected sites in Lake Purdy drainage area........................ 11 8. Water temperature measured at selected sites in Lake Purdy drainage area....... 12 9. Total recoverable iron measured at selected sites in Lake Purdy drainage area.. 13 10. Calcium at selected sites in Lake Purdy drainage basin...................................... 14 11. Sodium at selected sites in Lake Purdy drainage basin....................................... 15 12. Chloride at selected sites in Lake Purdy drainage basin ..................................... 16 13. Sulfate at selected sites in Lake Purdy drainage basin........................................ 17 14. Piper diagram of variation in water chemistry between all Lake Purdy and selected tributaries sites for the period of record............................................... 19 TABLES (Located in back of report) Table 1. Summary of surface-water data collection network 2. Annual mean discharges in decreasing order for water years 1987-91 3. Summary of water-quality analyses at sampling sites in Lake Purdy basin, water years 1987-91 iii CONVERSION FACTORS Multiply By To obtain inch 25.4 millimeter foot 0.3048 meter mile 1.609 kilometer square mile 2.590 square kilometer acre 0.4047 hectare cubic foot per second 0.02832 cubic meter per second ton per day 0.90718 metric ton per day gallon 3.785 cubic meter Temperature is degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows: °F=1.8(°C) + 32. IV STREAMFLOW AND WATER-QUALITY DATA FOR LAKE PURDY AND ITS TRIBUTARIES JEFFERSON AND SHELBY COUNTIES, WATER YEARS 1987-91 By V.E. Stricklin ABSTRACT Lake Purdy was created in 1911 by the impoundment of the Little Cahaba River and is used primarily as a supplemental water supply for the city of Birmingham and surrounding communities. Changes in land use, such as residential development and disposal of industrial waste within the basin, have caused concern about possible changes in water quality of the lake and its tributaries. Ten sites in the Lake Purdy Basin chosen for this study included six inflow sites, three lake sites, and one site at the outflow of the lake. Data collected during the study indicate that the Little Cahaba River provides approximately 80 percent of the total annual mean inflow to the lake. The Little Cahaba River drains 24.4 square miles, which represents 57 percent of the drainage area at the lake outlet. During the 1988 water year, a severely dry year, the Little Cahaba River provided approximately 88 percent of the total mean inflow into Lake Purdy. During the 1988 water year, daily mean inflow to Lake Purdy was 21.9 cubic feet per second and the mean outflow from the lake was 31.1 cubic feet per second. All constituents analyzed throughout the study area were within drinking-water limits except for total recoverable iron, total recoverable and dissolved manganese, and pH. The maximum concentration of total recoverable iron occurred at Lee Branch (site 6) and the maximum concentration for total recoverable manganese occurred at Little Cahaba River below Lake Purdy (site 10). The maximum concentration of total recoverable iron and total recoverable manganese occurred at Lee Branch (site 6). The maximum pH was at Lake Purdy at Irondale Bridge (site 4) and Lake Purdy near Cahaba Heights (site 9) and the minimum pH was at Cox Creek (site 5). Lake Purdy demonstrated minor spatial variation in water quality from the northern most lake site at Irondale Bridge (site 4), to the southern sites at U.S. Highway 119 (site 7), and at Lake Purdy Dam (site 9). The northern part of the lake is heavily influenced by the major contributor, Little Cahaba River, which has a consistently higher dissolved ion concentration than any other tributary to the lake. The southern part of the lake is buffered by Cox Creek, Lee Branch, and the unnamed tributary to Ike Pond Slough, which all have consistently lower dissolved ion concentrations than that of the lake. INTRODUCTION Lake Purdy, located in Jefferson and Shelby Counties in north-central Alabama, was created in 1911 by the impoundment of the Little Cahaba River (fig. 1). The principle function of Lake Purdy is to supplement the Birmingham water supply at the Cahaba River pump station on the Cahaba River about 2.8 miles southwest of the dam (fig. 2). The original dam was constructed at a height of 40 feet and created a lake with a storage capacity of 1.5 billion gallons. In 1929, an additional 20 feet was added to the height of the dam, increasing the lake's storage capacity to 5.7 billion gallons and surface area to 1,050 acres. Changes in land use and streamflow, due to development within the basin, cause concern for the quantity and quality of the water in the basin and reservoir. The city of Leeds has discharged sewage effluent into the Little Cahaba River upstream from Lake Purdy since 1936. Industrial effluents are also discharged in the river in the vicinity of Leeds. Suburban expansion in the Little Cahaba River Basin has accelerated during the data collection period, resulting in an increase in disposal of domestic sewage through septic tanks. Purpose and Scope In 1986, a monitoring program was established by the U.S. Geological Survey, in cooperation with the Birmingham Water Works, to collect water quantity and quality data of Lake Purdy inflow and outflow. This report summarizes streamflow and water-quality data for Lake Purdy and its tributaries for water years 1987-91. The hydrologic data provide a basis to assess effects of current and future land-use changes within the basin. Streamflow and water-quality data were collected at 10 sites in the Little Cahaba River Basin (fig. 2; table 1). Data-Collection Methods x All water samples were collected using depth-integrated sampling techniques as discussed by Guy and Norman (1970). Samples requiring filtration were filtered through a 0.45-micron filter. Preservation, as required, was performed onsite. Nutrient samples were preserved with mercuric chloride and chilled to 4 °C. Samples for major cations were preserved with nitric acid and samples for trace metals were preserved with nitric acid and potassium dichromate. Field determinations of discharge (except for sites 4,7, and 9) (fig. 2), specific conductance, pH, dissolved oxygen, water temperature, alkalinity, fecal coliform, and fecal streptococcal bacteria were made at the time of sampling. Chemical analyses were performed by the U.S. Geological Survey. Continuous streamflow data were collected at Little Cahaba River near Jefferson Park (site 1), Cox Creek near Cahaba Heights (site 5), and Little Cahaba River below Lake Purdy Dam near Cahaba Heights (site 10). Streamflow data were collected in conformance with methods described by Rantz and others (1982a, 1982b). 86°40 f 35 86°: DPUNATCN Bcsh Boundary - Dam 33035' ' / ' IST.CURU £ __ _*COUNTY / 30 33°25 Base from U.S. Geological Survey digital data. 1:100.000,1983 Albers Equal-Area Conic projection Standard parallels 29.5*and 455°, central meridian -96° Figure 1. Location of study area. 86 40 00 86 35 00 33 30 00 33 27 30 EXPLANATION