Streamflow and stream-quality data were collected for surface water in the coal-mining region of the Patoka River basin. Data were collected primarily in Pike County.

Data were collected 4 times at 29 surface-water sites during different seasons and conditions of Streamflow. Data were collected August 1983, July 1984, December 1984, and February through March 1985. Six sites were on the Patoka River. Although the percentage of drainage from coal-mined lands increases from the upstream to the downstream sites, the major land use for all sites on the Patoka River is agriculture. Ten sites were on 8 tributaries to the Patoka River (excluding the South Fork Patoka River), 3 sites were on the South Fork Patoka River (the largest tributary to the Patoka River), and 10 sites were on 10 tributaries to the South Fork Patoka River. The major land use for these sites is coal mining.

Data obtained at the sites included instantaneous Streamflow, pH, specific conductance, dissolved-oxygen concentration, water temperature and concentrations of alkalinity and hot acidity. Water samples were collected and analyzed to determine the concentrations of dissolved sulfate; dissolved, suspended, and total recoverable iron and manganese; dissolved solids; suspended sediment; and suspended sediment finer than 0.0625-millimeter diameter.

Streamflow in the Patoka River has been regulated since 1978 by Patoka Lake. Flow-duration analyses indicate that flow regulation by Patoka Lake generally has increased low streamflows and decreased high streamflows in the Patoka River.

When compared to sites on the tributaries, sites on the Patoka River generally had smaller values for specific conductance and concentrations of chemical constituents. Sites on the tributaries to the Patoka River (including the South Fork Patoka and its tributaries) had larger values due to the physical and chemical weathering of coal-mined material in their basins. Generally, for sites on the Patoka River, values of specific conductance and concentrations of dissolved sulfate and dissolved, suspended, and total recoverable manganese increased from the upstream to the downstream sites.

For the tributary sites, pH was near neutral at 11 sites (median pH value of 7.3 for all samplings), pH was low at 8 sites (median pH value of 3.7 for all samplings), and pH was variable at 3 sites depending on Streamflow. At sites where pH was near neutral, when compared with sites where pH was low,  specific conductance and concentrations of alkalinity, dissolved sulfate, suspended iron, suspended manganese, dissolved solids, and suspended sediment generally were larger, and concentrations of acidity, dissolved iron, total recoverable iron, dissolved manganese, and total manganese generally were smaller. At those sites where pH varied with streamflow, concentrations of chemical constituents also varied.

For sites on the Patoka River, loads of dissolved sulfate, total recoverable manganese, and dissolved solids generally increased from the upstream to the downstream sites; loads of total recoverable iron were variable. Generally, there was an inverse relation of streamflow to concentrations of chemical constituents the greater the streamflow, the smaller the concentrations. For sites on the tributaries, there was an inverse relation of streamflow to specific conductance and to concentrations of alkalinity, acidity, dissolved sulfate, and dissolved solids and a direct relation of streamflow to concentrations of dissolved, suspended, and total iron.

Data collected from 1965 through 1968 and during May and October 1979 were compared with data collected during the time of the study (1983-85). Few historical data were available, and those that were available were only for selected sites. Data for pH, alkalinity, acidity, and dissolved sulfate indicate minimal or no change in these constituents.