The Eastern Coal Province is divided into 24 separate hydrogic reporting areas. The division is based on hydrologic factors, location, size, and mining activity. Hydrologic units (drainage basins) or parts of units are combined to form each area. Area 23 is located at the southern end of the Eastern Coal Province, in the Mobile River basin, includes the Warrior, Cahaba, and edges of the Plateau coal fields in Alabama, and covers an area of 4,716 square miles. Each report is designed to be useful to mine owners and operators and consulting engineers by presenting information about existing hydrologic conditions and identification of sources of hydrologic information. General hydrologic information is presented in a-brief text and illustrations on a single water-resources related topic. Area 23, this report, is underlain by the Coker and Pottsville Formations and the pre-Pennsylvanian rocks. The Pottsville Formation contains coal beds and is overlain by the Coker Formation in the western and southern parts of the area. The pre-Pennsylvanian rocks crop out in two northeast-southwest trending belts or ridges along and near the eastern boundary where folding and faulting is common. The outcrop of rocks along the western ridge forms the divide between the Warrior and the Cahaba coal fields. The area lies in four river basins, the Black Warrior, Cahaba, Sipsey, and Buttahatchee. The Black Warrior River drains most of the Pottsville Formation with some outliers of the Coker Formation in the southern edge. The Sipsey and Buttahatchee Rivers are incised into the Pottsville Formation but drain, for the most part, the overlying Coker Formation. The Cahaba River flows over the Pottsville Formation in a valley between two ridges of pre-Pennsylvanian rocks. Area 23 has a moist temperate climate with an annual average rainfall of 54 inches and the majority of the area is covered by forest. The soils have a high erosion potential when the vegetative cover is removed. public supplies. The principal uses of water are for cooling water for thermoelectric power generation and for industrial and municipal supplies for the city of Birmingham. The U.S. Geological Survey operates a network of hydrologic data collection stations to monitor the streamflow and groundwater conditions. This network includes data for 180 surface-water stations and 49 groundwater observation wells. These data include rate of flow, water levels, and water-quality parameters. These data are available from computer storage through the National Water Data Exchange (NAWDEX). Hydrologic problems relating to surface mining are (1) erosion and sedimentation, (2) decline in groundwater levels, and (3) degradation of water quality. Average annual sediment yields can increase by four magnitudes in surface mined areas from 20 (tons/mi2)/yr from areas not affected by mining to 300,000 (tons/mi2)/yr from mined areas. Sediment yields increase drastically when vegetation is removed from the highly erosive soils and from unregulated surface mining operations. Decline in groundw...

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Ground water is obtained mostly from limestone and dolomite aquifers along the Sequatchie anticline and Murphrees Valley anticline and from sandstone aquifers in Sand Mountain and Blount Mountain synclinal areas. Wells tapping some limestone and dolomite aquifers produce as much as 1. 4 mgd (million gallons per day). Wells completed in sandstone of the Pottsville Formation underlying lower topographic areas may produce as much as 0. 3 mgd, but those completed in sandstone underlying higher topographic areas produce lesser quantities. Surface-water resources were appraised by use of average flow and 7-day Q2 (median annual 7-day minimum flow).' An average flow of about 640 mgd or about 1 mgd per square mile originates in the county. Streamflow during low flow conditions is small; only three streams have 7-day C^'s that exceed 2 mgd. Estimates of storage requirements are provided for sustained draft rates of 25 to 50 percent of the average flow ' 265578 Water from aquifers and streams in Blount County is generally of suitable chemical quality for most uses. Water from the Pottsville Formation generally contains iron in excess of 0. 3 mg/1 (milligram per liter) and water from limestone and dolomite aquifers and from some streams during low flows is moderately hard to hard and may need treatment for certain uses. Water use in the county was about 3. 2 mgd in 1968 and 46 mgd was diverted for use outside the county.

The 25 percent streamflow duration and corresponding depth were selected to represent ordinary high water. Statistical relations of 25 percent flow duration depth to eight basin parameters were analyzed using a stepwise linear regression procedure. A procedure for estimating "ordinary high water" depth was derived using one independent variable drainage area size. Two equations were derived; the standard error of estimate of the equation for hydrologic area 1, the Appalachian Plateaus, is 26 percent and for area 2, the Coastal Plains province, is 39 percent. The equations apply where the stream channels or streamflow is not significantly altered by man's activities.