No abstract

No abstract

Bar graph showing the biotic index values based on the results of the benthic invertebrate community survey in the Big Black Creek Basin, July

Point and non-point sources of pollution were evaluated during 1994 and 1996 for their affects on streams in Baldwin County. A synoptic water-quality survey of 32 stream sites was conducted first followed by periodic sampling at 8 of these sites. The synoptic survey indicated no significant point sources of pollution at the time of sampling. Analysis of the synoptic and periodic (fixed-stations) sampling site data shows marked difference in some constituents between northern and southern parts of the county. There is significantly more urban growth and agricultural activity in the southern part of the county than in the northern part. The streams that were sampled in Baldwin County were poorly buffered and slightly acidic. Measurements of pH at the fixed-station sites ranged from a high of 6.9 at Blackwater River to a low of 4.4 at Majors Creek. The generally low pH values are the result of the poor buffering capacity of the soils and water in Baldwin County and also due to the presence of natural organic acids such as tannin. One sample from the Blackwater River contained a dissolved-oxygen concentration of 5.0 milligrams per liter. This was the only measurement for dissolved oxygen of all of the fixed-station sites that was below the minimum concentration set by the Alabama Department of Environmental Management for publicwater supply, swimming, and fish and wildlife uses of water. All dissolved-solids concentrations were well below the recommended maximum concentration of 500 milligrams per liter for drinking water. The maximum measurement for dissolved solids was 58 milligrams per liter at Magnolia River. Ammonia and organic nitrogen yields seem to be consistent across the county indicating that the ammonia and organic nitrogen that is being released into the streams is near equilibrium with the processes converting this form of nitrogen into other forms such as nitrite and nitrate. Measurements of nitrate nitrogen show increased levels in basins with higher percentages of agricultural activity and urban areas. Majors Creek, the basin with the least agricultural activity and urban area had levels of nitrate nitrogen ranging from 0.01 to 0.06 milligrams per liter. Magnolia River, a basin with a higher percentage of agricultural activity and urban area had levels of nitrate nitrogen ranging from 1.79 to 3.1 milligrams per liter. One sample for pesticides was collected at each of three sites; Sandy Creek, Magnolia River, and Blackwater River. The only detections were for atrazine at all three sites and simazine at Sandy Creek and Blackwater River. The sites sampled for pesticides were chosen because of the relatively high degree of agricultural activity in the basin. Of the eight fixed-station sites, only Sandy Creek had median concentrations of fecal coliform bacteria greater than 200 colonies per 100 milliliters, the maximum allowable level for swimming and whole-body contact waters as set by Alabama Department of Environmental Management All eight sites have some measurements above 200 colonies per 100 millil...