Surface Water - Alabama Department of Environmental Management

Cahaba River (0315-0202)
Cahaba River CU (0315-0202)
The Cahaba is a major tributary of the Alabama River containing 17 sub-watersheds
and draining approximately 1,824 mi 2 in 8 counties (ADEM 2003b). Stretching for 191
miles, the Cahaba River is Alabama’s longest free-flowing river. Nationwide, the Cahaba
River has the most fish species per mile of any river of its size (TNC 2002). It supports 10
fish, mussel, and snail species currently listed as threatened or endangered (Federal
Register 1998). The Upper Cahaba River is located within the Ridge and Valley (67)
Ecoregion (Griffith et al. 2001), with its headwaters north and east of Birmingham. The
Lower Cahaba River basin crosses the Fall Line and is located in the Southeastern Plains
(65) Ecoregion (Griffith et al. 2001). The river flows through Birmingham, Alabama’s
largest city, and is a public water supply to approximately one-fourth of the State’s
population.
Landuse: Sixteen miles of the Little Cahaba River and 162 miles of the Cahaba River are
classified as Outstanding Alabama Waters (ADEM 2003e). A 13.3 mi. segment of the
Upper Cahaba River is designated Public Water Supply. Four segments of the Cahaba
River, draining 1,027 mi 2 , are currently on Alabama’s 2002 §303(d) list of impaired waters
for nutrient enrichment, siltation, and pathogens (Appendix C-2). Three segments have
been listed for“other habitat alteration”, which implies impaired aquatic communities
caused by degraded habitat quality. In the Cahaba River, the cumulative stresses of
excessive nutrients and sedimentation have contributed to impacts to threatened and
endangered species. ADEM is currently developing siltation, pathogen, and nutrient
targets to determine the Total Maximum Daily Load for these pollutants within the Cahaba
River (ADEM 2003d, ADEM 2003f). Segments of Lee Branch, Patton Creek, and Shades
Creek are also listed as impaired (Appendix C-2). Total maximum daily loads (TMDLs) of
pathogens have been developed and approved for segments of Cooley Creek, Mill Creek,
Mud Creek, Shades Creek, and Dry Creek (Appendix C-1).
Percent land cover estimated by local SWCD (ASWCC 1998)
Forest Row crop Pasture Mining Urban Open Water Other
65% 3% 13% 1% 15% 1% 2%
NPS impairment potential: There was a moderate potential for NPS impairment in 2 subwatersheds.
Pasture grazing, forestry, and sedimentation were the NPS concerns in the
CU. There was a moderate or high potential for impairment from urban sources within 7
sub-watersheds. Sedimentation from land development was also a concern (Appendix I)
Number of sub-watersheds with (M)oderate or (H)igh ratings for each nonpoint source category (Appendix D).
Category
Overall
Potential
Animal
husbandry
Aquaculture
Row
crop
Pasture Mining Forestry
(11
reported)
Sediment
Moderate 2 0 1 1 6 0 2 2
High 0 0 0 0 0 1 1 6
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