A one-dimensional, steady-state, dissolved-oxygen model and waste-load assimilation study for South Fork Wildcat Creek, Clinton County, Indiana

The Indiana State Board of Health is developing a State water-quality management plan that includes establishing limits for wastewater effluents discharged into Indiana streams. A digital model calibrated to conditions in South Fork Wildcat Creek was used to predict alternatives for future waste loadings that would be compatible with Indiana stream water-quality standards defined for two critical hydrologic conditions, summer and winter low flows.

Natural streamflow during the 7-day, 10-year low flow is zero, so no benefit from dilution is provided. The Indiana State Board of Health's projected ammonia-nitrogen concentration for the Frankfort wastewater-treatment facility will violate the in-stream total ammonia-nitrogen standards of 2.5 milligrams per liter and 4.0 milligrams per liter during summer and winter low flows, respectively.

The model indicates that nitrification and algal respiration were significant factors affecting the dissolved-oxygen dynamics of South Fork Wildcat Creek during two water-quality surveys.

Stream water quality during the two water-quality surveys was degraded by the discharge of wastewater receiving only primary treatment. Benthic deposits resulting from this wastewater discharge seem to exert a considerable oxygen demand. The discharge of partially treated wastewater should be eliminated when a new wastewater-treatment facility becomes operational in mid-1979. Therefore, benthic-oxygen demand due to benthic deposits should become negligible at that time.