Nishnabotna River Basin, Waste Load Allocation Study, 1974

(1974) Nishnabotna River Basin, Waste Load Allocation Study, 1974. Natural Resources, Department of

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Abstract

The Nishnabotna River Basin encompasses an area of approximately 2,819 square miles in the southwest section of Iowa. Topography is rolling and the drainage pattern of the basin is tree-shaped (dendritic). Stream flows per square mile in the Nishnabotna River Basin are generally less than those of the state of Iowa as a whole, especially for the 7-day, 1-in-10 year low flow. Most of the main streams in the basin have a Class B (warm water fisheries) water quality criteria classification. There is a lack of comprehensive water quality data on existing conditions within the basin. The limited data available show, under winter conditions and low flows, lowered water quality within the streams. Under these conditions, the water quality within the West Nishnabotna River falls below the applicable water quality criteria. This decrease in water quality is directly related to the impact of treated wastewater discharges upon the stream. Within the basin, 44 communities are incorporated. Of these, 33 have wastewater treatment facilities. Also, there are 8 industrial and one semipublic wastewater dischargers. Only 10 municipalities maintain wastewater treatment facilities which will not be required to adopt a controlled discharge mode of operation under the National Pollutant Discharge Elimination System (NPDES).