Date of this Version
Pursuant to National Pollutant Discharge Elimination System (NPDES) Permit No. NE 0111635, the Omaha Public Power District conducted an environmental monitoring program at the Nebraska City station. This study was undertaken to assess the effects of the station's cooling-water intake structure upon the aquatic biota of the Missouri River as required by Section 316(b) of the Federal Water Pollution Control Act. It included a study of fishes impinged on the intake structure's six traveling screens. From 29 May 1979 to 31 May 1982, daily fish impingement sampling occurred at 1200 and 2400 ± 2 hr. One of the traveling screens, in sequence, was sampled for 1 hr. A total of 1,508 fishes was impinged during daily sampling. These fishes included Osmerus mordax (36.1%), Carpiodes carpio (20.8%), Ictalurus punctatus (17.3%), and Aplodinotus grunniens (12.1%). The majority of these were age-class 0 (X length = 88 mm). The population of adult fishes in the vicinity of the station was sampled utilizing seining and electroshocking techniques. From October 1977 through December 1981, there were 17 sampling efforts utilizing the catch per unit effort procedure and 12 population estimates completed on a seasonal basis (spring, summer, and fall). This spectrum of fishery indicators points to fishery stability over long periods. Impingement is within compensatory capabilities of the fish population as shown by the stable population structure of adult fishes. In assessing effects of impingement, the controlled flow-regime of the Missouri River must be considered. Summer flows (ca 1,286 cms) are sufficient to provide abundant fishery spawning and nursery areas. The reduced flows (ca 571 cms) in the winter result in reduction of habitat that is combined with seasonal severity to limit over-wintering capability of the river's fishery. As a result, the summer fish production cannot be accommodated by the winter conditions of the river.