Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Wildlife and Fisheries Science


The standing crop, distribution, seasonal variation, and entrainment of benthos were studied at the Big Stone Power Plant cooling reservoir. Benthos samples were collected from January 1979 through March 1980 utilizing a stratified random sampling design in 3 areas related to the thermal discharge site and cooling water intake sites. Maximum surface and bottom water temperatures in the discharge area were 42.0 C and 33.5 C respectively. The intake area had a maximum surface and bottom temperature of 32.0 C and 30.0 C respectively. Reservoir temperatures ranged from 0.0 C to 42.0 C during the study. Dissolved oxygen ranged from 0.2 to 15.6 ppm. Chironomids were numerically and gravimetrically the most abundant organisms taken in the cooling reservoir. Numerically they constituted 94% of all organisms sampled. They were found in greatest numbers in the intakes area of the cooling reservoir. Chironomids comprised 95% of the total dry weight. Oligochaetes were numerically the second most abundant organisms. They constituted 4% of total numbers and 1% of total dry weight. The mean standing crop of benthos in the cooling reservoir (0.6 g/m2) was lower than the average for most North American lakes. Numerically the standing crop (1,460/m2) was closer to the average North American lakes. Benthos populations were less abundant in the discharge area of the cooling reservoir. The rip-rap area of the cooling reservoir was sampled with artificial substrate baskets. Numerically chironomids comprised 65% of all organisms colonizing the baskets. Gravimetrically Physa spp. Comprised 71% of the total mean biomass. This resulted from including the shells in the dry weight. This resulted from including the shells in the dry weight. Annual mean standing crop for the rip-rap area was 258g/m2. Calculated 24-hour estimates of benthic organisms entrained ranged from a high of 1,010,625 in June 1979 to none in December 1979. Chironomids were the most commonly entrained organisms.

Library of Congress Subject Headings

Big Stone Power Plant (S.D.)
Cooling ponds
Steam power plant


Includes bibliographical references (pages 49-54)



Number of Pages



South Dakota State University


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