Author(s): George D. Ashton; Nathan D. Mulherin

Linked Author(s): George Ashton

Keywords: No Keywords

Abstract: One of the critical gaps that persists in reservoir water temperature and quality modeling is the ability to know the temperature of the water at the time of freezeover. Prior to and after freezeover, existing simulation models are capable of following the temperature structure reasonably well, but the "after" simulation requires starting values or the time of initial ice cover formation. The few existing year-round simulation models either impose the ice cover when the 0°C surface temperature is reached or use a heuristic set of threshold criteria pro­posed by Ashton. The latter has not been well tested and the foRmer is known to fail at times, particularly when wind prevents for mation of a stable ice cover. We set out to determine what conditions of wind, water tempera­ture, and air temperature lead to the freezeover event for lakes and reservoirs by using historical data of release temperature, wind speeds, air temperatures, and reported dates of freezeover recorded at the mainstem dams of the Missouri River. We tested the criteria pro­posed by Ashton, a modified version of those criteria, and an index approach where the daily index is a combination of air temperatures, release water temperatures, and wind speeds. The limitations of an index approach are discussed, including the irregular behavior of freezeover and the conceptual difficulty of assessing how the ice cover gains sufficient integrity to withstand forces of wind and current dur­ing its formative stages.

DOI:

Year: 1990