A Heat Budget for Canyon Reservoir, A Subtropical Impoundment in Southcentral Texas

Date
2000-12
Authors
Bass, David A.
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Abstract
Annual heat budgets were constructed for a subtropical (30°N) reservoir over its 31-year history and used to examine the influence of local climatic variability on hydrological and thermal processes. Heat balances were calculated using both observed and derived hydrological and meteorological data, and some of the heat flux equations were modified to more accurately reflect the local climate. During this study period, surface heat exchange accounted for 67% of the annual heat flux. The magnitude and patterns of surface heat fluxes observed at Canyon Reservoir were intermediate between those of tropical and temperate lakes. The reservoir showed the sinusoidal pattern of heat gain seen in temperate lakes, but the amount of heat flux was more similar to tropical reservoirs. The climate of southcentral Texas is quite variable, and over its history Canyon Reservoir has experienced several major floods and droughts, providing insight into the role advection plays in reservoir heat dynamics. The reservoir acted as a trap for advected heat. The contribution advected heat made to the total heat budget averaged 33%, but varied from < 1% to > 95% depending on the volume of water entering the reservoir and time of year. To further explore the role advection played in Canyon Reservoir’s heat dynamics, data on the three wettest and driest years were compared. Net heat balances were quite different between the two groups of years. In the driest years, the reservoir lost 52 cal cm"2 d"1 more heat than the 31-yr mean, making the reservoir an overall heat source to its environment. During the wettest years, the reservoir gained 19 cal cm"2 d"1 more heat than the 31 -yr annual mean, increasing its role as a heat trap.
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Keywords
heat budget, climatic changes, water temperature, heat transmission, Canyon Lake, geophysics
Citation
Bass, D. A. (2000). A heat budget for Canyon Reservoir, a subtropical impoundment in Southcentral Texas (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.