| Summary: | This study examines the evaporation from a lichen-dominated upland ridge, a swamp and a shallow lake in the Hudson Bay lowlands evaluated by the energy-budget and equilibrium model approaches. Energy-budget calculations reveal that on average 54, 66 and 55 percent of the daily net radiation is utilized in the evaporative process over the ridge, swamp and lake surfaces respectively. For the ridge half-hourly and daily values of evaporation were approximated closely by equilibrium estimates, while for the other surfaces close approximation was achieved by the Priestley and Taylor (1972) model where the ratio of actual to equilibrium evaporation equals 1.26. A simple model, expressed in terms of incoming solar radiation and the screen height air temperature, is developed for each surface from the comparison of actual to equilibrium evaporation. Tests of the models at different locations indicate that the actual evaporation can be estimated on a daily basis within 6 percent for dry upland and saturated lowland swamp surfaces, while for shallow lakes, the evaporation can be determined within 10 percent over periods of two weeks. Doctor of Philosophy (PhD)
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