Micrometeorological measurements were conducted in three communities (open water, Phragmites australis, Scirpus acutus ) in a wetland in north-central Nebraska, during May-October, 1994. The Bowen ratio-energy balance method was used to calculate sensible and latent heat fluxes. In this presentation, we will discuss the results from the open water area of the marsh, focusing on the diurnal and seasonal patterns and magnitudes of energy fluxes. In particular, factors affecting heat storage in the water and its contribution to the overall energy budget will be examined. We will also examine the role of thermal stability (above the water surface) in controlling the diurnal variation of the rate of evaporation.