Water and solute transfer between a prairie wetland and adjacent uplands, 1. Water balance

The hydrology and water quality of lakes and wetlands are controlled by the exchange of water and solutes with adjacent uplands. We studied a small catchment in Saskatchewan, Canada, to evaluate the mechanisms of water and solute transfer between the wetland and the surrounding upland. Detailed measurements of hydrologic processes (precipitation, runoff, evapotranspiration, and subsurface flow) and chloride distribution are combined to improve the estimate of the transfer flux. This paper describes hydrologic processes and Part 2 describes the solute transport processes. Large snowmelt runoff occurs in the catchment, which transfers 30-60% of winter precipitation on the upland into the wetland to form a pond in the center. Snowmelt water and summer precipitation infiltrate under the central pond. Infiltration accounts for 75% of water leaving the central pond and evapotranspiration accounts for 25%, Most of the infiltrated water flows laterally in the shallow subsurface to the wet margin of the pond and further to the upland, where it is consumed by evapotranspiration without recharging deep groundwater. The net recharge rate of the aquifer underlying the catchment is only 1-3 mm year(-1). Snowmelt runoff transfers water from the upland to the wetland, and shallow subsurface flow transfers water in the opposite direction. When the two processes are combined, they provide the paths for cyclic transport of solutes. (C) 1998 Elsevier Science B.V. All rights reserved.