A Methodology for Reservoir Site Selection for the Maintenance of Impounded Water Quality

Abstract

A METHODOLOGY FOR RESERVOIR SITE SELECTION FOR THE MAINTENANCE OF IMPOUNDED WATER QUALITY Deterioration of the quality of impounded water due to an inflow of groundwater occurs in some surface reservoirs in Saskatchewan. A methodology to aid in reservoir site selection for the maintenance of high quality impounded waters has been developed as the result of an investigation of the cause of water quality deterioration in the Blackstrap Reservoir. A study region that encompasses the Blackstrap Reservoir and the area between the South Saskatchewan River and the Allan Hills Upland was established. Background information on pedology, geology, and geomorphology was reviewed. A base map of the study region was compiled from National Topographic System maps. Information from many hundreds of existing testholes and water wells was plotted on the base map. Water wells in the vicinity of the Blackstrap Reservoir, preferably those with completion records, were selected for water quality sampling. Water levels, pH and electrical conductivity measurements were taken in the field at the time the several stratigraphic cross-sections of the study region were prepared. By sampling water wells completed in both the glacial and the upper bedrock formations a hydrochemical profile was established. The stratigraphy, static water levels, and the water chemistry established the regional and local groundwater framework. A finite element model was used to confirm the evidence of groundwater discharge into the Blackstrap Reservoir. By defining the geology, hydrochemistry and the surface and ground water hydrology, the interaction between a reservoir and the physical environment may be predicted. This methodology provides a scientific basis for reservoir site selection for the maintenance of water quality.