Groundwater development and electric and digital modelling of the Upper Carbonate aquifer, Metropolitan Winnipeg area
Render, Francis William.
An extensive confined aquifer, currently pumped at a rate of 3 billion gallons per year, occurs in the fractured and jointed upper 100 feet of the thick Paleozoic carbonate rock sequence underlying metropolitan Winnipeg. The karstic bedrock surface, a controlling parameter of the groundwater flow system, slopes towards the Red River Valley from recharge areas located in uplands along the borders of the Red River Basin. The bedrock surface is mantled by 30 to 200 feet of glacial drift. The drift is composed of 5 to 30 feet of till overlain by lacustrine sediments, mainly clays, that average 40 feet in thickness. Groundwater has been a source of water supply in the Winnipeg area since the early 1800's. The Upper Carbonate aquifer, which during the first two decades of the twentieth century supplied all the city's water requirements, has a transmissibility ranging between 2,000 and 200,000 gallons per foot per day... Water in the aquifer is generally fresh to brackish, however south of the Assiniboine River the water is brackish to saline and is not potable. Groundwater withdraws have created a major drawdown cone in the central industrial area of metropolitan Winnipeg. The drawdown cone is at the center of a lateral radial flow system... A resistor-capacitor analog and a digital computer model of the Upper Carbonate aquifer and non-summer pumpage. The simulated drawdown correlated reasonably well with field drawdown observations. The digital model indicated that while the Red and Assiniboine River beds have a low hydraulic conductivity they still contriubte significant amounts of water to the aquifer. The models can be utilized to indicate the probable effects of increased aquifer development, and as an aid in the prediction of changing water quality patterns.