The Red Deer sandstone aquifer is found in the subsurface in an area north of the City of Red Deer. The mappable areal extent of the aquifer covers about 55 square miles. The aquifer ranges from 10 to 40 feet in thickness and occurs at depths of 134 feet in the Red Deer River valley area and up to 600 feet below surface at the major topographic divide east of the city. The aquifer material consists mainly of medium-grained, uniformly sized quartz grains. Permeability of the aquifer has been determined at points within a five square mile area north of Red Deer. The average hydraulic conductivity value for the aquifer outside the river valley area is 255 gpd/ft2 but a higher value of 561 gpd/ft2 was determined for the aquifer in the river valley area. A representative coefficient of storage for the aquifer is 1.6E-4. The relative permeabilities of the aquifer in the river valley area and outside the river valley area are 45 and 23, respectively, if the lowest permeability value in the geological sediments is considered to be 1.
The purpose of this presentation is to outline a method of calculating the yield of an aquifer, in this case the Red Deer sandstone. The method requires the construction of a vertical two-dimensional quantitative flow net representing regional groundwater flow, the application of Darcy's Law, and consideration of the concept of 'natural basin yield', as defined by Freeze (1969). A suitable hydrogeological model is required before a flow net can be drawn.