Executive Summary
The Regina East area has witnessed an intensification of growth and development, which has led to an increased demand for water. In the last decade, there have been increase in demand and supply of groundwater from the Zehner aquifer for municipal and domestic purposes in the Regina East area. Saskatchewan Water Security Agency (WSA) is the provincial body that governs all of Saskatchewan’s water resource management and ensures the sustainability and quality/viability of Saskatchewan’s surface and groundwater supply. The existing water balance and safe yield for the inferred 150 Km2 Zehner aquifer is based on Maathuis & van der Kamp’s, (1988) and Clifton Associates Ltd., (1989) report respectively. This estimation calculated more than 30 years ago seems to be outdated as various pumping tests, and chemical and isotope analysis have inferred several discontinuities within the Zehner aquifer (Lo, 2010; Lo, Melnik, & Walcer, 2014). WSA has therefore initiated the current study to refine the water balance and allocation limits for the Zehner aquifer, taking into consideration the existing discontinuities due to hydraulic barriers.
Prior studies and water level data from installed piezometers within the Zehner aquifer have shown that the general groundwater flows from northeast to southwest. In this study, based on the differences in annual drawdown and water level trends between piezometers, the Zehner aquifer was divided into the A, B, C and D Zone. Each of these zones has a different recharge and discharge function due to hydraulic discontinuities and the complex geology of the Zehner aquifer. The study has found that the water level and groundwater flow follow the topographic elevation. The northeast section has a high elevation, water level, and recharge function, while the southwest section has a low elevation, water level, and high discharge and pumping function. This study proposes a method for calculating the water balance of the different zones and the D-Zone was chosen to demonstrate the viability of this method. This water balance is based on the average 5-year period (2013-2017), with the withdrawal from production wells known for RM of Edenwold and Town of White City (SaskWater) wells. The ground water storage and recharge have been quantified on basis of the physical and hydraulic properties of the aquitard and aquifers in the D-Zone. Darcy’s law was used to estimate the recharge or flow of water from the aquitard into the Zehner aquifer as well as flow from the B and C-Zone to D-Zone of the aquifer. The discharge is back estimated after calculating recharge and change in storage.
The study and proposed methodology maybe used to similarly estimate the water balance functions in the A, B and C-Zone.