Regina East Aquifer Science and Monitoring Program

Kei Lo, Nolan Shaheen, Mike Famulak

Dans les comptes rendus d’articles de la conférence: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Hydrogeology and Groundwater

ABSTRACT: Rapid growth in the area east of the City of Regina has led to substantial expansion of industrial, urban, and rural residential development. The best available estimate of sustainable yield from the Zehner aquifer is 4,800 cubic decameters per year. Pumping test analyses showed the presence of previously unidentified hydraulic discontinuities within the Zehner aquifer, suggesting that the aquifer™s geometry and flow systems are more complex than previously thought. An adaptive science program will use data from 28 piezometers completed in key areas of the Condie and Zehner aquifers to provide information on aquifer(s) water levels, groundwater flow direction and gradient, groundwater recharge and discharge rates and to potentially identify unknown aquifer(s) users. The evaluation of this information, along with well(s) production data provided by the licensed users, will be used to continually reassess the sustainable yield estimates of the Zehner aquifer. A water sampling program is also being implemented to better understand groundwater quality and surface-groundwater interactions.

RÉSUMÉ: La croissance rapide à l™est de la ville Regina a conduit l™expansion de développement industriel, urbain, rurale, et résidentiel. Le meilleur estimé du rendement maximal soutenu de l™aquifère Zehner est de 4800 décamètres cubes par année. Des analyses d™essais de pompage démontrent la présence de discontinuités hydrauliques parmi l™aquifère Zehner, suggérant que la géométrie et le réseau d™écoulement sont plus complexes que pensé auparavant. Un program de science adaptif utilisera des donnés de 28 piézomètres installés à des lieux-clés des aquifères Condie et Zehner pour quantifier le niveau d™eau, la direction d'écoulement, le gradient, et les taux de recharge et de décharge des eaux souterraines et identifiera possiblement des utilisateurs inconnus d™aquifère. L™évaluation de cette information, accompagné des donnée de la production des puits fourni par les utilisateurs agréés, sera utilisé pour réévaluer continuellement les estimées du rendement maximal soutenu de l™aquifère Zehner. Un program d'échantillonnage de l'eau est aussi en cours de réalisation pour mieux comprendre la qualité d™eau souterraine et les interactions entre les eaux de surface et les eaux souterraines. 1.0 INTRODUCTION Economic, social and environmental factors are affecting the demand for fresh water in the Regina area. Rapid population growth in the area east of the City of Regina, has been occurring in the past several years and has led to strong increase in demand for groundwater. The Zehner and Condie aquifers have been providing a source of water for the area; however, it is unknown if the increasing water demands are sustainable. The Water Security Agency (WSA) has established a maximum sustainable yield limit on the Zehner aquifer at 4,800 decameters per year (dam3/year). The origin of the sustainable limit was derived from several studies undertaken to review the water balance in the Regina east area (Maathuis and van der Kamp, 1988; Clifton Associates, 1989; Stanley Consultants, 1987). Recent studies have been completed to address the water demands and population growth projections in the area, with a review of the water balance budget (AECOM 2009). In general, the 4,800 dam3/year sustainable yield estimate is based on annual inflow less natural outflow from the Zehner aquifer system. In the Regina area, the allocation of groundwater resources was based on previous investigations completed by the Saskatchewan Research Council (SRC) and other private consulting firms. The concept of groundwater allocation has been based on ‚safe yield,™ which allows users to withdraw no more groundwater than is naturally recharged. However, water supply studies completed by private firms provide estimates of the individual well or well field yields, but they generally do not provide evaluation of the cumulative impacts on the aquifer from withdrawals by multiple users. With the increasing water demands in the Regina east area, the estimated maximum sustainable yield of 4,800 dam3/year was re-evaluated by the water managers. Consequently, an adaptive science and monitoring plan was developed by WSA to address the sustainable yield estimate of the Zehner aquifer system. To protect the aquifer from potential over production, the WSA has introduced an additional margin of safety by initially limiting the regulatory groundwater allocation volume(s) from the Zehner aquifer to a volume less than 4,800 dam3/year. Depending on the aquifer response to pumping over time, the WSA will adjust all current and future allocations accordingly. The effect of stressing (pumping) the Zehner aquifer over time will be continually monitored and based on the results of this monitoring, the estimated sustainable aquifer yield will be revised (if required) on an ongoing basis.

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