Open File Report 1966-04

Open File Report 1966-04

OFR 1966-04

Pump Test of an Alluvial Aquifer at Redcliff (and results), 13-6-W4

Author(s) Research Council of Alberta Date 1966-10-01

This report describes the results of a 3 day constant-rate pump test of an alluvial aquifer on the north shore of the South Saskatchewan River in section 6, township 13, range 6, West of the 4th meridian. The purpose of the test was to assess the water-supply potential of the aquifer and, in particular, to determine its suitability for an induced-infiltration supply for the town of Redcliff. Such a supply, if feasible, could yield water in amounts capable of meeting municipal and industrial demands.

The test involved, in addition to the pumped well, four observation wells. Anomalous drawdown results were obtained in one of the wells and another failed to respond at all to the test pumping. The remaining test data indicated that there was no perceptible infiltration of water from the river and that the lateral dimensions of the aquifer were severely limited in at least one direction. There is, therefore, no possibility for the development of an induced-infiltration supply and the potential for any other groundwater development is limited.

The computed transmissibility, hydraulic conductivity and storage coefficient based on the constant-rate test results were 61,000 imperial gallons per day per foot (igpd/ft), 6,100 imperial gallons per day per square foot (igpd/ft2), and 0.022, respectively. These results were combined with those from a step-drawdown test to obtain a calculated 20-year single-well safe yield of 27.8 imperial gallons per minute (igpm). This estimate is probably optimistic because it assumes that the pumped-well drawdown trend in effect at the end of the pump test would be maintained for the rest of the 20-year production period. This is unlikely because of the probable limited areal extent of the aquifer unless:

a. aquifer thickness and lithology are the same at both well sites,

b. available drawdown i.e. the vertical distance from the undisturbed water table to the top of the well screen, is the same at both sites, and

c. well construction and development are the same for both wells.

Finally, it should be pointed out that, although, production can be increased by increasing the number of production wells, interference between wells will restrict the gains to be made thereby. In other words, doubling or tripling the number of wells, will fall considerably short of doubling or tripling the total safe yield. Thus, even under a well field type of development, the potential of the aquifer is low and is probably less than 100 igpm.