Ground Water Resources of British Columbia
Chapter 13 — Case Histories
13.3 THE USE OF GROUND WATER IN FISH HATCHERY OPERATIONS
An important use of ground water in British Columbia is directly related to the production of trout and salmon stock for sport and commercial fishing industries. In several hundred lakes in British Columbia good trout fishing is partly or entirely dependent on the regular liberation of young fish raised in provincial government hatcheries. Five to eight million fish are stocked annually from these hatcheries. Salmon stocks which were once so abundant in our coastal waters have dramatically declined over the years and a joint federal-provincial government program to build new facilities and upgrade natural habitats has been established.
The favoured fish spawning grounds are those regions in streams where there is an upwelling of ground water through clean sand and gravel. To simulate these natural conditions, facilities have been constructed in British Columbia which utilize ground water during the periods of egg incubation and later development of alevins and fry. The locations of public fish hatcheries in British Columbia using ground water supplies from wells and springs are shown in Figure 13.4.
Figure 13.4 Locations of public fish hatcheries in British Columbia using ground
water supplies from wells and springs (adapted from Foweraker et al, 1985)
Advantages of ground water for these facilities include stable temperatures usually between 6° and 14° C, the greater protection of a well source from surface contamination, low suspended solids content at all times of year, and the greater hardness of ground water which provide a buffering action against such things as toxic metals (Cd, Cu, and Zn). On the other hand, there are drawbacks to the use of ground water including well pumping costs, potential for mechanical breakdowns and the need for aeration of the water which is low in dissolved oxygen.
The Fraser Valley Trout Hatchery, owned by the provincial government, is an example of a hatchery dependent solely on a continuous supply of ground water for its operation. The hatchery is located at the eastern slope of the Abbotsford Aquifer within the Fraser Lowland, near the city of Abbotsford (Figure 13.2). The aquifer which covers an area of 60 km2 is part of a broad upland area which extends south of the Canada-United States Border (Kohut et al 1982). The aquifer is essentially an outwash plain of glacio-fluvial sands and gravels that developed during the downwasting of an ice mass during the last stages of Pleistocene ice retreat in the Sumas Valley to the east.
Figure 13.2 Southern Coastal Trough area, locations of selected
high capacity wells (adapted from Foweraker et al, 1985)
Ground water occurs under water table conditions and recharge to the Abbotsford Aquifer is provided by an average annual precipitation of 1425 mm. Spring flow along the eastern edge of the aquifer was formerly 250 L/s on a year round basis (Kohut et al 1982). However, high capacity production wells with yields of up to 158 L/s have reduced the flow in the springs substantially. The hatchery requires 950 L/s of ground water, but because this amount is not available, the hatchery has been designed to run on only 158 L/s. The reduction in daily demand has been accomplished through the recycling of a large portion of the water used. The water is treated after each cycle through filtration and aeration.
Four production wells have been constructed at the hatchery, but at the present time only one well, a 500 mm diameter screened well, tested at 159 L/s, is supplying the total hatchery demand (Zubel 1980b). This well penetrates 80 m of saturated sands and gravels. The well is fitted with a 44 m long screen assembly with blank sections. The well has a specific capacity of 14.9 L/s/m of drawdown.
Since the hatchery facilities were completed, there have been two periods of annual decline in ground water levels in nearby observation wells. The first decline occurred during the period 1976-79 and was due to below average precipitation, however, concern has been expressed that the second decline which started in 1982 and is continuing may be due to ground water "mining." The situation is being monitored closely.
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