Ground Water Resources of British Columbia
Chapter 9 — Ground Water Resources of the Basins, Lowlands and Plains
9.3 FORT NELSON LOWLAND
by
Kevin D. Ronneseth
The dissection of the Alberta Plateau by the Fort Nelson, Hay and Petitot Rivers and their tributaries has produced the Fort Nelson Lowland (See Chapter 8, Figure 8.2). The Fort Nelson Lowland is an area of extremely low relief, with an average elevation of 450 m. Drainage is poorly organized over much of the region resulting in extensive areas of muskeg. The Fort Nelson and Petitot Rivers are incised as much as 150 m below the general level of the lowland. Elsewhere, streams meander across a surface little changed since the retreat of glacial ice during the Pleistocene (Holland, 1964).
The lowland for the most part, is underlain by flat or gently dipping Cretaceous shale and sandstone. Bedrock out cropping is rare except along river channels (McLearn and Kindle, 1951).
During the Pleistocene, the Fort Nelson Lowland was covered by the continental Keewatin ice sheet. The lowland is covered with a veneer of glacial drift which is comprised of debris transported from Precambrian areas far to the east. The direction of ice flow is marked by the lineation of elongated drumlins and glacial fluting in the ground moraine. The ground moraine and pitted outwash are extensive with lakes occupying the numerous undrained depressions. There is also a complex of glacial meltwater channels associated with retreating ice (Holland, 1964).
Currently, there are no ground water maps available for the Fort Nelson Lowland area. Hydrogeological information presented below, comes from water well records and reports on file with the Ground Water Section of the Provincial Government.
Water well depths range from 12 to 140 m. Water well logs show local thickness of unconsolidated materials greater than 130 m. A number of water wells have been completed in unconfined water bearing sands and/or gravel deposits with yields up to 10 L/s (litres per second) being reported. The reported location of these high yielding sand and/or gravel aquifers are adjacent to the Muskwa River and the Fort Nelson River south of the Muskwa River. It was noted in one report, that local sands and/or gravel deposits, are thicker adjacent to the Muskwa River channel and become thinner away from the river. Other water well records report confined unconsolidated aquifer conditions. One water well record shows 125 metres of clay overlying water bearing gravels.
Twenty of the water wells on file with the Ground Water Section, report wells completed in bedrock. When recorded, the bedrock type was shale. Water yields were normally sufficient for domestic supplies, ranging from .06 to .4 L/s.
Three main types of aquifers are identified in this region. The unconfined sand and/or gravel aquifers which currently report the highest water yields. The quality of the ground water from these aquifers has been locally reported to be a bicarbonate of calcium and magnesium type (Hall, 1971). Total Dissolved Solids (TDS) range form 300 to 400 mg/L, hardness from 250 to 300 mg/L and iron has been reported up to 5 mg/L. The confined sand and/or gravel aquifers have TDS ranging from 600 to 700 mg/L, hardness from 400 to 500 mg/L and iron being recorded as high as 10 mg/L. These confined ground waters were also reported locally to be bicarbonate of calcium and magnesium type. The final ground water source is the bedrock aquifer. The ground water type from the bedrock was reported locally as being bicarbonate of soda (Hall, 1971). TDS ranged from 100 to 1500 mg/L, hardness was less than 100 mg/L and iron was reported up to 5 mg/L. The unwanted existence of natural gas was also reported in some of these bedrock aquifers.
Available information suggests ground water resources are historically developed to meet domestic, commercial, industrial and municipal water supplies. Government agencies and industry are responsible for the larger ground water exploration and development programs.
It should be noted, that the hydrogeological information presented here comes from a geographically small area of the Fort Nelson Lowlands. Therefore, the hydrogeological environment the water well logs describe, cannot be considered representative of the region as a whole. However, the confirmation of high yielding sands and/or gravels aquifers adjacent to present day stream channels indicate the probable existence of additional productive aquifers. In addition, the existence of large abandoned glacial meltwater channels offer the potential as a major ground water supply source. Highly productive aquifers have been developed in glacial meltwater channels south of this region on the Alberta Plateau. The available data suggests that ground water can be a major contributor to future water supplies in the Fort Nelson Lowland.
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