Ground Water Resources of British Columbia
Chapter 9 — Ground Water Resources of the Basins, Lowlands and Plains
9.2 INTERIOR BASINS AND PLAINS
9.2.1 FRASER BASIN
by
J.C. Foweraker
GENERAL SETTING
The Fraser Basin is located within the Interior System of the Province (Figures 8.5 and 8.6). The basin is classified as a distinct ground water sub-region. However, there is some disagreement between writers on the need for having a basin subdivision at all. Tipper (1971) for example, includes the Fraser Basin area within the boundaries of the Fraser and Nechako Plateaus.
The Fraser Basin boundary as described by Holland (1964) and adopted here, generally follows a 915 m contour. The basin is an irregular shaped area of low relief which lies below the surface of the Nechako Plateau on the north and west boundaries of the basin, and to the south the basin extends into the Fraser Plateau. At the most north eastern part of the basin where the boundary adjoins the Rocky Mountain Trench, the basin limit is set at the 610 m contour and elsewhere on the north east the McGregor Plateau forms the basin boundary.
The Fraser basin extends northward from near Lac la Hache to Mcleod Lake, and from Fraser Lake on the west to Sinclair Mills, southeast of Upper Fraser, on the east. Highway 97 traverses the basin in a north, south direction through the major centres of Prince George, Quesnel and Willams Lake, while Highway 16 traverses the basin in an east-west direction through Prince George, Vanderhoof and Fort Fraser. Fort St. James north of Vanderhoof also lies within the Fraser Basin.
PHYSIOGRAPHY
The Fraser Basin is described by Holland as a flat or gently rolling surface lying mostly below 915 m. The drainage is poorly organized over much of the basin and there are numerous lakes and poorly drained depressions.
Sinclair Mills, at the eastern boundary of the basin, marks the location where the Fraser River commences its swing around the north end of the Cariboo Mountains before flowing south through the Fraser Basin and on into the Fraser Plateau. The Fraser River is joined successively by the McGregor, Nechako, West Road and Quesnel Rivers, and just south of the basin boundary, by the Chilcotin River. The drainage of the Fraser River and its tributaries does not everywhere show the normal pattern of a southward flowing river. According to Holland (1964), it is apparent that at one time a divide existed in the vicinity of Riske Creek, south of Williams lake, between a south flowing ancestral Fraser River and a north flowing segment.
At Prince George, the Fraser River flows at an elevation of 565 m. South of Quesnel the river becomes more constricted and more deeply incised. At Soda Creek the river elevation is 425 m, and the valley walls rise to the floor of the Fraser Basin above, at an elevation of about 915 m (Holland, 1964). Downstream of Soda Creek, the river is constrained by a gorge over 305 m deep, incised in the bottom of the main valley.
GEOLOGY
Much of the Fraser Basin is covered by drift and there are few exposures of bedrock. Sedimentary and volcanic rocks underlie much of the unconsolidated deposits. According to Holland (1964), the Fraser Basin was occupied by ice during the glaciation period and the ice movement created drumlin and drumlin like forms in the glacial drift. These forms indicate an eastward and north eastward movement of ice in the basin area north of Prince George, and movement northward from the Quesnel area.
During deglaciation, the preglacial drainage channels were blocked with drift and wasting ice according to Holland (1964) and ice dammed lakes were formed in basins located about Prince George, Vanderhoof and Fort St. James. Unconsolidated deposits, including sand, silt and clay, were laid down at that time in the basins. According to Tipper (1971), the glacial lake level in the Prince George Basin generally lay below the 760 m level and the lake was largely formed by ice blockage to the south. Near Prince George, silt and clay deposits are over 120 m thick in places, and display typical varve structure. The Fort St. James and Vanderhoof basins drained easterly into the Prince George Basin which in turn drained northerly to the Peace River (Tipper 1971). Subsequent melting of the ice dams permitted rapid drainage and dissection of the lake deposits and the re-establishment of the major drainage system southward, Tipper (1971). At Prince George the channel of the present river is some 215 m below the upper level of the glacial lake clays (Holland, 1964).
GROUND WATER RESOURCES
The major rivers of the Fraser Basin have eroded into and reworked the glacial, glaciofluvial and lacustrine deposits which fill the large river valleys within the basin. Within the heterogeneous deposits there exist productive aquifers, water bearing sands and gravels, which have been developed for domestic, industrial and community water supplies.
The distribution of wells within the Fraser Basin shows a high density in the general areas of major population centres and a scattered distribution adjacent to roads and highways which traverse the basin. The majority of the wells are for domestic and livestock use. The higher capacity wells for industrial and community water supply use are, for the most part, located within the major river valleys, and near the major population centres of Prince George, Vanderhoof, Fort St. James, Quesnel and Williams Lake.
There are over 5,940 well records on file in the Ground Water Section, for the Fraser Basin area, and there may be many more wells in this area for which information is presently not available. The majority of well records, 83% or 5,030, are for low capacity wells producing less than 1 L/s.
It should be mentioned here that the well record information used in completing the following sections was supplied gratuitously to the Province by well drilling contractors and others, it may be incomplete and its accuracy and reliability has not been independently confirmed. The information summarized in the following sections should be used with caution.
Approximately 80% or 4,727 of the wells in the Fraser Basin which are on record, are completed in unconsolidated deposits, and 83% or 3,946 of these wells have either no reported well yields or the reported well yields are under 1 L/s. The remaining 17% or 781 `unconsolidated' wells are higher capacity wells, which fall into one of three groups based on reported potential well yield. Group 1 consists of 655 wells which range in yield from 1 L/s to less than 4 L/s. Group 2 consists of 33 wells which range in yield from 4 L/s to less than 7 L/s, and group 3 consists of 93 wells which have recorded yields of over 7 L/s.
Bedrock wells within the Fraser Basin account for 20% or 1,212 of the total number of wells in the basin. Approximately 89% or 1085 of these bedrock wells have either no record of well yield or the reported yield is less than 1 L/s. Only 10% or 125 of the remaining bedrock wells have yields between 1 L/s and 4 L/s. Two bedrock well records show reported potential yields estimated at over 7 L/s.
More detailed well record information on the high capacity wells completed in unconsolidated deposits of the Fraser Basin is presented below, commencing with the Prince George area.
In the Prince George area, within the glaciofluvial, fluvial, alluvial and lacustrine deposits located in the valleys of the Nechako and Fraser Rivers, high capacity wells have been completed for water supply and industrial use, with reported potential well yields between 7 L/s up to, and even exceeding in one case, 250 L/s. Estimates of aquifer transmissivity are in some locations very high, perhaps 1.7 x 10-1 m2/s. In some areas of the Nechako Valley these aquifers may be as much as 76 m below surface, or as shallow as 15 m. Static water levels are generally high. Specific capacity of these wells can be very high. One large collector unit when first constructed was estimated to produce about 789 L/s. The specific capacity was calculated at the time as 414 L/s/m of drawdown, and the transmissivity of the aquifer calculated at approximately 1.3 x 10-1 m2/s. These highly productive aquifers may in some locations be vulnerable to pollution from surface contaminants.
North of Prince George in the Willow River - Eaglet Lake area, two higher capacity wells estimated at over 7 L/s, have been completed in shallow sands and gravels, while near Bear Lake near Highway 97, two wells producing 11.4 and 18.9 L/s respectively are reported to have been completed in glaciofluvial deposits at a depth of 52 to 55 m.
East of Prince George in the Pineview area and further north, potential yields of 15.1 to 30.3 L/s have been reported in wells constructed in water bearing sand and gravel zones as deep as 40 to 46 m, and 116 to 128 m below surface. Overlying these aquifers are glacial deposits and lake beds. Aquifer transmissivity is calculated at 3.6 x 10-2 m2/s.
At Beaverley, south west of Prince George there are reports of wells yielding over 7 L/s, which have been developed in gravels located below lake deposits. These gravels are as deep as 55 to 114 m below surface.
South of Prince George, high yield wells of 15.1 L/s and more have been reported completed north of Tabor, in sands and gravels located less than 30.5 m deep, within the glaciofluvial and fluvial sequence. South of Tabor high yield wells, with low static water levels have been constructed in aquifers located below 90 to 122 m of lake beds and silts.
West of Prince George, within the Vanderhoof Basin area, in some cases near the Nechako River, several high capacity wells have been constructed in aquifers located at varying depths from 40 to 183 m. Overlying these water bearing sands and gravels are glacial, glaciofluvial, fluvial and lake bed deposits. Artesian flows as high as 7.6 to 30.3 L/s, and in one instance 69.4 L/s, have been recorded. When first constructed the 69.4 L/s flowing well had a specific capacity of 20.7 L/s/m of drawdown and the transmissivity of the aquifer was calculated as approaching 1.4 x 10-2 m2/s.
At Engen, on Highway 16, west of Vanderhoof, a well constructed into sands and gravels below 119 m of glacial, glaciofluvial, fluvial and lacustrine deposits, produced 15.1 L/s. The static water level was recorded at 30.5 m from surface. Further to the southwest of Vanderhoof in the upper reaches of the Nechako River Valley, near Murray Lake and the Kenney Dam, three wells have been completed with screens set in glaciofluvial and fluvial deposits located between 21 and 46 m in depth with reported yields of 7.6, 46.7 and 56.8 L/s respectively.
North of Vanderhoof, at Fort St. James, high capacity flowing artesian wells have been constructed in sands and gravels located at a depth of 94.5 to 100 m. This aquifer is overlain by glacial, glaciofluvial and lacustrine beds of the Fort St. James Basin. One high capacity water supply well for Fort St. James, when first constructed and tested, flowed at 265 L/s.
In the southern part of the Fraser Basin, just north of Quesnel and lying within the Fraser River Valley, a well constructed for industrial use, had a reported yield of 176 L/s. The well screen is located between 18 and 27 m below surface in sand and gravel of the valley fill deposits.
The City of Quesnel has constructed a number of high capacity wells, some records dating from the 1950s. A 53 L/s well is located on the east side of the Fraser Valley, north of Quesnel in a sand and gravel aquifer screened between 36 and 39 m. Another city well completed in 1963 produced 64.4 L/s from a site upstream of the confluence of the Quesnel River with the Fraser River at Quesnel. This well is screened in permeable valley fill deposits in a zone 21 to 30 m deep. On the west bank of the Fraser River, just downstream of where the Quesnel River enters the Fraser, is the site of a 53 L/s well which is screened between 23.8 and 29.9 m in permeable valley fill deposits.
On the east side of the Quesnel River, just north of Quesnel, two pulp mill wells have been completed at depths of 42.7 to 48.8 m in permeable valley fill deposits. One of the two wells was rated in 1970 at 40.1 L/s, the other at 30.3 L/s. The static water level in both wells was measured at 24.4 to 27.4 m from surface.
Between Quesnel and Williams Lake several higher capacity wells are located within the Fraser Basin. For example near Australian, between Highway 97 and the Fraser River, there are two reports of wells yielding 15.1 L/s which have been completed in a gravel aquifer at a depth of 26 m. Other higher capacity wells have been constructed at Alexandria, near Marguerite and Soda Creek according to the records available for those areas.
The city of Williams Lake has constructed a number of wells on Scout Island. A production well completed in 1965 and screened in gravels between 55 and 61 m produced 50.5 L/s. This aquifer is overlain by compact silts, sands and some gravel beds. Transmissivity at the Scout Island site has been calculated at 1.0 x 10-1 m2/s. Another city well completed at this site in 1976 produced 75.7 L/s, with the well screen set in sands and gravels at a depth of 47.2 to 59.4 m. A further city well constructed at this site is reported to have produced 126 L/s. The well specific capacity was calculated at 14.5 L/s/m of drawdown.
GROUND WATER QUALITY
In general, records of ground water quality analyses reviewed for the Fraser Basin, show the ground water is usually high in dissolved mineralization and also hard. The dissolved mineralization is in the form of calcium-magnesium-bicarbonate or calcium-magnesium-sodium-bicarbonate-sulphate. Locally as at Prince George and some other centres, iron and/or manganese can cause problems in water quality and ongoing well screen treatment may in some cases be required to maintain well yield.
Specific comments on a number of ground water analyses for wells located within the Fraser Basin are as follows:
North of Prince George near Bear Lake a high iron concentration of 10 mg/L, has been reported, the ground water is moderately hard, 150 mg/L, and the dissolved mineralization is of the calcium-magnesium-bicarbonate type.
In the immediate Prince George area, some ground water quality analyses from higher capacity wells located within the valleys of the Nechako and Fraser Rivers, show hard water in the range 180 mg/L to 400 mg/L (as Ca CO3) also a manganese concentration of 0.1 mg/L has been reported in this area. The manganese concentration here is above the maximum 0.05 mg/L objective set in the Guidelines for Canadian Drinking Water Quality 1989. Total dissolved solids vary from 150 mg/L up to 680 mg/L.
West of Prince George, at Vanderhoof, analyses show ground waters vary from moderately hard, 130 mg/L (as Ca CO3), to very hard, 330 mg/L (as Ca CO3). Dissolved mineralization is of the calcium-magnesium-sodium-bicarbonate-sulphate type.
South of Prince George at Red Rock, a ground water field analyses indicates a very hard water, 400 mg/L (as Ca CO3), and a high concentration of dissolved mineralization of 550 mg/L. This analyses showed a calcium-magnesium-bicarbonate-sulphate type ground water.
At Quesnel, records of analyses from several older city water supply wells located near the Fraser River, show the ground water to be moderately hard, 110 mg/L (as Ca CO3), moderately mineralized, 135 mg/L, and the dissolved mineralization to be of the calcium- magnesium-bicarbonate-sulphate type. Near Dragon Lake, at Quesnel, very hard ground water of 600 mg/L (as Ca CO3), and an iron concentration of 0.9 mg/L have been reported.
Further south at Australian on the east side of the Fraser River, hard ground water, 245 mg/L (as Ca CO3) and dissolved mineralization of the calcium-magnesium-bicarbonate type have been reported.
At Williams Lake ground water analyses taken from a high yield well on Scout Island, show the water to be very hard 330 mg/L (as Ca CO3) and highly mineralized 410 mg/L. The dissolved mineralization is of the calcium-magnesium-bicarbonate-sulphate type.
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