Ground Water Resources of British Columbia
Chapter 8 — Ground Water Regions of British Columbia
by
J.C. Foweraker
8.1 CLASSIFICATION OF GROUND WATER REGIONS
In order to describe the ground water resources of British Columbia, the province has been divided into nine ground water regions which are classified in relation to the physiography as described by Holland (1964). About 90% of the area of British Columbia lies within three physiographic divisions namely:
- the Western Systems
- the Interior System
- the Eastern System
The remaining 10 percent of the area of British Columbia lies within a fourth physiographic division called the Interior Plains.
These physiographic divisions or systems (Figure 8.1), form one part of the main framework for the classification of ground water regions and sub-regions, details of which are given in Table 8.1 .
Figure 8.1 Physiographic divisions
The Western System in British Columbia includes all that part of the province lying west of a rather sinuous line running northward from Keremeos through Lytton to Smithers and thence to Telegraph Creek and Atlin (Holland 1964).
The Eastern System lies along the eastern side of the Rocky Mountain Trench and along the eastern side of the Liard Plain. Within British Columbia northwest of the Narraway River, the Eastern System is bounded on the east by the Interior Plains.
Between the Coast Mountains of the Western System and the Rocky Mountains of the Eastern System, lies the Interior System.
The Interior Plains occupy the northeast part of the province.
The other main part of the framework for the classification of ground water regions and sub-regions given in Table 8.1, consists of three major divisions of physical features found in the province, mainly:
1. basins, lowlands and plains
2. plateaus and highlands
3. mountains
Table 8.1 provides provides a detailed breakdown of the ground water regions and sub-regions adopted in this classification. These are covered in detail in Chapters 9, 10 and 11. The order of presentation for each ground water region and sub-region in Chapters 9, 10 and 11 is also given in Table 8.1.
Figures 8.2 to 8.8 show the boundaries of the ground water regions and sub-regions.
Figure 8.2 Ground water regions
Figure 8.3 Coastal Basins, Lowlands and Plains ground water region
(south half)
Figure 8.4 Coastal Basins, Lowlands and Plains ground water region
(north half)
Figure 8.5 Interior Basins and Plains ground water region
Figure 8.6 Fraser Basin ground water subregion
Figure 8.7 Ground water regions of the Plateaus and Highlands
Figure 8.8 Mountain ground water regions
8.2 DESCRIPTIVE COMPONENTS OF GROUND WATER REGIONS
Where information is available, each ground water region or sub-region described in Chapters 9, 10 and 11 contains all, or at least some of, the following descriptive components. (The descriptive components have been adapted from Heath, 1984).
1. General Setting:
Highlights of the physiographic, hydrologic and geologic framework of the ground water systems within the sub-regions.
2. Important Aquifers:
Comments on the locations, geology, hydrogeology, ground water quality and use of the aquifers.
3. Withdrawals and Quality Trends:
Comments on location and purpose of major ground water withdrawals and long-term trends in water levels and ground water quality
4. Other Aquifers / Underdeveloped Aquifers:
Comments where information is available.
5. Maps and Schematic Cross-sections:
Areal distribution of principle developed aquifers and other aquifers, within a sub-region. Generalized schematic cross-sections.
8.3 IMPORTANT AQUIFERS IN BRITISH COLUMBIA
Much of the information on ground water resources in the province which is outlined in Chapters 9, 10 and 11 is to a large extent confined to the ground water regions and sub-regions where known major aquifers occur. These are the areas where major development of ground water has taken place and where information from well drilling records, hydrogeology, ground water potential, and ground water quality is more readily available.
The following are some brief introductory comments on these important aquifers in British Columbia with examples of individual well yields from Foweraker et al (1985). The reader may also refer to the glossary at the back of the publication in Appendix 1 for definitions of terms used.
On the west coast of the province between the Coast Mountains and the Vancouver Island Mountains and the Queen Charlotte Island Mountains lies the Coastal Trough. High capacity wells have been completed within the sub-till sands and gravels and in alluvial deposits near rivers, in the lowlands of this region. (Figure 8.9, Table 8.2, Site Nos. 1 and 2).
Only limited ground water storage is available during dry summer periods in many coastal areas where wells must be completed in fractured bedrock and well interference problems and high chloride content occur in a few production well operations. Yields of over 6.0 L/s have been obtained, however, from several bedrock wells in granite, for irrigation and municipal use, and one well completed in granite on Saanich Peninsula (Kohut et al 1983) produces 15.8 L/s (Figure 8.9, Table 8.2, Site No. 3). The largest settlement on the Queen Charlotte Islands is supported from water from wells in fractured rock.
In the Fraser Lowland, high capacity wells have been completed in many areas in unconsolidated deposits which are commonly greater than 180 m thick and may reach thicknesses of 300 m. A production well at Abbotsford for example, has a capacity of 158 L/s (Figure 8.9, Table 8.2, Site 4).
Between the Coast Mountains on the west and the Rocky Mountains on the east lies the Interior System of mountains, plateaus, basins highlands and in the south intermountain valleys (Figure 8.9). Unconsolidated deposits consisting of glacial, glacio-fluvial, lacustrine and alluvial materials mantle much of the lower slopes and floors of the intermountain valleys and testholes have recorded thickness of up to 579 m in these materials with aquifer thicknesses of 244 m recorded at one site. Within these materials high capacity community water supply wells and irrigation wells have been completed (Figure 8.9, Table 8.2, Sites Nos. 5 to 11). Individual specific capacities of some large irrigation wells completed at Keremeos are in the range 30 L/s/m to 66 L/s/m of drawdown and interference effects 23 m away are as low as 0.6 m.
On the Fraser and Nechako Plateaus in the central part of the province within the Interior System are found flat lying Tertiary lava flows. Well yields up to 1.6 L/s can be obtained from these lava in some areas while a yield of 11 L/s has been recorded in one well (Figure 8.9, Table 8.2, Site No. 12). However, to date there has only been limited exploration for, or exploitation of, ground water in the Tertiary volcanic lava flows.
Dissected into these plateaus is an area called the Fraser Basin. This basin has considerable ground water potential (Figure 8.9, Table 8.2, Site Nos. 13 to 17). At Fort St. James for example, a high capacity well was completed at a depth of 100 m. When initially completed this well had a free flow of 265 L/s, while at Vanderhoof a well 183 m deep free flows at 69.4 L/s. Transmissivity of the aquifer has been recorded at 1.4 x 10-2 m2/s at Vanderhoof.
Within the Alberta Plateau area in the northeast part of the province well yields are commonly reported to range between 0.4 L/s and 0.8 L/s in both bedrock and surficial deposits. One well has a reported yield of over 7.6 L/s. Buried valleys with sand and gravel deposits locally form limited aquifers.
Outside of these major developed aquifer zones the ground water potential is in many areas largely unknown and this is reflected in the minor coverage which is given to several of the ground water regions and sub-regions in Chapters 9, 10 and 11.
Figure 8.9 Important aquifers in British Columbia
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