Water Stewardship Information Sources
| Citation | GW Solutions Inc and VIU. 2009. RDN Electoral Area A: Groundwater Assessment and Vulnerability Study. Prepared for Regional District of Nanaimo. |
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| Organization | Regional District of Nanaimo |
| URL | http://www.southwellington.com/ocp_review-docs/Area-A-Groundwater-Assessment-2009.pdf |
| Abstract/Description or Keywords | This study has shown that the surface water and groundwater regimes in Area A are very complex, and still not very well understood. An overview of the data gaps indicates that work is still required to better define the water demand, the water supply, the interaction between surface water and groundwater, the aquifers, the water quality, and sensitive ecosystems. The following summarizes the results of the completed groundwater assessment and vulnerability study: 1. Area A includes three main groundwatersheds, referred to as Zone 1, 2, and 3. Zone 1 includes the lower section of Haslam Creek and the Nanaimo River. These river systems are very dynamic, transporting large amounts of water. They occupy the western half of Area A and discharge to the Nanaimo River Delta. Much less water movement occurs in the eastern half of Area A (Zone 2) because it consists predominantly of a flatter region where most of the water flows through a bedrock aquifer towards the Strait of Georgia. The southern tip of Area A (Zone 3) discharges south to Ladysmith Inlet. The following paragraphs summarize the water dynamic in these zones and identify the critical conditions. Water Dynamic ! Zone 1: Covering over 4500 ha, Zone 1 includes the Cassidy Aquifer (Aquifer 161, unconfined), and the Lower Cassidy confined aquifer (Aquifer 160). These two sand and gravel aquifers are collectively up to 30 m thick and are very productive. Zone 1 also includes the South Wellington bedrock aquifer, where residential wells of much lesser yield are located. The Cassidy Aquifer is closely connected to the Haslam Creek and the Nanaimo River. A gauge located just at the western boundary of Area A on the Nanaimo River reports flows ranging between 1 m3 /s and 1300 m3 /s. The water balance reflects the role played by the Nanaimo River: it is estimated that the river flow corresponds to 95% of the water transferring through Zone 1. Precipitation, with an approximate amount of 1 m per year, is the main water input. Groundwater will also reach zone 1 through its western boundary, but at a rate estimated to be 13% of the precipitation. ! Zone 2: Covering over 1700 ha, Zone 2 is predominantly composed of the Cedar, Yellow Point, North Oyster bedrock aquifer (Aquifer 162), and the Cedar, North Holden Lake confined overburden Aquifer (Aquifer 163). In the uplands, water will converge to local depressions. Otherwise, water will discharge to the Strait of Georgia, mostly as groundwater flowing through the bedrock fractures. Compared to Zone 1, water movement is much less dynamic. The volume of water transferring through Zone 2 is estimated to be only 1% to 2% of the water transferring through Zone 1. ! Zone 3: With over 1400 ha, it only covers 2% of Area A, south of the Nanaimo Airport. It corresponds to part of Area A where water drains south, predominantly as groundwater, through the Cassidy and Lower Cassidy Aquifers, towards Ladysmith Inlet. Water Use and Water Balance ! Zone 1: The aquifers provide water for residential, agricultural, commercial, and industrial use. Harmac is the largest water user and extracts an estimated total of 136,500 m3 /day (82,000 m3 /day from a well field and 54,500m3 /day from a surface water intake in the Nanaimo River). This water is removed from the Nanaimo River watershed to supply Harmac facilities, located outside of this watershed. The volume used by Harmac is equivalent to the total amount of the yearly precipitation over Zone 1. The second largest water user is the NCID, which, with 1240 m3 /day, represents 0.03 % of the water output for Zone 1 and approximately 1% of the water extracted by Harmac. The total use from the remaining users (residential properties and small systems) is equivalent to the use of NCID. ! Zone 2: Water input is solely precipitation, with the exception of water import via water delivery (trucked water). Evapotranspiration represents the largest water output in Zone 2 (62% of water input), followed by discharge to the foreshore (47% of water input). Water use for residential purposes represents a small percentage of the water balance (1%). ! Zone 3: The main elements of the water budget in Zone 3 are natural inputs and outputs. Groundwater extraction attributed to human activities represents a small percentage of the output (less than 1%). |
| Information Type | report |
| Regional Watershed | Vancouver Island South |
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| Comments | |
| Project status | complete |
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