Water Supply and Treatment

Our mandate is to provide and sustain an adequate supply of good clean water, now and into the future. This is made possible through the development and use of programs that include long-range planning, system operation, system maintenance and capital works. 

Jump Lake Reservoir

Most of us seldom consider where our water comes from or how, but the reality is, as our population grows, so does our demand for water. We therefore need to carefully manage and wisely use our water.

Our Water Source

Jump Lake Earth Dam

Our water begins with water that flows through mountain rivers, streams and creeks in the watershed of the South Fork of the Nanaimo River. Covering 230 square kilometres, an area three times the size of the City of Nanaimo, the watershed is located 20 kilometres south west of the City.

Two large storage lakes, Jump Lake and South Fork Lake, collect water, rain and snowmelt flowing from the mountains. The watershed is protected and access is strictly limited to safeguard our water supply from human contamination and other pollutants. Since the watershed is privately owned, a partnership between the City and Island Timberlands was formed to protect the source and quality of our water.

Water is transported to the City of Nanaimo, the Snuneymuxw first nation and the Community of Extension through a complex network of dams, supply pipelines, the South Fork Water Treatment Plant, balancing reservoirs, pumping stations and distribution mains.

South Fork Lake Reservoir

Dedicated staff work to ensure an adequate, safe supply of water. Nanaimo’s water system is operated on a self-sustaining basis. Current water rates and development charges cover water usage, the maintenance of existing facilities, new capital projects to sustain growth, and the administration of water regulations. Water supplied to our customers is metered individually and rates are set in an expanding block rate to promote water conservation.

Water Management since 1879

South Fork Dam and Fisheries Release

Nanaimo’s first public water system began just five years after the City was incorporated when, in 1879, the Vancouver Coal Company built the first wooden pipes to deliver water to the public from a spring on Wesley Street.

Significant progress was made when the City acquired water licenses for the Nanaimo River and built the South Fork Dam in 1930, setting a new benchmark for the public water utility. The concrete arch dam, which measures 50 metres across, stands 30 metres high and retains nearly 2 million cubic metres of water in South Fork Lake.


From the South Fork Dam, the water supply travels through parallel pipelines. The smaller of the two (a 750 mm diameter steel pipe) was constructed in 1954 and supplies up to 50,000 cubic metres of water per day. As demand increased, a second larger pipeline (a 1,200 mm diameter steel pipe) was constructed in sections, on an as-needed basis. Completed in 1993, this pipeline increased the volume capacity to 240,000 cubic metres per day.

Treatment Plant Pipeline

Jump Lake Dam

Jump Lake Flood Gates

Keeping pace with Nanaimo’s growth and increased requirements for water, the Jump Creek Dam was constructed above the South Fork in the early 1970’s. Floodgates were added to the dam’s spillway, which increased storage by 50%, to a total of 17 million cubic metres.

This addition allowed the smaller downstream dam to maintain full reservoir storage during peak summer periods. In addition, snow-pack and rainfall information is monitored by two automated measuring systems located in the watershed. This information is used to forecast stream flows and regulate the floodgates for summer storage.

Additional Storage 

Nine balancing reservoirs are located throughout the city to meet peak domestic demand and emergency fire flows. Emergency fire flows can exceed supply system capacity and draw reservoirs down for several hours. To serve the growing north end of the city, the first balancing reservoir was constructed at Lost Lake in 1969, followed by reservoirs at College Park and Rutherford Road. Additional reservoirs and pipelines were built at Duke Point Industrial Park, Langara Drive, and Tanya Drive to meet heavy growth in the 1980’s.

Jan. 2011 Weather Station 030
Reservoir No. 1

Continued growth of the City’s population resulted in the construction of another new reservoir in the village of Extension in 2010. More recently in 2014, the City replaced the open reservoir on Nanaimo Lakes Road with a new reservoir and energy recovery facility. The City generates revenue daily by selling electricity back to BC Hydro as the reservoir fills up with potable water. In April 2016, the City officially opened the South Fork Water Treatment Plant.

Last updated: November 29, 2022

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