Nelson city council has developed a contingency plan in case of an emergency water shortage.
Public works manager Colin Innes is leading the development of a small water treatment system to be installed in the city somewhere on the lake shore. It would treat water for a portion of the city — the lower part that would not require uphill pumping.
Introducing lake water into the city water mains without treating it would create the need for a boil water advisory, Innes said.
The treatment plant, consisting of pumps, filters, and chlorine mixing equipment, would cost upwards of $250,000 and city manager Kevin Cormack says this money is available in the current water budget. Innes says the proposal will go before council within the next couple of months and the plant would, if approved, be built in the spring.
The idea for an emergency water treatment plant has been around since the city wrote its water master plan in 2006, but Innes says that because of this past year’s water shortage, “it has been pushed to front burner.”
Nelson gets its water from Five Mile Creek and secondarily from two other creeks that originate in West Arm Park that are not glacier-fed but depend on annual precipitation. This past spring and summer, low precipitation and high temperatures resulted in a low supply of water and heavy use by residents until water restrictions were imposed in the summer. Those restrictions continue.
“We have got a quarter of the water normally available at this point in the year but we are able to meet the demand,” Innes says. “But we have very little extra.”
The chart accompanying this story shows the water available from the creek for each of the past four months, the average amount for each month going back to 1984, and the amount actually used by the city for each month. Most notable are the differences between the average availability over the years compared to this year (columns 1 and 2) and the small gap between this year’s availability and this year’s use (columns 2 and 3).
Innes added that if the city had not been making repairs to leaky water mains since 2006 we would already be running out of water.
Asked by email if water volumes were ever taken into account when deciding on new housing developments which would perhaps increase water demand, Cormack replied: “Water supply has not been identified as a restriction to growth in the past. Secondary source has always been identified as insurance against the loss of Five Mile due to slide or wildfire and resiliency to the potential impact of climate change.”
| City of Nelson water availability and use, in megalitres per day | |||
| 2015 creek discharge | |||
| July | 13.6 | 139.1 | 12.6 |
| August | 6.2 | 34.6 | 8.0 |
| September | 7.2 | 25.9 | 5.1 |
| October | 7.3 | 31.9 | 5.1 |
| Source: City of Nelson | |||