The ebb and flow of water in the Salmon River

By David Clements

When rainy days stretch into weeks, water quantity may seem like a non-issue here in the Lower Mainland. However, water does ebb and flow with the seasons and with human impacts on the water supply. Runoff from the heavy rains we get every fall and winter can be damaging to the environment, especially when excessive pavement and other impervious surfaces disrupt normal flows. In the summer months, water actually becomes scarce here, and if not conserved, salmon rearing streams can become death traps. The salvation of streams during these dry times is often provided by underground water reservoirs called aquifers.

Let us begin by looking at the mysterious supply of water that lies below the surface. Of course, we can never really see the water that exists in the aquifers, but we draw on this resource directly when we dig wells, and indirectly in many other ways. In Langley�s largest watershed, the Salmon River, which is home to approximately 14,000 people there are three aquifers , namely  Aldergrove, Hopington and Fort Langley. The largest of the three, the Hopington, is composed of up to 30 m of sand and gravel deposits. This aquifer is not confined by low permeability sediments, which means that is more vulnerable to pollution than a confined aquifer such as the Aldergrove aquifer.

Coghlan Creek, which runs into the Salmon River in Williams Park, is largely fed by water from the Hopington Aquifer. In the summer, fish get both the benefit of abundant water and the benefit of water that is cooler than the sun heated surface waters. The summer is also the season when the aquifers are tapped for crop irrigation. Although this agricultural practice may reduce the amount of water in the aquifers, the other side of the coin is that agricultural land is less disruptive of the mechanisms that recharge aquifers than urban land. An important pathway for water to take to get to the river when heavy rains come is through the ground, through a process called infiltration. Healthy soil and vegetated surfaces maintained through sound agricultural practices, allow the slow infiltration of water into the aquifers. Agricultural land with abundant vegetation along the river banks and a minimum of paved and other hard impervious surfaces discharges water in the river gradually and does not affect fish in a negative manner. If instead, changes in the landscape cause water to flow directly and rapidly into a river, the sudden influx of water can damage not just the river banks but also fish and other organisms living in the river.

If urban development must take place, it should be designed to minimize the area of impervious surfaces. If water is allowed to flow into grassed ditches or swales, rather than into storm sewers via curbs, large pulses of water entering rivers can be reduced. Avoiding wide roads and convoluted traffic patterns reduces the overall paved area. At present, road systems in the vicinity of the Hopington aquifer in Langley do follow these guidelines for the most part. There are many ways in which residents can contribute further to the healthy landscape of the watershed. For example, redirecting downspouts on to the property, rather than into gutters that lead to storm sewers would reduce the pulses of water entering the river.

The Salmon River watershed is the largest watershed in Langley, and it is sometimes hard to comprehend that activities on one part of the river can have effects many kilometres away, as the river stretches from Aldergrove (and beyond) to Fort Langley. In the lower Salmon River near the mouth, there are large areas of productive farmland and also golf courses that can be impacted by excess flows. Several years ago some work was done to manage flooding through the Davidson Ditch channel works. In April 1998, the upgraded pump station at the mouth of the Salmon River was officially opened. This project was financed by the Township of Langley, and by several other groups interested in flood control including the Fort Langley Farmers Association and Belmont Golf Course. The new pump has the two-fold advantage of being fish-friendly (a large number of fish were killed by the old one) and having better potential to regulate water levels. The capacity of the pump station, however, is dependent on careful planning for the entire watershed, such as designing roads and subdivisions to minimize large pulses of water moving downstream.

Other common sense measures can be followed throughout the year to conserve water. When my children leave the tap running too long, we always say �Save some water for the fish!� Indeed, there are times, especially during our dry summers, when we all can do more to conserve water. Without water being metered in our area, we may tend to take this precious resource for granted. A recent study noted that the level of the Hopington aquifer might be in decline. Water is a precious resource and if we are really concerned about the long-term economy of the Langley area, we need to be planning for the future availability of water for agriculture, for residents, and for the fish and wildlife that live here with us. The Salmon River watershed presently supports a healthy run of several thousand coho salmon that spawn in the river each fall. To keep this thriving river alive, we need to plan comprehensively for the entire landscape that the water flows over and under.

The Salmon River Watershed Management Parnership (SRWMP) is in the process of developing a plan, not only for water supply, but for all of the issues that affect the watershed. 

For additional information, contact the SRWMP coordinator, Andrew Appleton: [email protected]