Increased dredging of the Fraser River is expected to have a “substantial” impact on irrigation water for Richmond farms, according to a study by the Delta Farmers’ Institute.
The study assessed current salinity levels in the river and reviewed the impact climate change will have on water quality moving forward.
The study was intended to provide a baseline for the existing “salt wedge.”
The salt wedge is where salt water reaches up the river, at any given time of year. Too much salt and food crops will die.
The study indicates climate change can impact the salt wedge in two ways.
First, sea level rise will mean salt water will intrude further up the river. Second, less snowpack melt means the river will flow more slowly in the summer, allowing high tides to move further upstream. The study indicates that a 30 cm-rise in sea levels could reduce daily irrigation water availability, during low-river flows, by up to 25 per cent.
The study also looked at dredging scenarios. Deeper dredging would allow more ocean water to move up-river.
The study notes Port of Vancouver has publicly stated there are no plans for deeper dredging.
Farms along the river’s south arm in Richmond are particularly vulnerable to deeper dredging, as they can’t pull from the north arm.
“With this study, we now understand each of these issues and the sensitivity that the salt water wedge has to the different variables we are facing. The next phase of the work, the monitoring, will tell us under which circumstances we can expect to have a problem,” said cranberry farmer Bruce May.
