The Salt Wedge and Delta’s Agricultural Water Supply
Note to Reader:
Food security, protection of agricultural lands and water use are issues facing BC. In December 2015, the Feast AND Famine Workshop will address this question: How will water supply and agriculture be affected by rising sea levels and a changing climate in the Fraser Delta? To download a copy of the Program Overview, click on Feast AND Famine! – Solutions and Tools in Response to a Changing Climate.
Salt Wedge Changes with Tides and Seasons
“The ‘salt wedge’ is a phenomenon that occurs in all tidal estuaries of the world. Salty and dense ocean water entering the river mouth forms an underlying wedge beneath the lighter fresh water that is exiting. Water that is high in salinity (salt levels) can reduce or destroy crop yields, affect aquatic ecosystems and damage infrastructure,” wrote John Ter Borg in an article published in the Delta Farmer’s Institute Newsletter. The article is about his research findings for the Master of Land and Water Systems program at the University of BC.
“The distance that the salt wedge extends up the river changes with the tides and the seasons. During the spring snowmelt the river is high and the toe of the wedge stays near Steveston. During the late summer river flows are low and the salt wedge reaches Annacis Island. The elevated salinity levels impact the quantity of water available to local agriculture irrigation intakes.”
Potential for Unintended Consequences
“Climate models predict warmer, longer, and drier summers. This means that farms within the Lower Fraser River will require more irrigation water in the future. Local sea level is predicted to rise and may contribute to an increasing quantity of salt water pushing up the river. In addition, changes to river hydrology may occur due to the removal of the George Massey Tunnel, possibly further increasing salinity levels,” states John ter Borg.
“My Feast AND Famine Workshop presentation will provide an overview of the potential issues and the impact of changes in river hydrology and salinity on fresh water irrigation intakes and the agricultural water supply in the Fraser Delta.”
“Tunnel removal has been likened to removing a dam that currently restricts the intrusion of the salt wedge up the river. Existing salinity data for the Lower Fraser River is not sufficient to assess the impacts resulting from replacement of the tunnel with a bridge. The Delta Farmers Institute is working with other river user stakeholders to develop a salinity benchmarking study that would help to inform the decision process.”
To Learn More:
To download and read the complete article as published (on page 3) in the Delta Farmer’s Institute Newsletter published in October 2014, click on The Salt Wedge and Delta’s Agricultural Water Supply.