The provincial government has done comprehensive testing of the water in Shawnigan Lake several times in the last 40 years.
Dr Mazumder of UVic
Dr Mazumder and his group at UVic have been testing water quality in lakes around BC for many years. His presentation, given to the Shawnigan Watershed Watch group, is a little more pessimistic than the following Provincial reports.
Shawnigan Lake Water Quality Study 1984
This provincial study says, in the Summary: "Data were collected from 1977 to 1979 for a variety of parameters of water chemistry and biology at two deep water stations (main basin and south basin), as well as several shallow water stations, and the inflow streams."
Shawnigan Lake Water Quality Study 2004
A second provincial study has a series of recommendations:
- Ministry of Water, Land and Air Protection (WLAP) staff should continue spring overturn sampling, including water chemistry at multiple depths and biological parameters (chlorophyll a, phytoplankton, zooplankton).
- WLAP staff should conduct additional bacteriological sampling in 2004 to confirm results noted in this study. Efforts should be concentrated to areas in the lake within 10 m from domestic intakes as well as McGee Creek and the Shawnigan Creek inflow. Samples should be collected a minimum of five times in a 30-day period.
- WLAP should review and formalize the water quality objectives for Shawnigan Lake proposed by Nordin and McKean (1984).
- Support should be provided to organized lake stewards to continue with basic water quality sampling through the BC Lake Stewardship Society. Other activities for lake stewards could include monitoring of aquatic macrophyte growth and distribution, and tracking sportfishing catches to monitor fish populations, especially bass and trout.
- The Cowichan Valley Regional District should ensure residential and commercial land development within the watershed take into account the potential impacts on the water quality of any such activities. Appropriate best management practices and planning techniques should be applied to protect Shawnigan Lake for domestic purposes and other current and future water uses.
Water Quality Assessment and Objectives for Shawnigan Lake 2007
A second provincial study provided a series of water quality objectives - measured levels of nutrients, bacteria, cloudiness, etc - that if met would indicate that Shawnigan Lake water quality is satisfactory. We reproduce parts of the overview of that document. The report said that all measurements at that time fell well within the objectives.