Water quality testing is an important diagnostic tool to help residents of Otter Lake determine the health of the lake. By systematic testing and monitoring over time, it is possible to evaluate if water quality is improving or declining. By selective testing at strategic sites water quality indicators can help determine the source or cause of contamination. The trophic status of a lake is an assessment of the enrichment levels contained in the water. Oligotrophic lakes are clear and deep with few nutrients. Eutrophic lakes are laden with nutrients which stimulate algae and plant growth. Mesotrophic lakes are in between these two extremes. Otter Lake generally exhibits the characteristics of a mesotrophic lake although the deep bathymetry of the central and southern areas of the lake is more typical of an oligotrophic lake. The development pressure is relatively high on Otter Lake with approximately 330 cottages, homes and commercial properties. As it relates to shoreline length, this is a much higher rate than other lakes in the Rideau Lakes area and indicates that factors such as septic system leaching, fertilizer application and shoreline erosion can have a greater collective impact. For the above reasons OLLA in conjunction with the Rideau Valley Conservation Authority RVCA) monitors water quality, notably coliform levels, phosphorous and nitrogen content and dissolved oxygen at least 3 to 5 times during the year at a number of test sites. The map on the right shows the location of the major OLLA test sites. Note that sites 05 and 06 represent the location of greatest water depth.

     OLLA and RVCA annually perform tests for coliform bacteria (specifically E. coli), phosphorus and nitrogen levels at several test sites throughout the summer.The results of all the testing performed in 2009 are shown in the table on the left. E. coli was generally low or not detectable at most sites tested. The exception being site 07 (Barker's Creek) The higher value at 07 may have resulted from excessive runoff from Barkers Creek due to heavy rainfall. The phosphorous levels were a little higher than last year at several sites tested, but this may again have been due to agricultural runoff resulting from heavy rainfall. The very high reading at 05 (a deep water site) in May by RVCA did not repeat in later tests at this same site and was therefore probably an anomaly. The low E. coli counts, an average phosphorus level of 13.3 µg/L and the average Secchi disk readings of almost 7 meters (a measurement of water clarity) indicates that the lake remains oligotrophic.
    For comparison, the table below shows the results of all testing performed in 2008. Total coliform levels were quite high at all sites tested, but exceptionally high at 07 (Barkers Creek), 11 (accessed from Rd O4) and 14 (off Moonlight Bay Campground). Fecal coliform counts were also quite high at sites 07 and 14. E. coli counts at site 07 were moderately high in July but dropped in August and September. The high coliform was probably due to soil bacteria being flushed into the lake by heavy rainfall. Total coliform levels were higher on most lakes in 2008.The phosphate levels at all sites were quite low and nitrogen was around 400 µg/L. The average phosphorous level for the year of 7.8µg/L indicated that the lake was oligotrophic.

     We also tested for lead in 2008 and found it to be virtually undetectable. In 2007 we tested for mercury, since in most Canadian fresh and marine waters, levels of total mercury (inorganic mercury plus methyl mercury and other organic forms) should be less than 20ng/L of water in Ontario and Quebec. However some considerably higher levels have been found in some areas. More information on mercury in lakes and rivers from the National Guidelines and Standards Office of Environment Canada is available here. Mercury levels were low or non detectable at the selected test sites.
     The complete water quality report for 2008 is available here in PDF format. Test data for previous years and the lake stewards reports which contain more details about testing and all results obtained, can be found on the important notices for lake residents page.
    In 2007 the Township of Rideau Lakes implemented a voluntary septic system re-inspection program. In all 100 homes and cottages in the township were scheduled for a re-inspection of there waste water disposal systems. Some of these would likely have been on Otter Lake.The re-inspection program report that was submitted to the Township by Jamie Saunders in January, 2007 is available here in PDF format. Note that the report is 30 pages in length, but does contain a lot of useful information. The Township is planning on implementing this program again in 2010.

• OLLA Home Page

• The OLLA Board of Directors

• OLLA Membership, Policies and Constitution

• Some information about Otter Lake

• Water quality monitoring

• Water level information

• Sustainable Lake Plan

• Maps, Aerial photos and Satellite Images of Otter Lake

• Useful Information

• Important notices for lake residents

• Other links that may be helpful