Continuing our quest for viable restoration options for Lac La Nonne to improve water quality and reduce algal blooms, on Dec 4, 2006 environmental specialists from: AENV – Alberta Environment, ASRD – Alberta Sustainable Resource Development, AAFRD – Alberta Agriculture, Food & Rural Development. AAFC-PFRA – Alberta and Agri-food Canada – Prairie Farm Rehabilitation Administration, Cows and Fish – Alberta Riparian Habitat Management Society, Living by Water – Federation of Alberta Naturalists, and Aquality Environmental Consulting Ltd. met with members of Lac La Nonne Enhancement and Protection Association in a brainstorming workshop. Participants shared current knowledge of the state of the various components of the Lac la Nonne watershed and identified sources of nutrients (nitrogen and phosphorus) e.g. Pesticides, fertilizers, manure and human sewage. Much of this data was collected during the Stream Sampling Programs and from work carried out by the attending individuals in the watershed. In addition to external sources of nutrients it was identified that at present 70% – 80% of the loading in Lac La Nonne is self-sustaining internal loadings. In August 2007 a Nutrient Reduction Feasibility Study was contracted to Aquality Environmental Consulting Ltd. to expand upon the recommendations of the workshop and explore the viability of each.
Some options being considered:
• Reduction of External Loading: Reducing the input of nutrients from the watershed using various methods such as restoration of riparian areas i.e. 3 BMP Projects have been established on inflow streams to Lac La Nonne including preservation of a natural wetland on southern stream.
• Vacuum Dredging: Mechanical removal of phosphorus rich bottom sediments to prevent further release of phosphorus during anoxic conditions – coring samples and a Paleolimnology Study is being carried out by U of A Environment personnel & PHD students. Further coring is required to map lake loading. A committee is looking into available grants.
• Treatment with Ferric sulfate: Addition of iron salts to mix with upper level of phosphorus in lake bottom to provide a natural barrier to nutrient release from sediment. – A study is underway by a U of A Environment graduate student to determine compounds, quantity, and effects of applying ferric oxidesto lakes in watershed.
• Hypolimnetic Circulation: The use of bubblers or circulators to disrupt stratification, which will prevent anoxic conditions.
A multi-pronged approach addressing land use, external loading, point sources, riparian health and internal nutrient loading is being considered in deciding the most appropriate method. It is hoped that these restoration efforts will improve the health of the lake for current users and future generations even in the face of increasing development pressures around the lake.
Cultural eutrophication is a phenomenon in lakes where nutrients such as phosphorus have entered into lakes through leaky septic tanks, fertilizers and other human activities on shoreline and supply streams. University of Alberta PhD student Diane Orihel’s, solution involves a two-tiered approach: reduce phosphorus from entering the water externally and inhibit internal phosphorus loading by adding iron to the lake water. Orihel and her team introduced different levels of iron (ferric chloride) into the 15 floating plastic cylinders, called mesocosms, which extend to the bottom of the lake. Sampling will resume once the ice leaves Nakamun Lake
“The preliminary data from the mesocosm experiment on Nakamun Lake looks very promising! The iron treatments did indeed slow phosphorus release from sediments during the summer (but I don’t yet have data back from the lab as to what happened beyond the end of August). After a discussion with my University of Alberta supervisor, we decided to freeze the mesocosms into the ice so we can assess what happens under winter ice (mesocosms have been flagged and a snow fence will be put up to prevent snowmobilers from running them over). We have received word from AWRI that they will provide funding for the project.”