Turkey Lakes Watershed Study reference list: 1998

Same as 95-13 and 95-14, but covering the 1994 calendar year.

An assessment of the current status and trends in Canadian lake systems, and the predicted effect of emission controls required by the 1991 Canada/U.S. Air Quality Agreement. The TLW is included in the Algoma cluster. Modelling indicates that the number of damaged lakes (pH<6) will decline, but without further controls, sensitive ecosystems will continue to be damaged.Much of the information is based on the assessment presented in 97-03. The paper contains an extended abstract in French.

Following the Canada/U.S. Air Quality Agreement in 1991, sulphate deposition has been reduced, but in southeastern Canada where many lakes are acidified, lake acidity has not significantly improved. Results are presented from the Algoma lake cluster surrounding the TLW. Further controls will be needed to achieve lower chemical damage levels. This is a very brief summary of 97-03.

In central Ontario, 603 small water bodies (including some of the Turkey Lakes and others in the surrounding region) were monitored from 1988-1996 to determine their response to recent SO₂ emission reductions. DETECT software was used to look for significant monotonic trends. Sulphate concentrations declined in 27-56% of the lakes, base cations declined in 41-57%, but only 26-28% showed increasing trends for pH or ANC. Recovery of these ecosystems will depend on several environmental stressors, including acidification.

Critical S and N loads are formulated for Integrated Forest Study sites, (including the TLW), and data from Turkey Lakes and Huntington Forest in the Adirondacks are modelled for comparison using a steady-state mass balance approach. N leaching at the TLW site is accompanied by accelerated base cation leaching losses.

Critical loads were determined for 4 lake clusters in SE Canada (including an Algoma cluster that surrounds the TLW) using pH 6 as a damage threshold. Using damage versus deposition relationships, the critical load for Algoma was determined to be 8.0 kg wet SO₄ ha^-1·yr^-1. Wet SO₄ deposition currently exceeds critical loading by 9.2 kg wet SO₄ ha^-1·yr^-1, and modelling show that critical loads will be exceeded even after all SO₂ emission controls are implemented. The paper demonstrates the need for further controls on SO₂ emissions in North America.

The variability of N-export among forested catchments in the TLW is large. A rise in water table levels causing nutrients to be "flushed" from soils to surface water is important for explaining NO₃- export. Catchment specific "flushing" behaviours were quantified using the time interval required for a decline in N concentration to 37% of their initial concentration. Topography is postulated to be the key to flushing variability and export of NO₃-N. Additional research is needed to understand processing and export of DON.

The functional similarity concept was applied to the export of NO₃-N from catchments within the TLW. The similarity indices, which are topographically based, explained up to 58% of the export variance where base concentrations of NO₃-N were not elevated. Where catchments are functionally similar, dissimilar N-export responses can be accounted and responses in other regions can be generalized. The similarity indices captured NO₃-N concentrations exported from shallow flow paths but did not capture NO₃- exported from deep flow paths. Future similarity indices should include information about both flow paths.

The Turkey Lakes Watershed was used as a test region to examine variations in N export behaviour as a means of assessing N saturation in catchments. NO₃-N is the dominant N species, and export was seen to be regulated by a flushing mechanism related to topography. Results of modelling indicated that topography may be more important than landscape or other regional controls in influencing NO₃-N export behaviour.

This paper describes a new approach to integrated assessment modelling by providing an open architecture framework for linking models together in a decision support system, and to provide advice on Canada’s post-2000 emission control strategies for acid rain issues.

This report provides a brief, one-page summary of the many and varied scientific papers and reports produced by Environment Canada staff, as well as various collaborators in other federal and provincial agencies, universities and non-government organizations, as part of the Canadian Wildlife Service (Ontario Region) LRTAP program between 1980-1998. These publications often deal with various cross-cutting environmental issues and topics, although the primary focus has always been acid rain and ecological effects. Scientific results are reported on both abiotic and biotic processes, including aquatic resource risk assessment, toxicological considerations, limnological and other chemical characteristics, as well as broad food-chain relationships (aquatic invertebrates, fish, amphibians, waterfowl, wetland birds, small mammals, wildlife habitat), and predictive modelling and statistics. Annotations are provided for all peer-reviewed scientific papers, graduate theses, and technical publications totalling 58 individual entries, of which many summarize studies conducted wholly or in part in the Algoma region, including the TLW.

The TLW is one of the sites considered in a review of sulphur cycling in forests, and especially the impact of decreased sulphur inputs. Of 28 forested sites throughout the world, the TLW ranks eleventh in the magnitude of atmospheric S input. A useful comparison of TLW characteristics to those from other catchments.