experimental watershed liming study: comparison of lake and watershed neutralization strategies

The Experimental Watershed Liming Study (EWLS) was initiated to evaluate the application of CaCO3 to a forested watershed in an effort to mitigate the acidification of surface water. The objective of the EWLS was to assess the response of the Woods Lake watershed to an experimental addition of CaCO3...

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Bibliographic Details
Published in:Biogeochemistry 1996-03, Vol.32 (3), p.143-174
Main Authors: Driscoll, C.T, Cirmo, C.P, Fahey, T.J, Blette, V.L, Bukaveckas, P.A, Burns, D.A, Gubala, C.P, Leopold, D.J, Newton, R.M, Raynal, D.J, Schofield, C.L
Format: Article
Language:English
Subjects:
acid deposition
calcite
Chemical bases
Forest soils
Groundwater
Lake water
Soil chemistry
Soil water
Streams
Surface water
Water treatment
Watersheds
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Summary:The Experimental Watershed Liming Study (EWLS) was initiated to evaluate the application of CaCO3 to a forested watershed in an effort to mitigate the acidification of surface water. The objective of the EWLS was to assess the response of the Woods Lake watershed to an experimental addition of CaCO3. During October 1989, 6.89 Mg CaCO3/ha was applied by helicopter to two subcatchments comprising about 50% (102.5 ha) of the watershed area. The EWLS involved individual investigations of the response of soil and soil water chemistry, forest and wetland vegetation, soil microbial processes, wetland, stream and lake chemistry, and phytoplankton and fish to the CaCO3 treatment. In addition, the Integrated Lake/Watershed Acidification (ILWAS) model was applied to the site to evaluate model performance and duration of the treatment. The results of these studies are detailed in this volume. The purposes of this introduction and synthesis paper are to: 1) present the overall design of the EWLS, 2) discuss the linkages between the individual studies that comprise the EWLS, and 3) summarize the response of the lakewater chemistry to watershed addition of CaCO3 and compare these results to previous studies of direct lake addition. An analysis of lake chemistry revealed the watershed treatment resulted in a gradual change in pH, acid neutralizing capacity (ANC) and Ca2+ in the water column. This pattern was in contrast to direct lake additions of CaCO3, which were characterized by abrupt changes following base addition and subsequent rapid reacidification. Over the three-year study period, the supply of ANC to drainage waters was largely derived from dissolution of CaCO3 in wetlands. Relatively little dissolution of CaCO3 occurred in freely draining upland soils. The watershed treatment had only minor effects on forest vegetation. The watershed treatment eliminated the episodic acidification of streamwater and the near-shore region of the lake during snowmelt, a phenomenon that occurred during direct lake treatments. Positive ANC water in the near-shore area may improve chemical conditions for fish reproduction, and allow for the development of a viable fish population. The watershed CaCO3 treatment also decreased the transport of Al from the watershed to the lake, and increased the concentrations of dissolved organic carbon (DOC) and dissolved silica (H4SiO4) in stream and lakewater. The watershed treatment appeared to enhance soil nitrification, increasing concentratio
ISSN:0168-2563
1573-515X
DOI:10.1007/bf02187137