Heather J. Cross
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泭
M. Sc. Thesis
Natural and Manmade Variations in Groundwater Flow and Chemistry in the Birch Cove and Sackville Areas of Halifax County, Nova Scotia
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This study discusses the groundwater flow and quality in the Birch Cove and Sackville area of Halifax County, Nova Scotia, as related to geology and urban influence.
The groundwater flow systems are controlled by both the bedrock topography and the northeast striking joints in both areas. In Birch Cove, local flow systems predominate. In Sackville, a regional flow system exists in the bedrock, with local flow systems in the surficial material superimposed on it; the influence of groundwater from the surficial material recharging the bedrock aquifer can be seen by the high bicarbonate concentrations in some samples from wells completed in bedrock. The groundwater flow systems as determined from water table elevations are complemented by the results of chemical variation in the groundwater.
Seasonal responses in groundwater chemistry vary widely, but the magnitude and smoothness of the variation depends on well depth and the amount of overburden. Time lags in the order of 3-4 months were found for chloride and 6-8 months for nitrate. Some marked effects on groundwater chemistry and temperature were found to be associated with biological activities and permeability differences in the rock mass.
One result of urbanization is the presence of road salt in groundwater. In Birch Cove, salting effects were most apparent in wells close to the road and were apparently independent of well depth because of the predominance of steeply dipping joints in the bedrock and the lack of appreciable overburden material. In Sackville, salt effects were most noticeable in shallow dug wells, while drilled wells completed in bedrock were for the most part protected by the generally thick glacial till cover in the area. Many of these dug wells were put in before proper constructions regulations were available.
Another effect of urbanization is the presence of detergent in the groundwater. The magnitude of this problem is not considered in depth in this study, but is presently being studied by the Nova Scotia Department of Environment.
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Supervisors: / H. B. S. Cooke