Jillian Haynes

B.Sc. (Honours) Thesis

WHAT IS THE DOSAGE OF POWDERED LIMESTONE NEEDED TO RAISE WATER QUALITY TO WITHIN TARGET LEVELS IN SOUTHWESTERN NOVA SCOTIA?

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Acidification is a great problem for freshwater systems in Eastern Canada, but especially for Southwest Nova Scotia (SWNS) (Stoddard et al., 1999). This region’s granite and slate bedrock is low in base cations (Ca2+, and Mg2+) and weathers slowly, which leads to low Acid Neutralizing Capacity (ANC) in the soil produced from the weathering of this parent material (Clair et al., 2007). In turn, low ANC of soils give rise to low base cations in soil water, leading to surface waters that cannot effectively buffer acidic inputs (Clair et al., 2007). Chronic acidification was identified as a main cause of extirpation of Atlantic salmon (Salmo salar) during the 1980s and 1990s (Clair et al., 2004; DFO, 2013; Sterling et al., 2014-a). Population modelling suggests two of SWNS’s larger Salmo salar populations have a high probability of extirpation (87 and 73 %) if habitat improvements are not made within the next 50 years (DFO, 2013; Sterling et al., 2014-a). Liming, the introduction of base cations via limestone or dolomite to an acidified catchment, has proved to be an effective mitigation strategy in Norway and Sweden (Brown, 1988). While there are many types of liming methods used for mitigation of freshwater acidification, one of the most promising types is terrestrial liming (Sterling et al., 2014-a). Terrestrial liming studies in Sweden and Norway have had success in improving water quality in multiple catchments for over a year. Two experimental terrestrial liming studies are conducted within SWNS; a BACI analysis is chosen to determine if terrestrial liming can improve water quality in SWNS catchments, with the overall goal to determine a range of doses for effective terrestrial liming in NS. In-situ pH trends increase over time for each individual study. Similarly, Ca concentrations increase throughout each study period, while DOC levels in both studies decrease over time. Lastly, total Al levels remain fairly constant in Maria Brook, while slightly decreasing from June to September, 2015 for Ted Creek (the window of time used for analysis of terrestrial liming effects at Ted Creek). Therefore, terrestrial liming has been effective at improving water quality in both Maria Brook and Ted Creek, at least in the short-term. An in-stream liming dose of 375 t ha-1 used to maintain a ph of 6.0 in WRSH is converted into a terrestrial liming application rate of 0.012 t ha-1 yr-1; a reasonable rate for terrestrial liming standards. My research acts as a guideline for larger, future terrestrial liming projects in NS, and provides important information to stakeholders for the decision-making process regarding terrestrial liming. Helicopter application is recommended as the next step to better define the range of doses required for effective terrestrial liming in NS.

Keywords: watershed liming, terrestrial liming, catchment liming, recovery from acidification, effective liming, improvements in water quality
Pages: 72
Supervisor: Shannon Sterling