{"id":9658,"date":"2024-08-30T23:52:46","date_gmt":"2024-08-30T23:52:46","guid":{"rendered":"https:\/\/versicolor.ca\/sandylakebedford\/?page_id=9658"},"modified":"2026-03-19T17:16:06","modified_gmt":"2026-03-19T17:16:06","slug":"addendum-1-trends-in-conductivity-salt-content","status":"publish","type":"page","link":"https:\/\/versicolor.ca\/sandylakebedford\/waters\/lakes\/limnol-profiles\/2024-limnological-profiles-return-to-historic-trends\/addendum-1-trends-in-conductivity-salt-content\/","title":{"rendered":"Addendum 1: Trends in Conductivity\/Salt Content"},"content":{"rendered":"

DRAFTING<\/em> Last Revision on Sep 8, 2024.<\/small><\/p>\n

NAVIGATION
\nwww.versicolor.ca<\/strong><\/a>
\n\"\"\/sandylakebedford<\/strong><\/a> Home Page for Sandy Lake & Environs (Bedford, NS)<\/small>
\n\"\"\/Surface Waters<\/strong><\/a>
\n\"\"\/Sandy Lake<\/strong> <\/a> A Draft report On the State of Sandy Lake\u2026Feb 21, 2021<\/small>
\n\"\"\/Limnological Profiles<\/a><\/strong><\/p>\n

Subpages:
\n\u2013 2023 Limnological Profiles, effects of episodic precipitation and occurrence of a Metalimnetic Oxygen Minimum<\/strong><\/a>
\n\u2013 2024 Limnological Profiles \u2013 return to historic trends<\/strong><\/a>
\n\u2013 \u2013Addendum 1: Trends in Conductivity\/Salt Content<\/strong><\/a> (This Page<\/strong>)
\n\u2013 \u2013 Addendum 2: On Wetlands<\/strong><\/a><\/p>\n

\n
\"\"<\/a>

Fig 1. Specific Conductivity values for surface\u00a0 water and deep-near-the-bottom water at Sandy Lake 1971 to 2024<\/strong>. In the lower figure the 2023 data are excluded and the averages between surface and deep samples are plotted. SPC is a measure of salt content – EC (salt) Notes.<\/a><\/p><\/div>\n

In my DRAFT Report On the State of Sandy Lake, the Historical Trends and its Future Trajectory (Feb 23, 2021) I commented under 4.3 Relevance of information gathered or made available after 2014, 4: Road Salts<\/a><\/em> (in summary):<\/p>\n

Rising levels of salt in Sandy Lake are highly concerning. Currently, levels are below the the CCME Guideline for long term exposure (120 mg\/L chloride) which is also the WQO for chloride cited by AECOM (2014) for Sandy Lake. There is some salt stratification and it appears to be intensifying with time. At some point salt stratification could impair normal spring turnover if it is not already doing so in some years.<\/em><\/p><\/blockquote>\n

Observations subsequent to that date for 2021, 2022, 2023 and 2024, plotted in the figures at top right, suggest a leveling off of conductivity values after 2017 and even a significant decline associated with the extreme precipitation in 2023.<\/p>\n

This may be attributable to two factors:<\/p>\n

(i) A leveling off of new development within the watershed<\/strong>. Approximately 0%, 21% and 25% of the watershed was developed in 1967, 1986 and 2014-2020 respectively (see Land Use<\/a>) and there have not been a major development within the last several years. It is well documented that in the Halifax Region, Watershed Land Use is a good predictor of the springtime concentration of chloride (Scott et al., 2019<\/a>; Bermarija et al., 2023)<\/a>, although Scott et al., 2019<\/a> would predict a substantially higher equilibrium (leveling off) value, circa 400 uS\/cm than we are seeing currently (circa 175 uS\/cm) – See Fig 2 below.
\n<\/em><\/p>\n

(ii) Reduced need for salting associated with warmer winters<\/strong>. I could not find figures for salt usage in Halifax, however winters have been warming sufficiently that “Halifax Regional Municipality employees will no longer test ice on lakes and ponds” (CTV News Jan 17, 2024<\/a>). Reduced salt usage would result in lower chloride values as a function of land use than predicted by Scott et al., 2019. – see Fig 2, below.
\n<\/em><\/p><\/blockquote>\n

\"\"<\/a>

Fig 2. Relationship of Chloride and\u00a0 EC to Percent Land Area Developed for Halifax region.<\/strong> Graph adapted from Fig 6 in Scott et al., 2019<\/a>. Click on image for larger version. The orange-filled rectangle shows where 30% Development (the approx. current level at Sandy Lake*) would fit on the Scott et al., 2019 regression line relating chloride concentrations in the spring of 2013-2017 to the percent watershed developed for 9 Halifax lakes. EC values on the right correspond to the chloride values, based on the relationship given in AECOM (2020)<\/a>.p. 63.\u00a0 The current spring EC value for Sandy Lake is approx 190 uS\/cm. The CCME Guideline for long term exposure to chloride is 120 mg\/L (the dashed red line). So if Sandy Lake behaves like the other lakes, it would achieve a steady state value just above (orange rectangle) or just below (purple rectangle) 120 mg\/L chloride \u2013 at the current level of development, higher if further developed.* My estimate based on measurements shown under Land Use. The purple-filled rectangle\u00a0 represents 21% Developed, the approximate (interpolated) value cited by <\/a>Casey 2022<\/a>, Fig 2.2\u00a0 for Sandy Lake in 2020.<\/a><\/p><\/div>\n

It’s a virtual certainty that if a new development proceeds southwest of Sandy Lake as envisioned (re: HRM Future Service Communities<\/a> ), salt levels in the lake will begin rising again.\u00a0 Given the vagaries of precipitation, climate warming etc. it’s difficult to estimate by how much and whether it would reach levels that exceed guidelines for the protection of aquatic life (120 mg\/L chloride or approx 474 uS\/cm) or to impede normal lake turnover*
\n*Typically when the deeper waters reach over 200 mg\/L chloride or approx 1000 uS\/cm\u00a0 ( Novotny 2008<\/a>) but impedance of spring turnover in Mirror Lake (NY) occurred at chloride levels below 120 mg\/L chloride or approx 474 uS\/cm – see Mirror Lake \u2013 Sandy Lake comparison<\/a>.<\/small><\/p>\n

However both outcomes are possibilities, especially given that the envisaged development would be in area of concentration of\u00a0 headwaters and associated wetlands for Sandy Lake.<\/p>\n

UPDATE: 2025 values
\n2025 Conductivity values were consistent with a long term trend of increasing conductivity (salt content)<\/strong>, slowed in last few years<\/strong>, re: warmer winters and slowdown in development within the watershed, but likely to increase further in future if proposed major development goes ahead\/normal winter salting. <\/strong><\/p>\n

\"\"<\/a>

Fig 2. Specific Conductivity values for surface\u00a0 water and deep-near-the-bottom water at Sandy Lake 1971 to 2025<\/strong>. In the lower figure the 2023 data are excluded and the averages between surface and deep samples are plotted. SPC is a measure of salt content \u2013 EC (salt) Notes.<\/a><\/p><\/div>\n

\n

Related<\/strong><\/p>\n

Road salt lowers the risk of deadly collisions\u2014but it\u2019s also killing Halifax\u2019s lakes. What\u2019s the answer?<\/strong><\/a>
\nMartin Bauman in The Coast, Apr 5, 2024. Some extracts:<\/p>\n

Scott\u2019s 2019 paper, published in the Journal of Environmental Management, stands alone for its longitudinal work. Among its more salient findings are that urban development is the \u201cmost significant explanatory variable\u201d for chloride levels, and\u2014more troublingly\u2014that chloride lasts in Halifax\u2019s lakes long after the region\u2019s roads have been salted and washed away by the rain. If a lake is like a Jenga tower, then chloride might best be described as turmeric in a kitchen, or dog hair on a couch: Once it\u2019s there, it\u2019s not going away anytime soon.<\/small><\/p>\n

Perhaps surprisingly, some of the longest-lasting effects can be found in watersheds when salt doesn\u2019t wash right into a lake. When salt runoff makes its way from Halifax\u2019s roads into forests or grasslands before ending up in the groundwater, Jamieson says, it\u2019s possible to see higher chloride levels \u201cfor months, and sometimes even years, depending on how long it takes for that salt to travel through those hydrologic pathways.\u201d<\/small><\/p>\n

Councillors Sam Austin and Shawn Cleary are both well acquainted with the delicate health of Halifax\u2019s urban lakes. As councillors for Dartmouth Centre and Halifax West Armdale, respectively, the two live in\u2014and represent\u2014two of the most lake-rich areas in Halifax\u2019s urban core. (Those same districts also include some of the lakes most under threat from too much salt.) And while neither would claim to be a biologist\u2014\u201cas a councillor, you find yourself being a generalist in everything and an expert on nothing,\u201d Austin tells The Coast\u2014both have found themselves caught up in Halifax\u2019s internal tug-of-war over how to protect the region\u2019s urban lakes. In Cleary\u2019s district, community efforts to protect Williams Lake led to the creation of the Shaw Wilderness Park\u2014even if it made the Shaw Group millions in the process\u2014and in Dartmouth\u2019s Oathill Lake neigbourhood, Austin has played troubleshooter for keeping road salt levels low while maintaining a salted walking path on Lorne Avenue, which has no sidewalk of its own.<\/small><\/p>\n

\u201cWhere we have lakes that are still vibrant, we want to keep them as vibrant as possible for as long as possible,\u201d Cleary says, speaking by phone with The Coast.<\/small><\/p>\n","protected":false},"excerpt":{"rendered":"

DRAFTING Last Revision on Sep 8, 2024. NAVIGATION www.versicolor.ca \/sandylakebedford Home Page for Sandy Lake & Environs (Bedford, NS) \/Surface Waters \/Sandy Lake A Draft report On the State of Sandy Lake\u2026Feb 21, 2021 \/Limnological Profiles Subpages: \u2013 2023 Limnological … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":9324,"menu_order":10,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-9658","page","type-page","status-publish","hentry"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/9658","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/comments?post=9658"}],"version-history":[{"count":39,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/9658\/revisions"}],"predecessor-version":[{"id":11205,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/9658\/revisions\/11205"}],"up":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/9324"}],"wp:attachment":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/media?parent=9658"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}