by Paige Jessup, Climate Resilience Intern
Many pool and hot tub owners want to get away from the harsh chemicals like chlorine, bromide, and algaecides by switching to saltwater. Using saltwater is appealing because it is believed to be gentler on skin, hair, eyes, and swimwear, and pool-grade salt costs less to maintain than a chlorine pool. In contrast, salt water is corrosive to metal and natural stone, costs more to install, uses more energy to run and keep clean, and could also potentially be polluting aquatic ecosystems.
How is saltwater ending up in freshwater?
The main reason for increased levels of salt in freshwater is human activities such as application of road de-icing salts, water and resource extraction, and improper wastewater discharge. Without realizing it, you could be polluting our waterways by draining your swimming pool into the street or directly into a storm drain. Anything discharged into storm drains, including swimming pool water and hot tubs, will eventually end up in the nearest creeks, streams, or lakes without being treated.
What are the effects of salt in freshwater?
Excess salinity affects lakes in a few key ways. First, salinity changes lake physics by altering stratification in the spring. Stratification is caused by the warming of surface water from the heat of the sun, which changes water density and causes the water tables to mix. This is important for lakes because it allows oxygen to move through the water columns. However, when salt is added to an ecosystem, it makes the water denser and sits on the bottom of the lake, making it harder for it to mix (Ladwig, 2023). This means a lack of oxygen moving throughout the lake making it uninhabitable for some species, like coldwater fish species.
As our lakes increase in salinity, it opens them up to invasive species that tend to be more tolerant of salt than the native species. This is also true for seeing an increase in toxic types of algae blooms (Dugan, 2023). Salt tolerance varies in different species; in Canada, the threshold for the chloride concentration in freshwater is around 120 milligrams of chloride per liter, meaning 95% of freshwater species in this study could tolerate salt at these levels (Klassen, 2022). Most freshwater bodies near urban areas are well above this threshold.
How can we make a change?
When looking specifically at hot tubs and pools, the best way to tackle this issue is to explore alternatives to chlorine and saltwater such as ultraviolet light and active charcoal for cleaning. If you are thinking about getting a pool or hot tub, consider a natural pool or sauna instead as these have far less of an impact on the surrounding environment. If you have a chlorine or saltwater pool, make sure you are properly draining your hot tub or pool to make sure it does not end up polluting nearby lakes, rivers, and streams.
Some other ways to help this issue is to educate your neighbors by sharing information about the harmful effects of improper disposal of hot tub and pool water. Encourage people in your neighbourhood and community to adopt best practices, support new materials and technologies for wastewater management in your municipality, and keep updated on best practices and research related to hot tubs, pools, and its effects on freshwater.
Watersheds Canada is initiating an education awareness campaign to protect our freshwater ecosystems from hot tub and pool pollution. Your action could be the ripple effect needed to spark change! Share this education campaign with those in your network and community as we all join hands against pollution to our freshwater areas.
References
Dugan, H. (2023, April 12). Freshwater is the best water: How salt is a threat to our freshwater rivers and lakes. [Trent University]. Retrieved from https://www.youtube.com/watch?v=Etx2Y-LKpiA
Klassen, V. (2022). Human-induced salt pollution a major threat to biodiversity in lakes. Queen’s University. Retrieved from https://www.queensu.ca/gazette/stories/human-induced-salt-pollution-major-threat-biodiversity-lakes
Ladwig, R., Rock, L.A. and Dugan, H.A. (2023), Impact of salinization on lake stratification and spring mixing. Limnol. Oceanogr. Lett, 8: 93-102. https://doi.org/10.1002/lol2.10215
This blog is part of an education toolkit generously funded by:
