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The relationship between watershed protection and water quality: The case of Québec, Canada

Assigning formal protection status to watersheds can help secure water quality. However, little is known about what spatial proportion of a watershed should be protected, what type of formal protection status is required to ensure provision of clean water, or even whether protecting a watershed is sufficient to ensure provision of high-quality water. We explored the relationship between water quality (measured through 2 indices incorporating biological, physical, and chemical characteristics) and the percentage of International Union for Conservation of Nature Category II protection in 328 watersheds in the province of Québec, Canada. Using a suite of regression models, we found that when differences in watershed land use/land cover, size, and geographic location are also accounted for, the percentage of protection of a watershed was not associated with water quality. Instead, the percentage of forest, agriculture, anthropogenic development, and aquatic habitat were the strongest predictors of water quality. However, watersheds with any percentage of protection (n = 67) had better water quality than watersheds without any protection (n = 261). Protected watersheds also had higher amounts of natural land cover, which was correlated with water quality. Our findings highlight the positive effects that watershed protection can have on water quality but also illustrate that setting a target for protection to secure water quality is not as simple as increasing the proportion of watershed protection. Instead, good water quality also depends on the land use/land cover in both protected and unprotected parts of watersheds. As opportunities emerge to expand the network of formally protected areas, our findings can help determine appropriate strategies for practitioners seeking to use protection as a means to secure or improve the water quality provided by watersheds.