When beetles kill trees, it changes water chemistry for the folks downstream of the hammered watersheds. And not in a good way (DBP is “disinfection by-products”, study area is in Colorado):

Results demonstrate higher total organic carbon concentrations along with significantly more DBPs at water-treatment facilities using mountain-pine-beetle-infested source waters when contrasted with those using water from control watersheds. In addition to this differentiation between watersheds, DBP concentrations demonstrated an increase within mountain pine beetle watersheds related to the degree of infestation. Disproportionate DBP increases and seasonal decoupling of peak DBP and total organic carbon concentrations further suggest that the total organic carbon composition is being altered in these systems.

Mikkelson et al., Water-quality impacts from climate-induced forest die-off, Nature Climate Change (2012) doi:10.1038/nclimate1724