Geosmin is a naturally occurring compound that gives water an earthy odor and is very difficult to remove during water treatment. Geosmin is produced by some species of cyanobacteria (blue-green algae) and actinomycetes (filamentous bacteria).

Fort Collins Utilities monitors the occurrence, sources, and transport in both watersheds. Monitoring geosmin in our source watersheds provides early warning for potential taste and odor issues that can be mitigated through water treatment processes or operational changes.

Ongoing studies of Horsetooth Reservoir and C-BT waters upstream of Horsetooth Reservoir suggest a very complex system with respect to geosmin, with varying levels of geosmin production, transport and degradation throughout the system.

In 2010, Utilities staff produced an in-depth study on Geosmin Sources and Concentrations in Horsetooth Reservoir (PDF 2MB).

In the Upper CLP watershed, recent geosmin monitoring efforts have focused on the main stem of the Poudre River between Rustic and the Water Treatment Facility intake. The 2011 findings of this ongoing study are detailed in Assessing Geosmin Occurrence in the Poudre River (PDF 1.5MB).