Henderson Lake, Canada

    Henderson Lake is an urban water body located in Henderson Park in the eastern suburbs of the City of Lethbridge, Southern Alberta. The lake is of high recreational and aesthetic value and many amenities for residents have been developed around it. They include parklands, walkways, Japanese gardens and a golf course. Henderson lake is heavily enriched with phosphorus. This has led to a high incidence of cyanobacterial (blue green algal) blooms and prolific macrophyte growth.

    Henderson Lake receives regular inputs of water from the St. Mary River Irrigation System and from water pumped from the surrounding area (including the golf course, parklands and bowling greens). During extreme rainfall events, the city’s storm water flows into the lake. Due to the influence of water from non-point source locations, Henderson Lake has historically suffered from eutrophication. Water quality monitoring indicated that the lake is heavily enriched with phosphorus; which has led to a high incidence of cyanobacterial (blue green algal) blooms and prolific macrophyte growth. In recent years, a number of measures have been taken by the City of Lethbridge to reduce the frequency and severity of these blooms and control the growth of macrophytes. These included live liquid microorganisms, solar bees (mechanical mixers), grass carp, and aeration. However phosphorus levels remain high, and cyanobacteria continue to have a negative impact on water quality and the overall ecological condition of the lake.

    Due to the importance of the lake to Lethbridge residents, the City was interested in implementing further measures aimed at improving water quality and ecological conditions; hence the use of Phoslock in 2016.