The Lake Elsinore and Canyon Lake Nutrient TMDL – Understanding Water Quality Conditions and Challenges Related to Eutrophication, Elevated Salinity, and Support for Healthy Aquatic Communities
In 2004 a Total Maximum Daily Load (TMDL) was developed for Lake Elsinore and Canyon Lake and surrounding watersheds in response to hypereutrophic conditions in the lakes as a result of high nutrient concentrations, specifically nitrogen and phosphorous. In addition to reduced water clarity under eutrophic conditions, high algal productivity can result in low dissolved oxygen conditions for extended periods of time. Such conditions, among other associated factors, are likely responsible for a history of fish kills that have occurred in the lakes, particularly in Lake Elsinore.
Extensive water quality monitoring of Lake Elsinore and Canyon Lake was initiated in 2000 by the Santa Ana Regional Water Board. In 2000, the Lake Elsinore and San Jacinto Watersheds Authority (LESJWA) was also formed as a joint powers authority to improve water quality and wildlife habitats in Lake Elsinore, Canyon Lake, and the surrounding watersheds. A monitoring program specific to meeting the 2004 TMDL requirements was developed and has included a suite of chemical analyses and flow measurements for wet weather runoff, as well as in-lake monitoring including assessment of depth profiles for a variety of physical water parameters as well collection of samples for analysis of nutrients, ammonia, total dissolved solids, and chlorophyll-a. An enhanced assessment of chlorophyll-a concentrations and spatial variability is now being conducted using satellite imagery. The regional stakeholders have since implemented a number of large-scale best management practices to improve water quality in each of the lakes. In 2008, oxygen diffuser lines were installed in Lake Elsinore along the bottom of the lake as well as pump stations to circulate oxygen rich water towards the bottom. In Canyon Lake, alum applications were initiated in 2013 in an effort to reduce biologically available phosphorus to control algae blooms. Fisheries management consisting of carp removal and stocking of hybrid striped bass in Lake Elsinore have also been implemented to reduce negative impacts from carp which root in the sediments resulting in recycling of nutrients to the water column. A substantial body of information now exists with which to assess the effectiveness of these water quality enhancement projects and also to re-evaluate the applicability and appropriateness of existing TMDL requirements. As such a re-evaluation of the existing TMDL is currently underway utilizing the extensive knowledge gained over the past 16 years in the two lakes.
One leg of this approach is to understand the lakes historic and current ability to maintain a desired biological community that can both help maintain water quality conditions through natural processes (i.e. grazing of algae by zooplankton), and a fishery that benefits human recreation beneficial uses. The two lakes, though connected, are physically very different and both present unique challenges with regard to maintenance of desired water quality conditions in a Mediterranean climate that is becoming more extreme with global warming. This presentation is focused on the long term analysis of water quality parameters in both lakes relative to the TMDL guidelines and how management practices have affected these parameters. Risks to the biological community and drivers of the community structure will also be discussed.