The District previously wrote three articles for the Liberty Lake Splash and the District’s biannual newsletter discussing the algae conditions in Liberty Lake observed in 2015 and 2016 (Lake Management and LLSWD’s role, August 2016; A Closer Look at Blue Green Algae, October 2016; and Lake Studies in Motion, Spring 2017). These articles focused on the 2015 and 2016 lake algae blooms and a synopsis of the possible contributing factors. On July 12, 2016, the District received a petition with 166 signatures to “urge the District to take decisive and prompt action, employing all available technical and financial resources, to mitigate algae blooms and improve lake water quality.” Before we discuss the research grants the District received, it is important to recognize and summarize some of the contributing factors of algal blooms outlined in the District’s articles.

The growth and proliferation of algal blooms are the result from a combination of environmental factors such as nutrients (Phosphorus and Nitrogen), air and water temperatures, sunlight, ecosystem disturbance, hydrology (incl. snow pack, runoff, drought, ice cover), water volume (lake level), and water chemistry. The exact combination of factors that trigger and sustain an algal bloom is not well understood and it is not possible to attribute algal blooms to any specific factor. However, the District’s monitoring program dating back to 1968 is aimed to understand baselines and trends in an effort to recognize deteriorating water quality conditions and prescribe possible management strategies.

In response to the petition, the District has embarked on three primary campaigns: 1) Increase public education about lake health, ecology, and toxic algae blooms. 2) Hire an environmental consultant to conduct an assessment and evaluation of the existing long-term water quality data set, as well as climate and weather data, to determine the driving factors behind the blooms in 2015 and 2016. The key findings from this research will be used to help understand nutrient dynamics in the lake and how they influence algae growth. 3) Apply for Washington State Department of Ecology Freshwater Algae Control Grant(s) to conduct research into Liberty Lake water quality impairment, nutrient dynamics, algae bloom development, and potential algae and nutrient mitigating measures.

In February 2017, the District was informed that its Freshwater Algae Control Grant application for the development of an Algae Control Plan was awarded by Washington State Department of Ecology in the amount of $48,750 for fiscal year 2018. A year later, in February 2018 the District was awarded another Freshwater Algae Control Grant for $62,500 over two fiscal years for a Trophic Cascade Effects study. The purpose of the first grant, the Algae Control Plan, is aimed at identifying sources of water quality impairment, analysis of current nutrient dynamics, evaluation of other factors leading to harmful algal bloom development, as well as develop recommendations and preliminary design plans for algae and nutrient mitigation measures. The sec- ond grant, Trophic Cascade Effects on Algae Blooms in Washington Lakes, will analyze trophic cascade effects of trout stocking on plankton species in Liberty Lake using data collected over the past 50 years. The study will also evaluate trophic cascade effects on phytoplankton biomass and cyanotoxin concentrations in 85 other Washington lakes using water quality data routinely collected by local jurisdictions for over 10 years, along with cyanotoxin data compiled from the Washington State Toxic Algae Program and fish stocking data compiled from Washington Department of Fish and Wildlife.

The District has not yet initiated work on the Trophic Cascade Effects study. However, model results and management alternatives for the Algae Control Plan are now nearly complete. The District’s consultant, TetraTech, recently gave a public presentation at the August 13, 2018 LLSWD Board of Commissioners meeting. Results for the nutrient budget and model results were discussed. In summary, internal loading (e.g. phosphorus retention) for Liberty Lake makes up the sizable portion of the annual Total Phosphorus (TP) load to the lake. In fact, internal loading contributes to over 80% of the summer TP load. Fortunately, internal loading is not the only factor causing harmful algae blooms in Liberty Lake. Climate and hydrodynamic conditions (wind mixing, lake outlet flush- ing, etc.) contribute significantly to whether a bloom will occur or not. From the data analyzed, harmful algae blooms and poor water quality did not occur in years with wet hydrologic conditions and significant spring flushing, even with internal loading.

Examples even include the most recent years of 2017 and 2018 where we had above average snowpack, precipitation, lake outlet flushing, and near average climate. Perhaps the most important thing to recall in 2015 that was different from the previous decade of data is that the 2015 water year was the hottest and driest on record. Liberty Lake data shows that the lake experienced a long and stable period of stratification (lack of water column mixing) as a result of high temperatures with low winds. In addition, the drought impacted the lake volume where Liberty Lake hit the second lowest lake level observed in 62 years. 2016 was not much different. April 2016 was the second warmest on record and according to NOAA, June 2016 was the warmest June on record for the contiguous United States dating back to 1895. A culmination of back-to-back years of drought and above average climatic conditions.

So what is the best management strategy? Climate and hydrology are not manageable. The most practical management strategy is to reduce lake TP by reducing internal loading. TetraTech evaluated several different management methods for algae control and formulated recommendations in the Algae Control Plan. The consultant illustrated that implementation of a nutrient inactivation (i.e. Alum treatment) does not appear to be warranted given the good water quality conditions, however with climate change and increase in dry, hot summers; this may not always be the case. The consultant’s recommendation is to wait on implementation until the lake experiences several dry years back to back or until the water quality conditions worsen over a sustained period of time, but in the meantime prepare for such a treatment.

As previously described, it is not possible to attribute algal blooms to any specific factor, it is important to recognize that the decade’s past water quality data would suggest that the 2015 and 2016 climatic events is what most likely attributed to the water quality conditions observed in those years. In nature, as in humans, responses to extreme events (such as an injury) are immediate and the recovery from such an event is gradual. The District is committed to lake health and understanding algae blooms, if they will become more frequent and intense, we will determine what management strategies can be employed to abate future blooms. If you have any questions, we encourage you to contact us at (509) 922-5443. For more information visit https://libertylake.org/algae/ and https://www.nwtoxicalgae.org/.