The Assessment of Post-Wildfire Effects on Cyanobacteria in California Water Supply Reservoirs Using Remote Sensing
Water supply is decreasing globally at alarming rates. Typically water quantity is of greatest concern, while water quality is overlooked. Areas with Mediterranean climates, such as California (CA), United States, are at high risk of increased soil erosion from wildfires placing nearby water supplies at risk. Of concern are cyanobacteria harmful algal blooms (cyanoHABs), which may contain toxins (cyanotoxins) that can harm the immediate ecosystem and cause illness or in severe cases, death, to those that ingest it. CyanoHABs are a public concern, and with the increasing trend in wildfire severity over the past 20+ years, it is important to determine if these blooms will increase or become more intense over time. This research uses available satellite remote sensing imagery to map cyanoHABS in large lakes and reservoirs across CA to investigate a connection to wildfire occurrence imagery acquired by the Medium Resolution Imaging Spectrometers (MERIS) and Sentinel 3-Ocean Land Cover Imager (S3-OLCI) for the time periods 2002-2012 and 2016 -2019. The cyanoHAB data is from the San Francisco Estuary Institute (SFEI), who uses both satellites to create a cyanobacteria index (CI) from the change in the spectral shape at 681 nm where phycocyanin, a molecule uncommon in other freshwater algae, interacts with light. Previous research divided CA into three regions (Central, Northern, and Southern) and found median CI values for 2002-2012 (MERIS) had a positive monotonic trend, but Northern CA had a higher score compared to the other two. In addition, there was a limiting factor for algal boom presence and the frequency of wildfires when lakes were classified by their land class. To expand on this previous work, this study implements other environmental factors that may influence cyanoHABs such as climate, impervious surface coverage, tree canopy coverage, and post-fire sediment potential in the respective watersheds. CyanoHAB spatial extent, frequency, duration, and CI maximum was documented along with the median CI level to understand the relationship with wildfire regime (frequency, severity, and extent) further. CAs climate range and various ecosystems would allow a new insight on wildfires role on water quality that could be applicable to similar ecoregions around the world where wildfire and water scarcity risk is high.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021