UC Davis

Freshwater cyanobacterial harmful algal blooms (FCHABs) are an increasing threat to drinking water worldwide. Climate change and environmental degradation exacerbate naturally eutrophic water bodies and widen the geographic area where FCHABs are likely to occur. The health effects of toxin-producing cyanobacteria are well-known, but their concentrations are unregulated in drinking water. So monitoring efforts are voluntary, which limits the data available for comprehensive analyses and hinders water utilities’ ability to prepare for and manage FCHABs events. FCHABs can cause human health, economic, and ecological damages, however, their socioeconomic impacts have not been quantified for vulnerable communities that are exposed seasonally to toxin-producing FCHABs in drinking water sources. This multidisciplinary study sheds light on four issues: (1) the risk of FCHAB development related to climate change; (2) the efficacy of current treatment solutions for public water supply; (3) drinking water affordability, especially for vulnerable communities; and (4) the lack of regulation and funding mechanisms for FCHABs. Five analyses were performed to evaluate the impacts of FCHAB management on drinking water sources. First, a risk analysis was developed to predict microcystin concentrations based on cumulative winter inflow. Second, the efficacy of surface water treatment plants in Lake County was evaluated to assess if public water systems (PWSs) adequately remove microcystin concentrations from finished drinking water supplies. Third, a water rate analysis for the surface water systems in Lake County assesses if there is a relationship between FCHABs and water rates. Fourth, water treatment chemical costs for four water systems in Lake County were calculated over a period of five years to assess if a relationship exists between water treatment cost and FCHAB events. Finally, a regulatory analysis assesses if the current regulatory proceedings lack an adequate funding mechanism for increases in the cost of water treatment due to FCHABs. The results of this study indicate that (1) FCHABs will continue to worsen with climate change; (2) surface water systems in Lake County adequately remove microcystins from finished drinking water; (3) FCHABs create a disproportionate financial burden on vulnerable communities; (4) there is a positive relationship between the cost of water treatment and FCHABs; and (5) current funding mechanisms are inadequate for the increased cost of water treatment from FCHABs. The discussion explores an avenue for policy intervention to assist public water systems treating for FCHABs.