The Delta is a vital water source, providing drinking water to over 27 million people and irrigating 3 million acres of farmland. The Delta is a rich mosaic of farms, wetlands, and diverse habitats that support a wide array of fish and wildlife and serves as a critical stopover for migratory birds along the Pacific Flyway. In addition to its ecological importance, the Delta is a recreational hub, attracting thousands of visitors each year for fishing, boating, birdwatching, and other outdoor activities. Preserving the Delta’s water quality is essential for human uses and sustaining its vibrant ecosystems and the wildlife that depend on them.
Prior to 2013, water quality monitoring in the Delta was primarily conducted to meet regulatory requirements. The Delta Regional Monitoring Program (Delta RMP) was established to consolidate these fragmented efforts and assess the success of protection and restoration initiatives by providing a unified and effective approach to water quality monitoring.
The Delta RMP operates as a nonprofit public benefit organization overseen by a governing board and advisory committee. Its participants include publicly owned treatment works, municipal stormwater agencies, agricultural coalitions, Tribes, and state and federal agencies. To support the program, regulated permittees can choose to replace individual water monitoring requirements with participation in regional studies under the Delta RMP. This approach streamlines water quality monitoring, reduces costs, and provides critical data to inform policy and regulatory decisions by the Central Valley Water Board and other agencies.
At the February meeting of the Central Valley Regional Water Quality Control Board, Melissa Turner, program manager for the Delta Regional Monitoring Program (Delta RMP), highlighted the program’s achievements and ongoing research.
The mission of the Delta RMP is to deliver objective, cost-effective scientific insights about water quality trends to support decisions that protect and restore beneficial uses of Delta water. By improving the efficiency of data collection and management, the Delta RMP generates resources that inform and educate policymakers and the public. It raises awareness of Delta water quality conditions and their impacts on beneficial uses while promoting independent science, peer review, and transparency.
The Delta RMP utilizes a stakeholder-driven, adaptable, and collaborative approach. All validated data is publicly accessible, ensuring transparency. The program fosters consensus-building and science-based solutions in managing competing priorities like habitat restoration, flood protection, and water supply, making it a vital tool for addressing the complex challenges of the California Delta.
Monitoring to inform management decisions
The Delta RMP is focused on monitoring to answer key scientific questions in the Delta that inform management decisions of various stakeholders. Its work centers on developing and implementing comprehensive monitoring plans that track important water quality indicators in the Delta.
The first step in developing a monitoring program is planning; data gaps are identified, priorities are determined, and then a hypothesis-driven study design is developed. Once the study design is approved, monitoring occurs to collect data as the monitoring plan dictates. The final step is reporting, which includes assessing whether monitoring was conducted as planned and often an interpretive report to evaluate multiple years of monitoring and put it in the context of regulatory frameworks and beneficial use protection.
The budget for the Delta RMP varies from $9 to $14 million per year, most of which is used for the costs of monitoring rather than programmatic costs. Even so, Ms. Turner said there is much to balance between the objectives and available resources. The long-term planning process helps to allocate resources across years relative to upcoming policy decisions and management priorities to inform monitoring and reporting.
“To achieve the objectives of creating and developing water quality data, producing products, having awareness, and then keeping with independent science, we have to balance that with our money, time, and people resources,” she said.
Monitoring and what has been learned
Current use pesticides
The Delta RMP began monitoring for current use pesticides in 2015 to fill a knowledge gap about the concentration of pesticides within the Delta and the potential impact on aquatic life. Algae, invertebrates, amphipods, and fish underwent toxicity testing. The USGS has been conducting the monitoring and pesticide analysis since 2015 with more than 150 pesticides being analyzed. There have been some detections of pesticides, but generally, they are at low levels and with minimal toxicity. Data are publicly available through CEDEN, in addition to the USGS website.
“Overall, it is a robust and unique data set that is invaluable for understanding pesticide detections in the Delta,” Ms. Turner said. “One of our challenges in this program and with the current use pesticides has been maximizing the benefits of analyzing for pesticides over 150 suite of analytes using a cutting edge method, which may not be consistent with some regulatory requirements.”
Mercury
The information collected as part of the Delta RMP mercury monitoring sector has been critical for implementing the Delta methylmercury TMDL and informative for regulatory decisions related to water quality improvements and ecosystem restoration in the Delta. The seven-year dataset has resulted in a better understanding of mercury concentrations in fish tissue and water and was used to inform the 2020 Delta Mercury Control Program.
An interpretive report is being developed that will include data generated from 2016 – 2022 and assess trends in fish tissue and aqueous methylmercury concentrations as well as evaluate other factors impacting trends in methylmercury concentrations. The report will be accompanied by a four-page Mercury Fact Sheet.
Nutrients
Nutrient concentrations in the Delta contribute to various water quality problems, such as increased production of blue-green algae, invasive aquatic macrophytes, low phytoplankton production, low dissolved oxygen, and nutrient-related issues in drinking water systems. The Delta RMP has contributed to various efforts with nutrients, including a nutrient synthesis report, the Delta nutrient research plan, and biogeochemical modeling.
The Delta RMP recently began implementation of a multi-year study plan that is aimed at addressing data gaps associated with low nutrient scenarios and harmful algal blooms, biogeochemical modeling to assess the ranges of nutrient concentrations if there is a reduction in nutrient loading, and a bioassay study to evaluate thresholds that can limit harmful algal blooms and support the growth of desirable phytoplankton. It includes funds set aside for collaboration opportunities with other entities working on understanding more about harmful algal blooms.
CECs
Constituents of emerging concern or CECs are defined as any physical, chemical, biological, or radiological substance of matter or matter in the environment that may pose a risk to human and or ecological health and for which there is not a regulatory standard. In many cases, CECs are not regularly monitored, nor are their fate, transport, or toxicology well understood. CECs include various PFAS, pharmaceuticals, personal care products, flame retardants, disinfection byproducts, certain urban pesticides, microplastics, nanomaterials, and numerous biological agents.
The Delta RMP conducted a pilot study for the monitoring of CECs in the Delta to better understand methods of evaluating ambient concentrations and sources of CECs in different Central Valley surface water scenarios. The main goal of the pilot study was to inform Water Board managers of the status and trends of CECs in water. The first year of monitoring included monitoring water sediment, fish, and bivalves. Year two added additional source locations, including effluent and stormwater runoff, and then year three was designed as an attenuation study, which was downstream of two wastewater treatment plants. The Delta RMP is developing a CEC interpretive report to evaluate the data collected under the pilot project and use that data to inform future monitoring designs.
What’s next?
The Delta RMP recently concluded a long-term planning process for the next five years. The Delta RMP will focus on implementing the nutrient multi-year study plan, planning for future monitoring of CECs, continuing work on mercury monitoring, and the pyrethroid research plan and the need to understand pesticides in the Delta and changes in product use. The Delta RMP plans to continue monitoring pesticides, nutrients, mercury, and CECs for current use, increasing efforts to synthesize information collected and coordinating with other programs. They will continue emphasizing outreach and coordination with other collaborators to maximize resources and identify data gaps.
“It is a stakeholder driven collaborative process that the board has supported that is producing results and information so much beyond what individual results would be,” said Debbie Mackey, Central Valley Clean Water Association. “Now we have information that’s Delta-wide that didn’t exist in the past. It has helped answer some questions and promoted more science.”
