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Phosphates Details

Phosphate is a chemical compound that contains the element phosphorus, which is essential for plant growth. However, in excess, phosphate can lead to significant environmental issues, such as eutrophication, which is the over-enrichment of water bodies with nutrients. This process can result in harmful algal blooms that deplete oxygen in the water, negatively affecting aquatic life and overall water quality (Dodds & Smith, 2016).

Indicators of Stream Water Quality and Stream Health

Phosphate levels are key indicators of stream water quality. High phosphate levels can suggest pollution from sources such as fertilizers, animal waste, agricultural runoff, wastewater discharge, detergents and erosion (Dodds & Smith, 2016). High phosphate concentrations can trigger excessive algae growth, harming aquatic life and causing algal blooms. These blooms can deplete Dissolved Oxygen (DO) in the water, creating a potential health risk for humans and aquatic animals.

Hawaiʻi DOH and EPA Recreational Health Phosphate Level Thresholds for Freshwater Streams

The Environmental Protection Agency (EPA) and the Hawaiʻi Department of Health (DOH) do not have specific recreational health thresholds for phosphate levels in freshwater streams in Hawaiʻi. Instead, they provide recommended nutrient criteria for total phosphorus to manage and prevent nutrient pollution, ensuring the protection of aquatic life, recreational use, and drinking water sources.

Phosphate levels are a critical component of water quality monitoring due to their impact on eutrophication, which can lead to harmful algal blooms and oxygen depletion in water bodies. This can adversely affect aquatic life and the safety of recreational water use. Although specific numeric thresholds for phosphate in freshwater streams aren’t highlighted, Hawaiʻi’s water quality standards focus on comprehensive indicators such as nutrient levels, turbidity, and biological oxygen demand to gauge overall stream health.

The HDOH, through its Clean Water Branch (CWB), monitors and manages water quality by implementing Total Maximum Daily Loads (TMDLs) for various pollutants, including phosphate, under the Clean Water Act. TMDLs define the maximum amount of a pollutant that a body of water can receive while still meeting water quality standards, providing a framework for reducing pollutant loads and improving water quality over time​ (Hawaiʻi State Department of Health, 2023).​​

For community members and stakeholders, this means that while phosphate-specific thresholds might not be explicitly defined, the overall health of water bodies, including nutrient pollution, is continually assessed and managed. The CWB regularly updates the public on water quality conditions and TMDL projects through their website and public notices. These updates include information on nutrient pollution and its impacts, allowing the community to stay informed about the safety and quality of local water bodies​ (Hawaiʻi State Department of Health, 2023)​.

If you’re monitoring a specific stream and need to assess its safety, it’s important to look at a range of water quality indicators, such as dissolved oxygen levels, pH, turbidity, and the presence of pathogens like E. coli and Enterococcus, alongside nutrient levels like phosphate. Comprehensive water quality reports and advisories from the CWB can provide a clearer picture of stream health and safety for recreational use​ (Hawaiʻi State Department of Health, 2023).

EPA Guidelines

The EPA offers recommended ambient water quality criteria for phosphorus, which vary by ecoregion to reflect regional differences in water body conditions and natural background levels. For instance, the criteria for total phosphorus in streams typically range from 0.01 to 0.1 mg/L, depending on the specific ecoregion and the designated use of the water body (U.S. Environmental Protection Agency, 2021)​.

Hawaiʻi DOH Standards

Hawaiʻi DOH adopts water quality standards that align with the EPA’s guidelines while also considering local environmental conditions. These standards can be found in the Hawaiʻi Administrative Rules, which outline acceptable levels for various water quality parameters, including nutrients like phosphorus (Hawaiʻi State Department of Health, 2023)​ (U.S. Environmental Protection Agency, 2021)​.

Impact and Importance of Phosphate Levels in Streams

Phosphorus criteria are essential for several reasons:

  1. Aquatic Life: Excessive phosphorus can lead to algal blooms, which deplete dissolved oxygen (DO) levels in water, negatively impacting fish and other aquatic organisms (Dodds & Smith, 2016)​.
  2. Recreational Safety: High phosphorus levels can result in harmful algal blooms that produce toxins, posing health risks to humans and animals during recreational activities (U.S. Environmental Protection Agency, 2021)​. Cyanotoxins are found across the United States, including fresh waters in Hawaii. Studies indicate the presence of various cyanotoxins such as microcystins, cylindrospermopsins, and saxitoxins in inland lakes and reservoirs​ (Cyanotoxins in Inland Lakes of the United States: Occurrence and Potential Recreational Health Risks in the EPA National Lakes Assessment 2007, [USGS Publication Warehouse](https://pubs.er.usgs.gov/publication/70173805); (“New Study on Cyanotoxins in Lakes and Reservoirs Provides Insights into Assessing Health Risks”: [USGS News Release](https://www.usgs.gov/news/new-study cyanotoxins-lakes-and-reservoirs-provides-insights-assessing-health-risks). Cyanotoxins are harmful to human health and can cause a range of symptoms from skin irritation and gastrointestinal issues to more severe effects like liver damage and neurological problems, depending on the type and concentration of the toxin. Microcystins, for example, are known hepatotoxins and can lead to liver failure in severe cases of exposure​ (“Harmful Algal Blooms and Cyanobacteria: USGS Science to Protect Our Health and Environment” [USGS Website](https://www.usgs.gov/mission-areas/water-resources/science/harmful-algal-blooms-and-cyanobacteria-usgs-science-protect)
  3. Drinking Water: Elevated phosphorus can affect water treatment processes and lead to taste and odor problems in drinking water sources (Hawaiʻi State Department of Health, 2023)​ (U.S. Environmental Protection Agency, 2021)​.

Contributing Factors

Phosphate levels in streams are influenced by several factors, including erosion and sedimentation, land use practices, and natural sources such as soil erosion and plant decomposition (U.S. Environmental Protection Agency, 2021).

Relationship with Other Parameters

Understanding the interplay between phosphate levels and other water quality parameters is crucial:

  • Dissolved Oxygen (DO): High phosphate levels can lead to algal blooms, which consume oxygen when decomposing, reducing DO levels.
  • Conductance/Specific Conductance: Phosphate does not directly affect conductance but can indicate the presence of other ions that do.
  • pH: Phosphate levels can influence and be influenced by pH levels in water.
  • Salinity: Phosphate can bind to particles affected by salinity changes.
  • Pressure: Variations in atmospheric pressure can affect dissolved oxygen and, indirectly, phosphate dynamics.
  • Nitrites and Nitrates: These nutrients often co-occur with phosphate and contribute to eutrophication.
  • E. Coli and Enterococcus: High phosphate levels can correlate with higher levels of these bacteria, indicating pollution from runoff (Dodds & Smith, 2016) ​(U.S. Environmental Protection Agency, 2021)​.

Using Phosphate Data for Public Health and Safety

The Haʻikū Community Association website (https://www.haikumaui.org/water-quality-data/) will display phosphate levels measured at various stream locations. To ensure the public has information to help them decide if the streams are safe for their recreational use, the Haʻikū Community Association has made phosphate and other water quality data available on our website. By regularly checking these indicators, you can determine the safety of our streams. Here’s how:

  1. Consult Advisories: There are no established recreational safety limits for phosphate specifically. However, persistently high phosphate levels alongside other indicators like low DO or harmful algal blooms might suggest potential health risks. Consult local health advisories for specific guidance (Dodds, W. K., & Smith, 2016).
  2. Check the Latest Data: Visit our website (https://www.haikumaui.org/water-quality-data/) for real-time updates on phosphate levels and other water quality indicators.
  3. Understand the Trends: High phosphate levels, especially when coupled with low DO and high bacterial counts, suggest that a stream may be unsafe for recreational activities such as swimming or fishing.
  4. Be Informed: Awareness of how different indicators interact can help you make better decisions. For example, a stream with moderate phosphate levels but high E. Coli might still be unsafe due to bacterial contamination.
  5. Consider Other Parameters: Factors like DO, pH, and conductivity influence phosphate behavior. Low DO can limit plant and algae growth, reducing phosphate uptake. Conversely, healthy DO levels can promote algae growth, potentially leading to higher phosphate utilization. High conductivity can indicate the presence of dissolved salts, some of which may contain phosphate.

Additional Stream Health Indicators linked to phosphate.

Phosphate levels are just one piece of the puzzle. The website will also display data on:

  • Nitrates and Nitrites: Nitrogen compounds often found alongside phosphate from similar sources like fertilizers.
  • Erosion and Sedimentation: Can increase turbidity, impacting aquatic life and phosphate uptake.

The health of our streams is also monitored through several other indicators:

  1. Dissolved Oxygen (DO): Essential for aquatic life, low levels of DO can indicate pollution and poor water quality. Eutrophication caused by high phosphate levels can reduce DO, harming fish and other aquatic organisms (U.S. Environmental Protection Agency, 2021).
  2. Conductance/Specific Conductance: Measures the ability of water to conduct electrical current, which correlates with the concentration of dissolved salts and other chemicals. High conductance can indicate pollution from runoff or wastewater (U.S. Environmental Protection Agency, 2021).
  3. pH: Indicates the acidity or alkalinity of water. Extremes in pH can be harmful to aquatic life. Phosphate pollution can affect pH levels, influencing the solubility and toxicity of other substances in the water (U.S. Environmental Protection Agency, 2021).
  4. Salinity: Measures the concentration of salts in water. While primarily a concern in coastal areas, salinity can affect freshwater streams due to agricultural runoff and other sources (U.S. Environmental Protection Agency, 2021).
  5. Pressure: Used in conjunction with other indicators to assess water flow and quality. Changes in water pressure can impact the concentration of various pollutants, including phosphate (U.S. Environmental Protection Agency, 2021).
  6. Nitrites and Nitrates: Both are forms of nitrogen that, like phosphate, can contribute to nutrient pollution and eutrophication. Monitoring these compounds helps to assess overall nutrient levels and potential sources of pollution (Dodds & Smith, 2016).
  7. E. Coli and Enterococcus: Indicators of bacterial contamination, often from sewage or animal waste. These bacteria can pose serious health risks for recreational users. High phosphate levels can sometimes correlate with increased bacterial contamination due to shared pollution sources (Hawai’i State Department of Health, 2023).
  8. Erosion and Sedimentation: Physical processes that can increase phosphate levels in streams by washing soil and nutrients into the water. This can also impact habitat quality for aquatic organisms (Dodds & Smith, 2016).

Report Issues: If you notice unusual water conditions or have concerns about water quality, contact the Haʻikū Community Association.By staying informed and proactive, we can all contribute to preserving the health of our streams and ensuring they remain a safe, enjoyable resource for everyone.

For more detailed information and to view the latest water quality data, please visit our website Haʻikū Community Association Water Quality Monitoring at https://www.haikumaui.org/water-quality-data/.

Mahalo for your commitment to keeping our streams clean and safe!

References

  1. Dodds, W. K., & Smith, V. H. (2016). Nitrogen, phosphorus, and eutrophication in streams. Inland Waters, 6(2), 155-164.
  2. U.S. Environmental Protection Agency (EPA). (2021). Water Quality Criteria. Retrieved from https://www.epa.gov/wqc
  3. Hawai’i State Department of Health. (2023). Water Quality Monitoring and Assessment. Retrieved from https://health.Hawaiʻi.gov/cwb/site-map/clean-water-branch-home-page/water-quality-monitoring-and-assessment