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Introduction

As a hydrogeologist, I understand the importance of water well health in ensuring the efficient operation and longevity of water wells, which serve as critical sources of water supply for drinking water, irrigation, and various industrial processes. Monitoring and maintaining water well health requires a comprehensive understanding of the chemical indicators that can signal potential issues, such as well plugging, corrosion, or contamination. In this article, we will discuss the key chemical indicators for water well health and provide guidance for water system operators on how to interpret and act on this information to maintain the performance and service life of their water wells.

The Importance of Chemical Indicators for Well Health

Chemical indicators are valuable tools for assessing water well health and identifying potential issues that could compromise well performance. By regularly monitoring these indicators, water system operators can:

1. Detect early signs of well plugging, corrosion, or contamination: Changes in chemical indicators can signal the onset of these issues, enabling operators to implement timely interventions and prevent more severe or irreversible damage to well components.
2. Assess water quality: Chemical indicators can provide information on the overall water quality within the well, helping operators ensure that the groundwater meets established quality standards for its intended use.
3. Monitor well conditions: Tracking chemical indicators over time can help operators identify trends, seasonal variations, or changes in well conditions that may warrant further investigation or corrective actions and plan for optimal well rehabilitation timing.
4. Ensure regulatory compliance: Regular monitoring of chemical indicators can help water system operators verify compliance with local, state, or federal regulations governing groundwater quality and well operation.

Key Chemical Indicators for Water Well Health

The following chemical indicators are essential for assessing water well health and identifying potential issues related to water well performance:

1. pH: The pH level, which measures the acidity or alkalinity of water, is an important indicator of water well health. A pH level outside the optimal range (typically between 6.5 and 8.5) can indicate corrosion, scaling, or the presence of contaminants.
2. Conductivity: Electrical conductivity is a measure of the water’s ability to conduct electricity and is related to the concentration of dissolved ions in the water. Elevated conductivity levels can signal increased mineral content, which may lead to scaling or plugging, as well as potential contamination by salts or other contaminants.
3. Total dissolved solids (TDS): TDS is a measure of the total amount of dissolved substances in water, including salts, minerals, and metals. High TDS levels can indicate mineral scaling potential, increased salinity, or the presence of contaminants that could affect water quality or well performance. Generally, drinking water should have a TDS of less than 500 mg/L.
4. Hardness: Water hardness is primarily determined by the concentrations of calcium and magnesium ions. High hardness levels can cause mineral scaling and reduce the efficiency of water treatment processes.
5. Alkalinity: Total alkalinity is a measurement of the capacity for water to resist changes in pH. High alkalinity can increase the potential for mineral scaling in wells and can also impact the effectiveness of chlorine disinfection.
6. Langelier Saturation Index (LSI): The Langelier Saturation Index (LSI) is an approximate indicator of the degree of saturation of calcium carbonate in water. It is calculated using the pH, alkalinity, calcium concentration, total dissolved solids, and water temperature of a water sample collected at the tap. LSI is commonly used as an indicator of the scaling potential of a well, with a positive LSI indicating calcium saturation and the potential for the formation of calcium carbonate deposits in wells.
7. Calcium: Calcium is a component of the hardness calculation, the Langelier Saturation Index, and a constituent of both calcium carbonate and calcium sulfate. Deposits of calcium carbonate scale can develop if the pH is >7.5, hardness is >250 mg/L or calcium is above 180 mg/L, and alkalinity is >220 mg/L.
8. Oxidation-Reduction Potential (ORP): The oxidation-reduction potential (ORP) is the measure of the tendency of a solution to gain or lose electrons when it is subjected to change by the introduction of a new species (chemical or biological). Positive readings are more oxidative, while negative readings indicate a more reductive chemical environment. ORP readings can be indicative of the type of bacteria that may be present. For instance, anaerobic bacteria would dominate in the more reductive environment, while many aerobic bacteria forming persistent biofilms would be present within the more oxidative zone.
9. Iron and manganese: Elevated concentrations of iron and manganese can lead to the formation of mineral deposits on well components and screens. reducing well efficiency and potentially causing plugging or staining. Iron and manganese deposits can also be biogenic in origin and associated with biofouling.
10. Chloride, sulfate, and nitrate: Elevated levels of these anions can indicate potential contamination from sources such as septic systems, fertilizers, or industrial activities. High concentrations of chloride and sulfate can also contribute to corrosion in well components. Elevated levels of sulfate can indicate the potential for calcium sulfate (gypsum) deposits in wells and may also indicate bacterial activity.
11. Metals: The presence of heavy metals, such as lead, copper, and arsenic, can signal potential contamination or corrosion within the well, posing risks to human health and well performance.

Interpreting and Acting on Chemical Indicator Data

Water system operators should regularly monitor and evaluate chemical indicator data to maintain water well health. To effectively interpret and act on this information, operators should:

1. Compare results to established standards: Chemical indicator results should be compared to established water quality standards or guidelines, such as those set by the United States Environmental Protection Agency (EPA), to determine if the groundwater meets the required criteria for its intended use.
2. Identify trends and variations: Analyzing chemical indicator data over time can help operators identify trends, seasonal variations, or changes in well conditions that may warrant further investigation or corrective actions. The best way to do this is to develop a spreadsheet-based dashboard to track constituent trends and take appropriate corrective action as the trends indicate.
3. Investigate potential issues: If chemical indicator data suggest potential well performance issues, such as plugging, corrosion, or contamination, water system operators should conduct further investigations to identify the source of the problem and implement appropriate interventions.
4. Implement corrective actions: Depending on the specific issue identified, various corrective actions can be employed to address well performance issues. These may include well rehabilitation, modifications to well design or construction, changes in water treatment processes, or the implementation of additional source water protection measures.
5. Monitor and adjust: Regularly review chemical indicator data to assess the effectiveness of implemented interventions and make any necessary adjustments to maintain water well health.

Conclusion

Monitoring chemical indicators is an essential aspect of maintaining water well health and ensuring the efficient operation and longevity of water wells. By regularly assessing these indicators, water system operators can detect early signs of well plugging, corrosion, or contamination, implement timely interventions, and prevent more severe or irreversible damage to water well components.

I encourage water system operators to prioritize the monitoring of chemical indicators as part of their routine well maintenance and management practices. By vigilantly tracking these indicators and proactively addressing potential issues, operators can safeguard their valuable groundwater resources, ensure the continued provision of high-quality water, and extend the service life of their water well infrastructure. Remember, the key to effective water well management is early detection, prevention, and timely action.

For further information on chemical, biological and physical parameters to determine water well health, download our Well Health Check Resource Guide.