Groundwater is a vital resource for billions, crucial for drinking, agriculture, and industry. However, its quality, significantly impacted by human and geological factors, directly influences public health and agricultural productivity. The Sevathur mine region in South India exemplifies these challenges.
A recent study “Groundwater quality assessment for drinking and irrigation purposes and its human health risks in the Sevathur mine region, south India” provides a comprehensive evaluation of groundwater quality in this area, assessing its suitability for drinking, irrigation, and associated health risks.
The Sevathur region characterised by a semi-arid climate and limited surface water, heavily relies on groundwater. Spanning 451 square kilometers, this region exhibits diverse geological features, including charnockites and gneisses, which, coupled with human activities like mining and agriculture, contribute to complex groundwater chemistry.
The study aimed to comprehensively analyse the hydrogeochemical properties of groundwater in the region, evaluate its suitability for both drinking and irrigation purposes, assess potential health risks associated with contamination, particularly focusing on fluoride levels, and finally recommend mitigation strategies for sustainable water management.
Hydrogeochemical characteristics
Groundwater samples were collected from 35 wells across the Sevathur region and analysed for physicochemical parameters, including pH, Total Dissolved Solids (TDS), major ions, and fluoride. Key findings include:
Hydrochemical facies: The region's groundwater exhibit diverse water types, including Ca-Mg-Cl, Ca-Mg-Cl-SO4, Na-K-Cl-SO4, and Ca-Mg-HCO3. This diversity reflects the interplay between natural geological processes and human influences.
pH and TDS: The groundwater had a mildly alkaline nature, with pH ranging from 7.2 to 8.7. TDS levels varied widely, with many samples exceeding the World Health Organization (WHO) limit of 500 mg/L, indicating significant mineral dissolution and anthropogenic impacts.
Fluoride levels: Approximately 26% of samples exceed the WHO permissible limit of 1.5 mg/L for fluoride, posing health risks such as dental and skeletal fluorosis.
Water Quality Index (WQI) analysis
The Water Quality Index (WQI) is a crucial tool for assessing the overall quality of groundwater by integrating multiple physicochemical parameters into a single score. It provides a clear understanding of water suitability for drinking purposes and helps identify areas requiring urgent intervention. The study categorised the groundwater samples as follows:
Excellent quality: 23% of the samples fell into this category, indicating minimal contamination and safe usability for drinking without any treatment.
Good quality: Another 23% of the samples were rated as good, suitable for drinking with minor treatment measures to address specific contaminants.
Poor to very poor quality: Approximately 34% of samples exhibited significant contamination levels, requiring comprehensive treatment to ensure safety.
Unfit for drinking: Alarmingly, 17% of the samples were deemed unfit for human consumption due to high concentrations of TDS, fluoride, and other contaminants.
The WQI analysis highlights the heterogeneity of groundwater quality in the Sevathur region. Areas classified as "Poor" or "Unfit" were predominantly located near mining zones and regions with intensive agricultural activities, where anthropogenic impacts exacerbate natural geochemical processes.
Implications of WQI findings
The WQI framework enabled the precise identification of high-risk zones with elevated TDS and fluoride levels, primarily concentrated in the central and southern regions of Sevathur. This spatial data allows policymakers to prioritise resource allocation and implement targeted interventions in the most affected areas.
Moreover, classifying water quality into distinct categories raises community awareness about the quality of their local water sources, empowering residents to adopt appropriate water treatment practices. By combining WQI analysis with geospatial mapping, the study provided a robust foundation for understanding groundwater quality dynamics in the region and its broader implications for health and agriculture.
Suitability for irrigation
Agriculture in the Sevathur region depends heavily on groundwater. The study assessed its suitability for irrigation using parameters like Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Permeability Index (PI), and Kelley Ratio. These metrics determine how groundwater quality influences soil health and crop productivity.
Sodium Adsorption Ratio (SAR): All groundwater samples fell within the "excellent" category for SAR, indicating minimal sodium-related risks to soil structure. Low SAR values ensure that sodium does not accumulate excessively in the soil, preserving its permeability and aeration, which are critical for root development.
Residual Sodium Carbonate (RSC): About 94% of samples were suitable for irrigation based on RSC, while 6% were classified as marginal. RSC values assess the potential impact of carbonates and bicarbonates on soil quality. High RSC levels can lead to soil alkalinity, impairing its productivity over time.
Permeability Index (PI): The majority of groundwater samples were classified as suitable based on PI. PI evaluates the impact of sodium, calcium, and magnesium on soil permeability. Groundwater with high PI values supports healthy soil structure, enabling efficient water infiltration and root absorption.
Kelley Ratio: This parameter examines the balance between sodium and other cations in groundwater. While most samples were deemed acceptable, some exhibited slightly elevated sodium levels that could, over time, affect soil permeability and fertility.
Implications for agriculture
Sustainability of crop yield: The overall suitability of groundwater for irrigation ensures that most agricultural activities in the region can continue without significant adverse effects on soil health. However, areas with marginal RSC and elevated sodium levels require careful monitoring and management to prevent long-term soil degradation.
Crops and soil type: Farmers in Sevathur should consider cultivating crops tolerant to slightly saline or alkaline conditions in areas with borderline water quality. Examples include barley, cotton, and certain legumes.
Need for soil amendments: In zones with marginal groundwater quality, applying soil amendments such as gypsum can help neutralise excess sodium and improve soil structure. Regular soil testing should be integrated into agricultural practices to guide these interventions.
Efficient irrigation practices: Adopting modern irrigation techniques like drip irrigation and sprinkler systems can minimise water wastage and reduce the accumulation of salts in the soil. These practices optimise the use of groundwater and enhance crop productivity.
The findings underscore the critical balance between groundwater usage and soil health. Ensuring the sustainability of agricultural practices in Sevathur requires continued monitoring of irrigation water quality and proactive measures to mitigate potential risks.
Health risks of fluoride exposure
Fluoride contamination in groundwater poses significant health risks, particularly in the Sevathur region where 26% of samples exceeded safe limits. The study evaluated the Hazard Quotient (HQ) for different age groups, revealing:
Infants: 37% of samples had HQ > 1, indicating potential health risks.
Youngsters (2-8 years): 89% of samples exceeded the HQ threshold.
Teenagers (8-18 years): 71% of samples posed health risks.
Adults: 63% of samples had HQ > 1.
These findings highlight the need for urgent interventions to mitigate fluoride exposure, particularly among children, who are more vulnerable to its adverse effects.
Geospatial analysis of contaminants
The study employed Geographic Information System (GIS) techniques to map the spatial distribution of groundwater quality parameters. Key insights included:
TDS and Electrical Conductivity (EC): Higher values were concentrated near mining zones, reflecting the impact of mineral dissolution.
Major ions: Elevated concentrations of calcium, magnesium, and sodium were observed in central areas, influenced by rock-water interactions and anthropogenic activities.
Fluoride distribution: High fluoride levels were prevalent in southern and central regions, linked to the weathering of fluoride-rich minerals such as pyroxenes and apatites.
Hydrogeochemical processes
The study identified several key processes influencing groundwater chemistry. These include the dissolution of minerals like charnockites and gneisses, releasing calcium, magnesium, and fluoride into the groundwater. Additionally, ion exchange processes occur where sodium and potassium replace calcium and magnesium, altering the ionic composition of the water. Furthermore, anthropogenic activities such as agricultural runoff and wastewater discharge contribute significantly to elevated levels of nitrate and chloride in the groundwater.
Policy and management implications
The findings underscore the need for integrated water resource management to address groundwater quality issues in the Sevathur region. Recommended actions include:
Advanced water treatment: To ensure safe drinking water, the implementation of advanced treatment technologies such as reverse osmosis and ion exchange is crucial. These systems can effectively remove fluoride and other contaminants, making groundwater safer for consumption.
Groundwater recharge and conservation: Enhancing natural recharge through rainwater harvesting and artificial recharge structures can help dilute contaminants and replenish aquifers. These measures align with sustainable water management practices.
Regulating anthropogenic activities: Stricter regulations on agricultural practices, industrial discharges, and mining activities are essential to prevent further contamination. Promoting the use of organic fertilisers and eco-friendly practices can mitigate pollution.
Public awareness and health interventions: Educating communities about the risks of fluoride exposure and the importance of water treatment can empower residents to take preventive measures. Health screenings and nutritional interventions, such as calcium and vitamin D supplementation, can reduce the impact of fluoride toxicity.
Regional monitoring and research: Regular monitoring of groundwater quality using geospatial techniques can provide real-time data to guide interventions. Further research into the geochemical interactions and long-term trends in groundwater quality is essential for informed decision-making.
The Sevathur mine region’s groundwater quality reflects a complex interplay of natural geological processes and human activities. While the water is largely suitable for irrigation, significant portions are unfit for drinking due to high fluoride levels and other contaminants.
Addressing these challenges requires a multifaceted approach that integrates advanced water treatment, sustainable agricultural practices, and community engagement. By prioritising these actions, the region can safeguard its groundwater resources, ensuring health and agricultural productivity for future generations.