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Droughts, increasingly frequent and severe due to climate change, significantly impact the water quality of both surface and well water sources in Sri Lanka. With a heavy reliance on these water sources for agriculture, drinking water, and industry, the deterioration in water quality during prolonged dry periods poses substantial challenges to public health, agriculture, and overall socio-economic stability. This article analyses the comprehensive findings from the National Drought Plan (NDP) for Sri Lanka, offering insights into the consequences of drought-induced water quality deterioration, examines public health risks, and highlights the necessity for improved water management practices to safeguard Sri Lanka’s water resources.
Understanding Droughts in Sri Lanka
Sri Lanka experiences four main climatic seasons influenced by the Southwest and Northeast monsoons. The country’s water resources, including 103 rivers, numerous reservoirs, and groundwater aquifers, are significantly affected by variations in rainfall patterns. Prolonged dry spells, aggravated by global warming and local environmental changes, have increased the frequency and severity of droughts, particularly in the Dry Zone.
According to the NDP, droughts in Sri Lanka manifest in various forms:
- Meteorological Droughts: Reduced rainfall below the long-term average.
- Agricultural Droughts: Inadequate soil moisture affecting crop production.
- Hydrological Droughts: Decline in surface and groundwater levels.
- Socioeconomic Droughts: Disruption of water-dependent economic activities.
These droughts lead to reduced river flows, lowered reservoir levels, and diminished groundwater reserves, intensifying the strain on available water resources. A study assessing the influence of climate change on surface water resources in Sri Lanka’s Northern Province revealed that annual total rainfall has increased at a rate of 24.6 mm per decade, while temperature has risen by 0.54°C per decade. Despite the increase in rainfall, the reduction in the number of rainy days has led to significant runoff, reducing water availability in reservoirs and rivers. Read here
Impact of Droughts on Surface Water Quality
1. Reduced Water Volume and Increased Contaminant Concentration
Droughts lead to a significant reduction in surface water levels in rivers, lakes, and reservoirs. This reduced water volume concentrates existing pollutants, including nitrates, phosphates, and heavy metals, elevating contamination levels beyond safe thresholds. For example my previous study on Nilwala River, a crucial water source in the Southern Province, has shown increased concentrations of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) during drought periods, indicating heightened organic pollution levels. Read here
2. Temperature Rise and Algal Blooms
Reduced water volumes during droughts lead to higher water temperatures. Elevated temperatures decrease dissolved oxygen levels, creating an ideal environment for algal blooms. These blooms not only disrupt aquatic ecosystems but also release harmful toxins into the water.
- Eutrophication: Drought-induced nutrient concentration coupled with warmer temperatures accelerates eutrophication, leading to oxygen depletion and fish kills.
3. Sediment Resuspension and Contaminant Release
Lower water levels expose riverbeds and reservoir sediments. Occasional rainfalls following droughts can resuspend these sediments, releasing previously settled contaminants, including heavy metals and pesticides, back into the water column.
4. Salinity Intrusion in Coastal Areas
In coastal regions, reduced river flows during droughts allow seawater to intrude upstream, increasing the salinity of freshwater sources. This phenomenon has been documented in rivers like the Kelani and Nilwala, impacting both drinking water supplies and agriculture.
Impact of Droughts on Groundwater and Well Water Quality
1. Lowering of Water Tables and Increased Contamination
Droughts significantly lower groundwater tables due to reduced recharge and increased extraction. As water tables drop, the concentration of naturally occurring contaminants, such as fluoride and arsenic, increases. As the results, in regions like the North Central Province, high fluoride levels in well water during droughts have been linked to dental and skeletal fluorosis.
2. Saltwater Intrusion into Aquifers
Excessive groundwater extraction during droughts in coastal areas leads to saltwater intrusion into freshwater aquifers, rendering well water saline and unfit for consumption. For example, saltwater intrusion has been a persistent issue in the Jaffna Peninsula, compromising drinking water sources during prolonged dry spells.
3. Leaching of Agricultural Pollutants
Droughts limit the natural flushing of soils, allowing pesticides and fertilizers to accumulate. Subsequent rainfall events can lead to rapid leaching of these chemicals into shallow aquifers, contaminating well water.
4. Heavy Metal Mobilization
Changes in aquifer chemistry during droughts can mobilize heavy metals like arsenic, iron, and manganese. These metals pose significant health risks when they enter drinking water supplies.
- CKDu – chronic kidney disease of Unknown Etiology: The prevalence of CKDu in Sri Lanka’s Dry Zone has been linked to heavy metal contamination in groundwater, exacerbated during droughts.
Read also: How climate change might be amplifying Sri Lanka’s mysterious kidney disease
5. Bacterial Contamination
Lowered water tables and reduced water pressure increase the risk of bacterial contamination in wells. Pathogens such as E. coli can infiltrate wells, especially those that are shallow or poorly maintained.
Read here
Public Health Implications
The deterioration in water quality during droughts has profound public health implications:
- Waterborne Diseases: Increased concentrations of pathogens lead to outbreaks of diseases like cholera, dysentery, and hepatitis.
- Chemical Exposure: Elevated levels of nitrates, heavy metals, and pesticides in drinking water can cause chronic health issues, including neurological disorders, cancers, and kidney diseases.
- CKDu Crisis: The rise in CKDu cases in the North Central Province highlights the severe health risks associated with contaminated groundwater, particularly during droughts.
Socio-Economic Consequences
1. Agricultural Losses
Drought-induced water scarcity and poor water quality severely impact agriculture:
- Reduced Crop Yields: Contaminated water affects soil health and crop productivity.
- Livestock Losses: Animals suffer from water scarcity and are exposed to contaminated drinking sources.
2. Increased Household Expenses
Families are forced to purchase bottled water or invest in water purification systems, straining household budgets.
3. Migration and Displacement
In extreme cases, prolonged droughts and water scarcity force communities to migrate in search of better living conditions.
4. Economic Burden
The economic costs of droughts, including healthcare expenses, agricultural losses, and reduced labor productivity, place a significant burden on the national economy.
Strategies for Mitigating Water Quality Deterioration
1. Integrated Water Resource Management (IWRM)
The NDP emphasizes the need for IWRM, promoting the coordinated development and management of water resources to optimize social and economic welfare without compromising ecosystem sustainability.
2. Rainwater Harvesting
Rainwater harvesting offers a sustainable solution to water scarcity. The government and NGOs have initiated several projects promoting household and community-level rainwater harvesting systems.
3. Conjunctive Use of Surface and Groundwater
Combining surface water and groundwater use ensures a more reliable water supply and reduces the over-extraction of groundwater, mitigating the risk of saltwater intrusion.
4. Pollution Control Measures
- Regulating Agricultural Practices: Encouraging organic farming and reducing chemical fertilizer use.
- Improving Wastewater Treatment: Upgrading treatment facilities to prevent industrial and domestic effluents from contaminating water sources.
5. Early Warning Systems and Drought Monitoring
Developing robust drought monitoring and early warning systems enables proactive management and minimizes the adverse impacts of droughts.
6. Community Engagement and Awareness
Educating communities on water conservation practices and the health risks of contaminated water is vital for fostering sustainable water management.
Conclusion
Droughts pose a severe threat to Sri Lanka’s surface and groundwater quality, with far-reaching implications for public health, agriculture, and socio-economic stability. Addressing these challenges requires a holistic approach, integrating scientific research, policy interventions, and community participation. By adopting sustainable water management practices and strengthening resilience against climate-induced droughts, Sri Lanka can safeguard its vital water resources for future generations.
References:
https://www.researchgate.net/publication/357734743_Impacts_of_water_pollution_in_Sri_Lanka
https://doi.org/10.2166/wpt.2024.119
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Central Environmental Authority
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