The Silent Link Between Drought and Contaminated Water
How dry spells intensify pollution and overwhelm treatment systems

When we think of drought, we imagine dry land and vanishing streams. But there's a hidden danger we often ignore: water quality. Drought doesn’t just mean less water; it means dirtier, riskier water too.

Why does water quality get worse during drought?

Less water means pollutants like heavy metals, salts, nutrients, and pathogens become more concentrated. Higher temperatures during drought reduce dissolved oxygen, harming aquatic life and making water taste and smell unpleasant. With rivers and lakes flowing more slowly or even stagnating, harmful algal blooms and bacterial growth can flourish. Exposed soils and increased erosion add sediments, making water cloudy and harder to treat [1].
During droughts, wastewater treatment plants face significant challenges that go far beyond water scarcity. Lower inflows reduce the stream’s ability to dilute pollutants. As incoming water becomes more concentrated, levels of ammonia, nitrate, phosphate, total suspended solids, and total dissolved solids rise sharply, pushing systems toward their operational limits. Warmer water temperatures intensify bacterial activity, increase biochemical oxygen demand, and disrupt processes like sludge settling and aeration [2]. Structural risks also emerge, as dry, contracting soils can crack pipes and degrade infrastructure. These stressors can cause odor issues, algal blooms in clarifiers, and even visible degradation downstream. In extreme conditions, streams may experience stagnant, low-oxygen water, pathogen buildup, and fish kills [3]. Drought doesn’t just challenge our water quantity; it fundamentally strains the capacity, cost, and compliance of water treatment across entire regions [4].
Why does this matter for water treatment?
Most treatment plants are built for “normal” water quality not the extreme concentrations of pollutants seen during drought. Removing nitrates, sulfates, and heavy metals becomes much harder and more expensive. In rural areas without advanced treatment facilities, poor water quality can directly threaten public health. Drought pushes water treatment systems beyond their design limits, risking system failure and unsafe water for millions.
Therefore, the recommendations for wastewater treatment management during drought are:
1. Implement real-time monitoring systems for key water quality parameters such as nutrient concentrations (ammonia, nitrate, phosphate), total suspended solids, and total dissolved solids to detect changes early.
2. Develop and regularly update a comprehensive drought response plan that outlines operational adjustments, resource allocation, and contingency measures to ensure uninterrupted treatment performance.
3. Adjust treatment processes to handle higher pollutant concentrations by optimizing aeration, sludge management, and chemical dosing to maintain treatment efficiency under stressed conditions.
4. Conduct frequent inspections and maintenance of pipelines and treatment infrastructure to prevent damage caused by soil contraction and corrosion during drought.
5. Ensure staff receive regular training on drought-related operational challenges and promote collaboration with environmental agencies for shared resources and expertise.

Reference
[1] Peña-Guerrero MD, Nauditt A, Muñoz-Robles C, et al. Drought impacts on water quality and potential implications for agricultural production in the Maipo River Basin, Central Chile. Hydrol Sci J [Internet]. 2020;65(6):1005–1021.
[2] Marino A, Bertolotti S, Macrì M, et al. Impact of wastewater treatment and drought in an Alpine region: a multidisciplinary case study. Heliyon [Internet]. 2024;10(15):e35290.
[3] Mosley LM. Drought impacts on the water quality of freshwater systems; review and integration. Earth-Science Rev [Internet]. 2015;140:203–214.
[4] Wright B, Stanford BD, Reinert A, et al. Managing water quality impacts from drought on drinking water supplies. J Water Supply Res Technol [Internet]. 2014;63(3):179–188.