Climate change affects Karachi’s water tanks in four ways. Hotter weather makes bacteria grow faster in stored water. Heavier monsoon bursts flood underground tanks and push sewage into supply lines. Longer shortages mean water sits in tanks for more days and more of it comes from tankers and bores. Rising seas make groundwater saltier, which corrodes tanks and leaves scale. Each has a practical answer at household level, and most of those answers involve how the tank is built, sealed and cleaned.
This article sets out what is changing, using recorded events, and then what a house, a building or a business can do about it.
Climate Change in Karachi
Karachi is a hot, dry coastal city with a short monsoon. Three recent events show the direction of travel.
- Heat. In June 2015 the temperature reached 45°C, the highest in Karachi since 1979. About 2,000 people died across the region. Failures of the electrical grid left many areas without fans or working water pumps (Wikipedia).
- Rain. In August 2020 the city received 484 mm of rain, the most for any August since 1931, including a record 223.5 mm in a single day (Wikipedia). Whole neighbourhoods were under water.
- Salt. A 2025 study of groundwater in one Karachi locality found total dissolved solids between 1,550 and 4,920 mg/L and concluded that it was severely affected by seawater intrusion (Naseem and Bano).
The pattern scientists expect for this coast is more of each: hotter and longer summers, rain that is less frequent but more violent, and a rising sea.
Water Tanks in Karachi
Karachi stores its water at home because supply is rationed. The city needs about 1,200 million gallons a day and receives about 650 (Geo News). Line water arrives for a few hours on set days and waits in an underground tank, then an overhead tank, until it is used.
That makes every household tank a small reservoir, exposed to the same weather as the city’s large ones. The underground tank is exposed to floods and groundwater. The overhead tank is exposed to sun, heat and storms. See underground water tanks and overhead water tanks for how each works.
Impact of Climate Change on Water Tanks
Rising Temperatures and Evaporation
- Faster bacterial growth. Most waterborne bacteria multiply faster as water warms. Legionella grows between 20 and 50°C, with 35°C as its optimum (WHO), which is the temperature of a rooftop tank for much of the Karachi year.
- Naegleria. The amoeba Naegleria fowleri lives in warm fresh water, and infections tend to occur after long hot periods (CDC). Karachi records deaths from it most summers.
- Chlorine disappears sooner. Heat drives chlorine out of water, so any protection from the supply is gone within a day or two.
- More algae. Warm water plus any light gives rapid growth. See preventing algae growth.
- Plastic ages faster. Sun and heat make cheap tanks brittle. Lids fail first.
- Evaporation concentrates salts. In open or poorly sealed tanks the water level drops and scale forms at the waterline.
Increased Flooding Risk
- Floodwater enters underground tanks. A cover at floor level goes under when the street floods. That water carries sewage.
- Sewage mixes into supply lines. Flooded sewers leak into cracked water mains. Researchers who tested Karachi’s water in 2017 found E. coli in a third of samples and attributed it to this kind of mixing (Dialogue Earth). After heavy rain it gets worse. Floods also spread industrial waste from nullahs. See the impact of industrialization on water quality.
- Saturated ground pushes water through cracks. An underground tank with hairline cracks takes in groundwater when the soil around it is soaked. See detecting and preventing leaks.
- Storm winds strip rooftop lids. An open tank collects dust, leaves and bird droppings. See bird contamination in rooftop tanks.
- Mosquitoes. Standing water after rain and open tanks give dengue mosquitoes places to breed.
Changes in Precipitation Patterns and Decreased Rainfall
Long dry stretches lower the reservoirs that feed the city and increase rationing.
- Water sits longer. When supply comes weekly instead of on alternate days, water in the tank is older and staler.
- More tanker water. Tanker loads often carry sand and silt, and each delivery stirs up the tank floor.
- More boring water. It is hard and brackish and leaves scale. See Karachi’s hard water problem.
- Low levels expose sludge. A nearly empty tank delivers the dirtiest water it holds.
Salinity Intrusion
As the sea rises and bores pump the aquifer down, seawater moves inland underground.
- Bore water turns brackish and unfit for drinking, and coats tanks and fittings with salt and scale.
- Concrete and steel corrode. Salts in wet ground attack underground tanks from outside, rust the reinforcing steel and crack the concrete.
- Metal tanks and fittings fail early in salty, humid air.
Material choices for these conditions are covered in choosing the right tank material.
Consequences for Water Supply
Drinking Water Quality
Hotter tanks, dirtier inflow and longer storage all push in the same direction. Sindh’s household survey found E. coli in 79.1% of Karachi’s water at source and 85.5% at household level, as reported by Geo News. The water gets worse between the supply point and the glass, and a warmer, wetter, less predictable climate widens that gap unless tanks are looked after.
Water Supply and Demand
Heat raises demand at the same time as it strains supply. Pumping stations depend on electricity, and power failures during heatwaves and storms cut water to large parts of the city for days. Households respond by storing more, buying more tankers and drilling more bores, and each of those has consequences for the tank.
Health Implications
- Diarrhoeal disease, typhoid, hepatitis A and E and cholera rise after floods, when sewage and drinking water mix. Sindh reported 234 laboratory-confirmed cholera cases in the first five months of 2022 (WHO).
- Naegleria and Legionella are warm-water organisms and benefit directly from hotter tanks. See the Legionella threat in Karachi’s water tanks.
- Dengue follows mosquitoes, which follow open stored water.
- Dehydration and heat illness are worse when the tank is empty because the pump had no power.
The diseases themselves are described in waterborne diseases common in Karachi.
Mitigation and Adaptation Strategies
Infrastructure Upgrades at Home
| Risk | What to do to the tank |
|---|---|
| Flooding | Raise the neck of the underground tank 15 to 30 cm above the floor. Fit a sealed cover. Slope paving away from it. |
| Seepage | Inspect for cracks at every cleaning. Seal and re-waterproof with a drinking-water-safe product. |
| Heat | Shade the overhead tank. Choose an insulated, multi-layer tank. Do not oversize it. |
| Storms | Use a lid that screws or clamps. Strap down light tanks. Mesh vents and overflows. |
| Salt | Use sulphate-resisting cement below ground near the coast. Avoid ordinary steel. Keep sweet and bore water in separate tanks. |
| Power cuts | Keep the overhead tank full. Consider a solar pump. See solar-powered pumps. |
| Shortage | Size storage for your real supply gap. Fix leaks and overflows. |
Placement is covered in choosing the right location for your tank, and sizing in choosing the right size.
A cleaning calendar that follows the climate
- March or April: clean and disinfect before the heat.
- Before each monsoon spell: check lids and covers.
- Immediately: if floodwater or sewage enters a tank, stop using the water and have it cleaned and disinfected.
- September or October: clean after the rains.
We recommend cleaning every 6 months as the baseline. See how often to clean your water tank and the best time to clean it.
Rainwater Harvesting
The same bursts of rain that flood streets can fill a tank. A 120 square yard roof collects about 4,000 litres from a 50 mm spell. Storing it for washing and the garden, or sending it into a recharge pit, reduces both flooding and demand. See the benefits of rainwater harvesting.
Community Awareness Programs
Shared tanks in mosques, schools and apartment buildings serve the most people and get the least attention. Putting cleaning dates on a notice board, naming a person responsible for lids, and agreeing a post-flood routine cost nothing. For buildings, see who is responsible for tank cleaning in apartment buildings.
Government Initiatives
Supply, drainage and sewage treatment are public responsibilities. The Karachi Water and Sewerage Board was converted into a corporation in 2023 with the mayor as chairperson (Dawn), with the aim of improving its performance and finances. Whatever progress that brings, the water will still pass through private tanks before anyone drinks it. The framework is described in government regulations on water quality in Karachi.
Real-life Examples of Climate Impact
- June 2015 heatwave. With the grid failing, pumps could not lift water, and people faced extreme heat without it. An overhead tank kept full is a basic precaution.
- August 2020 floods. Ground floors and basements stood in water for days. Underground tanks with low covers were filled with floodwater and had to be cleaned and disinfected before use.
- Naegleria deaths. By July 2026 Karachi had recorded three deaths in the year, and health experts again urged residents to chlorinate underground and overhead tanks (ARY News).
Success Stories in Mitigation
Since 2024, a project led by NED University’s Panjwani Hisaar Water Institute has diverted used ablution water from more than 20 Karachi mosques into recharge wells instead of the sewer (Arab News). Community-built recharge wells elsewhere in the city take rain from flooded roads into the ground (ProPakistani). Both reduce flooding and refill the aquifer at the same time.
Lessons Learned
- The underground tank’s cover height decides whether a flood contaminates your water.
- A lid that stays on in a storm is worth more than any treatment afterwards.
- Heat makes the pre-summer cleaning the most important one of the year.
- After any flood, clean and disinfect before drinking. Do not rely on the water looking clear.
- Stored water is a reserve only if the tank is clean.
Future Outlook
The pressures will increase. Karachi will keep growing, summers will keep getting hotter, and rain will keep arriving in fewer, heavier bursts. Homes will go on relying on stored water, so the condition of household tanks will matter more, not less. The households that cope best will be those with sealed, shaded, properly sized tanks that are cleaned on a schedule. For the wider approach, see rainwater harvesting and tank cleaning for sustainable living.
Frequently Asked Questions
Do I need to clean my tank more often because of the heat?
Every 6 months is still the baseline. Make sure one cleaning falls just before summer, and clean sooner if the tank is in full sun and the water smells or turns green.
What should I do if floodwater gets into my underground tank?
Stop using the water for drinking and cooking. Have the tank emptied, cleaned and disinfected, and find out how the water got in before the next rain.
Is my boring water getting saltier because of climate change?
Possibly. Seawater intrusion is documented in parts of Karachi, driven by over-pumping and a rising sea. A TDS meter will show you the trend over time.
Will a bigger tank protect me from shortages?
Only up to a point. Very large tanks hold water for too long. Size storage to your real supply gap and keep it clean.
Prepare Your Tank for the Season
Call or WhatsApp 0313-2796778 for cleaning before summer, after the monsoon, or after a flood. We work across Karachi, including Keamari, Shah Faisal Town and Malir. The method is on our service procedure page.
About the author: Ahmar Shoaib is the founder of Karachi Tank Cleaning. He holds a BS in Chemical Engineering from Karachi University and has run the company’s cleaning and disinfection work since 2007. This article follows our editorial policy.
Sources: Wikipedia, 2015 Pakistan heat wave and 2020 Karachi floods; Naseem and Bano, Impact of Seawater Intrusion on Coastal Aquifers of Karachi (2025); PCRWR and Sindh MICS figures reported by Geo News (May 2025); WHO fact sheet, Legionellosis; CDC, About Naegleria fowleri infection; PCRWR testing (2017), reported by Dialogue Earth; WHO Disease Outbreak News, Cholera in Pakistan (June 2022); Dawn (July 2023); ARY News (July 2026); Arab News (June 2025); ProPakistani (August 2022).
