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On a blistering afternoon in Tanzania’s eastern Bagamoyo district, 16-year-old Lucy Michael, a student at Kingani Secondary School, was struck by intense stomach pain that soon led to relentless vomiting. “I felt dizzy and confused,” she recalled. Diagnosed with typhoid fever and chronic stomach ulcers, Michael’s doctor traced her illness to the consumption of contaminated water.
Kingani, like many other schools in Tanzania’s coastal region, has long suffered from water crises, exacerbated by seawater intrusion. The Indian Ocean’s saltwater has been seeping into local freshwater aquifers, leaving students with no choice but to drink brackish water. “If you can’t afford bottled water, the only option is to drink salty water,” said Michael.
The problem of seawater intrusion — where saltwater flows into freshwater aquifers — is becoming increasingly common. This phenomenon, caused by reduced riverflow due to severe drought and rising sea levels, poses a growing threat to freshwater sources along East Africa’s coastline. Scientists have attributed much of this to climate change, which has resulted in higher sea levels that inundate wetlands and low-lying areas, further raising the salinity of rivers and underground water sources.
Across the globe, saline intrusion affects over a billion people who rely on groundwater for drinking and irrigation. In Tanzania, this issue is acutely felt by coastal communities. “When freshwater becomes salty, it’s dangerous for human consumption because it contains high levels of dissolved solids and inorganic matter,” said Jason Raphael, a water engineer at Bagamoyo district council.
Thanks to a rainwater harvesting project supported by the United Nations Environment Programme, the water situation at Kingani Secondary School has improved significantly. “Now we have enough rainwater stored in the tank for daily use,” said Michael.
The school’s deputy headteacher, Sylolian Stephen, explained how this initiative has transformed the students’ lives. “The seeping saltwater from the Indian Ocean severely impacted their performance. Many experienced dizziness, fatigue and severe dehydration after drinking salty water,” he noted. “Students spent hours searching for clean water instead of focusing on their studies.”
During the dry season, the water situation worsened, with the salty water becoming unusable even for laundry. But since the rainwater harvesting system was installed, the school now enjoys a stable supply of clean water. The system, which includes rooftop guttering and large storage tanks, has effectively solved Kingani’s water crisis.
Across Tanzania, nearly 43 per cent of the population lacks access to clean water, with women and girls bearing the brunt as they spend hours each day searching for water. At Kingani, 15-year-old Hadija Juma stands proudly beside the new rainwater harvesting tank. “This tank has changed our lives,” she said. “Before, it was hard to wash clothes with salty water, but now we have a steady supply of fresh water.”
To tackle growing water scarcity across both urban and rural areas, the Tanzanian government has adopted a rainwater harvesting policy. This policy is part of the country’s strategy to address the worsening impacts of climate change by promoting sustainable and efficient use of rainwater. The government is implementing initiatives to scale up rainwater harvesting, such as constructing reservoirs in schools and hospitals, training communities and providing subsidies for rainwater harvesting equipment.
“We are committed to ensuring every family can access and use rainwater effectively,” said Mwajuma Waziri, permanent secretary at ministry of water. “By investing in these initiatives, we will secure water resources for our communities and enhance our resilience against climate change.”
Various rainwater harvesting systems are being rolled out across Tanzania, each designed to meet the needs of different regions. “Rooftop harvesting is efficient and cost-effective. It uses existing structures to provide clean water for households,” said Jitihadi Rajabu, a senior water engineer at Ministry of Water.
Experts have welcomed the government’s efforts to promote rainwater harvesting, highlighting the importance of these systems in addressing the water crisis. “Water harvesting is essential for Tanzania, especially with the increasing variability in climate,” said Mengiseny Kaseva, professor of environmental engineering at Ardhi University. “Capturing and storing rainwater ensures a reliable water supply during dry periods, vital for both agricultural and domestic needs.”
Kaseva noted that rainwater harvesting not only provides immediate relief but also contributes to long-term sustainability by recharging groundwater, reducing soil erosion and improving water quality. He stressed the need to expand such initiatives across the country and calls for increased investment and collaboration between the government, private sector and communities. “With adequate funding, training and technology, we can make a substantial impact,” he said.
At Kingani Secondary School, teacher Joyce Lweno, 37, shared how rainwater harvesting has made a difference in her community. “Our school now has enough water for the students, even during dry spells,” she said.
In Nyandira village, located in Tanzania’s Morogoro region, farmers are relying on traditional water harvesting methods to address water scarcity and improve agricultural productivity. “We dig trenches along the land’s natural slope and build bunds to keep the water in place, allowing it to seep into the ground. It’s simple but effective,” said farmer Baraka Mkumbo.
These traditional techniques, known as fanya chini and fanya juu — Swahili for “make down” and “make up” — are widely used to prevent soil erosion and retain rainwater. Fanya chini involves digging trenches along a hillside and using the excavated soil to build a barrier on the downhill side, slowing water runoff and allowing it to soak into the soil. Fanya juu, by contrast, involves digging ditches and throwing the soil uphill, forming ridges that trap rainwater.
The methods have changed how Peter Ulanga, a Dodoma farmer, cultivates his fields. “Before we used fanya chini, our fields dried up quickly after the rains. Now, we can grow a variety of crops even during the dry season,” he said.
While rainwater harvesting has proven its potential, there is still much work to be done to ensure its sustainability. Observers call for increased investment and continuous education to expand the reach of these systems across Tanzania.
“I’m grateful for the rainwater harvesting system,” said Michael. “It’s given us the chance to focus on our studies without worrying about where our next drink of clean water will come from.”