The Indian-Based Centre for Science and Environment is cautioning that several African countries may face an impending groundwater crisis due to excessive use of water extraction systems for various needs.

Countries like Tanzania and Uganda, despite being rich in water resources, are experiencing water scarcity.

In Tanzania, for example, freshwater resources are essential for hydroelectric power and the extensive wetlands, spanning over 85,000 hectares, support both the economy.

The country also hosts about 5.7% of its land area covered by Lake Victoria, Lake Tanganyika, and Lake Nyasa, along with several smaller lakes. Nevertheless, a significant portion of its rural population still struggles with limited access to water sources.

“Despite being home to approximately 25 per cent of the world's freshwater resources, it could see a water-stressed future. The country manages its water demand through its rivers Pangani, Wami, Ruvu, Rufiji and Ruvuma; lakes Nyasa, Rukwa, Tanganyika and Victoria; and internal drainage basins of Lake Eyasi, Lake Manyara and the Bubu depression; and its southern coast. The rivers are largely perennial barring a few that are intermittent and ephemeral,” the report said.

According to the 2024 State of Africa Environment report, released yesterday in Nairobi, Tanzania is entirely dependent on rainfall for its water supply. All of its rivers are rain-fed, and both surface and groundwater sources rely on rainwater.

“More than 70 per cent of the population live in rural areas and depend to a large extent on groundwater reserves, mostly rainwater seeping into aquifers. In addition, groundwater is used for domestic purposes in peri-urban and urban areas, where there is no distribution network. While urban areas depend on borewells, rain-fed shallow wells are common in most of the country. Almost 65 per cent of the groundwater is used for domestic supplies,” it stated.

The report identifies population growth, industrial and agricultural activities, and rapid urbanization as major challenges driving increased water demand in Tanzania. This has led to excessive groundwater extraction, raising concerns about the sustainability and yield of groundwater sources, particularly in hard-rock areas with low recharge rates. For instance, in the Dodoma region, many local government areas have non-functional taps, reflecting the low sustainability of available water sources.

Rainfall distribution in Tanzania is highly variable with the southern regions receiving the majority of their rainfall over two to three months each year. For the rest of the year, they rely heavily on groundwater, which is often challenging to access.

"Rainfall pattern is also highly variable. The highlands in southwest Tanzania receive 1,200 mm per year of rainfall while the internal drainage basin receives less than 600 mm per year of rainfall."

Similar to Tanzania, the primary source of water for rural Uganda is spring water, supplemented by boreholes and shallow wells with hand pumps. In Uganda, 61% of the country's water is derived from groundwater sources, accessed primarily through springs and boreholes located around Lake Victoria and in the southwestern region.

According to the report, groundwater is the primary source of water supply in rural Uganda, including in semi-arid and arid regions. It is typically found in weathered or fractured basement rocks and has a yield ranging from 0.5 to 80 cubic meters per hour.

“There has been groundwater use since the 1930s through the construction of deep boreholes, shallow wells and protected springs. On average, 1,200 tubewells and 900 shallow wells are constructed annually in Uganda. Approximately 40,000 deep boreholes, 16,000 shallow wells and 30,000 protected springs have been constructed in the country mainly for rural domestic water supply. Boreholes and shallow wells are normally installed with handpumps,” it explained.

The situation in Uganda mirrors that of Tanzania, with high population growth and agricultural and industrial expansion leading to unplanned groundwater development and usage. This has raised concerns about the future yield and sustainability of groundwater in certain areas, particularly in the north-eastern and south-western regions, where natural groundwater recharge is lower compared to other parts of the country.

“There are reports of poor-quality groundwater mainly due to inadequate sanitation facilities—in many areas high nitrate and bacteriological contamination of groundwater have been reported. High fluoride and iron and manganese above permissible limits have also been found in the groundwater due to natural reasons, impacting public health and the economy of Uganda,” the report statement.

Why rainwater harvesting system?

The report is advocating for rainwater harvesting and recharging the groundwater sources to improve both quality and quantity of reserves in African countries. “Rural areas need to implement groundwater recharge structures efficiently as more than 90 per cent of Tanzania’s rural water schemes are dependent on groundwater.”

The report presents an intriguing argument that modern water supply systems for villages may be more costly compared to traditional water-harvesting methods still widely used in rural areas for both irrigation and drinking water. It clarifies that "traditional systems" do not imply outdated or dilapidated structures but rather refer to approaches distinct from large, capital-intensive, government-managed systems. In addition to their high financial costs, modern systems often impose significant ecological costs and may conflict with fundamental principles of sound agroclimatic planning. Conversely, traditional community-based structures not only support sustainable water use but also enhance social cohesion.

“The responsibility of taking decisions and action should be left to individuals, groups and local communities working together, encouraging economic independence and optimization of local resources at the micro-level. Traditional systems use low-cost, user-friendly techniques and are easily kept in good operational condition by local communities.”

Potential of rainwater harvesting

Further analysis in the report examines the typical rainwater potential of a small plot of land by using a hectare that receives 100 mm of rainfall annually. It highlights that this amount of rainwater can yield up to 1 million liters, which is sufficient to satisfy the drinking and cooking water needs of 182 people, assuming a generous daily requirement of 15 liters per person.

“Even if you are not able to capture all that water — this would depend on the nature of rainfall events and type of runoff surface, among other factors — you could still, even with rudimentary technology, capture at least half-a-million litres a year.”

According to calculations by CSE, Sub-Saharan Africa has a rainwater harvesting potential of 13,365,000 million cubic meters. To put this into perspective, this is nearly 44,550 times the daily volume of water that flows through the Nile River.

Other studies, including those by the UN Environment Programme (UNEP) and the World Agroforestry Centre, support this view, indicating that African countries experiencing water shortages due to climate change have significant rainwater harvesting potential. Countries like Ethiopia and Kenya, for example, have the capacity to meet the needs of six to seven times their current populations through rainwater harvesting.

Per the study, the total amount of rain falling across Africa is sufficient to meet the needs of 9 billion people, which is one and a half times the current global population. Additionally, around a third of the continent is considered suitable for rainwater harvesting if the threshold for effective collection is set at 200 millimeters of rainfall—a relatively low measure. This indicates that Africa is not water-scarce; in fact, the rainfall is more than adequate to meet the needs of the current population multiple times over.

The study further explains that Africa's water crisis is more an issue of economic investment rather than physical scarcity. It uses Kenya as an example, suggesting that if rainwater harvesting were factored in, Kenya would not be classified as a 'water-stressed country.' This highlights that the challenges are more about inadequate investment and infrastructure rather than a fundamental lack of water resources.

Ethiopia's national rainwater harvesting initiative, known as "My Dam at My Door," along with Tanzania’s MKUKUTA and WSDP policies, and similar projects in Zimbabwe and Malawi, are focused on promoting the sustainable and efficient use of rainwater. These policies, designed to address the escalating impacts of climate change, involve governments, private sectors, and individuals in various efforts to enhance rainwater harvesting. Initiatives include constructing large-scale reservoirs in public institutions such as schools and hospitals, training local communities, and offering subsidies for rainwater harvesting equipment.

In Malawi, for example, the Rainwater Harvesting Association of Malawi (RHAM) has implemented over 200 "calabash" rainwater harvesting systems since 2021. These systems are engineered to capture and store rainwater during the rainy season, providing a reliable water source for agriculture and domestic use throughout the entire year.