Increasing Water Supply: Strategies & Sustainable Futures

Meeting the Demand: Options for More Water

As global water demand rises, governments and communities are pursuing two broad types of response. Large-scale engineering solutions — dams, reservoirs, inter-basin transfers and desalination plants — can move or create vast volumes of water but cost billions, reshape landscapes and often create new problems alongside the ones they solve. Sustainable, small-scale approaches — conservation, groundwater management, grey-water recycling and community rainwater harvesting — work with natural cycles and can be implemented quickly and cheaply where large infrastructure is unaffordable. Both approaches are essential, and both have trade-offs that geographers must evaluate critically.

Key Fact

Four main strategies to increase water supply: diverting and storing water (dams and reservoirs), inter-basin water transfers (moving water by canal or tunnel from wet to dry regions), desalination (removing salt from seawater), and sustainable approaches (conservation, groundwater management, recycling and grey-water reuse). Each carries very different costs, scales and environmental footprints.

Strategies to Increase Water Supply

Dams and reservoirs are the most widespread large-scale approach. Dams trap river water, creating reservoirs that can release water year-round regardless of seasonal rainfall variability. They also generate hydroelectric power. However, reservoirs flood valleys, displace communities (China's Three Gorges Dam displaced around 1.4 million people) and alter downstream river flow, reducing sediment deposition that farmers depend on.

Water transfers move water by canal, pipeline or tunnel from regions of surplus to regions of deficit. They can supply millions of people and irrigate vast farmland but require enormous capital investment, complex international or inter-regional agreements, and can deplete the source basin if transfers exceed what it can sustainably lose.

Desalination removes salt from seawater or brackish groundwater to create drinking water. Around 21,000 desalination plants operate globally, producing roughly 95 million cubic metres of fresh water a day. The Middle East — particularly Saudi Arabia, UAE and Israel — depends heavily on desalination. Its main disadvantages are high energy cost (it takes roughly 3–10 kWh of energy to produce 1 cubic metre of fresh water) and the disposal of concentrated brine, which harms marine ecosystems if discharged carelessly. Solar-powered desalination is cutting the carbon cost in sunny regions.

Desalination works well in wealthy, coastal, sun-rich countries like Saudi Arabia and Israel, which have the money to build plants and the energy (increasingly solar) to run them. But for a landlocked, low-income country in Central Asia or sub-Saharan Africa, it is irrelevant — there is no coast and no capital for infrastructure. The technology also produces highly concentrated brine: Saudi plants discharge billions of cubic metres of brine a year into the Arabian Gulf, raising salinity and water temperatures, damaging coral reefs and fish nurseries. Any strategy must be evaluated in its geographic context.

Case Study: China South–North Water Transfer Project

The South–North Water Transfer Project (SNWTP) is the world's largest water transfer scheme. China's south — particularly the Yangtze River basin — is relatively water-rich, while the north, including Beijing, Tianjin and the North China Plain (which produces a large share of China's wheat and maize), faces acute water scarcity because the Yellow River and its tributaries have been heavily over-abstracted.

The project was formally approved in 2002 and construction began in 2003. It consists of three routes:

The Eastern Route — follows the ancient Grand Canal northward, pumping water from the Yangtze to the Huang–Huai–Hai Plain and Tianjin. Around 1,150 km long; operational from 2013.
The Central Route — draws water from the Danjiangkou Reservoir on the Han River (a Yangtze tributary) and sends it around 1,267 km north by gravity canal to Beijing and Tianjin. Operational from 2014. Beijing now receives around 70% of its daily drinking water via the project as a whole, with the Central Route being its primary source.
The Western Route — the most ambitious and controversial, planned to divert water from upper Yangtze tributaries through the Tibetan Plateau to the Yellow River. It remains unbuilt due to extreme engineering challenges, high cost and environmental concerns.

By 2023 the two operational routes had transferred over 60 billion cubic metres of water northward and supplied drinking water to more than 185 million people.

Advantages of the SNWTP:

Supplies drinking water to over 185 million people in water-scarce northern China, including Beijing and Tianjin.
Has helped reduce over-abstraction of the Yellow River and northern aquifers, giving some recovery to groundwater levels in the North China Plain.
Supports irrigated agriculture in the North China Plain, which produces a disproportionate share of China's food supply.

Disadvantages of the SNWTP:

Displacement: expanding the Danjiangkou Reservoir for the Central Route required resettling approximately 330,000 people, many of whom report inadequate compensation and poor relocation conditions.
Environmental damage: reducing Yangtze and Han River flows has lowered water levels in Dongting and Poyang lakes — China's largest freshwater lakes — threatening the Yangtze finless porpoise and other endemic species. Downstream water quality and sediment supply have also deteriorated.
Cost: total estimated cost exceeds 500 billion yuan (roughly £55 billion), making it one of the most expensive infrastructure projects in human history. The cost is reflected in higher water prices for consumers in receiving cities.
Source basin risk: climate projections suggest that rainfall in the upper Yangtze and Han basins may become less reliable under climate change, potentially reducing the volumes available to transfer.

Key Fact

By 2023 the SNWTP had transferred over 60 billion cubic metres of water and supplied more than 185 million people. However, it displaced around 330,000 people, damaged Yangtze and Han River ecosystems, and cost an estimated 500 billion yuan — roughly £55 billion.

Moving Towards Sustainable Water Futures

Large engineering projects can increase supply, but sustainable approaches aim to reduce demand and improve the efficiency of existing supplies:

Water conservation reduces demand through metered supply (consumers pay per litre, so they use less), drought-resistant landscaping, low-flow taps, showerheads and toilets, and public education campaigns. In Singapore, per-person daily water use fell from 165 litres in 2003 to 141 litres in 2020 through consistent conservation policy.
Groundwater management involves monitoring aquifer levels, licensing how much water can be extracted, and recharging aquifers artificially — injecting treated water back underground. In the Ogallala Aquifer of the US Great Plains, managed aquifer recharge programmes and new irrigation efficiency rules are slowing (though not reversing) the rate of depletion.
Recycling and reuse treats wastewater to a standard safe for irrigation (or even drinking). Singapore's NEWater recycled water meets around 40% of national demand, with the ultimate aim of achieving full self-sufficiency. Israel recycles over 85% of its wastewater for agricultural irrigation — the highest rate in the world.
Grey water — water from sinks, baths and washing machines that is not contaminated by faeces — can be collected and reused for toilet flushing or garden irrigation without full treatment, using simple household systems costing a few hundred pounds.

Local LIC/NEE Scheme: Wakel River Basin, Rajasthan, India

The Wakel River Basin Project in Rajasthan, western India, shows how community-managed water harvesting can transform rural water security in a semi-arid, low-income setting. Rajasthan receives only 100–400 mm of rain a year, mostly during the monsoon. Groundwater had fallen sharply by the 1990s as population grew and bore wells were sunk without regulation. By the early 2000s, many villages faced water shortages for nine months of the year.

From around 2000 onwards, the NGO Seva Mandir and local communities rebuilt a traditional water-harvesting system of johads (earthen check-dams) and small earthen bunds across seasonal streams in the Wakel catchment. The johads slow run-off during the monsoon, spread it over a wide area and allow it to percolate slowly into the ground, recharging the shallow aquifer. Over 50 johads were restored or newly built across the basin.

The results were significant:

Groundwater levels in the area rose by up to 6 metres within a few years of the johads' restoration.
Wells that had dried up refilled, giving communities reliable water for drinking and year-round small-scale irrigation of vegetables and pulses.
Grain yields in fields near the johads increased, reducing hunger and out-migration — people who had left during drought years returned when water became available.

Johads are ancient technology — some date back over 1,000 years — that communities built and maintained without external expertise. They use local earth and stone, require hand tools to construct, need no electricity and recharge groundwater (rather than storing it in open reservoirs where it evaporates). The contrast with the SNWTP is striking: the Chinese scheme costs £55 billion and moves water around 1,267 km; a johad costs a few thousand rupees and works with the monsoon rather than against it. Both solve real problems, but the johad does so with almost no environmental risk and full community ownership.

Conclusion

From the largest engineering project in human history to an earthen dam built with hand tools, the solutions to water insecurity span every scale and income level. The challenge is matching the right approach to the right context: China's cities needed the SNWTP; Rajasthan's villages needed johads. A sustainable water future will require engineering where scale demands it, but above all it requires using water more efficiently — because the cheapest litre of water is always the one you do not waste.