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This lesson examines sustainable (often "soft engineering") approaches to water management, including water conservation, rainwater harvesting, wastewater recycling, integrated drainage basin management and appropriate technology. It addresses Edexcel A-Level Geography (9GE0) Paper 1, Topic 5, Enquiry Question 4: What are the different approaches to managing water supply and how do they work?
Sustainable water management meets the water needs of the present without compromising the ability of future generations to meet their own needs. It works with natural processes rather than against them, and seeks to balance economic, social and environmental objectives.
| Principle | Explanation |
|---|---|
| Demand management | Reducing water consumption through efficiency, pricing and behaviour change (rather than simply increasing supply) |
| Catchment-based approach | Managing water at the drainage basin scale, considering all stakeholders and the whole system |
| Ecosystem services | Recognising and maintaining the natural water-regulating functions of ecosystems (wetlands, forests, floodplains) |
| Equity | Ensuring fair access to water for all, including the poorest and most vulnerable |
| Resilience | Building capacity to cope with variability and change (including climate change) |
| Integration | Linking water management with land use planning, agriculture, energy and urban development |
Water conservation aims to reduce demand and minimise waste. It is often the most cost-effective approach to improving water security.
| Measure | Water Saving | Implementation |
|---|---|---|
| Water metering | 10–15% reduction in household use | Universal metering in UK would save ~700 million litres/day |
| Low-flow fixtures | Taps: 50% reduction; showers: 30% | Building regulations; retrofitting; product standards |
| Dual-flush toilets | Saves 4–6 litres per flush (old toilets: 13L; dual-flush: 4/6L) | Standard in new builds in UK since 2001 |
| Greywater recycling | Reuse of bath/shower/washing water for toilet flushing and garden irrigation | Can reduce household water use by 30–40% |
| Drought-resistant gardens | Reduces outdoor water use (25%+ of summer domestic use is gardening) | Xeriscaping; native plant selection |
| Education and awareness | 5–10% reduction through behaviour change | Campaigns; real-time usage feedback; water labelling |
Agriculture uses 70% of global freshwater — so even small efficiency gains have large absolute impacts.
| Method | Efficiency | Detail |
|---|---|---|
| Flood/surface irrigation | 40–50% efficient | Traditional; very wasteful; still used on 85% of irrigated land globally |
| Sprinkler irrigation | 70–80% efficient | Better than flood but still significant evaporative losses |
| Drip irrigation | 90–95% efficient | Delivers water directly to plant roots; minimal evaporation; pioneered by Israel |
| Deficit irrigation | Variable | Deliberately under-irrigating at non-critical growth stages; reduces water use by 20–40% with only 10–15% yield reduction |
| Crop selection | N/A | Switching to less water-intensive crops (millet instead of rice; sorghum instead of wheat) |
| Soil moisture monitoring | Reduces over-irrigation by 15–25% | Sensors measure when irrigation is actually needed |
Exam Tip: Drip irrigation is a key example of appropriate technology for water conservation. It is widely used in Israel (covering ~75% of irrigated land), saving 50–70% of water compared with flood irrigation. However, it requires capital investment and technical knowledge, making adoption difficult for subsistence farmers in LICs.
| Measure | Detail |
|---|---|
| Closed-loop cooling | Recycling cooling water rather than using once-through systems; reduces industrial water use by 90%+ |
| Process optimisation | Redesigning manufacturing to use less water; semiconductor fabrication now uses 30% less water per chip than in 2010 |
| Water pricing | Volumetric charging incentivises efficiency; many countries still subsidise industrial water |
Rainwater harvesting (RWH) is the collection and storage of rainwater for later use. It is an ancient technology experiencing a modern revival.
| Type | Scale | Method | Context |
|---|---|---|---|
| Rooftop RWH | Household | Collection from roof via gutters into tanks (500–10,000 litres) | Urban and rural areas globally; very common in Bermuda, Singapore, parts of India |
| Surface RWH | Community | Collection of runoff from paved/ground surfaces into ponds, tanks or aquifers | Semi-arid regions (India, sub-Saharan Africa) |
| Check dams | Community/village | Small barriers across streams that slow flow and allow infiltration/recharge | Rajasthan (India); thousands built through community action (e.g. Tarun Bharat Sangh) |
| Johads and stepwells | Village | Traditional Indian water harvesting structures; earthen dams creating small reservoirs | Revival in Rajasthan has raised water tables and restored rivers |
| Sand dams | Community | Low dams built in seasonal riverbeds; sand accumulates behind dam and stores water in pore spaces | Kenya (Africa Sand Dam Foundation: 1,000+ dams built); each dam stores 2–40 million litres |
The NGO Tarun Bharat Sangh (led by Rajendra Singh) has revived traditional johad (earthen check dam) technology in the Alwar district of Rajasthan:
Wastewater recycling (or water reclamation/reuse) treats used water to a quality suitable for various purposes, reducing demand on freshwater sources.
| Treatment Level | Quality | Suitable Uses |
|---|---|---|
| Primary | Removal of solids | Industrial cooling; irrigation of non-food crops |
| Secondary | Biological treatment (removes organic matter) | Irrigation of food crops (restricted); industrial use |
| Tertiary/advanced | Filtration, UV, chemical treatment | Parks and golf courses; toilet flushing; groundwater recharge |
| Potable reuse | Reverse osmosis, UV, advanced oxidation | Drinking water supply (direct or indirect) |
Singapore is one of the most water-stressed countries in the world — a city-state of 5.9 million people with virtually no natural freshwater resources. It imports about 50% of its water from Malaysia under an agreement that expires in 2061.
Singapore's "Four Taps" strategy:
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