Factors influencing water resources: supply, demand, security
Water Resources and Management
Factors Influencing Water Resources
Water resources are shaped by three main forces: Supply, Demand and Security. Think of them as the three legs of a tripod that keeps the water system balanced.
Supply
Supply is the amount of water that enters the system. It can be visualised as a garden hose: the more pressure (rainfall, glacier melt) the more water flows.
- 🌧️ Precipitation – rain and snow.
- ❄️ Glaciers & Ice Caps – meltwater during warmer months.
- 💧 Groundwater Recharge – water seeping into aquifers.
- 🌊 River Flow – influenced by upstream catchment.
| Source | Example | Contribution (%) |
|---|---|---|
| Rainfall | Annual average 800 mm in temperate zones | 70% |
| Glacier Melt | Alps, Himalayas | 15% |
| Groundwater | Aquifers under the UK | 10% |
| River Flow | Amazon Basin | 5% |
Demand
Demand is the amount of water people and industries want to use. Picture a busy supermarket: the more shoppers (population) and more sales (industry) the higher the demand.
- 👥 Population Growth – more mouths to fill.
- 🏭 Industrial Use – factories, mining, energy production.
- 🌾 Agriculture – irrigation for crops.
- 🌡️ Climate Change – hotter climates increase evaporation and water use.
Demand can be expressed by the equation:
$$D = P \times U + I + A$$
Where P = population, U = per‑capita usage, I = industrial demand, A = agricultural demand.
Security
Security is about how reliably water can be accessed and used. Think of it as the safety net that keeps the water system from breaking.
- ⚖️ Governance – laws, policies, and institutions.
- 🏗️ Infrastructure – dams, pipelines, treatment plants.
- 🛡️ Political Stability – conflict can disrupt supply.
- 🧪 Water Quality – pollution can make water unsafe.
Security can be quantified by the Water Security Index (WSI):
$$WSI = \frac{S \times Q}{P}$$
Where S = supply reliability, Q = quality, P = population pressure.
Revision
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