Case study UK
Water in the Thames basin
Southern Britain
The Thames connects water supply, groundwater and tidal flood management. Following its stores and transfers shows why a river basin can experience both shortage and flood risk.
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Location: 51.50°, -0.12°
Rainfall entering the Thames basin can become surface runoff, soil water or groundwater before reaching the river. Abstraction changes the amount available in these stores. A regional shortage can develop when demand and other losses exceed replenishment over the period being considered.
The lower river is tidal, and the Thames Barrier helps manage tidal-surge flood risk upstream. Compare this with water-supply management: both concern water, but they act on different flows, timescales and decisions within the basin.
Exam-style question
Why can a reservoir in the Thames basin fall in a dry summer even though the global water cycle is closed?
Teacher hint: A local store shrinks when abstraction and other losses exceed recharge; global conservation of water does not ensure local availability.
Sources
- UKCEH / Environment Agency
- Thames Water / Defra abstraction