Simple mass balance and unit conversions
Mass balance means comparing what flows into a store against what flows out. Unit conversion means changing a measurement into a different unit so you can compare figures fairly.
Real World
The UK Environment Agency uses water balance calculations for the River Severn catchment: annual precipitation (~1,200 mm) minus evapotranspiration (~500 mm) and river discharge (~650 mm) reveals roughly 50 mm going into groundwater storage each year.
Exam Focus
Show every step of your working and include units — marks are awarded for method even if the final answer is wrong.
Essay Framework
Use PEEL to structure every paragraph. Tap each step for guidance and an example.
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