UPSC Prelims 2021 Q62: Geography – Hydrology / Water distribution
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (b) 2 only
Explanation
Distribution of Water on Earth
| Water Reservoir | Share of Total Water | Rank |
|---|---|---|
| Oceans (saline) | 97.5% | 1st |
| Polar ice caps + glaciers | ~1.9% (~68% of freshwater) | 2nd |
| Groundwater | ~1.5% (~30% of freshwater) | 3rd |
| Lakes, rivers, atmosphere | ~0.01% | 4th |
Only ~2.5% of Earth's water is freshwater. Of this freshwater:
- Polar ice caps + glaciers = ~68% (largest freshwater reservoir)
- Groundwater = ~30%
- Surface water (rivers, lakes) = ~1-2% (very small)
Statement 1 (rivers/lakes > groundwater) = FALSE. Groundwater is vastly more than rivers/lakes.
Statement 2 (ice caps > groundwater) = TRUE. Polar ice + glaciers exceed groundwater volume.
Answer: (b) 2 only.
Why each option is right or wrong
- (a) Incorrect. Statement 1 is wrong - groundwater vastly exceeds river/lake water (30% of freshwater vs 1-2%).
- (b) CORRECT. Only statement 2 is correct - polar ice caps and glaciers (~68% of freshwater) exceed groundwater (~30% of freshwater) in volume. Statement 1 is wrong (rivers/lakes are only ~1-2% of freshwater).
- (c) Incorrect. Statement 1 is factually reversed.
- (d) Incorrect. Statement 2 is a documented fact from IPCC and USGS.
Key point
Global water: 97.5% oceans + 2.5% freshwater. Freshwater breakdown: ice caps/glaciers 68% > groundwater 30% > surface (rivers/lakes) ~1-2%. So polar ice > groundwater > rivers/lakes. Only statement 2 correct.
Remember
Polar ice caps and glaciers contain more water than groundwater (statement 2 correct - ~68% vs ~30% of freshwater). Rivers and lakes are only ~1-2% of freshwater - far LESS than groundwater (statement 1 wrong). Correct answer: (b) 2 only.
Common mistakes
- Assuming rivers and lakes hold major freshwater. They hold only ~1-2% of freshwater and 0.01% of total water.
- Not knowing groundwater is the SECOND LARGEST freshwater reservoir after ice caps.
- Missing that climate-induced melting of ice caps is shifting freshwater from ice storage to oceans (raising sea levels but reducing freshwater availability).
Exam tip
Freshwater pyramid: Ice caps + glaciers (68%) > Groundwater (30%) > Lakes (0.3%) > Soil moisture (0.05%) > Atmosphere (0.04%) > Rivers (0.006%). Surface water is a tiny fraction of freshwater despite dominating human use.
Sources
- USGS Water Science School - Global Water Distribution
- NCERT Class XI Fundamentals of Physical Geography - Chapter on Hydrology