- Asked 3/30
- 2079 Baisakh · 6 marks
- 2069 Asar · 4 marks
- 2067 Asar (old course)
Water sources: quality and quantity
Short answer
Surface sources are rivers, lakes, ponds, and impounded reservoirs; rivers are plentiful but turbid and polluted, lakes are steady but may have algae, ponds are poor and seasonal, reservoirs are reliable. Ground sources like springs, wells, and infiltration galleries are clear and need less treatment. Surface water generally requires sedimentation, filtration, and disinfection.
Describe the various sources of water (surface water in particular) used in water supply schemes with respect to their quantity and quality (suitability, merits and demerits).
Sources of water are of two kinds: surface sources (rivers, streams, lakes, ponds, impounded reservoirs) and ground sources (springs, wells, infiltration galleries). Rain water is a minor source.
Surface sources
| Source | Quantity | Quality | Merits | Demerits |
|---|---|---|---|---|
| Rivers/streams | Large, varies with season; may fall to low flow in dry season | Turbid in monsoon, soft, polluted by sewage/industrial waste downstream | Plentiful, easy to tap | Needs full treatment; flood and low-flow problems |
| Lakes | Large and steady | Usually clear, soft; may have algae, taste, odour | Large storage, less turbid | Pollution from bank activities; algae growth |
| Ponds | Small, dries in summer | Poor, polluted by washing, cattle, vegetation | Local and cheap | Unsafe; seasonal |
| Impounded reservoirs | Large and controlled by dam | Settled water, less turbidity; algae possible | Reliable all year, can serve flood control and power | High cost; evaporation, silting; submergence |
Surface water is generally soft and has more turbidity, bacteria and organic matter than ground water, so it requires sedimentation, filtration and disinfection.
Ground sources
- Springs: small to moderate yield, clear and bacteriologically good; the best choice in the hills.
- Wells and tube wells: steady yield, hard water, free from turbidity; may contain iron, manganese or arsenic.
- Infiltration galleries: naturally filtered river-side water.
Choice
Surface water suits large urban supplies where big quantity is required, whereas ground sources suit small towns and rural areas where quality is good and treatment is not easy.
✓ Answer checked by Claude Opus 5.5 (high effort)
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