Q.Mention any two reasons for the deterioration of water quality in India.
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Start your 14-day free trial to unlock the full solution →Concept understanding — Water Resource Depletion
Water Resource Depletion – A First Look
Imagine a bucket with a small hole in the bottom. You keep pouring water in, but the hole lets water out faster than you can pour. Over time, the bucket gets emptier. That is the core idea behind water resource depletion: we are using freshwater faster than nature can replenish it, so the total amount available for us keeps shrinking.
The Intuition: Why Should You Care?
Earth looks blue from space, but 97.5% of that water is salty ocean. Of the remaining 2.5% freshwater, most is locked in glaciers and ice caps. The tiny fraction left — rivers, lakes, groundwater — is what we drink, grow food with, and use in factories.
Now here is the problem: that tiny fraction is not infinite. Rain and snow refill rivers and recharge groundwater, but that process takes time — months for surface water, centuries for deep aquifers. When we pump groundwater for irrigation faster than rain can seep down to replace it, or when we divert entire rivers for cities, we are depleting the resource. The bucket is emptying.
The Precise Statement
Water resource depletion is the sustained reduction in the availability of freshwater in a region, caused by withdrawal rates exceeding natural recharge rates, often compounded by pollution that renders existing water unusable.
Three key parts to remember:
- Rate mismatch – We take water out (withdrawal) faster than nature puts it back (recharge). This is the root cause.
- Sustained reduction – A one-time drought is not depletion. Depletion means the total stock keeps falling year after year.
- Quality matters – Even if water is physically present, if it is contaminated by sewage, industrial waste, or agricultural runoff, it is effectively depleted for human use.
The Two Main Forms of Depletion
Surface water depletion – Rivers and lakes shrinking. The Colorado River in the US, the Yellow River in China, and the Yamuna in India all have stretches that run dry for parts of the year because so much water is diverted upstream. …
Part (a): Water quality declines due to untreated sewage/industrial effluents and chemical run-off from farms.
Part (b): Water is conserved through rainwater harvesting and watershed management (check dams, percolation tanks, afforestation).
Two main reasons for the deterioration of water quality in India:
- Untreated sewage and industrial effluents: most towns lack adequate treatment plants, so raw domestic sewage (carrying disease-causing pathogens and lowering dissolved oxygen) and factory effluents (carrying toxic heavy metals like lead, mercury and chromium, dyes and solvents) flow directly into rivers and lakes such as the Ganga and Yamuna, making the water unfit for use.
- Agricultural run-off: the heavy use of chemical fertilisers and pesticides on farms is washed by rain into surface water bodies and seeps down to contaminate groundwater with nitrates and toxic chemicals.
Concept understanding — Watershed Management
Watershed Management — From Intuition to Precision
Think of your kitchen sink. When you turn on the tap, water flows down the drain and into a pipe. That pipe connects to a larger network, and eventually the water leaves your house. Now imagine the entire neighbourhood — every roof, every road, every garden. Rain that falls anywhere in that neighbourhood eventually finds its way into the same network of drains and streams. That whole area — the land that drains to a common point — is a watershed.
A watershed is simply the area of land where all the water that falls on it (rain, snowmelt) drains to a single outlet — a river, a lake, or the ocean. Every piece of land on Earth belongs to some watershed, from a tiny hill slope to the entire Ganga basin.
Now, watershed management is the practice of taking care of that entire piece of land — not just the water, but the soil, the forests, the farms, and the people living there — so that the water is used wisely, the soil stays fertile, and the ecosystem remains healthy.
The Intuition: Why Manage a Watershed?
Imagine a village at the foot of a hill. The hill is the upper part of the watershed. If the villagers cut down all the trees on the hill to grow crops, what happens?
- Rain hits bare soil directly. The soil gets washed away into streams (erosion).
- The streams carry silt downhill, clogging the village pond and reducing its capacity.
- Without trees to slow the water, rain rushes down in a flood, then the land dries up quickly — no water for the dry season.
- The village runs out of drinking water and the fields lose fertility.
Now imagine the opposite: the villagers plant trees on the hill, build small check dams across streams, dig trenches along contours, and harvest rainwater on their rooftops. What changes?
- Rain soaks into the ground instead of running off. Groundwater levels rise.
- Soil stays in place. The pond stays clean and full.
- Water is available even in summer. Crops grow better. The village thrives.
That is watershed management in action — managing the land so that water behaves the way you want it to.
The Precise Statement
Watershed Management is the integrated use and conservation of land, water, and vegetation resources within a watershed, aimed at preventing soil erosion, improving water availability, and sustaining livelihoods — all while maintaining the ecological balance of the area.
Key points to remember:
- It is integrated — you don't manage water alone; you manage the entire system (soil, forests, agriculture, livestock, people).
- It works at the watershed scale — the natural boundary of the drainage area, not political or village boundaries.
- The goal is sustainable development — meeting present needs without destroying the resource for future generations.
The Core Components
| Component | What it involves |
|---|---|
| Soil conservation | Contour ploughing, terracing, bunding, afforestation — to stop soil from washing away |
| Water harvesting | Check dams, percolation tanks, rooftop harvesting, farm ponds — to capture and store rainwater |
| Vegetation management | Planting trees (afforestation), protecting forests, growing grass on slopes — to bind soil and recharge groundwater |
Part (a): Water quality declines due to untreated sewage/industrial effluents and chemical run-off from farms.
Part (b): Water is conserved through rainwater harvesting and watershed management (check dams, percolation tanks, afforestation).
Two effective methods for the conservation of water in India:
- Rainwater harvesting: rainwater from rooftops, courtyards and open ground is collected and either stored in tanks for use or channelled into pits to recharge the groundwater. Several states (e.g. Tamil Nadu) have made it mandatory for buildings, reducing dependence on piped supply and raising the water table. …
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