Water Resources: Class 10 Geography · Chapter 3

Picture a city in July. Streets are knee-deep in rainwater, buses stall and schools close for the day. Come May, the same families wait beside a tanker with buckets, because the taps have run dry. How can one place have too much water and too little in the same year? This chapter is about that puzzle: where our water comes from, why it runs short, and how people have learnt to store it and share it.

Seen from space, Earth looks like a water planet, since oceans cover about 71 per cent of its surface. Yet almost all of that water is salty. Of every 100 litres on Earth, only about 2.5 litres are fresh, and most of that is locked in ice and glaciers or lies deep underground (Fig. 3.1). The water people actually draw on, in rivers, lakes and reachable groundwater, is less than one per cent of the total.

Luckily, fresh water is not used up the way coal is. The sun's heat lifts water from seas, lakes and leaves as vapour; the vapour cools into clouds; and the clouds return it as rain and snow. Some of it flows over the land into streams and rivers as surface runoff. Some soaks into the soil and rock to refill groundwater. This endless loop is the hydrological cycle (जलीय चक्र). Because it keeps refilling our rivers and wells, water counts as a renewable resource (Fig. 3.2).

So here is the puzzle. If water keeps coming back, why do so many places run short? Why do farmers in some districts drill deeper every few years, and why do whole cities depend on tankers in summer? The answer has less to do with how much rain falls, and more to do with how we use, share and spoil the water we get.

3.1 Water Scarcity and the Need for Water Conservation and Management

Most water shortages are made by people. That may surprise you, because the words "water shortage" usually bring to mind a desert village and a long walk to a well. Some regions do start with less water, since rain varies from place to place and season to season. But three human habits do most of the damage. We over-exploit sources, pumping and diverting more than rain puts back. We use too much, as when a garden hose runs through a hot afternoon. And access is unequal: one colony gets water round the clock while the next waits for a weekly tanker.

Usable fresh water reaches us in three ways: as rain itself, as surface water gathered in rivers, lakes and tanks, and as groundwater pumped from wells. A place can have all three and still go short, as Fig. 3.3 shows. Scarcity begins when demand outgrows the usable supply, and the usable supply shrinks whenever water is polluted. So a city with heavy rain but a fast-growing population, careless pumping and dirty lakes can be as thirsty as a desert town.

3.1.1 More people, more demands

India's population has more than tripled since the 1951 Census. Every extra person needs water at home, but the bigger need is hidden in food. Growing rice, wheat or sugarcane takes far more water than any household uses, and irrigated agriculture is the largest user of water in India. To feed more people, farmers now irrigate fields through the dry months as well. Part of the answer lies in crops bred to survive drought and in dry-farming methods that make the most of every shower.

Drive past farms in Punjab, Haryana or western Uttar Pradesh and you will see private tube-wells running for hours. Each farmer gains by pumping more, but together they pull water out faster than the rain can put it back. The water table, the top of the water-soaked layer underground, sinks year after year (Fig. 3.4). Shallow wells dry up, borings must go deeper and pumping costs climb. If the groundwater runs out, both drinking water and the food grown with it are at risk.

Factories add a double demand. They draw water directly for cooling, washing and processing, as steel plants, textile dyeing units and paper mills do. They also draw it indirectly through the electricity they consume, part of which comes from hydroelectric dams. Meanwhile, India's towns have swollen into cities. A flat with running taps, flush toilets and a washing machine uses far more water than a village home, and many housing societies bore their own wells. In several cities, groundwater has been pumped out faster than it can recover.

3.1.2 When water is there but unsafe

Scarcity is not only about quantity. A town may stand beside a large river and still lack safe water. The river may carry untreated sewage, factory waste, and pesticides and surplus fertilisers washed off farms. Drinking such water spreads diarrhoea, cholera and typhoid. Even groundwater can be unsafe: in some districts it naturally contains harmful fluoride or arsenic. So a region can be short of usable water even when its rivers are full.

Safe drinking water at home is now a national goal. The Jal Jeevan Mission, launched in 2019, aims to give every rural household a working tap with a regular supply of safe water. The target is 55 litres per person per day (Economic Survey 2020–21, quoted in your textbook).

3.1.3 Why we must conserve and manage water

Put these pressures together and the case for careful water management is clear. Conserving water and managing it well:

• protects our health, because enough clean water prevents disease;
• secures our food, since much of our grain depends on irrigation;
• keeps livelihoods going, from farming and fishing to weaving and dyeing;
• keeps industries and power stations running;
• saves rivers, wetlands and the life in them from drying up or dying.

The opposite path is easy to picture: lakes turned into rubbish dumps, rivers that no longer reach the sea, and villages abandoned when the last well fails. Water mismanaged today becomes an ecological crisis tomorrow.

3.2 Multi-purpose River Projects and Integrated Water Resources Management

How do you hold on to water that arrives in a few monsoon months and must last the whole year? Indians have been answering this question for more than two thousand years, as the timeline below shows, with walls of piled stone across streams, artificial lakes, earthen embankments and canals. Independent India scaled the idea up, and today almost every major river basin has at least one big dam.

3.2.1 Dams and multi-purpose projects

A dam (बाँध) is a barrier built across a river so that people, rather than the river, decide where its water goes and when. Behind it the water collects in an artificial lake, the reservoir. Every dam also needs a safe way to get rid of surplus water, usually a spillway, so that floodwater never pours over the top and wrecks the structure.

Step through Fig. 3.5 and count the jobs a single reservoir can do: watering fields through canals, spinning turbines for electricity, and supplying towns and factories. It can also soak up floodwater and let it out slowly, and carry boats, fish farms and visitors. Older dams were usually built for the first job alone. A project planned from the start to combine several of these jobs is called a multi-purpose river project.

Two classic examples show the idea. In the Satluj–Beas basin, the Bhakra–Nangal project generates hydroelectricity and also feeds canals that irrigate large parts of Punjab, Haryana and Rajasthan. On the Mahanadi in Odisha, the Hirakud project stores water for farms and power and shields the delta downstream from floods.

Imagine India in 1947. Most farms depended on the monsoon, most villages had no electricity, and the Bengal famine of 1943 was a fresh memory. Big dams promised to tackle all of this at once, sending water to farms and power to factories, so that villages and cities could grow together. Jawaharlal Nehru, India's first Prime Minister, called them the "temples of modern India".

Your textbook includes a map of India's major rivers and dams. We do not draw maps here, so practise with an outline map of India instead. The dams in Table 3.4 are the ones most often asked in board map work.

3.2.2 The debate over large dams

In recent decades, large dams have faced searching questions and organised protests. Scientists, affected communities and activists point to costs that early planners underestimated. Supporters reply that India cannot feed its people or light its homes without stored water. A good exam answer, like a good citizen, considers both sides.

Follow the river downstream through Fig. 3.6. Behind the wall, the rising reservoir has drowned forests and soil, which rot slowly under water. The river still brings silt and sand, but in the still reservoir they settle out, so year by year the reservoir fills up and stores less. At the wall itself, fish that swim upstream to breed, such as the hilsa, can go no further. Below the dam, the river runs almost free of silt and scours its bed down to bare rock, a poor home for fish, insects and water plants.

Flood control, one of the main reasons for building many dams, does not always work. A silted reservoir has less room for floodwater. In a spell of extreme rain, its operators may have to release huge volumes at once, flooding the valley below. Farms on the floodplain also lose the free load of fertile soil that floods used to spread, so they grow poorer. Large reservoirs have been linked to earthquakes triggered by the weight of water; the Koyna earthquake of 1967 in Maharashtra is often cited. Their still water can also breed mosquitoes, water-borne diseases and pests.

Canal irrigation has changed what farmers grow, too. With assured water, many switched to thirsty cash crops such as sugarcane and paddy. Over-watering in hot, dry areas raises the water table and brings salts to the surface, a process called salinisation (लवणीकरण) that leaves white crusts on once-fertile fields. Finally, the people whose villages lie in a reservoir's path must leave their homes and land. Critics argue that many displaced families have never been fully resettled.

The government has also tried to get more out of the water we already have. The Pradhan Mantri Krishi Sinchayee Yojana (PMKSY), launched on 1 July 2015, aims to bring at least protective irrigation to every farm in the country. Its broad goals are:

• Har khet ko pani (water for every field): expand the farmland that has assured irrigation;
• Per drop more crop: grow more with each drop, through drip and sprinkler irrigation and less wastage;
• use water more efficiently on the farm, so that it lasts longer through the season;
• spread sustainable conservation practices, such as watershed development and rainwater harvesting.

3.3 Rainwater Harvesting

Long before cement and diesel pumps, Indian villages kept water through the dry season without any big dam. Their secret was local knowledge: which months brought rain, which slopes shed it and which soils held it. From that knowledge came dozens of small, cheap structures, each built for its own landscape, to catch rain, floodwater, streams and groundwater. As objections to big dams grew, many planners and activists turned back to these methods as a cheaper, fairer and greener alternative. Collecting rain where it falls and storing it is called rainwater harvesting (वर्षा जल संग्रहण).

3.3.1 A method for every landscape

Each region worked out a method that suits its land and rain, as Table 3.7 shows.

High in the cold desert of Spiti, Himachal Pradesh, a kul may wind for kilometres from a glacier-fed stream to a round village tank, as at Kaza. Villagers open the tank and let water out to their fields when the crops need it, often taking turns.

A khadin works like a sponge with a wall (Fig. 3.7). Rain falling on rocky high ground runs down onto a farm field. An earthen bund on the lower side stops it from escaping, so the water stands on the field for weeks and soaks deep into the soil. Once it has gone, farmers sow a winter crop in the moist earth. Wells below the bund fill with the water that seeped through. Johads are small crescent-shaped earthen dams found elsewhere in Rajasthan; they too hold back runoff and recharge wells.

3.3.2 Tankas of the Thar

Imagine the first storm of the monsoon in Phalodi, in western Rajasthan. Instead of rushing to save every drop, the family lets the water run to waste, because it is washing a year's dust off the roof and the pipe. Only from the next shower is the pipe turned towards the tanka: an underground tank under the courtyard or inside the house, sometimes as large as a room. Towns such as Bikaner, Phalodi and Barmer once had a tanka in almost every home (Fig. 3.8).

Why go to such trouble? Because a well-kept tanka holds water right through the dry months, long after ponds and wells have failed. People in the region call rainwater palar pani and prize it as the purest water there is. A full tanka also works as a cooler: some families built a room underground beside it to escape the summer heat.

Neighbours sometimes shared roofs: a photograph in your textbook shows a long pipe carrying rain from a neighbour's roof into a family's tanka. Canal water has changed this. Since the perennial Indira Gandhi Canal began bringing water to western Rajasthan all year round, fewer families bother to clean and fill their tankas. A few still do, for a simple reason: they think rainwater tastes better than tap water.

3.3.3 Old ideas, new roofs

The same idea is now spreading to modern homes, schools and offices in villages and cities. A modern rooftop system (Fig. 3.9) carries rain from the roof down a pipe and sends the dirty first flush away. Layers of sand and gravel clean the rest, which is stored in an underground sump for daily use. When the sump is full, the overflow goes into a recharge pit, an old dug well or a hand-pump bore. There it sinks down and tops up the groundwater.

How much can a roof collect? One millimetre of rain falling on one square metre of roof is exactly one litre of water. Some is always lost to splashing, evaporation and the first flush, so we multiply by the share actually collected, called the collection efficiency:

Laws and campaigns are spreading the habit. In 2003, after several years of drought, Tamil Nadu made rainwater harvesting compulsory for every public and private building in the state. Buildings that failed to comply risked losing their water connection. Your textbook describes it as the first state to make rooftop harvesting compulsory for all houses. Campaign posters, like one reproduced in your textbook, urge every family to become a "water harvester".

3.3.4 Bamboo drip irrigation in Meghalaya

In the hills of Meghalaya, farmers have used a clever system for about 200 years to water crops such as betel leaf and black pepper on steep slopes. Bamboo pipes tap a spring or stream high on the hill, and gravity does the rest (Fig. 3.11). Your textbook notes that 18–20 litres of water enter the pipes at the top, but only 20–80 drops a minute reach each plant at the end.

The design is simple but careful. Nothing is pumped: the spring lies higher than the fields, so the water runs downhill on its own for hundreds of metres. Farmers swing a length of pipe to send water to one patch or another, and where the line must cross a footpath, it is carried overhead on tall bamboo posts. Near the plants the channels get narrower and narrower, until what reaches each root is only a slow drip. It is drip irrigation, built from a local plant.