Chapter 8 — ଜଳ ସମ୍ବଳ

About three-fourths of the earth's surface is covered with water, yet water is a scarce resource, because only a tiny fraction of it is fresh and usable. Of all the water on the planet about 97.5 per cent is salt water in the oceans. Of the remaining 2.5 per cent, about 70 per cent is locked in the ice caps and glaciers of Antarctica, Greenland and the mountains, and most of the rest lies deep underground. The fresh water actually available to people in rivers, lakes, soil and shallow aquifers is well under 1 per cent of the total.

This fresh water is nevertheless a renewable resource, because it is continually recycled through the hydrological cycle. The sun evaporates water from the oceans, lakes and soil and plants transpire it; the vapour rises, cools and condenses into clouds; it falls as rain or snow; and the water runs off over the surface into streams and rivers or infiltrates into the ground, and returns to the sea to begin again. The cycle means that water is not used up but only moved and, sometimes, made unfit for use. The quantity of fresh water that a region receives each year is fixed by its share of the cycle, which is why water must be managed within that share.

India receives nearly 4 per cent of the global precipitation and ranks 133rd in the world in terms of water availability per person per year. Its annual precipitation is about 4,000 cubic kilometres, but because of evaporation and run-off to the sea only about 1,900 cubic kilometres is the usable surface and groundwater resource, and by 2025 the availability per person is expected to fall below the level at which a country is called water-stressed. The total renewable water resources of India are estimated at about 1,897 cubic kilometres a year.

India's water comes from four sources. Rainfall, almost all of it from the south-west monsoon between June and September, is the primary source, averaging about 118 centimetres a year but ranging from over 1,000 centimetres in Meghalaya to under 20 in western Rajasthan. Surface water in rivers and lakes: the Himalayan rivers, the Ganga, Indus and Brahmaputra, are perennial, fed by snow as well as rain; the peninsular rivers, the Mahanadi, Godavari, Krishna, Kaveri, Narmada and Tapi, are rain-fed and shrink in the dry season. Groundwater, stored in the pores of soil and rock, is the largest source for irrigation and drinking, and its annual replenishable resource is about 430 cubic kilometres. Lakes, tanks and ponds, natural and man-made, are the traditional stores of the villages.

The sea itself is a resource for fisheries and salt and, with desalination, for drinking on the coast, but at present the cost is high. The problem of India's water, which the next section takes up, is not that there is too little but that it comes at the wrong time, in the wrong place, and is used carelessly.

Water scarcity means that the water available in a region is not enough to meet the needs of its people, farms and industries, in quantity or in quality, at the time it is needed. It is not the same as low rainfall: a desert with few people may have no scarcity, while a wet city with millions may have severe scarcity. Scarcity is a relation between supply and demand, and both sides of it must be studied.

The natural causes lie in the way the monsoon delivers India's water.

Seasonal unevenness. About three-quarters of India's rain falls in the four months of June to September; the remaining eight months are dry over most of the country. Rivers that are in flood in August are trickles by April; tanks and wells fill in the monsoon and empty by summer. Unless water is stored, the whole year's supply must be caught in a few weeks, and when the monsoon fails or arrives late, the shortage is immediate.

Regional unevenness. Rainfall ranges from over 400 centimetres in the north-east and on the west coast to under 40 centimetres in Rajasthan, western Gujarat, the Deccan rain shadow and Ladakh. The Brahmaputra basin has far more water than it can use; the Deccan and the north-west have far less than they need. Within Odisha the coast receives about 150 centimetres and the western interior about 120, and the west suffers drought while the coast suffers floods.

Variability. The monsoon is not only seasonal but unreliable. A failure of the rains by 20 or 30 per cent in a year causes drought over large areas, as in 1965-66, 1972, 1987, 2002 and 2009; a surplus causes floods. The dry regions have the greatest variability, so the places that can least afford a failure suffer it most often. Climate change appears to be increasing the variability, with heavier bursts and longer dry spells.

Physical limits on storage. Much of the rain falls on steep, deforested hills and runs off to the sea within days, carrying soil with it; the hard rocks of the peninsula, including most of Odisha, hold little groundwater compared with the deep alluvium of the north, so wells in the plateau regions yield little and dry early.

Evaporation. High temperatures evaporate a large share of the water from tanks, reservoirs and fields, particularly in the dry regions where it is most needed.

These natural causes explain why India, with ample rain in total, has always had to store, move and share water, through tanks, wells, canals and dams. But they do not explain why the scarcity has grown in the last half-century while rainfall has not changed much. That is the work of the human causes described next.

The scarcity that India now faces is largely the result of human action on both the demand and the supply side.

Growing population. India's population has grown four-fold since independence while its water has not. A large and growing population means more water for domestic use and for the food that must be grown, and the water availability per person has fallen from over 5,000 cubic metres a year in 1951 to about 1,400 today, close to the threshold of stress.

Intensive agriculture. Agriculture uses about 80 per cent of India's water. The green revolution, with its high-yielding varieties of rice and wheat, needs assured irrigation, and the area under irrigation has expanded from about 22 million hectares in 1951 to about 70 million hectares today. Much of it is served by tube-wells pumping groundwater, which has made India the world's largest user of groundwater. Water-hungry crops such as paddy and sugarcane are grown in dry regions; flood irrigation wastes half the water applied; and free or cheap electricity encourages over-pumping. In many districts of Punjab, Haryana, Rajasthan, Gujarat, Tamil Nadu and Maharashtra the water table falls a metre or more each year, and wells that once found water at 10 metres now go to 100.

Industrialisation and urbanisation. After independence the number of industries multiplied, and industries are heavy users of both water and the hydro-electricity that requires water; thermal and nuclear power stations use enormous volumes for cooling. Cities have grown many times over, with housing colonies and industrial estates that each sink their own wells and tap the same aquifer, so that urban water tables collapse and municipal supplies cannot keep up. The multiplying urban centres with large and dense populations and urban lifestyles have added to the water and energy requirements.

Pollution. Scarcity may also be caused by bad quality of water: where water is available in plenty but is polluted by domestic sewage, industrial effluents, chemicals, pesticides and fertilisers from farms, it is unfit for use and the region is effectively short of water. Most Indian rivers below cities and industries, including the Ganga, the Yamuna, the Brahmani and the Kathajodi at Cuttack, are polluted, and groundwater in many areas is contaminated by arsenic, fluoride, nitrate or salt.

Poor management. Leaking canals and pipes lose a third of the water they carry; tanks and ponds that once stored the monsoon have been silted, encroached or filled; forests that held rain in the catchments have been cleared; and water is priced so low that nobody saves it.

Unequal access. Scarcity also arises when water is unevenly shared, so that some have plenty while others have none; the poor in cities pay the most for the least, and in villages the wealthy with deep tube-wells dry the shallow wells of the rest.

The consequences are failing crops and farmer distress, falling water tables, drying rivers and wetlands, disease from bad water, conflicts between states such as those over the Kaveri, Krishna and Mahanadi, between city and village, and between farmers over wells, and the daily burden on women who walk for water. The scarcity is a threat to food security, health and peace, and it makes the conservation of water, the subject of the later sections, one of the most urgent tasks of the country.

The answer that India chose after independence to the problem of seasonal and regional scarcity was to build dams that store the monsoon flood and release it through the year. A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. Dams are classified by their structure, as timber, embankment or masonry dams, by their height as large and major dams or, alternatively, as low dams, medium height dams and high dams, and by their purpose. Dams were traditionally built to impound river water and to irrigate fields; today most large dams serve several purposes at once, and a project built to serve many purposes is called a multipurpose river valley project.

The purposes that a single project can serve are: irrigation of the fields below through canals; hydro-electric power generated by the water falling through turbines at the dam; flood control by holding the flood peak in the reservoir and releasing it slowly; domestic and industrial water supply to towns and factories; navigation on the reservoir and the regulated river; fish breeding in the reservoir; recreation and tourism; and afforestation and soil conservation in the catchment. Because water is stored once and used many times, the multipurpose project was seen as the most efficient way to develop a river.

The idea was borrowed from the Tennessee Valley Authority of the United States, and Jawaharlal Nehru proudly proclaimed the dams as the temples of modern India, because they would integrate the development of agriculture and the village economy with rapid industrialisation and the growth of the urban economy. The multipurpose projects, launched after independence with their integrated water resources management approach, were the centre of the early Five Year Plans.

The great examples are a roll of Indian rivers. The Bhakra Nangal project on the Sutlej-Beas basin, with its 226-metre dam, serves Punjab, Haryana and Rajasthan with irrigation and power. The Hirakud project on the Mahanadi in Odisha, described in the next section, is the longest earthen dam in the world and serves irrigation, power and flood control. The Damodar Valley project in Jharkhand and West Bengal, the first to copy the Tennessee model, tamed the river of sorrow with a chain of dams. The Nagarjuna Sagar on the Krishna, the Tungabhadra in Karnataka and Andhra Pradesh, the Rihand on a Ganga tributary in Uttar Pradesh, the Kosi in Bihar, the Chambal projects of Rajasthan and Madhya Pradesh, the Sardar Sarovar on the Narmada in Gujarat, the Tehri on the Bhagirathi in Uttarakhand and the Indira Gandhi canal from the Harike barrage into the Thar are among the others. India has built more than 5,000 large dams, the third largest number in the world after China and the United States.

The projects transformed the regions they served: the Punjab-Haryana plain became the granary of India on Bhakra water, and the Sambalpur-Bargarh plain became the rice bowl of Odisha on Hirakud water. But they also imposed costs that were not foreseen, and the evaluation of dams is the subject of the section after Hirakud.

The Hirakud dam is Odisha's greatest work of water engineering and one of the first multipurpose projects of independent India, and every student of the state should know it in detail.

Background. The Mahanadi, rising in Chhattisgarh and flowing about 850 kilometres to the Bay of Bengal, drains a basin of about 1,41,600 square kilometres and carries one of the largest monsoon floods of any Indian river. For centuries its floods devastated the delta of Cuttack and Puri. After the great flood of 1937 the engineer M. Visvesvaraya proposed storage in the upper basin, and the project was surveyed in the 1940s. The foundation stone was laid by Jawaharlal Nehru on 12 April 1948, and the dam was inaugurated by him on 13 January 1957.

The dam. Hirakud lies about 15 kilometres upstream of Sambalpur, where the river leaves the hills. The main dam, of earth, concrete and masonry, is about 4.8 kilometres long between the hills of Laxmidungri and Chandilidungri, and with its dykes on either side the whole barrier runs about 25.8 kilometres, the longest earthen dam in the world. Its maximum height is about 61 metres. The reservoir, Hirakud lake, is one of the largest artificial lakes in Asia, about 743 square kilometres at full level with a shoreline of over 600 kilometres and a gross storage of about 5.8 cubic kilometres, though siltation has reduced the live capacity. Two observation towers, Gandhi Minar and Nehru Minar, overlook it.

Purposes and benefits. Flood control was the first aim: the reservoir holds back the flood peak and has moderated, though not ended, the floods of the delta; the Mahanadi delta still floods when the reservoir is full and the lower catchment pours in. Irrigation through the Bargarh, Sasan and Sambalpur canals serves about 1.6 lakh hectares in kharif and 1.1 lakh in rabi in Sambalpur, Bargarh, Balangir and Sonepur, and the regulated flow supports about 4.4 lakh hectares more in the delta below; it made Bargarh the rice bowl of Odisha with two crops a year. Hydro-electricity is generated at two power houses, at Burla at the dam and at Chiplima 22 kilometres downstream, with a total capacity of about 350 megawatts, which powered the early industries of the state including the Hindalco aluminium smelter at Hirakud and the Rourkela steel plant. The reservoir supports fisheries, supplies water to industries at Sambalpur and Jharsuguda, and the Debrigarh sanctuary and the lake draw tourists.

Costs. The reservoir submerged about 250 villages and displaced about 1.5 lakh people, many of them tribal, and thousands were never properly resettled; their descendants still seek compensation. Fertile land and forest were drowned. The command area developed waterlogging and salinity where drainage was not provided. Siltation from the deforested catchment has cut the live storage, and the dam's flood protection has been criticised when releases during the 2008 and 2011 floods worsened flooding downstream. Industries around the reservoir now compete with farmers for its water, and the barrages built upstream in Chhattisgarh since the 2000s have reduced the dry-season inflow, leading to a dispute between the two states before a tribunal since 2018.

Hirakud thus shows in one project everything that the multipurpose idea promised and everything that it cost, which is why the examination asks about it so often.

In recent years the multipurpose projects and large dams have come under great scrutiny and opposition, and a balanced judgement is needed.

Advantages. Dams store the monsoon water that would otherwise run to the sea and make it available through the year, turning single-crop rain-fed land into double-crop irrigated land and raising food production; the green revolution rested on assured irrigation. They generate hydro-electricity, which is renewable, clean at the point of use and cheap once built, and which India's industrialisation needed. They moderate floods by holding back the peak. They supply water to cities and industries and provide navigation, fisheries, recreation and tourism. They integrate the development of a whole river basin and, in a country of seasonal rain, there is no substitute for storage on the scale they provide.

Disadvantages. Regulating and damming rivers affects their natural flow, causing poor sediment flow and excessive sedimentation at the bottom of the reservoir, which reduces its life and starves the delta of the silt that once renewed its soil and held back the sea. Dams fragment rivers, making it difficult for aquatic fauna to migrate, especially for spawning; the hilsa of the Mahanadi no longer reaches above Hirakud. The reservoirs created on the flood plains submerge the existing vegetation and soil, leading to its decomposition over a period of time, and the drowned forests release greenhouse gases. Dams displace large numbers of people, often tribal, who lose land, forest and livelihood, and rehabilitation has been poor; Hirakud, Rengali, Upper Indravati, Sardar Sarovar and Tehri all bear this record. Irrigation from dams has changed the cropping pattern, with farmers shifting to water-intensive and commercial crops, which has caused salinisation of the soil and waterlogging where drainage was neglected. Dams have increased the social gap between the richer landowners of the command area and the landless poor, and between the region that gains the water and the region that loses its land. They have caused inter-state water disputes, as over the Kaveri, Krishna, Narmada and Mahanadi. Ironically, dams built to control floods have sometimes triggered floods when heavy rain filled a full reservoir and forced emergency releases, as at Hirakud in 2008 and 2011 and on the Damodar and in Maharashtra and Gujarat in 2006; and sedimentation in the reservoir makes the floods worse over time. Dams also carry risk in earthquake zones and have induced earthquakes, as at Koyna in 1967. Finally, the big dams have been costly and slow, often taking decades and running far over budget, and much of the water they store is lost by evaporation and canal leakage before it reaches a field.

The judgement. The lesson drawn in India today is not that dams are wrong but that they were built without weighing their full costs, that the people who paid those costs were not the people who gained, and that smaller and gentler alternatives, watershed development, rainwater harvesting, tank restoration, groundwater recharge and efficient irrigation, were neglected. A modern water plan uses large dams where storage is unavoidable, builds them with proper rehabilitation, catchment protection, drainage and environmental flows, and puts the greater effort into the decentralised methods that the later sections describe.

The costs of large dams gave rise to popular movements that changed the water debate in India, and a student should know the main ones and what they stood for.

Narmada Bachao Andolan. The Save Narmada Movement is a non-governmental organisation that mobilised tribal people, farmers, environmentalists and human rights activists against the Sardar Sarovar dam being built across the Narmada river in Gujarat. It began in the 1980s under Medha Patkar and others. It originally focused on the environmental issues related to the trees that would be submerged under the dam water; recently it has re-focused the aim to enabling poor citizens, especially the oustees, to get full rehabilitation facilities from the government. The movement took the matter to the Supreme Court, which allowed the dam to proceed on condition of rehabilitation, and it drew the world's attention to the human cost of dams; the World Bank withdrew from the project in 1993.

Tehri Dam Andolan. The movement against the Tehri dam on the Bhagirathi in the Garhwal Himalaya, led by Sunderlal Bahuguna, opposed the dam on the grounds of earthquake risk in a seismic zone, the submergence of the old town of Tehri and the displacement of its people, the loss of a sacred river's free flow and the doubtful life of the reservoir; the dam was completed in 2006 but the movement shaped later policy on Himalayan dams.

Other resistance. Multipurpose projects and large dams have been the cause of many new social movements: the Silent Valley agitation in Kerala in the 1970s that stopped a dam in a rain forest; the opposition to the Koel-Karo project in Jharkhand; the movements of the displaced of Hirakud, Rengali and the Indravati projects in Odisha for rehabilitation; and the protests against the Polavaram project on the Godavari, which affects Odisha's Malkangiri district. Resistance to these projects has primarily been due to the large-scale displacement of local communities, who have had to give up their land, livelihood and their meagre access and control over resources for the greater good of the nation. The local people often had to bear the cost while the benefits went elsewhere.

Inter-state disputes. Objections have also arisen because of the failure of dams to serve the purposes for which they were built, and between states over the sharing of water. The Sabarmati basin farmers in Gujarat were agitated and almost caused a riot over the higher priority given to water supply in urban areas, particularly during droughts. Inter-state water disputes are becoming common with regard to the sharing of the costs and benefits of multipurpose projects; the Krishna-Godavari dispute over the objections raised by Karnataka and Andhra Pradesh governments regarding the diversion of more water at Koyna by the Maharashtra government for a multipurpose project reduced the downstream flow, and Odisha's dispute with Chhattisgarh over the Mahanadi is of the same kind. Tribunals under the Inter-State River Water Disputes Act of 1956 settle such cases, slowly.

Alternatives. The movements did not merely oppose; they pointed to alternatives. Small check dams and tanks that store water where it falls; the revival of traditional harvesting systems; watershed development that treats the whole catchment; groundwater recharge; efficient irrigation by drip and sprinkler that halves the water used; cropping patterns suited to the rain of a region; and the participation of local people in every decision. These are now part of national policy, and the next sections describe them.

Odisha is, by Indian standards, a water-rich state, but its water is as seasonal and as unevenly spread as the country's.

Rainfall. The state receives an average of about 150 centimetres a year, about 80 per cent of it from the south-west monsoon between June and September, with some from the retreating monsoon and from cyclones in October and November. The coast and the northern hills receive 150 to 180 centimetres; the western interior of Balangir, Nuapada, Kalahandi and Bargarh receives 120 to 130 and is the driest and most drought-prone part of the state; the Eastern Ghats of Koraput and Kandhamal receive over 150. The rain is erratic: the western districts have had drought in about one year in three, and the coast has floods almost every year.

Rivers. Eleven river systems drain the state, and a student should know them in order from north to south. The Subarnarekha enters from Jharkhand and drains Balasore. The Budhabalanga rises in Similipal and reaches the sea near Balasore. The Baitarani rises in the Keonjhar hills and drains Keonjhar, Jajpur and Bhadrak, joining the Brahmani at the Dhamra mouth. The Brahmani, formed by the Sankh and Koel near Rourkela, drains Sundargarh, Angul, Dhenkanal, Jajpur and Kendrapara, carrying the waste of Rourkela and Talcher; the Rengali dam stands on it. The Mahanadi, the great river, rises in Chhattisgarh, enters at Padampur, passes Hirakud, Sambalpur, the Satkosia gorge and Cuttack, and builds the delta with its branches the Kathajodi, Kuakhai, Birupa, Devi and Daya, the last flowing into Chilika; it carries about half the state's surface water. The Rushikulya rises in the Kandhamal hills and drains Ganjam, entering the sea near Chhatrapur past the turtle beach. The Vamsadhara and the Nagavali rise in Kalahandi and Rayagada and flow through Andhra Pradesh to the sea. The Indravati, the Kolab or Sabari and the Machkund or Sileru rise in the Koraput plateau and flow west and south to the Godavari, the only Odisha rivers that do not reach the Bay of Bengal directly. The Tel, the largest tributary of the Mahanadi within Odisha, drains Kalahandi, Balangir and Sonepur; the Ib joins the Mahanadi at Hirakud from the Jharsuguda coal field.

The state's surface water resource is estimated at about 85 to 90 cubic kilometres a year, of which only a part is usable because most flows to the sea in the monsoon, and its replenishable groundwater at about 17 cubic kilometres, of which well under half is used. The groundwater is plentiful in the alluvium of the coast and the river valleys and poor in the hard rocks of the plateau, and it is the main source of drinking water in the villages and of rabi irrigation in the delta.

Lakes and wetlands. Chilika, Ansupa near Cuttack, Kanjia at Nandankanan, the tanks of every village and the Hirakud and Rengali reservoirs are the standing waters of the state. The next section describes how Odisha has developed its water.

Odisha has developed its water through a set of major, medium and minor projects, and lives with three water disasters that no project has fully tamed.

Major projects. Hirakud on the Mahanadi, 1957, irrigation, power and flood control, is the first and largest. Rengali on the Brahmani in Angul district, completed in the 1980s, is a 70-metre dam with a reservoir of about 380 square kilometres, 250 megawatts of power and canals that irrigate over 3 lakh hectares in Angul, Dhenkanal, Cuttack, Jajpur and Kendrapara, with flood control for the Brahmani delta; it displaced about 30,000 people. Upper Indravati in Kalahandi and Nabarangpur, completed in the 1990s, diverts the Indravati across the watershed into the Tel-Mahanadi basin through a tunnel, generates 600 megawatts at Mukhiguda and irrigates about 1.3 lakh hectares in the drought-prone Kalahandi plain. Upper Kolab in Koraput, 1980s, generates 320 megawatts and irrigates Koraput and Jeypore. Balimela on the Sileru in Malkangiri, a joint project with Andhra Pradesh of the 1970s, generates 510 megawatts. Machkund, the oldest, of 1955, is shared with Andhra Pradesh. The Mahanadi delta irrigation from the Naraj and Mundali barrages near Cuttack, the Salandi in Bhadrak, the Anandpur barrage on the Baitarani, the Lower Indra, Lower Suktel and Ret projects in the west, and the Subarnarekha project in Balasore are among the medium and major works, together with several hundred minor irrigation projects, lift irrigation points on rivers and canals, and lakhs of wells and tube-wells. Yet only about a third of the state's cultivated area is irrigated, and the western uplands remain largely rain-fed.

Floods. The Mahanadi, Brahmani, Baitarani and Subarnarekha flood the coastal plain almost every year when the monsoon swells them beyond the capacity of their channels and embankments, and the worst floods, as in 1982, 2001, 2008 and 2011, submerge thousands of villages. Hirakud and Rengali have reduced but not removed the floods, because the catchment below the dams is large and the delta channels have silted; embankments protect some areas and worsen the floods in others; and drainage congestion behind embankments and roads keeps fields under water for weeks. Flood management combines reservoirs, embankments, drainage, forecasting and evacuation.

Droughts. The western and southern uplands, Kalahandi, Balangir, Nuapada, Bargarh, Boudh, Sonepur, Koraput and parts of Kandhamal, suffer drought whenever the monsoon fails or breaks, because the rain is erratic, the hard rock stores little groundwater and irrigation is scarce. The Kalahandi-Balangir-Koraput region became a byword for famine-like distress in the 1960s, 1980s and 1990s, and though roads, relief and irrigation have improved, crop failure and migration still follow a bad monsoon. Drought management rests on watershed development, tanks and check dams, drought-tolerant crops and employment guarantee.

Cyclones. The coast is struck by cyclones from the Bay of Bengal in October-November and April-May, which bring storm surges that flood the delta with salt water and rain that adds to the river floods; the super cyclone of 1999 killed about ten thousand people. Odisha's cyclone shelters, early warning and evacuation, which held the deaths in Phailin in 2013 and Fani in 2019 to a few dozen, are a model for the world, and mangroves and shelter belts are the natural defence.

Water development in Odisha thus means storing the monsoon for the dry west, draining it from the wet coast, and defending the shore, three tasks that pull in different directions and demand a plan for the whole state.

Long before the large dams, the people of India had developed methods of catching and storing rain suited to each region, and the revival of these methods is now a central part of water conservation. Rainwater harvesting is the collection and storage of rain where it falls, for use later or for recharge of the ground. In ancient India, along with the sophisticated hydraulic structures, there existed an extraordinary tradition of water harvesting, and people had in-depth knowledge of rainfall regimes and soil types and developed techniques to harvest rainwater, groundwater, river water and flood water in keeping with the local ecological conditions and their water needs.

In the hills. In hill and mountainous regions people built diversion channels like the guls or kuls of the western Himalaya for agriculture, carrying stream water along the hillside to terraced fields. In Meghalaya a two-hundred-year-old system of tapping stream and spring water by using bamboo pipes is prevalent: about 18 to 20 litres of water enters the bamboo pipe system, gets transported over hundreds of metres, and finally reduces to 20 to 80 drops per minute at the site of the plant, a form of drip irrigation used for betel leaf and black pepper.

In the plains. Rooftop rainwater harvesting was commonly practised to store drinking water, particularly in Rajasthan. In the flood plains of Bengal, people developed inundation channels to irrigate their fields.

In the dry lands. In arid and semi-arid regions, agricultural fields were converted into rain-fed storage structures that allowed the water to stand and moisten the soil, like the khadins of Jaisalmer and the johads of other parts of Rajasthan. In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tankas or tanks for storing drinking water. The tankas could be as large as a big room; one household in Phalodi had a tanka that was 6.1 metres deep, 4.27 metres long and 2.44 metres wide. The tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard, connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops would travel down the pipe and was stored in these underground tankas. The first spell of rain was usually not collected as this would clean the roofs and the pipes; the rainwater from the subsequent showers was then collected. The rainwater can be stored in the tankas till the next rainfall, making it an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers. Rainwater, or palar pani as it is commonly referred to in these parts, is considered the purest form of natural water, and many houses constructed underground rooms adjoining the tankas to beat the summer heat as it would keep the room cool. Today in western Rajasthan the practice of rooftop harvesting is on the decline as plenty of water is available from the Indira Gandhi canal, though some houses still maintain the tankas since they do not like the taste of tap water.

In the south and east. The tanks of Tamil Nadu, Karnataka and Andhra Pradesh, tens of thousands of them chained down the valleys, and the ponds and tanks of Odisha, one or more in every village, some ancient like the great tanks of the temple towns, stored the monsoon for paddy, cattle, bathing and fish; the kata and munda of western Odisha were embankments across small streams that flooded fields above and irrigated fields below. These systems declined with canal irrigation and neglect, and their revival is now a state programme.

Given the disadvantages and rising resistance against multipurpose projects, water harvesting is now seen as a viable alternative both socio-economically and environmentally, and modern methods have been added to the traditional ones.

Rooftop rainwater harvesting. Rain falling on the roof of a house, school or office is led by gutters and pipes through a filter of sand and gravel either into a storage tank for direct use or into a recharge pit, trench or abandoned well that lets it soak into the ground and raise the water table. A roof of 100 square metres in a place with 100 centimetres of rain can collect about 80,000 litres a year after losses. The system is cheap, needs little space and can be fitted to any building; it is compulsory for new buildings in Tamil Nadu, where in 2001 the state made it mandatory for all houses across the state, and in many cities including Bhubaneswar. In Gendathur, a remote backward village in Mysuru district of Karnataka, villagers have installed rooftop rainwater harvesting in about 200 households and the village has earned the rare distinction of being rich in rainwater; with an annual rainfall of about 1,000 millimetres and 80 per cent collection efficiency, each house can collect about 50,000 litres a year, and the 200 houses together about one crore litres. In Shillong, where the rainfall is heavy but the town is short of water, nearly every house has a rooftop system that supplies 15 to 25 per cent of household needs.

Groundwater recharge. Beyond roofs, rain can be led into recharge wells, percolation tanks, check dams and contour trenches that hold it long enough to soak into the aquifer. Recharge is the answer to the falling water tables of the tube-well regions, and it stores water without the evaporation of an open reservoir.

Check dams and tanks. Small dams of earth, stone or concrete across streams hold back the monsoon flow, irrigate the fields below, recharge wells and cost a tiny fraction of a large dam. The revival of johads by Tarun Bharat Sangh in Alwar district of Rajasthan under Rajendra Singh in the 1980s and 1990s brought back the flow of five rivers and raised the water table across a thousand villages; the restoration of the tanks of Tamil Nadu and the ponds of Odisha does the same.

Watershed development. The most comprehensive method treats a whole small catchment, the watershed, from ridge to valley: plantations and contour trenches on the upper slopes, bunds and gully plugs on the middle slopes, check dams and farm ponds in the valley, and matching changes in crops and grazing, so that rain is caught at every step, soil stays in place and wells fill. Ralegan Siddhi in Maharashtra under Anna Hazare and Hiware Bazar are the famous examples; the national watershed programmes have treated large areas in the drought-prone west of Odisha, in Balangir, Nuapada, Kalahandi and Bargarh, with visible rises in water tables and cropping.

Odisha's programmes. The state's Mo Pokhari and other pond schemes renovate village tanks; rooftop harvesting is required in Bhubaneswar and Cuttack buildings; check dams and farm ponds are built under watershed and employment programmes; and the Odisha Lift Irrigation Corporation and the pani panchayats manage local water. The revival of the katas and mundas of the west is part of this.

Harvesting is not a substitute for all storage; a delta needs its flood defences and a state needs its power. But it is the cheapest, fairest and most sustainable way to meet the local needs of drinking water and small irrigation, and it puts the control of water in the hands of the people who use it.

The unit closes with the principles of water management that India and Odisha are now adopting, and with what each person can do.

Use less. Since agriculture takes 80 per cent of the water, the largest saving lies in the field. Drip and sprinkler irrigation deliver water to the root and can halve the water used for the same crop; laser levelling and lined canals cut losses; alternate wetting and drying of paddy saves a third of its water; and crops suited to the rain of a region, millets and pulses in the dry west of Odisha rather than paddy and sugarcane, cut demand at the root. In industry, recycling of cooling and process water, as at the Nalco and steel plants, reduces intake. In homes and cities, the repair of leaks, which lose a third of urban supply, metering, water-efficient fittings and the reuse of treated waste water for gardens and industry all reduce demand.

Store more, where it falls. Rainwater harvesting on roofs, in tanks and ponds, in check dams and through watershed development, described above, and the protection of forests in the catchments, which are the natural reservoirs, add to the supply without the costs of large dams. The restoration of wetlands such as Chilika and Ansupa keeps the natural stores that floods fill.

Recharge the ground. Groundwater is the largest store and the most abused; recharge structures, the regulation of tube-wells in over-exploited blocks, the pricing of electricity for pumping and the mapping of aquifers can bring the water table back. Odisha's groundwater is still under-used in most blocks, but the coastal and urban aquifers are already stressed and saline intrusion threatens the coast.

Keep it clean. Sewage treatment in every town, the treatment of industrial effluent before discharge, the control of mine drainage in the Brahmani and Baitarani basins, the reduction of chemical fertiliser and pesticide run-off, and the clean-up of the Kathajodi, the Daya and the other polluted stretches turn wasted water back into usable water.

Share fairly. Water is a common resource, and its allocation between farm, factory and town, between upstream and downstream, between states, and between rich and poor must be decided openly. The pani panchayats of Odisha, which give canal water users a voice in its distribution, the participatory irrigation management law of 2002, and the tribunals that settle inter-state disputes are the institutions of sharing. Priority to drinking water, then to ecology, then to agriculture and industry, is the order set by the National Water Policy.

Plan for the climate. Heavier bursts of rain, longer dry spells, stronger cyclones and a rising sea will test every part of Odisha's water system; the answer is more storage in small structures, better forecasting, flood-proof and drought-proof farming, coastal defences and the preservation of the mangroves and wetlands that buffer the shore.

What a student can do. Close taps, mend leaks, harvest the rain on the school roof, keep the village pond clean, plant trees in the catchment, choose the crops and habits that waste least, and count water as the precious and finite thing it is. Water scarcity is the sum of millions of small wastes, and its cure is the sum of millions of small cares.

In the examination this unit yields questions on the distribution of water, the causes of scarcity, the definition and examples of multipurpose projects, Hirakud in detail, the advantages and disadvantages of dams, the Narmada and Tehri movements, the rivers and projects of Odisha, the traditional methods of harvesting by region, the tankas of Rajasthan and the bamboo drip of Meghalaya, rooftop harvesting and its calculation, and water conservation. Prepare each with a definition, an Indian example and an Odisha example.