“Water is probably the only natural resource to touch all aspects of human civilization – from agricultural and industrial development to cultural and religious values embedded in society”(USSR, 1978).
Global Water Resources
Earth’s water has been estimated to be 1.385 billion km3, 96.5 % of which is in the oceans and is saline. Of the remaining 3.5% water on land, approximately 1% is contained in deep, saline ground waters or in saline lakes, leaving only 2.5% of the earth’s water as freshwater. Of this freshwater, only 1.3% is mobile in the surface and atmospheric phases of the hydrologic cycle.
Table 1.1.Quantities of water in different phases of the hydrologic cycle (Source: USSR, 1978)
| Sl.No. | Item | Area106 km2 | Volume (km3) | Percent of total water | Percent of freshwater |
| 1. | Oceans | 361.3 | 1,338,000,000 | 96.5 | |
| 2. | Ground water:FreshSaline | 134.8134.8 | 10,530,00012,870,000 | 0.760.93 | 30.1 |
| 3. | Soil moisture | 82.0 | 16,500 | 0.0012 | 0.05 |
| 4. | Polar ice | 16.0 | 24,023,500 | 1.7 | 68.6 |
| 5. | Other ice and snow | 0.3 | 340,600 | 0.025 | 1.0 |
| 6. | Lakes:FreshSaline | 1.2 0.8 | 91,00085,400 | 0.0070.006 | 0.26 |
| 7. | Marshes | 2.7 | 11,470 | 0.0008 | 0.03 |
| 8. | Rivers | 148.8 | 2,120 | 0.0002 | 0.006 |
| 9. | Biological water | 510.0 | 1,120 | 0.0001 | 0.003 |
| 10. | Atmospheric water | 510.0 | 12,900 | 0.001 | 0.04 |
| 11. | Total water | 510.0 | 1,385,984,610 | 100 | |
| 12. | Freshwater | 148.8 | 35,029,210 | 2.5 | 100 |
As per WHO estimates, only 0.007% of all water on earth is readily available for human consumption.
Water Resources of India
India receives annual precipitation of about 4000 km3. The rainfall in India shows very high spatial and temporal variability and paradox of the situation is that Mousinram, Cherapunji, which receives the highest rainfall in the world, also suffers from shortage of water during the non-rainy season, almost every year. The total average annual flow per year for the Indian rivers is estimated as 1953 km3. The total annual replenishable ground water resources are assessed as 432 km3. The annual utilizable surface water and ground water resources of India are estimated as 690 km3and 396 km3 per year, respectively. Thus, the total utilizable water resources of the country are assessed as 1086 km3. Rainfall in India is dependent on the South‑West and North‑East monsoons, on shallow cyclonic depressions and disturbances and on local storms. Most of it takes place under the influence of South‑West monsoon between June to September except in Tamil Nadu, where it is under the influence of North‑East monsoon during October and November. India is gifted with a river system comprising of more than 20 major rivers with several tributaries. Many of these rivers are perennial and some of these are seasonal. The rivers like Ganges, Brahmaputra and Indus originate from the Himalayas and carry water throughout the year. The snow and ice melt of the Himalayas and the base flow contribute the flows during the lean season. More than 50% of water resources of India are located in various tributaries of these river systems. Average water yield per unit area of the Himalayan rivers is almost double that of the south peninsular rivers system indicating the importance of snow and glacier melt contribution from the high mountains.
The peninsular rivers such as Narmada, Mahanadi, Godavari, Krishna, Cauvery etc. carry flows from rainfall and are supported by base flow discharges. Thus, these rivers carry less water during the lean season of the non-monsoon period. Apart from the water available in the various rivers of the country, the ground water is also an important source of water for drinking, irrigation and industrial uses etc. It accounts for about 80% of domestic water requirement and more than 45% of the total irrigation in the country. The ground water aquifers work like a regulating reservoir for storing water during the rainy season and releasing it during the lean season. In spite of availability of substantial quantity of water in India, the actual utilizable quantity is limited and a freshwater crisis is gradually unfolding in India. The crisis unfolds by the way of lack of access to safe water supply to millions of people as a result of inadequate water planning and environmental degradation.
Monsoon in India
Normal duration of monsoon in India is about 100 to 120 days beginning from first June. In India, the two monsoon seasons (the southwest monsoon in June to September and the northeast monsoon in November-December) bring forth rains – many a times in intensities and amounts sufficient to cause serious floods creating hazardous situations.
Precipitation Variability
The long-term average annual rainfall for the country is 1160 mm, which is the highest anywhere in the world for a country of comparable size. The annual rainfall in India, however, fluctuates widely. The highest rainfall in India of about 11,690 mm is recorded at Mousinram, Cherrapunji in Meghalaya in the northeast. In this region rainfall as much as 1040 mm is recorded in a day. At the other extreme are places like Jaisalmer, in the west, which receives barely 150 mm of rain. Though the average rainfall is adequate, nearly three-quarters of the rain pours down in less than 120 days, from June to September. As much as 21 percent of the area of the country receives less than 750 mm of rain annually while 15 percent receives rainfall in excess of 1500 mm. Precipitation generally exceeds 1000 mm in areas to the east of Longitude 780 E. It reaches nearly to 2500 mm along almost the entire west coast and over most of Assam and sub-Himalayan West Bengal.Large areas of peninsular India receive rainfall less than 600 mm. Annual rainfall of less than 500 mm is experienced in western Rajasthan and adjoining parts of Gujarat, Haryana and Punjab. Rainfall is equally low in the interior of the Deccan plateau, east of the Sahyadris. A third area of low precipitation is around Leh in Kashmir. Rest of the country receives moderate rainfall.
Surface Water Resources of India
National Commission for Integrated Water Resources Development (NCIWRD, 1999) estimated the basin-wise average annual flow in Indian river systems as 1953 km3. Utilizable water resource is the quantum of withdrawable water from its place of natural occurrence. Within the limitations of physiographic conditions and socio-political environment, legal and constitutional constraints and the technology of development available at present, utilizable quantity of water from the surface flow has been assessed by various authorities differently. According to NCIWRD (1999), the utilizable annual surface water of the country is 690 km3. There is considerable scope for increasing the utilization of water in Ganga-Brahmaputra basins by construction of storages at suitable locations in neighbouring countries.
Table 1.2.Basin-wise average flow and utilizable water (in km3/ year) (Source:NCIWRD, 1999)
| S.No. | River Basin | Average Annual Flow | Utilizable Flow |
| 1 | Indus | 73.31 | 46 |
| 2 | Ganga-Brahmaputra-Meghna Basin | ||
| (a) Ganga | 525.02 | 250 | |
| (b) Brahmaputra sub-basin | 629.05 | 24 | |
| (c) Meghna (Barak) sub-basin | 48.36 | ||
| 3 | Subarnarekha | 12.37 | 6.81 |
| 4 | Brahmni-Baitarani | 28.48 | 18.3 |
| 5 | Mahanadi | 66.88 | 49.99 |
| 6 | Godavari | 110.54 | 76.3 |
| 7 | Krishna | 69.81 | 58 |
| 8 | Pennar | 6.32 | 6.86 |
| 9 | Cauvery | 21.36 | 19 |
| 10 | Tapi | 14.88 | 14.5 |
| 11 | Narmada | 45.64 | 34.5 |
| 12 | Mahi | 11.02 | 3.1 |
| 13 | Sabarmati | 3.81 | 1.93 |
| 14 | West flowing rivers of Kachchh and Saurashtra including Luni | 15.1 | 14.98 |
| 15 | West flowing rivers south of Tapi | 200.94 | 36.21 |
| 16 | East flowing rivers between Mahanadi and Godavari | 17.08 | 13.11 |
| 17 | East flowing rivers Between Godavari and Krishna | 1.81 | |
| 18 | East flowing rivers Between Krishna and Pennar | 3.63 | |
| 19 | East flowing rivers Between Pennar andCauvery | 9.98 | 16.73 |
| 20 | East flowing rivers south of Cauvery | 6.48 | |
| 21 | Area of North Ladakh not draining into Indus | 0 | NA |
| 22 | Rivers draining into Bangladesh | 8.57 | NA |
| 23 | Rivers draining into Myanmar | 22.43 | NA |
| 24 | Drainage areas of Andman, Nicobar and Lakshadweep Islands | 0 | NA |
| Total (Rounded) | 1953 | 690 |
Groundwater Resources
The annual potential natural ground water recharge from rainfall in India is about 342.43 km3, which is 8.56% of total annual rainfall of the country. The annual potential ground water recharge augmentation from canal irrigation system is about 89.46 km3. Thus, total replenishable groundwater resource of the country is assessed as 431.89 km3 (342.43 km3 + 89.46 km3).After allotting 15% of this quantity for drinking, and 6 km3 for industrial purposes, the remaining can be utilized for irrigation purposes. Thus, the available ground water resource for irrigation is 361 km3 of which utilizable quantity (90%) is 325 km3.
Table 1.3.Groundwater resources of India, in km3(Source: CGWB, 1995)
| Total Replenishable Ground Water Resource | 432 |
| Provision for Domestic, Industrial and other Uses | 71 |
| Available Ground Water Resource for Irrigation | 361 |
| Utilizable Ground Water Resource for Irrigation (90% of the Sl. No. 3) | 325 |
| Total Utilizable Ground Water Resource (Sum of Sl. No. 2 and 4) | 396 |
Table 1.4.Ground water potential in river basins of India, in km3/year (Source: IWRS, 1998)
| S.No. | Name of the basin | Total replenis-able ground water resources | Provision for domestic, industrial and other uses | Available ground water for irrigation | Net draft | Balance ground water potential | Level of ground water development (%) |
| 1 | Brahmani with Baitarni | 4.05 | 0.61 | 3.44 | 0.29 | 3.15 | 8.45 |
| 2 | Brahmaputra | 26.55 | 3.98 | 22.56 | 0.76 | 21.80 | 3.37 |
| 3 | Chambal Composite | 7.19 | 1.08 | 6.11 | 2.45 | 3.66 | 40.09 |
| 4 | Cauvery | 12.30 | 1.84 | 10.45 | 5.78 | 4.67 | 55.33 |
| 5 | Ganga | 170.99 | 26.03 | 144.96 | 48.59 | 96.37 | 33.52 |
| 6 | Godavari | 40.65 | 9.66 | 30.99 | 6.05 | 24.94 | 19.53 |
| 7 | Indus | 26.49 | 3.05 | 23.43 | 18.21 | 5.22 | 77.71 |
| 8 | Krishna | 26.41 | 5.58 | 20.83 | 6.33 | 14.50 | 30.39 |
| 9 | Kutch &Saurashtra Composite | 11.23 | 1.74 | 9.49 | 4.85 | 4.64 | 51.14 |
| 10 | Madras and South Tamil Nadu | 18.22 | 2.73 | 15.48 | 8.93 | 6.55 | 57.68 |
| 11 | Mahanadi | 16.46 | 2.47 | 13.99 | 0.97 | 13.02 | 6.95 |
| 12 | Meghna | 8.52 | 1.28 | 7.24 | 0.29 | 6.95 | 3.94 |
| 13 | Narmada | 10.83 | 1.65 | 9.17 | 1.99 | 7.18 | 21.74 |
| 14 | Northeast Composite | 18.84 | 2.83 | 16.02 | 2.76 | 13.26 | 17.20 |
| 15 | Pennar | 4.93 | 0.74 | 4.19 | 1.53 | 2.66 | 36.60 |
| 16 | Subarnarekha | 1.82 | 0.27 | 1.55 | 0.15 | 1.40 | 9.57 |
| 17 | Tapi | 8.27 | 2.34 | 5.93 | 1.96 | 3.97 | 33.05 |
| 18 | Western Ghat | 17.69 | 3.19 | 14.50 | 3.32 | 11.18 | 22.88 |
| Total | 431.43 | 71.08 | 360.35 | 115.21 | 245.13 | 31.97 |
Water Requirements of India
Traditionally, India has been an agriculture-based economy. Hence, development of irrigation to increase agricultural production to make the country self-sustained and for poverty alleviation has been of crucial importance for the planners. Accordingly, irrigation sector was assigned a very high priority in the 5-year plans. Giant schemes like the BhakraNangal, Hirakud, Damodar Valley, Nagarjunasagar, Rajasthan Canal project etc. were taken up to increase irrigation potential and maximize agricultural production. As per the international norms, if per-capita water availability is less than 1700 m3 per year then the country is categorized as water stressed and if is less than 1000 m3 per capita per year then the country is classified as water scarce. Table 1.5 provides details of the population of India and per capita water availability as well as utilizable surface water for some of the years from 1951 to 2050 (projected). The availability of water in India shows wide spatial and temporal variations. Most of rainfall is received in a few months, and that too within 100 hours of rainy days. Also, there are very large inter annual variations. Hence, the general situation of availability of per capita availability is much more alarming than what is depicted by the average figures.
Table 1.5.Per capita per year availability and utilizable surface water in India (in m3) (Source:NCIWRD, 1999)
| Year | Population(in millions) | Per-capita surface water availability | Per-capita utilizable surface water |
| 1951 | 361 | 5410 | 1911 |
| 1955 | 395 | 4944 | 1746 |
| 1991 | 846 | 2309 | 816 |
| 2001 | 1027 | 1902 | 672 |
| 2025(Projected) | (a) 1286 (Low growth)(b) 1333 (High growth) | 15191465 | 495 |
| 2050(Projected) | (a) 1346 (Low growth)(b) 1581 (High growth) | 14511235 | 421 |
Domestic Use
Community water supply is the most important requirement and it is about 5% of the total water use. About 7 km3 of surface water and 18 km3 of ground water are being used for community water supply in urban and rural areas. Long-term planning has to account for the growth of population.
A number of individuals and agencies have estimated the likely population of India by the year 2025 and 2050. According to the estimates adopted by NCIWRD (1999), by the year 2025, the population is expected to be 1333 million in high growth scenario and 1286 million in low growth scenario. For the year 2050, high rate of population growth is likely to result in about 1581 million people while the low growth projections place the number at nearly 1346 million. Keeping in view the level of consumption, losses in storage and transport, seed requirement, and buffer stock, the projected food-grain and feed demand for 2025 would be 320 million tonnes (high demand scenario) and 308 million tonnes (low demand scenario). The requirement of food grains for the year 2050 would be 494 million tonnes (high demand scenario) and 420 million tonnes (low demand scenario).
Different organizations and individuals have given different norms for water supply in cities and rural areas. The figure adopted by the NCIWRD (1999) was 220 litre per capita per day (lpcd) for class I cities. For the cities other than class I, the norms are 165 for year 2025 and 220 lpcd for the year 2050. For rural areas, 70 lpcd and 150 lpcd have been recommended for the year 2025 and 2050. Based on these norms and projection of population, it is estimated that by the year 2050, water requirements per year for domestic use will be 90 km3 for low demand scenario and 111 km3 for high demand scenario. It is expected that about 70% of urban water requirement and 30% percent of rural water requirement will be met by surface water sources and the remaining from ground water.
Irrigation
The irrigated area in the country was only 22.6 million hectare (M-ha) in 1950-51. Since the food production was much below the requirement of the country, due attention was paid for expansion of irrigation. The ultimate irrigation potential of India has been estimated as 140 M-ha. Out of this, 76 M-ha would come from surface water and 64 M-ha from ground water sources. The quantum of water used for irrigation by the last century was of the order of 300 km3 of surface water and 128 km3 of ground water, total 428 km3. The estimates indicate that by the year 2025, the water requirement for irrigation would be 561 km3 for low demand scenario and 611 km3 for high demand scenario. These requirements are likely to further increase to 628 km3 for low demand scenario and 807 km3 for high demand scenario by the year 2050.
Hydroelectric Power
The hydropower potential of India has been estimated at 84044 MW at 60% load factor. At the time of independence (1947), the installed capacity of hydropower projects was 508 MW. By the end of 1998, the installed hydropower capacity was about 22000 MW (24.85 % of the total installed capacity of 88543 MW). The status of hydropower development in major basins is highly uneven.
Industrial Water Requirement
Rough estimates indicate that the present water use in the industrial sector is of the order of 15 km3. The water use by thermal and nuclear power plants with installed capacities of 40000 MW and 1500 MW (1990 figures) respectively, is estimated to be about 19 km3. In view of shortage of water, the industries are expected to switch over to water efficient technologies. If the present rate of water use continues, the water requirement for industries in the year 2050 would be 103 km3; this is likely to be nearly 81 km3 if water saving technologies are adopted on a large scale.
Total Water Requirements
Total annual requirement of water for various sectors has estimated and its break up is given following table.
Table 1.6.Annual water requirement for different uses, in km3
| Uses | Year 1997-98 | Year 2010 | Year 2025 | Year 2050 | ||||||
| Low | High | % | Low | High | % | Low | High | % | ||
| Surface Water | ||||||||||
| Irrigation | 318 | 330 | 339 | 48 | 325 | 366 | 43 | 375 | 463 | 39 |
| Domestic | 17 | 23 | 24 | 3 | 30 | 36 | 5 | 48 | 65 | 6 |
| Industries | 21 | 26 | 26 | 4 | 47 | 47 | 6 | 57 | 57 | 5 |
| Power | 7 | 14 | 15 | 2 | 25 | 26 | 3 | 50 | 56 | 5 |
| Inland Navigation | 7 | 7 | 1 | 10 | 10 | 1 | 15 | 15 | 1 | |
| Environment – Ecology | 5 | 5 | 1 | 10 | 10 | 1 | 20 | 20 | 2 | |
| Evaporation Losses | 36 | 42 | 42 | 6 | 50 | 50 | 6 | 76 | 76 | 6 |
| Total | 399 | 447 | 458 | 65 | 497 | 545 | 65 | 641 | 752 | 64 |
| Ground Water | ||||||||||
| Irrigation | 206 | 213 | 218 | 31 | 236 | 245 | 29 | 253 | 344 | 29 |
| Domestic | 13 | 19 | 19 | 2 | 25 | 26 | 3 | 42 | 46 | 4 |
| Industries | 9 | 11 | 11 | 1 | 20 | 20 | 2 | 24 | 24 | 2 |
| Power | 2 | 4 | 4 | 1 | 6 | 7 | 1 | 13 | 14 | 1 |
| Total | 230 | 247 | 252 | 35 | 287 | 298 | 35 | 332 | 428 | 36 |
| Grand total | 629 | 694 | 710 | 100 | 784 | 843 | 100 | 973 | 1180 | 100 |
| Total Water Use | ||||||||||
| Irrigation | 524 | 543 | 557 | 78 | 561 | 611 | 72 | 628 | 807 | 68 |
| Domestic | 30 | 42 | 43 | 6 | 55 | 62 | 7 | 90 | 111 | 9 |
| Industries | 30 | 37 | 37 | 5 | 67 | 67 | 8 | 81 | 81 | 7 |
| Power | 9 | 18 | 19 | 3 | 31 | 33 | 4 | 63 | 70 | 6 |
| Inland Navigation | 0 | 7 | 7 | 1 | 10 | 10 | 1 | 15 | 15 | 1 |
| Environment – Ecology | 0 | 5 | 5 | 1 | 10 | 10 | 1 | 20 | 20 | 2 |
| Evaporation Losses | 36 | 42 | 42 | 6 | 50 | 50 | 6 | 76 | 76 | 7 |
| Total | 629 | 694 | 710 | 100 | 784 | 843 | 100 | 973 | 1180 | 100 |
