annual precipitation (rainfall+snowfall) is estimated as 4000 billion cubic meters (BCM). Out of total annual precipitation, 3000 BCM falls during the monsoon season (Jun to September) (Central Water Commission 2014). Around 53.3% of total annual precipitation is lost due to evapotranspiration, which leaves a balance of 1986.5 BCM. The total annual utilizable water resources of India are 1123 BCM, which consists of 690 BCM surface water and 433 BCM of groundwater (Central Water Commission 2014). The National Commission on Integrated Water Resources Development (NCIWRD) projected that total water demand to expect 973 (low demand scenario) to 1180 BCM (high demand scenario). The water used for agriculture is the highest projected demand (70%), followed by households (23%) and industries (7%) (NCIWRD 1999). The per capita average water availability in India in the year 2001 was 1816 m3, and it is expected to reduce to 1140 m3 in 2050 (MoWR 2015). The people of the Indian state of Andhra Pradesh have the highest access to safe treated water, i.e., 36%, and it is lowest for Bihar (2%) (Forbes India 2015). The annual surface water availability of India has decreased since the year 1950 (Table 1.1).
Rivers are the primary sources of surface water in India and are considered as the lifeline of Indian cities. There are 15 large, 45 medium, and 120 minor rivers in India (Raj 2010). The rivers are either rainfed and/or based on the Himalayan glacier. The annual water potential in the major river basins of India is 1869.35 BCM, but the utilizable potential is 690 BCM. The Ganga basin has the highest utilizable potential, i.e., 250 BCM. The detailed account of surface water potential of Indian rivers is depicted in Table 1.2.
Table 1.1 Annual surface water availability of India.
Source: Govt. of India (2009).
| S. no | Year | Annual surface water availability (m3/capita/year) |
|---|---|---|
| 1 | 1951 | 5177 |
| 2 | 1991 | 2209 |
| 3 | 2001 | 1820 |
| 4 | 2025 | 1341 |
| 5 | 2050 | 1140 |
Table 1.2 Overview of surface water potential of Indian rivers.
Source: Central Water Commission, http://cwc.gov.in/water‐info.
| S. no | River basin | Catchment area (sq km) | Average water resources potential (BCM) | Utilizable surface water resources (BCM) |
|---|---|---|---|---|
| 1 | Indus (up to border) | 321 289 | 73.31 | 46 |
| 2 | (a) Ganga | 861 452 | 525.02 | 250 |
| (b) Brahmaputra | 194 413 | 537.24 | 24 | |
| (c) Barak and others | 41 723 | 48.36 | ||
| 3 | Godavari | 312 812 | 110.54 | 76.3 |
| 4 | Krishna | 268 948 | 78.12 | 58 |
| 5 | Cauvery | 81 155 | 21.36 | 19 |
| 6 | Subarnarekha | 29 196 | 12.37 | 6.8 |
| 7 | Brahmani and Baitarani | 51 822 | 28.48 | 18.3 |
| 8 | Mahanadi | 141 589 | 66.88 | 50 |
| 9 | Pennar | 55 213 | 6.32 | 6.9 |
| 10 | Mahi | 34 842 | 11.02 | 3.1 |
| 11 | Sabarmati | 21 674 | 3.81 | 1.9 |
| 12 | Narmada | 98 796 | 45.64 | 34.5 |
| 13 | Tapi | 65 145 | 14.88 | 14.5 |
| 14 | West flowing rivers from Tapi to Tadri | 55 940 | 87.41 | 11.9 |
| 15 | West flowing rivers from Tadri to Kanyakumari | 56 177 | 113.53 | 24.3 |
| 16 | East flowing rivers between Mahanadi and Pennar | 86 643 | 22.52 | 13.1 |
| 17 | East flowing rivers between Pennar and Kanyakumari | 100 139 | 16.46 | 16.5 |
| 18 | West flowing rivers of Kutch and Saurashtra including Luni | 321 851 | 15.1 | 15 |
| 19 |
Area of inland drainage of Rajasthan
|