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The 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	36 202	0	NA
20	Minor river basins draining into Myanmar and Bangladesh		31	NA
	Total		1869.35	690

India is the largest and fastest consumer of groundwater, which fulfills the demands of nearly 80 and 50% of the rural and urban population, respectively (Shankar et al. 2011). The groundwater resources of the country are estimated to be 433 BCM, which is 39% of the total water resources of India (CGWB 2017). The net groundwater availability is 396 BCM, while the available for potential use is 245 BCM. The stage of groundwater development is 61% (CGWB 2017). The Indian state Uttar Pradesh has the highest net annual groundwater availability (~72 BCM) and Delhi has the least (0.29 BCM) (CGWB 2014). Around 85% of the rural population uses groundwater for drinking purposes. The volume of groundwater is inadequate to fulfill the demand of the large population, agricultural practices, rampant industrialization, and urbanization. The overall account of groundwater resources assessment 2004–2017 is presented in Table 1.3.

The per capita average water availability in India is continuously decreasing. India has a huge potential in river and precipitation water (rainfall+snowfall), but currently, not even 50% of the potential is being used. Due to the lack of use of the water potential of river and precipitation, groundwater resources are under tremendous pressure and the water table is continuously increasing in most parts of the country over time.

Table 1.3 Groundwater resources assessment from 2004–2017.

Source: CGWB (2017).

Year	Annual replenishable groundwater resources (BCM)	Net annual groundwater availability (BCM)	Annual groundwater draft for irrigation, domestic, and industrial uses (BCM)	Stage of groundwater development
2004	433	399	231	58%
2009	431	396	243	61%
2011	433	398	245	62%
2013	447	411	253	62%
2017	432	393	249	63%