Watershed Hydrology 3(2+1)

Lesson 1 Water Resources Availability and Requirements of India

1.1 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	Area 106 km2	Volume  (km3)	Percent of total water	Percent of freshwater
1.	Oceans	361.3	1,338,000,000	96.5
2.	Ground water: Fresh Saline	134.8 134.8	10,530,000 12,870,000	0.76 0.93	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: Fresh Saline	1.2      0.8	91,000 85,400	0.007 0.006	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.

 

1.2 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 km^3.  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 km³ and 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.

 

1.2.1 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.

 

1.2.2 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.

 

1.2.3 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 and Cauvery	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

 

1.2.4 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

 

1.3 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)	1519 1465	495
2050 (Projected)	(a) 1346  (Low growth) (b) 1581 (High growth)	1451 1235	421

 

1.3.1 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.

 

1.3.2 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.

 

1.3.3 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.

 

1.3.4 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.

 

 

1.3.5 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

(Source:NCIWRD 1999)

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

References

• USSR(1978).Committee for the International hydrological Decade.World Water Balance and Water Resources of the Earth.English translation, Studies and Reports in Hydrology, Vol. 25, UNESCO, Paris.

• CGWB (1995).Ground Water Resources of India, Central Ground Water Board, Govt. of India, New Delhi.

• NCIWRD (1999).Integrated Water Resources Development – A Plan for Action. Report of The National Commission for Integrated Water Resources Development. Govt. of India, Ministry of Water Resources, New Delhi.

• IWRS(1996). Theme paper on “Inter Basin Transfers of Water for National Development - Problems and Prospects”. Indian Water Resources Society, Roorkee.

• IWRS (1998). Theme Paper “Five Decades of Water Resources Development in India”. Indian Water Resources Society, Roorkee.

 

Suggested Reading

• Water Management Forum (2003).Inter-basin transfer of water in India – Prospects and Problems”. New Delhi, February, Water Management Forum, 2003, The Institution of Engineers (India).

• Seth, S.M. (2000). Integrated water resources management – role of research and development in hydrology.Proceedings of International Conference on Integrated Water Resources Management for Sustainable Development, New Delhi.Organized by National Institute of Hydrology, Roorkee.