Chapter 2 Water Management in Agriculture
2.2. C URRENT P RACTICES AND C HALLENGES
Substantial area under rainfed: About 72 million hectares (Mha) of net sown area (52%) is still completely dependent on rainfall. Further, irrigated area except from reservoir as a source, is also dependent on rainfall. Such irrigated areas are served by ground water, tanks, minor/micro water harvesting structures and account for about 42 Mha. Rainfed agriculture cannot compete with conventional standards and definitions of productive agriculture and requires specific interventions, norms, standards and attention. Rainfed areas constitute about three fourth of land mass under arid, semi arid, and dry humid situations, and are therefore, more vulnerable to weather aberrations and are characterized by low levels of productivity and low input usage. The extent of arid, semi-arid and dry sub humid regions in the country count to 15 M ha, 15 M ha and 42 M ha respectively. Rainfed areas if managed properly have tremendous potential to contribute larger share in foodgrain production and faster agricultural growth compared to irrigated areas that have reached a plateau. The essential pre-requisite is crop alignment with agro-climatic status.
Regional imbalance: There exist huge temporal and spatial variations in rainfall and water availability in the country. Most of the water is available during monsoon period and that too, through few spells of intense rainfall, resulting in floods in major rivers. While average annual rainfall of the country is about 1,170 mm, it varies from an average high of 10,000 mm per year in North East and a low of just 100 mm per annum in some parts of Western Rajasthan. It has been estimated, that while the lower rainfall zone (less than 750 mm annual rainfall) accounts for 33 per cent, the medium rainfall zone (750-1,125 mm) accounts for 35 per cent, the high rainfall zone (1,125 to 2,000 mm) covers 24 per cent and very high rainfall zone (more than 2,000 mm) accounts for the remaining 8 per cent of net sown area. The basin- wise availability of water is also quite varied. The Ganga-Brahmaputra river basin contributes to more than 50 per cent of total annual water availability, whereas, Southern and Western basins account for only about 15 per cent each.
Sub-optimal utilization of created facilities: One of the major shortcomings in the prevailing irrigation system is the wide gap between irrigation potential created (IPC) and irrigation potential utilized (IPU). The reasons are: inadequate maintenance of canal system, lack of participatory management, changing land use pattern, deviation from the designated cropping pattern, soil degradation and delay in command area development. As against the gross created irrigation potential of about 118 million ha area, the gross irrigated area used is only 96 million ha, resulting in a gap of about 22 million ha. This gap can be bridged to the advantage of agriculture and farmers.
Poor irrigation efficiency: Gross irrigated area in the country is about 96 Mha from nearly 650 BCM (billion cubic metre) of water which gives a delta of 0.68 metre (m) per ha. of gross irrigated area. Taking 70 per cent of the average rainfall of 1,170 mm (1.17 m) as effective for crop consumptive use, the gross water use is about 1.48 m per ha. of the gross irrigated area.
This is very high as compared to water use in irrigation systems in developed countries, like USA where water allocation is about 90 cm/ha. This overuse in the country reflects low irrigation efficiency of about 35 per cent to 45 per cent in most surface irrigation systems, and about 65 per cent in case of ground water use.
Improper crop and cropping system: Presently, high proportion of cultivated area under water guzzling crops like rice, sugarcane etc. is witnessed. Water being the most critical input for agriculture, its judicious use is important to ensure sustainable agricultural development and food security. There is a need for adopting a policy that encourages optimum cropping pattern, that utilises available water resources in an efficient manner. This necessitates a study and analysis of current cropping system. Based on the principle of maximizing annual income returns and efficiency of water use for long term sustainability, crop diversification from rice and sugarcane to low duty crops such as pulses and oilseeds may be a better option. These alternate crops would enable cultivation of larger area benefiting higher number of small and marginal farmers. The additional advantage is greater certainty of water through all stages of crop growth from the same quantum of water. About 2.89 M of ha area is covered under rice crop in 68 districts of India which receive a normal rainfall (50 years average from 1951 to 2000) less than 650 mm. This covers about 6.72 per cent of total rice cultivated area (43 M ha) in India. About 0.721 M ha area is covered under sugarcane cultivation in 91 districts of India, which receive normal rainfall (50 year average from 1951 to 2000) less than 700 mm. This covers about 12.9 per cent of total sugarcane cultivated area (5.6 M ha) in the country. Crops like rice, sugarcane and such other water guzzlers need to be discouraged particularly in over- exploited ground water regions, allowing only surface water resources for rice cultivation. This may facilitate diversification of rice to other low duty crops by the farmers in a phased manner.
Suitable low duty crops for diversification include maize, pulses & oilseeds.
Imbalanced use of ground water: Ground water has emerged as the main source of growth in irrigated area and it now accounts for over 63 per cent of the country’s irrigated area. Power for irrigation in many states is provided either free or at highly subsidized tariff, and this has incentivized use of ground water for agriculture. Apart from wasteful energy consumption,
subsidized or free power has also encouraged farmers to overdraw water from deep aquifers, causing substantial depletion of water table and water quality deterioration in many cases.
There has been unprecedented crop diversification to heavy water duty crops due to unregulated ground water use. The preference for high water duty crops like rice, sugarcane, banana, cotton etc. is common in regions, which does not fit into the rainfall pattern or ground water availability status. Notwithstanding the huge significance of ground water in agricultural growth, it is in need of urgent understanding and attention from the perspective of sustainability.
Recent assessment report of Central Ground Water Board (CGWB) shows that 1,034 of the 6,584 assessed Community Development Blocks are over-exploited (referred to as ‘dark zones’). Besides, 253 are critical, 681 are semi-critical and 96 blocks are completely saline.
The number of over-exploited and critical administrative units is significantly higher in Delhi, Haryana, Himachal Pradesh, Karnataka, Punjab, Rajasthan,Tamil Nadu and Uttar Pradesh.
Competing demand: The demand for water for various purposes is increasing due to population growth, urbanization and industrialization. Presently agriculture sector is using about 80 per cent of the total available water resources. Let alone there being any further scope for higher water allocation for agriculture, there is in fact increasing demand from competing domains like industries, urban centres and infrastructure. Hence water availability for agriculture may decline to 68 per cent by 2050. Water requirement for various sectors as assessed by “Standing Sub-Committee for Assessment of Availability and Requirement of Water” and by NCIWRD are given in Table 2.2.
Table 2.2 Sector-wise demand for water
Sector
Water Demand in BCM
Standing sub-committee of MoWR NCIWRD
2025 2050 2025 2050
Irrigation 910 1072 611 807
Drinking Water 73 102 62 111
Industry 23 63 67 81
Energy 15 130 33 70
Others 72 80 70 111
Total 1093 1447 843 1180
Water logging and soil salinity: Another challenge relates to over-use of surface water that has resulted in drainage problems causing water logging in some areas. Problem of water logging is very often observed in canal irrigation system and also in areas with poor drainage leading to accumulation of water.
Climate change: Climate change impacts on agriculture are being witnessed all over the world, but countries like India are more vulnerable in view of the high population depending on
agriculture, excessive pressure on natural resources and poor coping mechanisms. Agriculture is particularly vulnerable to climate change. Higher temperatures tend to reduce yields of many crops; and encourage weed and pest proliferation. Climate change will have negative effects on irrigated crop yields across regions, including in India both due to temperature rise and changes in water availability, while rainfed agriculture will be primarily impacted due to rainfall variability and reduction in number of rainy days. Long term data indicates that rainfed areas witness 3-4 drought years in every 10-year period. Of these, 2-3 are of moderate and one may be of severe intensity. Parts of western Rajasthan, southern Gujarat, Madhya Pradesh, Maharashtra, northern Karnataka, northern Andhra Pradesh, and southern Bihar are likely to be more vulnerable in terms of extreme events. Irrigation requirements in arid and semi-arid regions are estimated to increase due to rise in temperature. Adverse effects of climate change on freshwater systems will aggravate the impacts of other stresses, such as population growth, changing economic structure, land use change and urbanization. Yield declines are likely to be caused by shortening of growing period; negative impacts on reproduction & grain filling;
decrease in water availability and poor vernalization. Climate change is projected to reduce wheat yield by 6-25 per cent towards the end of the century with significant spatio-temporal variations. A one degree Celsius rise in mean maximum and minimum temperatures during vegetative and grain filling period is likely to cause a yield reduction of 360 and 265 kg/ha, respectively.