Notes on Global Water Resources:

Source: Agronomy facts for Competitions by RS Meena

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Global Water Resources:

• Earth's surface is 3/4 covered by oceans.
• Total water on Earth: 1400 million km3 (enough to cover Earth with a 3 km deep layer).
• Only 2.7% of Earth's water is fresh:
• 68.7% frozen in polar regions
• 30.1% groundwater
• Rest in lakes, rivers, atmosphere
• Only 1% of water is usable by humans.
• Global water withdrawal: 4500 km3 (availability: 4200 km3).
• Expected withdrawal by 2030: 6900 km3 (availability: 4100 km3).
• Expected global water deficit by 2030: 40%.
• Expected withdrawal in India by 2030: 1500 km3 (availability: 744 km3).
• Expected water deficit in India by 2030: 50%.

Irrigation World: Key Facts and Figures

Global Land Use:

• 11% (1.5 billion ha) of the global land surface is used for crops.
• Asia has 32% of the world's arable land, followed by North Central America (20%) and Africa (12%).
• 20% of global arable land is irrigated (324 million ha in 2012).
• Rainfed agriculture is practiced on the remaining 80% of arable land.

Largest Irrigated Areas:

• China has the highest total irrigated area (69.4 million ha).
• India follows closely behind with 68.4 million ha of irrigated land.

Water Use:

• Developing nations use over 90% of withdrawn water for irrigation.
• India, China, and Egypt use the most water for irrigation globally.
• Per capita water use: USA > France > Egypt > India

India's Water Resources:

• Total area: 328.762 million ha (2.45% of global land).
• Total precipitation: 3838 km3 (390-400 BCM).
• Available water: 2301 km3 (60%).
• Utilisable surface water: 690 km3 (37% of surface water resources).
• Utilisable groundwater potential: 432 km3.

Groundwater Resources:

• Annual groundwater recharge: 432 km3 (8.56% of total rainfall).
• Available groundwater resources for irrigation: 361 km3.
• Net utilizable groundwater resources for irrigation: 325 km3 (90%).
• Stage of Ground Water Development: 61.00%.

Groundwater Use:

• 89% of extracted groundwater is used for irrigation.
• 9% for domestic use.
• 2% for industrial use.
• 50% of urban and 85% of rural domestic water needs are met by groundwater.

Additional Notes:

• 1 km3 = 1 billion cubic meters = 1 BCM = 0.1 million ha meters.
• Groundwater is the highest category user of water in India.

Water Budget of India: Key Facts and Figures

Precipitation:

• Average annual precipitation: 1194 mm (119.4 cm)
• Total precipitation: 400 Mha m (392.5 Mha m)
• Monsoon season: 300 Mha m (75%)
• Rest of the year: 100 Mha m (25%)

Water Flow:

• Total rainfall input = Surface water flow + Groundwater recharge + Evapotranspiration
• Surface water flow: 180 Mha m (including 20 Mha m from outside India and 45 Mha m from regenerated groundwater)
• Groundwater recharge: 50 Mha m (from rainfall: 105 Mha m, snowfall: 10 Mha m)
• Evapotranspiration: 165 Mha m (soil moisture: 77%, groundwater: 23%)

Irrigation:

• Net irrigated area: 68.4 million hectares (34% of net sown area, 30% of cultivable area)
• Gross irrigated area: 96.46 million hectares
• Maximum per cent irrigated area: Punjab
• Irrigation sources:
• Canals: 16.18 M ha (23.6%)
• Tanks: 1.72 M ha (2.5%)
• Other wells: 11.35 M ha (16.6%)
• Tube wells: 31.61 M ha (46.2%)
• Other sources: 7.52 M ha (11.0%)
• Groundwater usage: 60% of net irrigated area
• Largest groundwater well-equipped irrigation system in the world (39 million hectares)
• States with 70% or more irrigation potential: Tamil Nadu (100%), Punjab (84%), Rajasthan (74%)

Well irrigation:

• Used in alluvial plains of UP, Bihar, Gujarat, Karnataka, and Tamil Nadu

Canal irrigation:

• Second most important source after wells and tube wells
• Used in lands with large plains, fertile soil, and perennial rivers
• Common in North India and low coastal lands, parts of Peninsular India
• States using canal irrigation: Andhra Pradesh, Assam, Haryana, Jammu & Kashmir, West Bengal, Punjab, Rajasthan, Bihar, Karnataka, Tamil Nadu, Uttar Pradesh

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