SWC 302 IRRIGATION AND

DRAINAGE ENGINEERING (2+1)

Dr.K.Shanmugasundaram Professor & Head

Dept. of SWC Engg. and Agrl. Structures

AEC&RI, KUMULUR

World’s Water Resources

Total Water on Earth 1.36x108 M ha m

Ocean salt water 97.2%

Fresh Water 2.8%

Surface water 2.2%

Glaciers & Ice ___ 2.15%

Lakes & Streams.. 0.01%

Other forms .. 0.04%

Ground water 0.6%

Renewable G.W.. 0.25%

Total Available Freshwater 0.3%

Basic facts about surface water

Total water available in planet earth is constant

The fresh water available on earth is less than 1% away from poles

The major source of water supply to surface water remains to be rain fall

Rain fall is not evenly distributed in quantity, space and time

Basic facts about ground water

Ground water occurs below the surface of earth

Ground water is not evenly distributed in quantity, space and time

Power operated water lifting devices are required to bring ground water to surface

It is impossible to provide power to irrigate entire cultivable area with ground water

Indian Water BudgetInitial estimates• Average rainfall(119.4 cm) on 328 M h ≈ 400 M h m

– Lost to atmosphere .. 70 M ha m– Surface run off .. 115 M ha m– Infiltration ..215 M ha m

• Surface runoff total ≈180 M ha m +– Including 20 M ha m from outside

45 M ha m from regenerated G.W

• Soil moisture ≈ 165 M ha m

• Groundwater ≈ 50 M ha m– Groundwater contribution from flood ..5 M ha m– Groundwater contribution from irrigation ..12 M ha m◊Total Ground water 67 M ha m

Available water resource

Total river flow 186.9 M ha m

– Utilizable surface water by conventional method.. 69 M ha m

– Utilizable ground water.. 45 M ha m

Total potential utilizable water.. 114 M ha m

Irrigation efficiency

Canals ≈ 38%

Wells ≈ 60%

Total irrigation potential estimated = 114 M ha

(assuming 1 meter water depth requirement)

Tamil Nadu scenarioGeographical area of - 130 L.ha.

Net area sown in Tamil Nadu - 55 L.ha.

Irrigated area - 30 L.ha.

Major and Medium reservoirs - 65

canals - 12,611 km

Tanks - 39,202,

Wells - 18,39,754

Ultimate surface water potential - 2.70 Mham.

Potential created - 2.40 Mham, (89 %).

Ultimate ground water potential - 3.35 Mham

Potential developed - 2 Mham.

Need for conjunctive use

Surface water stored and transported to needy places is affected by rain fall pattern

Ground water is fairly evenly distributed to supplement surface water

Providing irrigation at critical periods of crop growth sustains the yield significantly

It is also not feasible to bring entire irrigated area under conservation irrigation

CONJUNCTIVE USE OF FOUR WATERSCONJUNCTIVE USE OF FOUR WATERS

Soil water (2)

W.T.

Ground water (unconfined) (4)

Ground water (confined) (4)

Surface water (3) Energy required Small vs. big

Rainfall (1)

HE WHO PROVIDES WATER DESERVES TWO NOBEL PRIZESONE FOR PEACE AND THE OTHER FOR SCIENCE

-John F. Kennedy-