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 Earth1.36x10 8 M ha m Ocean salt water97.2% Fresh Water2.8% Surface water2.2% Glaciers & Ice ___ 2.15% Lakes & Streams % Other forms % Ground water 0.6% Renewable G.W % 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 Budget Initial estimates Average rainfall(119.4 cm) on 328 M h ≈ 400 M h m –Lost to atmosphere.. 70 M ha m –Surface run off 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 flow186.9 M ha m –Utilizable surface water by conventional method.. 69 M ha m –Utilizable ground water.. 45 M ha m Total potential utilizable water M ha m Irrigation efficiency Canals ≈ 38% Wells ≈ 60% Total irrigation potential estimated = 114 M ha (assuming 1 meter water depth requirement)

Tamil Nadu scenario  Geographical area of 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 Mham.  Potential created Mham, (89 %).  Ultimate ground water potential 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 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 PRIZES ONE FOR PEACE AND THE OTHER FOR SCIENCE - John F. Kennedy -