IDE 301 drainage engineering lecture 1,2.pptx

It is engineering course

1. Introduction to Drainage Lecture -1

2. Ponding Accumulation of excess water on soil surface

3. Reasons for ponding Excess Rain Irrigation Low Infiltration rate Shallow Impervious layer

4. Water logging Accumulation of excess water in the root zone Above field capacity Reasons Seepage from upstream irrigated area or foot of hills Seepage from unlined canals Capillary rise from water table Lack of natural or artificial drainage Excess Rain Irrigation Low Infiltration rate Shallow Impervious layer

5. Effect of Water Logging on Plants Oxygen depletion in root zone Microorganisms responsible for nitrification of organic matter die No nitrate formation Less plant growth Pores filled with water Lack of space for root growth

6. Categorization of Water Logging Safe Area Water table below 3 m from the land surface Potential for Waterlogging Water table between 2 m and 3 m from the land surface Waterlogged Area Water table within 2 m from the land surface

7. Salinization Accumulation of salts at surface in root zone Affects plant growth Reasons Salt from irrigation water Secondary salinization Parent material from which soil formed Primary salinization Measurement criteria Total dissolved salts ppm Electrical conductivity of soil at field capacity deciSiemens /metre (dS/m) 640 ppm = 1 dS/m (approximately )

8. Effect of Excess salt on plants Osmosis Water from Lower to higher Concentration Water uptake – affected More Na Phosphate , Mn , Zn uptake affected Soil structure broken down Hydraulic conductivity & infiltration affected

9. Need for Drainage To manage Ponding Waterlogging Salinization Removal of excess surface & subsurface water from land enhance crop growth removal of dissolved salts from the soil

10. Surface drainage to remove Ponding Surface drainage is the diversion or orderly removal of excess water from the surface of the land by means of improved natural or constructed drains, supplemented when necessary by the shaping and grading of land surfaces to such drains.

11. Subsurface drainage for Waterlogging Removal of excess water & dissolved salts from root zone Aiding flow to drains control water table & salinity Note open drains are also subsurface drains

12. Subsurface Drainage to Control Salinisation To remove salts from the soil, water is used as a vehicle: more irrigation water is applied to the field than is required for crop growth. This additional water infiltrates into the soil and percolates through the root zone. During percolation the water takes up part of the salts from the soil and removes these through the subsurface drains. This process, in which the water washes the salts out of the root zone, is called leaching Leaching is the removal of soluble salts by the passage of water through soil.

13. An example

14. Vertical Drainage or Well drainage

15. A drainage system Artificial system of land forming surface and/or subsurface drains related structures pumps (if any) which removes excess water from an area.

16. Benefits of Drainage Improved plant performance Improved crop yield & quality More rapid warming of soils in Winter improving germination Improved environment for soil organisms Better access to water and oxygen for plant roots Better crop uptake of soil mineral nitrogen

17. Benefits of Drainage Better access to land Reduced risk of waterlogging Quicker accessibility of fields following any period of wet weather Crop inputs more likely to be applied at optimum time An extended growing and grazing season

18. Benefits of Drainage Improved speed of work and fuel use Better traction Fewer cultivation passes Reduced draught forces Reduced wear and tear Fewer wet areas to avoid

19. Benefits of Drainage Benefits to soil structure and the environment Less structural damage to soils Reduced frequency and extent of livestock poaching Better water infiltration Reduced surface runoff and erosion Reduced phosphorus and pesticide losses to water

20. Benefits of Drainage Reduced risks to livestock health Reduced survival of parasitic larvae Snails carrying liver fluke do not thrive Footrot and foul of the foot are less common Udder hygiene for grazing stock is improved Reduced risk of soil contamination during silaging operations

21. Water Logging & Salinity Tamil Nadu state Not very much Some extent in Cauvery Delta Central soil salinity Research Institute, Karanal , Haryana

22. FACTORS RELATED TO DRAINAGE Agricultural objectives Agricultural operations Ploughing to Harvest Environmental parameters Irrigation Rainfall Water table Water-transmitting properties of soil Natural, surface or subsurface drainage Topography Engineering factors Structural aspects of Drainage system

23. Engineering Factors

24. Field Drainage Systems & Crop Production

25. Water Table and Crop Production

26. Environmental factors & Agricultural objectives interaction

27. Soil Structure Good soil structure Soil aeration Storage of soil water Reduces impedance to root growth Stable traction for farm implements Good drainage system Good soil structure

28. Soil Temperature Reduced Water content & Increased Air content Optimal soil moisture Good drainage system Good soil temperature

29. Soil Workability and Bearing Capacity Improves with Drainage

30. Soil Subsidence Providing Drainage to clay soils Subsidence Loss of water from pores Providing drainage to Peat soils Larger subsidence Loss of water from pores Decomposition of organic matter due to optimal soil moisture & air

31. Nutrient Supply from the Soil Activity of bacteria, fungi & other organisms depend on Soil aeration and the drainage status of the soil. Nitrogen (N) fixation & nitrification by micro-organisms Good Drainage

32. Drainage coefficient or Drainage Surplus Amount of water that must be removed from an area within a certain period so as to avoid an unacceptable rise in the levels of the groundwater or surface water Depth/day

33. Estimation f Drainage coefficient Components of water balance

34. Intensity-Duration-Frequency Rainfall

35. Drainage coefficient Example 50 mm in 40 hours = 30 mm/day

36. Soil water Drainable porosity at any location Difference between Saturated water content & field capacity Above field capacity due to capillary rise

37. Total Drainable pore space For each depth Water content before – Water content after Sum up through the depth

38. Factors to be decided before executing a Drainage Project During rainy season How much depth of water would stand? How long ? How fast it must be removed? Present salinity of topsoil & subsurface during sowing and during crop growth How much is target salinity to be achieved? Number of days needed for doing agricultural operations like ploughing, harvesting & intercultural operations What is the state of the field at present during the agricultural operations? What must be the target state of the field during these operations?

39. Thank you