Definitions of Key Terms in Soil and Water Conservation Engineering

 

Key Terms and Definitions

1. Drainage Coefficient:
   The depth of water, measured in inches, to be removed from a drainage area over a 24-hour period. It is expressed as $Dc=ipd=\text{in/day}$.

2. Permeability:
   A specific property of soil that measures how readily it transmits water, expressed as a velocity, typically in inches/hour or cm/hour for agricultural purposes.

3. Infiltration:
   The downward movement of water into the soil surface, with the rate commonly expressed in inches per hour (in/hr).

4. Transpiration:
   The process by which soil water passes through a plant's system, primarily through the leaves, and evaporates into the atmosphere.

5. Stilling Basin:
   A structured device designed to hold a pool of water, cushioning the impact and retarding the flow of falling water, such as from an overflow weir, chute, or drop.

6. Mole Drain:
   A type of drain created by tractor-drawn machinery that forms cylindrical channels in the subsoil without creating a trench from the surface.

7. Strip Cropping:
   An agricultural practice involving the cultivation of alternating strips of clean cultivated crops and close-growing crops within the same field.

8. Check Gate:
   A gate placed across a stream intended to divert water, functioning similarly to a dam or a diversion weir in a canal system.

9. Head Gate:
   A gate used to divert water from a main canal into farm delivery systems or lateral canals.

10. Flume:
    Specially shaped and stabilized channel sections that may also be employed to measure flow, designed to minimize the accumulation of floating debris and sediments.

11. Culvert:
    A closed conduit, typically circular, square, or rectangular, used for conveying water across and under elevated roadways, embankments, or dikes.

12. Run-off Coefficient:
    The ratio of the depth of runoff to the depth of precipitation that produces the runoff over a designated drainage area.

13. Furrow Coefficient:
    An irrigation method involving the wetting of only part of the surface (from ½ to 1/5), which reduces evaporation losses, minimizes soil puddling, and facilitates earlier soil cultivation after irrigation.

14. Corrugation:
    A method of irrigation that uses small, shallow furrows.

15. Spillway:
    A structure designed for the controlled release of surplus water not required for storage or diversion.

16. Water Way:
    Any open or closed ground or surface channel designated for the passage of water.

17. Total Dynamic Head:
    The sum of static head, pump, pipe, discharge head losses, and velocity head in a fluid system.

18. Consumptive Use:
    The total volume of water utilized by vegetation for transpiration and the building of plant tissues, plus that evaporated from adjacent ground or intercepted precipitation, divided by the specified area over a defined time.

19. Volume Weight (Apparent Specific Gravity):
    The ratio of the weight of soil to an equal volume of water.

20. Field Capacity:
    The percentage of water retained in the soil 2 to 3 days following a heavy rainfall.

21. Watershed:
    A topographically defined area that drains into a specific reference point in a stream.

22. Percolation:
    The downward movement of water through soil.

23. Irrigation:
    The deliberate application of water to soil to provide necessary moisture for plant growth.

24. Drainage:
    The process of removing excess water from agricultural land using either open or covered drains.

25. Moisture Capacity:
    The moisture content in the soil per unit depth, typically expressed in inches per foot.

26. Seepage:
    The flow of water through porous media or the loss of water from irrigation canals.

27. Wilting Percentage:
    The estimation of a crop's wilting point by dividing field capacity by a factor ranging from 2.0 to 2.4, depending on the soil's silt content.

28. Soil Texture:
    The relative proportion of various size groups of individual soil grains.

29. Available Soil Moisture:
    The volume of water in the soil available for plant use, determined by the difference between field capacity and permanent wilting percentage.

30. Check Contour:
    An irrigation method designed with longitudinal ditches parallel to the land's contour, connecting at desirable locations with cross ditches.

31. Basin Method of Irrigation:
    The application of water in small basins to retain moisture and encourage infiltration, with basins potentially formed in furrows or several feet in dimension.

32. Hygroscopic Water:
    A form of immobile soil moisture that can be driven off only through heat application.

33. Irrigation Requirement:
    The total quantity of irrigation water, exclusive of precipitation, necessary for crops to achieve normal growth under field conditions.

34. Soil:
    A natural body comprising mineral and organic materials on the Earth's surface that supports plant life.

35. Drop Structures:
    Irrigation structures designed to move water from a higher elevation to a lower one, which may be inclined or vertical.

36. Porosity:
    The physical property of rock or soil materials that defines the degree to which they contain void spaces, relative to their total volume.

37. Hydraulic Radius:
    The ratio of the cross-sectional area of the flow in an open channel (A) to the wetted perimeter of that flow (P). It can be calculated using the formula:

$$R=\frac{A}{P}$$

38. Contour Line:
    An imaginary line representing a constant elevation on the land's surface.

39. Fertigation:
    The process of applying irrigation water mixed with dissolved fertilizers to agricultural fields.

40. Soil Conservation:
    The application of engineering principles to solve soil management issues, utilizing methods that aim to conserve and optimally utilize soil.

41. Soil Erosion:
    The removal or wearing away of soil particles from the Earth's surface due to wind or water action.

42. Raindrop Erosion:
    Erosion caused by the impact of raindrops hitting the soil, leading to particle displacement. This is often exacerbated by soil puddling, which can be mitigated by using vegetative cover and mulch.

43. Sheet Erosion:
    The uniform removal of soil in thin layers from sloped land due to rainwater runoff. This type of erosion results from the combined action of raindrop impact and surface flow.

44. Rill Erosion:
    The removal of soil via water flow in small, well-defined channels during periods of significant overland flow. Rills can typically be corrected using standard tillage practices.

45. Gully Erosion:
    Erosion resulting in larger channels than those formed by rill erosion, which carry water during and shortly

46. Graded Terrace: constructed by cutting a shallow channel on the uphillside and using only this soil to build the embankment.