Water Erosion

1. Water Erosion “It is the detachment, transportation & deposition of soil particles by the force of water from one place to another.” “It is the movement of soil by rain water including melted snow, running rapidly over exposed land surfaces.”

2. Factors Affecting Water Erosion 1. Climate. Precipitation Temperature Wind Humidity Solar radiation

3. 2.Soil Physical properties of soil such as texture, structure etc. Organic matter contents in soil. Moisture contents in soil. Soil density or compactness. Chemical and biological characteristics.

4. 3. Vegetation Reduce rain drop velocity. Resist runoff Increase infiltration Enhance microbial activity. Improve soil structure.

5. 4. Topography. Degree of slope of an area Length of slope of an area Size and shape of water shed

6. Forms of Water Erosion Raindrop or Splash Erosion: Result from the impact of water drop directly on the soil particles or thin water surfaces. Splash losses are 50-90 times greater than the wash off losses. On bare soil 224 Mg ha-1 is splashed into air due to heavy rains. It is first stage of water erosion. Raindrops can be a major problem for farmers when they strike bare soil. Soil particles can jump up to 2.5 feet.

7. The relationship between erosion and rainfall momentous and energy is determined by • Rain drop size • Mass • Size distribution • Shape • Velocity • Direction

8. Energy equation has been developed by Wischmerer & Smith (1958) is: E = 12.1 + 8.9 log i E = Kinetic energy in Mg ha-1 i = intensity in mm h-1 Factors affecting direction & distance of soil splash are: • Shape • Wind • Surface condition

9. Raindrop Erosion

10. Sheet Erosion Uniform removal of soil in thin layers from sloping land. Occurrence is rare. In reality the loose soil merely runs off with the rain. The beating action of raindrops combined with surface flow causes initial microscopic rilling. From energy point of view, raindrop erosion is more important because raindrops have velocities of 6-9 ms-1 (20-30 fs-1) whereas overloaded flow velocities are about 0.3-0.6 ms-1 (1-2fs-1).

11. Sheet Erosion

12. Rill Erosion Transitional phase between sheet erosion and gully erosion Its effects can be easily removed by tillage It occurs when soil is removed by water from little streamlets that run through land with poor surface draining Rills can often be found in between crop rows

13. Rill Erosion

14. Gully Erosion It is last stage of water erosion. Gullies are larger than rills and cannot be fixed by tillage. Gully erosion is an advanced stage of rill erosion. Major concentrations of high-velocity run-off water in these larger rills remove vast amounts of soil. This results in deeply incised gullies occurring along depressions and drainage lines.

15. Gully Erosion

16. Stream Erosion. When water flow in gullies become permanent, it is called a stream which may be permanent or seasonal is called as stream erosion.

17. Areas of Water Erosion • Nothern Hilly Areas • Pothwar Pleatue • Foothills of Himalayas in Punjab • Western hilly Areas

18. Damages of Water Erosion • Loss of soil specially fertile layer • Low fertile soil decrease farmer income • Remove organic matter from the soil • Decrease infiltration capacity of soil • Increase runoff • Increase flood hazard • Damage the wild life fisheries etc • Fill up the streams and dams

19. Mechanism of Water Erosion A. Detachment.: it is first to occur and is independent variable. Soil clods are broken into small particles. B. Transportation.: it is dependent variable and depends upon detachment. C. Deposition: is dependent variable and depend upon detachment and transportation.