1. HOW MUCH WATER ENTERS THE SOIL? Infiltration

2. PrecipitationEvaporation Runoff Infiltration

3. What Factors Control Infiltration?

4. A) Soil Characteristics

5. What Factors Control Infiltration? A)Soil Characteristics 1) Grain Size (size of pores in soil)

6. Large Grains

7. Medium Grains

8. Large Grains Medium Grains Fine Grains

10. What Factors Control Infiltration? A)Soil Characteristics 1) Grain Size (size of pores in soil) 2) Antecedent moisture

11. HYGROSCOPIC WATER

12. CAPILLARY WATER

13. FREE or GRAVITATIONAL WATER

14. FREE or GRAVITATIONAL WATER

15. MAXIMUM RATES OF INFILTRATION

16. Initial Infiltration Rate is high Dry Soil. Hygroscopic Water only. Lots of soil air to fill with water.

17. MAXIMUM RATES OF INFILTRATION Initial Infiltration Rate is high Moist soil. Capillary Water. Progressively fewer voids to fill with water. Exponential decline in rate

18. MAXIMUM RATES OF INFILTRATION Initial Infiltration Rate is high Saturated soil. Free or Gravitational Water. Voids to fill with water determined by rate of loss. Minimum rate, or “field capacity” set by drainage Exponential decline in rate

19. What Factors Control Infiltration? A)Soil Characteristics 1) Grain Size (size of pores in soil) 2) Antecedent moisture B)Rainfall intensity (how fast rain is arriving!)

20. PrecipitationEvaporation Runoff Infiltration Overland Flow

21. CONSTANT HEAVY RAIN FOR FOUR HOURS

22. Rainfall that could be Infiltrated Rainfall to Overland Flow DECREASING INFILTRATION RATE FOR FOUR HOURS

23. INCREASING OVERLAND FLOW FOR FOUR HOURS No Overland Flow