1 / 17

Infiltration

Infiltration. Reading AH Sec 4.3 to 4.4. q. Saturation Zone. Transition Zone. Transmission Zone. Wetting Zone. Wetting Front. depth. Infiltration. General Process of water penetrating from ground into soil Factors affecting

jagger
Download Presentation

Infiltration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Infiltration Reading AH Sec 4.3 to 4.4

  2. q Saturation Zone Transition Zone Transmission Zone Wetting Zone Wetting Front depth Infiltration • General • Process of water penetrating from ground into soil • Factors affecting • Condition of soil surface, vegetative cover, soil properties, hydraulic conductivity, antecedent soil moisture • Four zones • Saturated, transmission, wetting, and wetting front

  3. Infiltration • Infiltration rate • Rate at which water enters the soil at the surface (in/hr or cm/hr) • Cumulative infiltration • Accumulated depth of water infiltrating during given time period

  4. Infiltrometers Single Ring Double Ring http://en.wikipedia.org/wiki/Infiltrometer

  5. Infiltration Methods • Horton and Phillips • Infiltration models developed as approximate solutions of an exact theory (Richard’s Equation) • Green – Ampt • Infiltration model developed from an approximate theory to an exact solution

  6. Hortonian Infiltration • Recall Richard’s Equation • Assume K and D are constants, not a function of q or z • Solve for moisture diffusion at surface f0 initial infiltration rate, fc is constant rate and k is decay constant

  7. Hortonian Infiltration

  8. Philips Equation • Recall Richard’s Equation • Assume K and D are functions of q, not z • Solution • Two terms represent effects of • Suction head • Gravity head • S – Sorptivity • Function of soil suction potential • Found from experiment

  9. Green – Ampt Infiltration Ponded Water Ground Surface Wetted Zone Wetting Front Dry Soil

  10. Green – Ampt Infiltration (Cont.) Ground Surface Wetted Zone • Apply finite difference to the derivative, between • Ground surface • Wetting front Wetting Front Dry Soil

  11. Green – Ampt Infiltration (Cont.) Ground Surface Wetted Zone Wetting Front Dry Soil Evaluate the constant of integration Integrate

  12. Green – Ampt Infiltration (Cont.) Ground Surface Wetted Zone Wetting Front Dry Soil Nonlinear equation, requiring iterative solution.

  13. Soil Parameters • Green-Ampt model requires • Hydraulic conductivity, Porosity, Wetting Front Suction Head Effective saturation Effective porosity

  14. Ponding time • Elapsed time between the time rainfall begins and the time water begins to pond on the soil surface (tp)

  15. Potential Infiltration Infiltration rate, f Rainfall Actual Infiltration Time Accumulated Rainfall Infiltration Cumulative Infiltration, F Time Ponding Time • Up to the time of ponding, all rainfall has infiltrated (i = rainfall rate)

  16. Example • Silty-Loam soil, 30% effective saturation, rainfall 5 cm/hr intensity

More Related