26.6. Infiltration Equations and Models

Try these first

1. 1.

   What does f(t) represent in Horton’s Equation?

   Hint

   Think about what we measure as time passes.

2. 2.

   Name one factor that Philip's Equation considers.

   Hint

   Focus on the components influencing water movement.

3. 3.

   What does Horton’s Equation model?

   • Initial infiltration rates
   • Declining infiltration rates over time
   • Cumulative infiltration values

   Hint

   Think about how infiltration changes from the start of rain.

4. 4.

   True or False: Philip's Equation does not consider the effect of gravity.

   • True
   • False

   Hint

   Recall how water naturally behaves under the influence of gravity.

5. 5.

   Given a soil with a hydraulic conductivity of 15 mm/hr, a saturated moisture content of 30%, and an initial moisture content of 10%, use Green-Ampt Equation for a ponded situation to find cumulative infiltration after 2 hours. Show all calculations.

   Hint

   Set up the equation with the known variables, prioritize calculating suction head and subsequent infiltration.

6. 6.

   A drainage engineer finds that a field's infiltration rate starts at 100 mm/hr and stabilizes at 20 mm/hr. Create a scenario using Horton’s Equation to calculate the decay constant, k, after the first three hours. Provide detailed reasoning.

   Hint

   Consider dividing the change over time post-initial period and applying accordingly using estimates from the equation.