Green-Ampt Infiltration Parameters: Difference between revisions

The porosity value represents the volume of dry voids per volume of soil and provides the maximum moisture deficit that is available, the difference between the moisture content at saturation and at the start of the simulation. Sandy soils tend to have lower porosities than clay soils, but drain to lower moisture contents between rainfall events because water is not held as strongly in the soil pores. Therefore, values of porosity tend to be higher for sandy soils when compared to clay soils. As shown in Figure 79, the higher the porosity value, then the less runoff that is generated due to increased infiltration although the model is not particular sensitive to the porosity value.<br>

The three initial moisture sensitivity tests have been undertaken with the Green-Ampt method using both a pre-2023 release of TUFLOW and a post-2023 release of TUFLOW. Figure 911 shows how variations in the initial moisture affect the simulated cumulative infiltration, whereas Figures 1012 and 1113 show the effects of varying the initial moisture on flows at the catchment outlet when using the pre-2023 and post-2023 releases of TUFLOW. As the initial moisture is increased at the beginning of your simulation, there is less infiltration (as you are closer to soil capacity) and more runoff, causing the catchment outflows to exhibit a faster response to rainfall upstream. As the event progresses, soils become more saturated and the influence of the initial moisture parameter becomes less significant. In the examples shown here, the catchment outflows, as visible in Figures 1012 and 1113, show a higher responsiveness to variations in initial moisture at the beginning of the simulations, and attain higher peak values, when using the post-2023 TUFLOW releases.