Infiltration (hydrology)
[2] Infiltration is caused by multiple factors including; gravity, capillary forces, adsorption, and osmosis.
Rainfall leads to faster infiltration rates than any other precipitation event, such as snow or sleet.
In this case, the soil can develop large cracks which lead to higher infiltration capacity.
[4] Hydrophobic soils can develop after wildfires have happened, which can greatly diminish or completely prevent infiltration from occurring.
Organic materials in the soil (including plants and animals) all increase the infiltration capacity.
Vegetation can also reduce the surface compaction of the soil which again allows for increased infiltration.
When no vegetation is present infiltration rates can be very low, which can lead to excessive runoff and increased erosion levels.
Increased abundance of vegetation also leads to higher levels of evapotranspiration which can decrease the amount of infiltration rate.
[5] Debris from vegetation such as leaf cover can also increase the infiltration rate by protecting the soils from intense precipitation events.
On sandy loam soils, the infiltration rate under a litter cover can be nine times higher than on bare surfaces.
The low rate of infiltration in bare areas is due mostly to the presence of a soil crust or surface seal.
[6] When the slope of the land is higher runoff occurs more readily which leads to lower infiltration rates.
[5] The process of infiltration can continue only if there is room available for additional water at the soil surface.
The maximum rate at that water can enter soil in a given condition is the infiltration capacity.
If the arrival of the water at the soil surface is less than the infiltration capacity, it is sometimes analyzed using hydrology transport models, mathematical models that consider infiltration, runoff, and channel flow to predict river flow rates and stream water quality.
Robert E. Horton[8] suggested that infiltration capacity rapidly declines during the early part of a storm and then tends towards an approximately constant value after a couple of hours for the remainder of the event.
When these lines are compromised by rupture, cracking, or tree root invasion, infiltration/inflow of stormwater often occurs.
This circumstance can lead to a sanitary sewer overflow, or discharge of untreated sewage into the environment.
The rigorous standard that fully couples groundwater to surface water through a non-homogeneous soil is the numerical solution of Richards' equation.
A newer method that allows 1-D groundwater and surface water coupling in homogeneous soil layers and that is related to the Richards equation is the Finite water-content vadose zone flow method solution of the Soil Moisture Velocity Equation.
An easy example of double counting variables is when the evaporation, E, and the transpiration, T, are placed in the equation as well as the evapotranspiration, ET.
The Richards equation is computationally expensive, not guaranteed to converge, and sometimes has difficulty with mass conservation.
[11] This method approximates Richards' (1931) partial differential equation that de-emphasizes soil water diffusion.
This was established by comparing the solution of the advection-like term of the Soil Moisture Velocity Equation[12] and comparing against exact analytical solutions of infiltration using special forms of the soil constitutive relations.
Results showed that this approximation does not affect the calculated infiltration flux because the diffusive flux is small and that the finite water-content vadose zone flow method is a valid solution of the equation [13] is a set of three ordinary differential equations, is guaranteed to converge and to conserve mass.
It requires the assumption that the flow occurs in the vertical direction only (1-dimensional) and that the soil is uniform within layers.
It is a function of the soil suction head, porosity, hydraulic conductivity, and time.
These values can be obtained by solving the model with a log replaced with its Taylor-Expansion around one, of the zeroth and second order respectively.
[16] in integrated form, the cumulative volume is expressed as: Where This method used for infiltration is using a simplified version of Darcy's law.
