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The Richards equation represents the movement of water in unsaturated soils, and is attributed to Lorenzo A. Richards who published the equation in 1931. [1] It is a quasilinear partial differential equation ; its analytical solution is often limited to specific initial and boundary conditions. [ 2 ]
Hooghoudt's equation can be written as:. [3] Q L 2 = 8 Kb d (Dd - Dw) + 4 Ka (Dd - Dw) 2. where: Q = steady state drainage discharge rate (m/day) Ka = hydraulic conductivity of the soil above drain level (m/day) Kb = hydraulic conductivity of the soil below drain level (m/day) Di = depth of the impermeable layer below drain level (m)
In epidemiology, a rate ratio, sometimes called an incidence density ratio or incidence rate ratio, is a relative difference measure used to compare the incidence rates of events occurring at any given point in time.
The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes. [1]Erosion models play critical roles in soil and water resource conservation and nonpoint source pollution assessments, including: sediment load assessment and inventory, conservation planning and design for sediment control, and for the advancement of scientific understanding.
Apparent infection rate is an estimate of the rate of progress of a disease, based on proportional measures of the extent of infection at different times.. Firstly, a proportional measure of the extent of infection is chosen as the disease extent metric.
In contrast, a disease that has a short duration may have a low prevalence and a high incidence. When the incidence is approximately constant for the duration of the disease, prevalence is approximately the product of disease incidence and average disease duration, so prevalence = incidence × duration. The importance of this equation is in the ...
The available volume for additional water in the soil depends on the porosity of the soil [7] and the rate at which previously infiltrated water can move away from the surface through the soil. The maximum rate at that water can enter soil in a given condition is the infiltration capacity.
Threshold host density (N T) only applies to density dependent diseases, where there is an "aggregation of risk" to the host in either high host density or low host density patches. When low host density causes an increase in incidence of parasitism or disease, this is known as inverse host density dependence, whereas when incidence of ...