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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 ]
The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. In practice, the sample size used in a study is usually determined based on the cost, time, or convenience of collecting the data, and the need for it to offer sufficient statistical power. In complex studies ...
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)
Where w s is the mean source width, ρ w is the density of water, R 0 is the average precipitation rate, W* is the width of the channel head, ρ s is the saturated bulk density of the soil, K z is the vertical saturated hydraulic conductivity, θ is the slope at the channel head, and φ is the soil angle of internal friction.
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. It is defined as:
ρ p: Actual particle density (g/cm 3) ρ g: Gas or sample matrix density (g/cm 3) r 2: Least-squares coefficient of determination. The closer this value is to 1.0, the better the data fit to a hyperplane representing the relationship between the response variable and a set of covariate variables.
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.
Summary of hydrologic and physical properties of rock and soil materials as analyzed by the Hydrologic Laboratory of the U.S. Geological Survey 1948-1960. U.S. Geological Survey Water Supply Paper 1839-D. 42 p. De Wiest, R. J. (1966). On the storage coefficient and the equations of groundwater flow. Journal of Geophysical Research, 71(4), 1117 ...