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The Holliday-Segar formula is a formula to help approximate water and caloric loss (and therefore the water requirements) using a patient's body weight. [1] Primarily aimed at pediatric patients, the Holliday-Segar formula is the most commonly used estimate of daily caloric requirements. [2] To date, the formula continues to be recommended in ...
v. t. e. In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes ). It contrasts with mass flow rate, which is the other main type of fluid flow rate.
Water retention curve for a sand (Ss), either silt or clay-loam (Uu), either loam-silt or clay (Lu), and either clay or peat (Tt). Water retention curve is the relationship between the water content, θ, and the soil water potential, ψ. This curve is characteristic for different types of soil, and is also called the soil moisture characteristic.
Definitions. Volumetric water content, θ, is defined mathematically as: where is the volume of water and is equal to the total volume of the wet material, i.e. of the sum of the volume of solid host material (e.g., soil particles, vegetation tissue) , of water , and of air . Gravimetric water content[1] is expressed by mass (weight) as follows:
Torricelli's law, also known as Torricelli's theorem, is a theorem in fluid dynamics relating the speed of fluid flowing from an orifice to the height of fluid above the opening. The law states that the speed of efflux of a fluid through a sharp-edged hole in the wall of the tank filled to a height above the hole is the same as the speed that a ...
Water balance. The law of water balance states that the inflows to any water system or area is equal to its outflows plus change in storage during a time interval. [2][3] In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological or water domains, such as ...
Streeter–Phelps equation. The Streeter–Phelps equation determines the relation between the dissolved oxygen concentration and the biological oxygen demand over time and is a solution to the linear first order differential equation [ 1 ] This differential equation states that the total change in oxygen deficit (D) is equal to the difference ...
The above groundwater flow equations are valid for three dimensional flow. In unconfined aquifers, the solution to the 3D form of the equation is complicated by the presence of a free surface water table boundary condition: in addition to solving for the spatial distribution of heads, the location of this surface is also an unknown. This is a ...