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Charles Carlston (1963) [8] determined an equation to express the mean annual flood runoff, Q2.33, for a given drainage basin as a function of drainage density. Carlston found a correlation between the two quantities when plotting data from 15 drainage basins and determined the following equation:
The grain size is often visualized in a cumulative distribution graph which, for example, plots the percentage of particles finer than a given size as a function of size. The median grain size, D 50 {\displaystyle D_{50}} , is the size for which 50% of the particle mass consists of finer particles.
The soil bulk density of cultivated loam is about 1.1 to 1.4 g/cm 3 (for comparison water is 1.0 g/cm 3). [48] Contrary to particle density, soil bulk density is highly variable for a given soil, with a strong causal relationship with soil biological activity and management strategies. [49]
A drainage equation is an equation describing the relation between depth and spacing of parallel subsurface drains, depth of the watertable, depth and hydraulic conductivity of the soils. It is used in drainage design.
The resistance of a semi-confining top layer of an aquifer can be determined from pumping tests. [ 10 ] When calculating flow to drains [ 11 ] or to a well field [ 12 ] in an aquifer with the aim to control the water table , the anisotropy is to be taken into account, otherwise the result may be erroneous.
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. [1]
Roughly speaking for agriculture (top layer soil), soil is 25% water, 25% air, 45% mineral, 5% other; water varies widely from about 1% to 90% due to several retention and drainage properties of a given soil. The role of soil water retention is profound; its effects are far reaching and relationships are invariably complex.