They are also used during aquifer testing, and measurements related to groundwater … 10.8 Ground water movement Courtesy USGS . the flow (Q) through a horizontal tube can be described as: Q = -p*D 4 /(128*m)*dp/dx (Poiseuille's law) => size of the capillary tubes is important! Adjusting for the porosity (n) what drives groundwater flow? It is useful in connection with extraction of groundwater from an aquifer through wells for water supply, irrigation, and industrial use and for investigation and remediation of groundwater contamination. Water level measurements help determine flow directions, identify changes in gradients and seasonal fluctuations. So the equation to estimate flow velocity is as follows: $V=\dfrac{K\times i}{n}$ where V is the velocity of the groundwater, and n is the porosity (expressed as a proportion, so if the porosity is 10%, n = 0.1). Groundwater Level & Flow. DAVE ADAMSON: And then on the other hand, you'd use the seepage velocity, also the interstitial velocity, to get the rate of plume migration. It is instructive for you to calculate how far groundwater would move in a year at 0.3 feet per day, an actual groundwater velocity in nature. Darcy's law is an equation that describes groundwater movement in aquifers based on three variables: horizontal hydraulic conductivity, horizontal hydraulic gradient and effective porosity. This is analogous to water flow in aquifers-the darcian velocity (V d) is the average flow rate, but because only a fraction of the aquifer is pore space, and so can transmit water, the actual velocity of the moving water (V actual) must be greater. Darcy's Law is a primary tool for groundwater flow modeling. Average ground water flow rate of 15 m per day is common. A velocity of 1 foot per second equals about 16 miles per day. In practice, a groundwater velocity of a foot per day is generally not seen and most velocities are on the order of tenths of feet per day. The low velocities of ground-water flow can have important implications, particularly in relation to the movement of contaminants. And number 1 is use the Darcy velocity, also called specific discharge, to get flow information as this term is the groundwater flow per area. An accurate estimate of groundwater velocity can be calculated using Darcy's Law. If the water flux is uniform in the porous media, groundwater fluxes causes a temperature distribution on the surface of the cylinder varying as a function of the direction and magnitude of groundwater flow velocity (range from 0,5 to 90 cm.day −1). traffic flow. A basic measurement in groundwater studies is that of water levels in wells. We can apply this equation to the scenario in Figure 14.2.1. Highly permeable materials like gravels can have flow velocities of 125 m per day. Groundwater in an aquifer is under pressure called hydrostatic pressure. water flows from high elevation to low elevation and from high pressure to low pressure, gradients in potential energy drive groundwater flow Darcy's law. How to Calculate Groundwater Velocity. Groundwater flow rate can then be calculated using Darcy’s law, which says that the flow rate is linearly proportional to the hydraulic gradient:  q = − ρ g k μ ( ∇ h ) where q is the Darcy flux, or flow rate per unit surface area, and μ is fluid viscosity.