The exponential integral, called the Well Function W(u), is easily programmed on a calculator using the infinite series2: W(u)=∫∞ue−uudu=−γ−lnu+u−u22⋅2! +u33⋅3!
What is the well function?
The Theis’ well function (a well in a confined aquifer) It describes the transient flow to a fully penetrating well in a confined aquifer after the well starts pumping at time zero.
How do you calculate the specific capacity of a well?
How do you calculate the radius of influence for a well?
Solution to drawdown problem Radius of influence (R) for a well may be calculated using the following equation: R = b*(SQRT(K/(2*N))), where b is the thickness (100m), K is hydraulic conductivity (1e-5 m/sec), and N is the recharge (0.75 m/yr or 2.378e-8 m/sec).
How is transmissivity calculated?
Define transmissivity mathematically. We have T = KhD where T is the transmissivity, Kh is the average horizontal conductivity and D is the aquifer thickness.
What is specific yield of a well?
Specific Yield means the measurement of the water removed from the aquifer by the force of gravity to wells. It is defined as the ratio of the volume of water which an aquifer, after being saturated, will yield by gravity to the volume of the aquifer drained. The ratio is usually expressed as a percentage.
What is specific capacity of open well?
The Specific Capacity of a well is the pumping rate (gpm) (Q) divided by the drawdown in feet (s). Specific Capacity can also be used to provide the design pumping rate or maximum yield for the well and to estimate the transmissivity of the surrounding formations penetrated by the well screens.
What is a well radius?
The radius is the distance from the well to a point where groundwater (and contaminant) travel time to the well is 2 years (or 5 years). Input data requirements are limited, consisting of the pumping rate, open (screened interval) of the well, porosity of the aquifer, and the selected TOT.
What is the radius of influence of aquifer?
What is well development?
How long does a well last?
The average lifespan for a well is 30–50 years. 2. How deep is the well? Drilled wells typically go down 100 feet or more.
How many types of wells are there?
There are three types of wells: dug, driven, and drilled. Drilled are the most common today.
What is K in Darcy’s law?
k is called the permeability, a parameter specific to each soil or rock, which can be a scalar or a second-order tensor if the medium is anisotropic, and μ is the dynamic viscosity. Physically, Darcy’s law is the result of the integration of the Navier–Stokes equations in the very complex geometry of the pore space.
What is well Loss?
The term “well loss” is a non-linear term, and represents turbulent flow in the vicinity of the well and in the well. The well loss can be a substantial fraction of total drawdown when pumping rates are large.
What are assumptions made in theis method?
How do you calculate hydraulic conductivity?
Q = K•A [(h1-h2) ÷ L] The following variables and coefficients apply to this formula: “K” = Hydraulic Conductivity; “Q” = Discharge Rate; “A” = Area of Cross-Section that Water Flows; “h” = Hydraulic Head (h = p/rg + z); and “L” = Length/Distance of Water Table Elevation Change.
How do you calculate residual drawdown?
The residual drawdown (s’) is computed by subtracting the static water-level measurement from the measurement at time t’ after pumping ceases. The ratio of log10 t/t’ is determined graphically by plotting log10 t/t’ against corresponding value of s’.
How do you calculate the yield of an open well?
Total quantity of water percolated into the well is calculated by knowing cross-sectional area and rise in the water level after stoppage of pumping. The rate of percolation or the yield of well can be arrived at by dividing the quantity of water by the time.
How do you calculate specific yield?
The specific yield is then determined by comparing the volume of dewatered material with the total volume of discharged water. The calculation of the volume of dewatered material requires the solution of an exponential series that converges very slowly and is, therefore, time consuming.
How do you calculate water yield?
Water Yield can be calculated by dividing the mean annual volume of streamflow that is produced in a nested watershed (expressed in cubic meters per year), by the area of the nested watershed (expressed in square kilometers).
What is a good well flow rate?
The Water Well Board suggests that a minimum water supply capacity for domestic internal household use should be at least 600 gallons of water within a two-hour period once each day. This is equivalent to a flow rate of 5 gallons per minute (gpm) for two hours.
