Spacing of Drainage Wells in a Layered Aquifer

Abstract

A theory is presented to determine spacing of identical drainage wells that, by discharging groundwater simultaneously from a layered aquifer, will lower a water table to a preassigned level and maintain it. The theory has been developed by solving a mathematical boundary value problem. The wells are located on a certain regular grid, and the aquifer receives a uniform vertical recharge from rainfall or excess irrigation. The theory shows that the spacing depends on the thickness and hydraulic conductivity of each permeable layer tapped by the wells, the maximum allowable drawdown, the uniform vertical recharge, the radius of the wells, and the well grid geometry. A table of values of a function, useful for determining spacing of wells to be tapped in an aquifer that may consist of any number of permeable layers, is given.

Ground‐Water Flow Patterns in Confined Aquifers and Pollution

“…The first is the potential function </>(r,0), as found on the bound ary. On the boundary the value of r (say R) for every value of 0 must be assumed known; therefore it may be said that <f>(r,Q) goes over to a function <£ (6), which can be denoted as / (8). The / (6) corresponds to the f(x) of Kirkham and Powers.…”

“…where / v(0) is the Mh approximation to /(O) of Eq (8). For N-> oo, the right side of Eq (12) becomes equal to /(6) of Eq (1) for every value of 6.…”

“…The method described for producing the flow net of Fig. 7 should work when the outer boundary of the flow region has an arbitrary potential value 0(0) = /(6) not only the value /(O) = 1 given by Eq (8). Here one would enter each known head value /(O) in Eq (8) for the numerical integration.…”

An iterative method for estimating solute travel times to ditch drains under steady recharge and ponded conditions

“…Kirkham and Affleck (1977) provided expressions for predicting travel times of solute from injection points to a well in a confined aquifer that fully penetrates the aquifer utilizing the piston flow assumption of solute movement along streamlines. Utilizing the same assumption, Cushman and made use of the analytical model of Khan and Kirkham (1971) to work out mathematical expressions for predicting travel times of solutes to fully penetrating wells in a multilayered aquifer underlain by an impervious barrier, both for the cases when the outer boundary is a constant head zone and when it is a no flow one. Kirkham and Sotres (1978) mathematically studied the influence of unscreened casing length of a well in a phreatic aquifer on the travel times of solutes and observed the travel times to be positively correlated with casing depth of the well.…”