work by Herrera and Yates [1977], and we state that their solution of the multiple-aquifer problem requires a constant pumping rate Q applied at time to and held ...
VOL. 15, NO. 4
WATER RESOURCES RESEARCH
AUGUST 1979
Correction In the introductionto the paper 'An Iterative Quasi-ThreeDimensional Finite ElementModel for HeterogeneousMultiaquiferSystems'by Don W. Chorleyand Emil O. Frind (Water ResourcesResearch,•4(5), 943-952, 1978) we review the work by Herrera and Yates [1977], and we state that their solution of the multiple-aquiferproblem requiresa constant pumpingrate Q appliedat time toand held constantthereafter and that a change in the pumping regime would require a superpositionof solutionsand the addition of new influence terms to the solution.This was basedon our interpretationof section2 of Herrera and Yates' paper, particularly equation (1) and the precedingmaterial.This equationdoesnot contain a source-sinkterm. Unfortunately,we overlookedthe fact that
The two methodsare indeedvery similarin effect,although
they differ in the theoryused.Our methodmay perhapsbe somewhatmore generalfor complexsystems havingboth inhomogeneous aquifersand aquitards.We understandthat Herrera'ssolutioncan now handleinhomogeneous aquifersby introduction of suitablemodificationsto the equations.In any
case,a systematic comparison of the relativemeritsof thetwo methodsmay be worthwhile. We are presentlyin the processof adaptingour methodto handledewateringproblemsin connectionwithopen-pitmin-
ingor quarryoperatio,ns. Thisrequires theremoval of aquifer andaquitardelements at successive timesto simulatetheprogressingexcavation.We are alsoinvestigating the problemof representing pinched-outunitsin the multipleaquifermodel.
the source-sink term is introduced later in section 5, The
Numerical Method, and is incorporatedinto the matrix equation (27), which representsthe discretizedaquifers.This term
REFERENCE
containsthe extractionrate Qt,, for node i and aquifer3•, whichcan be a functionof time. The start-upof a new wellcan
Hererra, I., and R. Yates, Integrodifferential equationsfor systemsof
be represented by changingQt, from zeroto the appropriate value at that node. No newtermsare required.Our evaluation of the Herrera
and Yates model is therefore
incorrect.
leakyaquifersandapplications, 3, A numerical methodof unlimited applicability,WaterResour.Res.,•3(4), 725-532, 1977.
We
apologizefor the misinterpretation. (ReceivedMarch l, 1979.)
Copyright¸ 1979by the AmericanGeophysicalUnion.
Paper number 9W0384. 0043-1397/79/009W-0384501.00
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