PUBLICATIONS - Techniques of Water-Resources Investigations, manual "A digital model for aquifer evaluation" by George F. Pinder. UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY WATER RESOURCES DIVISION WASHINGTON, D. C. 20242 July 30, 1969 4037 0001 GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 70.3 To: Regional Hydrologists and District Chiefs, WRD From: Chief, Ground Water Branch, WRD Subject: PUBLICATIONS - Techniques of Water-Resources Investigations, manual "A digital model for aquifer evaluation" by George F. Pinder. The subject TWRI manual chapter is now in progress of publication, but it will not be available for distribution for several months. In the interim a limited number of duplicated copies can be furnished on request. The program, which is written in FORTRAN IV for the IBM 360 system, provides a digital computer aquifer model for arrays of data up to 48 x 65 nodes. Recharge and discharge boundaries, variations in transmissivity and storage coefficient, vertical leakage, and nodal location of pumpage can be accommodated by the model. Expansion of the array is easily accomplished, if equipment large enough and fast enough to handle the problem is available. (s) C. L. McGuinness WRD Distribution: A, B, S, FO, PO