"Status of ground-water modeling in the U.S. Geological Survey," UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY RESTON, VIRGINIA 22092 GW Branch August 27, 1976 Code 4351 5016 GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 76.11-T Subject: PUBLICATIONS - Report: "Status of ground-water modeling in the U.S. Geological Survey," by Charles A. Appel and John D. Bredehoeft, U. S. Geological Survey Circular 737. The enclosed report summarizes USGS developments in the use of models for the analysis of ground-water problems. Some general types of problems for which models have been, or are being developed include: (1) ground-water flow in saturated or partially-saturated materials, (2) land subsidence resulting from ground-water extraction, (3) flow in coupled stream-aquifer systems, (4) coupling of rainfall-runoff basin models with soil moisture accounting and aquifer flow models, (5) interaction of economic and hydrologic considerations, (6) predicting the transport of contaminants in an aquifer, and (7) estimating the effects of development alternatives for geothermal systems. The status of modeling activity for various models is reported as being in a developmental, verification, operational, or continued- improvement phase. References that provide useful details on the characteristics of the models are identified. We recognize that we may have overlooked some of the modeling development of ongoing district programs by limiting references to cases where documentation presently is available or definitely planned for completion in the very near future. Please bring to our attention any modeling activities that should have been, but were not, acknowledged. (s) Charles A. Appel for Chief, Ground Water Branch Water Resources Division Enclosure WRD Distribution: A, B, S, FO, PO