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Michael G. McDonald

Publications and source records attributed to Michael G. McDonald.

6 recordsLinked to original sources
USGS2000

MODFLOW-2000, The U.S. Geological Survey modular ground-water model: User guide to modularization concepts and the ground-water flow process

MODFLOW is a computer program that numerically solves the three-dimensional ground-water flow equation for a porous medium by using a finite-difference method. Although MODFLOW was designed to be easily enhanced, the design was oriented toward additions to the ground-water flow equation. Frequently there is a need to solve additional equations; for example, transport equations and equations for estimating parameter values that produce the closest match between model-calculated heads and flows and measured values. This report documents a new version of MODFLOW, called MODFLOW-2000, which is designed to accommodate the solution of equations in addition to the ground-water flow equation. This report is a user's manual. It contains an overview of the old and added design concepts, documents one new package, and contains input instructions for using the model to solve the ground-water flow equation.

Open-File Report↗
USGS1985

U. S. G. S. MODULAR GROUND-WATER FLOW MODEL: DESIGNED TO BE UNDERSTOOD AND ADAPTED.

The paper discusses a carefully designed model program and its complementary complete description of all of the physical and mathematical concepts used in the model. The model program consists of a series of independent subroutines called modules. Modules are grouped by hydrologic function into 'packages. ' A report describing the model was written in three levels. At one level the hydrologic concepts on which the model is based are explained. The second level describes how the concepts were incorporated into the program. The third level describes specific modules in sufficient depth to permit modifications to the model.

Conference Paper↗
USGS1980

Ground water of coal deposits, Bay County, Michigan

A coal deposit in Bay County, Mich., typical of Pennsylvanian-coal deposits in the State, was studied to determine the degree to which hydrologic factors might affect future coal mining. The coal deposit, which averages about 0.5 meters in thickness, lies 50 meters below land surface. It is part of a multi-layered aquifer system that contains sandstone, shale, sand and gravel, and clay units in addition to beds of coal. Hydrologic characteristics (hydraulic conductivity and storage coefficient) of each unit were evaluated by analyses of aquifer tests and a finite-difference groundwater flow model. A model simulating groundwater flow to a hypothetical mine was developed. Results of the study indicate that seepage will probably not be great enough to preclude mining coal. Also, pumping water to keep the mine dry will have little effect on heads in aquifers outside the mine during the first decade of mining. Although coal was mined in Michigan during 1860-1950, significant reserves remain. These deposits, part of the Saginaw Formation of Pennsylvanian age, are near the industrialized parts of the State. The quantity of pumped water needed to keep mines dry and the effect of pumping on aquifers surrounding the mines is a major factor in determining the feasibility of opening new mines.

Michigan↗
USGS1978

Model analysis of the impact on ground-water conditions of the Muskegon County wastewater disposal system, Michigan

A digital model was developed to study the impact on ground-water conditions of the Muskegon County wastewater disposal system. At the disposal site, wastewater is stored in two 850-acre (344-ha) lagoons and then spray-irrigated on crop land. About 70 miles (105 km) of drainage tile, which underlies the irrigated land, has caused the water table to be lowered substantially. The decline in water levels has been partially offset by irrigation and leakage from the lagoons; at some places the water table is higher than it was prior to construction. Predictive simulations by the model were used to study the effects of varying tile drainage, amount of irrigation water applied, lagoon leakage, and natural ground-water recharge. If the effectiveness of the tile to collect drainage is reduced by 75 percent, large areas within the wastewater site would become waterlogged. However, the effect outside of the wastewater site would be negligible.

Michigan↗
USGS1978

Three-dimensional finite-difference model of ground-water system underlying the Muskegon County wastewater disposal system, Michigan

The spray irrigation system used by Muskegon County for wastewater treatment is the largest of its kind in the United States. It has 2200 hectares of irrigated farm land, 688 hectares of treatment lagoons, and 105 kilometers of drainage tile. The system has a design capacity of 1.8 cubic meters of wastewater per second. A three-dimensional finite-difference model was developed to study the effect of the disposal operation on ground-water conditions. Model calculations show that the water table at and adjacent to most of the wastewater site is lower as a result of the operation of the system to date. However, along the northwest boundary of the site, where irrigated land was not undertiled, the water table is 1 to 2 meters higher than it would be under natural conditions. Predictive simulations indicate that, even if the drainage tiles lost 75 percent of their effectiveness, the impact of disposal operations on ground-water levels would be negligible outside of the wastewater site.

Michigan↗