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Steven P. Larson

Publications and source records attributed to Steven P. Larson.

4 recordsLinked to original sources
USGS2006

Representation of multiaquifer well effects in three-dimensional ground-water flow simulation

The presence of multiaquifer or multilayer wells changes the nature of the equations which must be solved in a three-dimensional ground-water flow simulation and, in effect, alters the stencil of computation. A method has been devised which takes this change into consideration by allowing simulation of the hydraulic effects of a multiaquifer well on the aquifer system. It also allows for calculation of the water level and individual aquifer discharges in such a well. The method is valid for the case of a single well located at the center of a square node block. Where more than one well per node is involved, the effects of the stencil alteration still must be considered, although difficulties arise in estimating and justifying the parameters to be utilized.

Groundwater↗
USGS1977

Distribution of injected wastewater in the saline-lava aquifer, Wailuku-Kahului wastewater treatment facility, Kahului, Maui, Hawaii

Field studies and digital modeling of a lava rock aquifer system near Kahului, Maui, Hawaii, were employed to define and describe the distribution of planned injected wastewater from a secondary treatment facility. The lava rock aquifer contains water that is almost as saline as seawater. The saline water is below a seaward-discharging freshwater lens, and separated from it by a transition zone of varying salinity. Injection of wastewater at an average rate of 6.2 cubic feet per second is planned through wells open only to the aquifer deep within the saline water zone. The lava rock aquifer is overlain by a sequence of residual soil, clay, coral reef deposits, and marine sand that form a low-permeability caprock which semiconfines the lava rock aquifer. A two-dimensional finite-difference model was used to describe initial conditions within the freshwater part of the aquifer, and to indicate response of the freshwater part of the system to injection of wastewater. Steady-state distribution of the wastewater within the saline and the freshwater parts of the lava rock aquifer was simulated by use of a three-dimensional finite-difference model. This model, using vertical-to-horizontal ratios of hydraulic conductivity of 1:10 and 1:100, shows that wastewater with a lesser density than that of either the saline or freshwater aquifer, will form a roughly cylindrical column around the injection well base and rise through the transition zones into the freshwater lens flow system. The column diameter varies with the ratio, and the column, or plume, widens progressively through the transition zone, then maintains virtually constant size through the freshwater part of the lava rock aquifer. Seaward flow within the freshwater lens tends to distort the plume seaward. Under conditions measured and assumed for the study, it is evident that wastewater injected at the planned rate will move upward, then seaward without significant change. After reaching a new steady state, the wastewater will discharge into and through the caprock sequence within an area measuring approximately 1,000 feet inland, 1,000 feet laterally on either side of the injection site, and about 2,000 feet seaward. Little, if any, of the injected wastewater may be expected to reach the upper part of the caprock flow system landward of the treatment plant facility.

Hawaii↗
USGS1976

An appraisal of ground water for irrigation in the Appleton area, west-central Minnesota

Supplemental irrigation of well-drained sandy soils has prompted an evaluation of ground water in the Appleton area. Glacial drift aquifers are the largest source of ground water. The surficial outwash sand and gravel is the most readily available and the most areally extensive drift aquifer, and it underlies much of the sandy soil area. Saturated thickness of the outwash is more than 80 feet (24 m) in places, and potential well yields may exceed 1,200 gal/min (76 1/s) in some areas. In about 17 percent of the area, yields of more than 300 gal/min (19 1/s) are obtainable. Recharge to the outwash aquifer occurs primarily during the spring thaw and averages about 5 inches (12.7 cm) annually. Most discharge from the aquifer appears as base flow in the Pomme de Terre River. Despite dissolved-solids concentrations ranging from 280 to 1,350 mg/1, the water is chemically suitable for irrigation. Mathematical models of a part of the aquifer were made to evaluate the effects of 20 successive years of ground-water withdrawal for three irrigation-development patterns. It was estimated that the present annual withdrawal rate of 1,410 acre-ft (1.74 hm 3 ) would result in water-level declines of less than 3 feet (0.9 m). However, annual withdrawals of 8,450 acre-ft (10.4 hm 3 ) would cause aquifer dewatering and decreased well yields in some places. After a new state of equilibrium was established in response to withdrawals, most of the withdrawal would be supplied by diverted base flow from the Pomme de Terre River.

Minnesota↗