Leslie Patrick | Geology Reports

USGS1989

Simulation of ground-water flow at Anchorage, Alaska, 1955-83

The groundwater system at Anchorage, Alaska was analyzed by using a two-layer three-dimensional mathematical model. By use of existing data, both nonpumping and pumping steady-state conditions and transient conditions were simulated. Under steady-state conditions, calculated directions of groundwater flow were similar to observed flow patterns, and calculated stream discharges generally were within 10% of observed values. However, in many parts of the modeled area computed hydraulic head values were more than 20 ft higher or lower than observed values. Hydraulic conductivity and transmissivity are the most sensitive hydraulic parameters under steady-state conditions. Under steady-state conditions, a pumping rate of 18.8 Mgal/d lowers heads in the confined aquifer by as much as 30 ft, but reduces streamflow by less than 5%. Transient conditions show that drawndowns due to withdrawals by production wells follow similar patterns of nearby observation wells. On the basis of analytical techniques, the confining layer does not appear to hold significant quantities of water. (USGS)

Water-Resources Investigations Report↗

USGS1981

Results of exploratory drilling at Point MacKenzie, Alaska, 1981

The Matanuska-Susitna Borough anticipates industrial development near Point MacKenzie, Alaska. Because little hydrologic information is available for the area, the Borough contracted for the drilling of two test wells. It was found that: Both wells penetrated unconsolidated stratified clay, silt, sand, and gravel; each well penetrated a shallow unconfined and deeper confined aquifers; the water levels in the wells rise and fall with the tide; the chemical analyses indicate that the water quality meets the Alaska Drinking Water Standards, except for slightly high levels of manganese and pH; and the potential for saltwater intrusion should be evaluated as part of future studies. (USGS)

Open-File Report↗

USGS1980

Effects of artificial-recharge experiments at Ship Creek alluvial fan on water levels at Spring Acres Subdivision, Anchorage, Alaska

A subdivision developer encountered water while digging trenches associated with developing property at Spring Acres Subdivision, Anchorage, Alaska, during the summer of 1975. He reported encountering water at a depth of about 8 feet in June 1975 and also reported a rise in water level to approximately land surface by early August. Neither incident was expected by the developer. The U.S. Geological Survey, in cooperation with the Municipality of Anchorage, had conducted an artificial-recharge experiment approximately 9,000 feet northeast of Spring Acres Subdivision from May 20 through September 19, 1975. Recharge experiments were also conducted in 1971, 1973, and 1974. The proximity of the 1975 recharge experiment to the subdivision caused speculation on the possible connection between the experiment and the water problems encountered by the developer. The effect of the artificial-recharge experiments on water levels at Spring Acres Subdivision was evaluated by using two digital-computer models constructed to simulate the water-level rises induced by the artificial recharge. The models predicted that the artificial recharge would have caused water levels in the aquifer immediately underlying Spring Acres Subdivision to rise approximately 0.2 foot from May 20 to August 7, 1975. The models also predicted a total rise in ground-water levels of 1.1 feet at this location from July 16, 1973, to August 7, 1975, as a result of the artificial-recharge experiments. Water-level data collected for auger holes in March 1975 by a consulting firm for the contractor indicated a depth to water of 6 to 7 feet below land surface at Spring Acres Subdivision at this time. Water levels measured in and near Spring Acres Subdivision several years before and after the 1973-75 artificial-recharge experiments showed seasonal rises of 2 to 12.4 feet. A depth to water below land surface of 2.6 feet was measured 600 feet from the subdivision in 1971 and in the subdivision in 1977. Average depth to water in the area was 7.0 feet from early 1976 to September 1979.

Alaska↗