Assessment of Potential Well Yield, Gallatin Regional Park MT

Stephan G. Custer

Earth Sciences, Montana State University

This assignment is used in a junior/senior level college ground-water resources course, ESCI 440.

Students need to be able to read or learn to read well logs and hydrogeologic information on the well logs: total depth, pumping water level, static water level, yield, well screen, seals, specific capacity, and BLM well location method. Some knowledge of the geology of a Basin and Range valley is helpful. Knowledge of recovery tests in single wells is conceptually helpful but is not required to do the exercise.

This project is assigned about midway into the hydrogeology course after the geology of alluvial valley fill in a basin and range setting has been developed and after the concept of specific capacity and well yield have been assigned. The project could be followed by a model pump test, but is not currently used that way.

The exercise includes data acquisition, analysis, and writing.
Students use a large data base on the web, well log analysis, geologic analysis of ground-water occurrence, well yield analysis using specific capacity, water resource evaluation.

Critical thinking, analysis of uncertain data, identification of important data, spatial analysis of geologic and hydrologic data, address a hydrogeologic problem commonly asked by the public, recognition of limitations of existing data.

This exercise involves writing, plotting data on a map, development of tables, use of a web-based data archive. Working in groups is encouraged for data collection and analysis, but each student should write their report in their own words.

This project helps familiarize students with data commonly available from well drillers, the Department of Natural Resources and Conservation, and the Montana Bureau of Mines and Geology. Such data is often used to produce consulting reports. In this exercise, students practice working with available data and writing a consulting report while working on a real project of local interest. The question involves the probability of success in drilling a large well for a new county park. Students are given various maps and are guided through the use of a statewide database that contains well logs and well data. The outcome is a written report that describes the location and general geology of the site, uses the available data to summarize the types of materials that a driller might encounter, answers the questions that the client is interested in, and identifies problems or advantages presented by the groundwater system as indicated by available data.

Evaluation is based upon the written work. A grading rubric is included in the files below.

To prepare for this analysis, students should read about or receive lecture on specific capacity, well yield, empirical specific-capacity-well yield-equations, well logs, well construction and basin and range alluvial valley fill. The exercise is on the web, as are a tutorial on data acquisition, and specific capacity.

Custer, S., Christner, W.T., Dixon, S., Burton, G., Snyder, R., Aspinall, R., Rupp, G., and Roark, T., 2002. Spatial Data for Septic Assessment, Local Water Quality District, Gallatin County, MT. Bozeman, MT, Montana State University, http://www.montana.edu/uessc/SepticAssessment/010lwqdsepindx2010.html [Accessed February, 2013]

Custer, S., and Dixon, S., 2002a, Hydrogeologic coverage (for Gallatin Local Water Quality District, Gallatin County, MT): http://www.montana.edu/uessc/SepticAssessment/022hydrogeology.html [Accessed February, 2013]

Custer, S., and Dixon, S., 2002b, Hydrogeologic unit map (for Gallatin Local Water Quality District, Gallatin County, MT): http://www.montana.edu/uessc/SepticAssessment/hydgeoimg.html [Accessed February, 2013]

Custer, S., and Dixon, S., 2002c, Transmissivity map (for Gallatin Local Water Quality District, Gallatin County, MT): http://www.montana.edu/uessc/SepticAssessment/transm.html [Accessed February, 2013]

Custer, S.G., Donohue, D., Tanz, G., Nichols, T, Sill, W., Wideman, C., 1991, Groundwater potential in the Bozeman Fan Subarea, Gallatin County, Montana: Montana Department of Natural Resources, Helena, Montana, 336 p.

Driscoll, F.G., 1986, Groundwater and Wells (2nd ed.): Johnson Division, St. Paul, Minnesota, p. 1021.

Kauffman, M. H., 1999, An investigation of ground water - surface water interaction in the Flint Creek Valley, Granite County, Montana: Master of Science Thesis, Montana State University, Bozeman, Montana, 196 p. (p. 31)

Ratzack, M., and Huntley, D., 1991, Assessing transmissivity from specific capacity data in large heterogeneous alluvial aquifers: Ground Water, v. 29, p. 856-861.