Part 4

Water Supplies

Water, too, is a mineral resource, and our most necessary one. The source of nearly all water is rain and snow, which collect in lakes and streams or seep into the ground to form our two types of water supplies—surface water and ground water.

Ground water in Illinois collects underground in deposits of sand and gravel or in the porous sandstone or limestone layers of bedrock. These rock materials are called “aquifers” because of their ability to hold water and to allow it to flow into wells that are drilled into them.

The aquifers are not equally distributed throughout Illinois, so ground-water supplies are abundant in some parts of the state but are scarce in others. Some Illinois cities depend wholly or partly on surface supplies from lakes and rivers.

The sand and gravel aquifers yield more ground water than any others in Illinois. The major sand and gravel aquifers were deposited by streams and lie along river valleys. Some of these river valleys are no longer visible to us because they were buried by glacial drift. They are recognized, however, from well records or drilling records.

The northern third of Illinois has the most abundant supplies of ground water. Bedrock formations of Devonian through Cambrian age are favorable aquifers and supply drinkable (potable) water at depths of from 200 to 2,000 feet. These formations, however, lie much deeper in the Illinois Basin, where the water they furnish is too salty for most uses.

West of the Illinois River and at the southern tip of the state, the Mississippian, Devonian, and Silurian limestones are the chief aquifers. Their yield, however, is small.

In the Illinois Basin all these formations are overlain by Pennsylvanian rocks which offer only small, scattered supplies of ground water.

ILLINOIS STATE GEOLOGICAL SURVEY

A city or farmer needs a new water supply. Where can suitable water-bearing formations be found? A new limestone quarry is considered. Where are the most suitable limestone deposits? A coal mine is being planned. How deep must a shaft be sunk to reach the nearest minable coal and what will the mining conditions be? A land owner has a clay deposit on his land. What uses can be made of it? A road is to be constructed. Are sand and gravel or limestone deposits available nearby for construction materials? A farmer wants to know whether there might be oil on his property. Are oil-bearing structures present and, if so, at what depth?

These are typical questions brought to the Illinois State Geological Survey by the industries and people of Illinois. From its accumulated store of information and experience, the Survey provides answers. This storehouse of knowledge is the result of the Survey’s continuous program of geologic exploration, mapping, research, and organization and interpretation of data.

The Survey explores and maps the geology and mineral resources of the state, does research to find new and improved uses for our mineral resources, and organizes and interprets basic geologic information gathered from well logs, rock samples, and field studies, putting them all into usable form.

Such knowledge is shared with the public through publications, maps, lectures, and personal consultations with industries, drillers, engineers, land owners, teachers, and others in need of geologic information.

The discovery of facts about the rich mineral resources of Illinois has, in effect, only begun, and it is the task of the Geological Survey to continue to collect and apply new information so that our resources can be used to the best advantage.

EDUCATIONAL EXTENSION PROGRAM

The Educational Extension Section of the Geological Survey conducts six field trips each year, in various parts of the state, for teachers, students, and laymen. It also assembles and distributes rock and mineral collections for Illinois educational groups, gives lectures, prepares exhibits, and identifies rocks and minerals for the public.

Educational Extension publications, such as this book, are simplified discussions of geological subjects. Available for 25 cents each, these include:

Educational Series 4: Guide for Beginning Fossil Hunters, by Charles W. Collinson. Educational Series 5: Guide to Rocks and Minerals of Illinois. Educational Series 6: Field Book of Pennsylvanian Plant Fossils of Illinois, by Charles Collinson and Romayne Skartvedt.

Many technical discussions of the various phases of Illinois geology also are published by the Geological Survey. Regional reports on the geology and mineral resources of some areas are available in many school and public libraries or they may be purchased from the Survey. Some of the regional reports include:

Beardstown, Glasford, Havana, and Vermont Quadrangles, Bulletin 82, $1.00. Buda Quadrangle, Circular 275, no charge. Carlinville Quadrangle, Bulletin 77, $1.00 Chicago Region, Bulletin 65, Part 1, 50 cents. Marseilles, Ottawa, and Streator Quadrangles, Bulletin 66, $1.00.

“Mineral Production in Illinois in 1959,” Circular 300 (no charge), is one of a series of annual economic summaries. “Caves of Illinois,” Report of Investigations 215, price 50 cents, will be available by September 1961.

Illinois State Geological Survey Educational Series 7 24 pages, 1 plate, 12 figures, 1961

GEOLOGIC MAP OF ILLINOIS showing BEDROCK BELOW THE GLACIAL DRIFT 1961 KEY T Tertiary (Pliocene omitted) K Cretaceous P² Pennsylvanian (Above No. 6 Coal) P¹ Pennsylvanian (Below No. 6 Coal) P³ Pennsylvanian (Above No. 6 Coal) M² Mississippian (Upper) M¹ Mississippian (Middle and Lower) D Devonian SD Silurian and Devonian S Silurian O Ordovician C Cambrian F Fault OSDM Complex faulted area Physiographic base map by James A. Bier Price, 25 cents

Transcriber’s Notes

—Silently corrected a few typos.

—Retained publication information from the printed edition: this eBook is public-domain in the country of publication.

—In the text versions only, text in italics is delimited by underscores.