Excerpt from Surface Water Supply of Illinois: Central and Southern Portions, 1908 1910 The investigations have been concentrated upon streams in the central and southern portion of the State where water supply, prevention of overflow and reclamation of swamp land make the strongest appeal for immediate study of the problems. It is essential that records of stream ow shall be maintained during a period of years sufficient to cover all stages, in order that within reason able limits the entire range of ow from the absolute maximum to the absolute minimum may be determined. The length of such a period manifestly varies for different streams and cannot be absolutely deter mined. Experience has shown that the records should cover from five to ten years, or for some streams twenty years or more, the limit being determined by the relative importance of the stream and the inter dependence of the results and other long-time records on adjacent streams. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."