ABSTRACT
The design of water intakes is almost always based on a combined consideration of the water supply needs and the characteristics of the source water body. The water supply requirements generally consist of a required withdrawal or passage rate, some measure of reliability, and some measure of quality ranging from temperature in the case of selective withdrawal structures to the exclusion of debris or trash. The source water body may be a lake, a reservoir, the ocean, or a river. It is not surprising therefore that there is a wide range of types, sizes, arrangements, and concepts for specific intake designs. Where ice forms in or on the source water body, consideration must also be given either to preventing its ingestion into the intake or ingesting it in such a condition that it does not interfere with the water usage. At first glance one is tempted to treat ice at intakes simply as a debris problem. This is generally a naive approach because the quantities of ice are orders of magnitude larger than those of debris, and the nature of ice, other than its slight buoyancy, is often very different. Because of the diversity of intakes, the approach taken in this text is to characterize ice conditions that occur in the vicinity of intakes and then describe the principles behind various counter measures that have been used both successfully and unsuccessfully to avoid or mitigate ice problems. Finally some case studies will help demonstrate the large measure of engineering judgment that must be used to effectively accommodate ice conditions at intakes.
