ISBN: 9781236573162

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not … Plus…

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 edition. Excerpt: ...disagreeable effects of stagnation are not dependent upon the depth of a pond, except in so far as the depth affects thermal stratification. They depend somewhat upon the character of the water stored, but much more upon the amount and character of the organic matter at the bottom and upon the length of the stagnation periods. If the bottom of the reservoir contains no organic matter the phenomena described above will not occur. It has been found that in the Wachusett reservoir of the Boston water-supply, where the organic matter was carefully removed from the bottom, the dissolved oxygen at the bottom does not become exhausted during the stagnation periods, although it is appreciably reduced in amount. The author once collected a sample from Lake Champlain at a depth of nearly 400 ft. The temperature was 39.20--i.e., maximum density--and the water was probably in a state of permanent stagnation. The sample was bright, clear, colorless, and without odor. The material on the bottom was found to be almost perfectly clean gravel. Organic matter at the bottom of shallow reservoirs will cause a deterioration of the water stored in them. If there is no summer stagnation the water at the bottom becomes warm, and decomposition goes on rapidly. The products of decay taken up by the water support the growth of organisms--particularly the blue-green algae. Moreover, during the winter when the surface is frozen these shallow ponds grow stagnant and the conditions become similar to those in deep ponds. After the periods of winter stagnation, shallow ponds often contain heavy growths of diatoms. Organic matter at the bottom of a shallow reservoir affects the quality of the water in another way. It offers support for fixed aquatic plants, and these may... George Chandler Whipple, Books, History, The Microscopy Of Drinking Water Books>History <