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Show HAWAII 715 area the piezometric surface is about the same. These are are called "isopiestic" areas, that is, areas of practically equal artesian pressure. Several isopiestic areas have been mapped on Oahu. The Honolulu artesian system.-The Honolulu District contains four major isopiestic areas and one minor one. This artesian structure has been the principal source of domestic water supply for the city, and has served important industrial and agricultural purposes as well. Adjoining it on the west is an isopiestic area within which very large quantities of water have been withdrawn for use by sugar plantations. Physical and Legal Interrelationships Direct physical relationships exist among the large bodies of ground water in the Islands. Water in the dike reservoirs overflows or leaks at certain points in the form of springs, which contribute to the perennial water supplies of surface streams. Water leaks from the dike complexes and joins the body of basal water. Some water in the surface streams flows directly into the sea, while some leaks into bodies of perched water, the contents of which in turn may discharge into the sea at shallow depths or may percolate to the basal water table. Some water perched on alluvium in the stream bed may likewise reappear on the surface downstream; such waters, whether or not they reappear on the surface in substantial quantities, may conform to the legal classification of a "definite underground stream" and in places may conform to the phase known as the "underflow" of a surface stream. And the basal "percolating" water, while mostly nonartesian, consists in places of artesian water of great economic importance. Following are two examples of the legal and physical interrelationships. (1) Water in a gravel stratum underlying the stream bed in a section of the channel of Wailuku (Iao) Stream, Maui, was involved in a controversy over water rights in that stream .22S This water was not found to be contributing to the surface flow. The importance of the gravel stratum to the downstream night-time rights arose from the necessity of resaturating a portion of the gravels each evening because of the reduced level of the stream during the day, when water was being diverted under day-time rights that had been transferred upstream. This occasioned a lag in the flow over the gravels when the water was released upstream in the evening, and hence delayed its arrival at the downstream headgates. (2) A second example was a case, of outstanding judicial importance in Hawaii, involving artesian waters under Honolulu.226 A physical relationship existed, but was not in issue in the proceedings and was not established legally or even discussed in the opinion of the court. The decision purported to lay down the broad principle that the owners of land under which there is an 225Hawaiian Commercial & Sugar Co. v. Wailuku Sugar Co., 15 Haw. 675, 693-694 (1904). 226City Mill Co. v. Honolulu Sewer & Water Comm'n, 30 Haw. 912 (1929). |
