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Show lateral canals or stabilization of stream flow, of augmenting the natural recharge of ground water reservoirs; in subsequent months to reimburse such reservoirs for the reduction in natural re- charge due to the quick melting of the snow. Unseen Reservoirs as Stabilizers Areas underlain by large ground water re- servoirs are affected relatively little by extreme climatic fluctuations. There, during droughts, the ground water is available for use when sur- face runoff is low and artificial reservoirs are depleted or lacking. The ground water reservoirs provide whatever stream flow occurs between rains. When climatic conditions swing to the opposite extreme and too much water is available, the areas with the largest ground water capacity are again fortunate; for their surplus water is stored underground and paid out slowly, and thus the low flow of streams is augmented. The total flow of ground water through springs and seepage into the Nation's streams is of the utmost importance. The average annual rain- fall in the United States is about 30 inches. Of this, a little more than 21 inches is evaporated or used by vegetation, and a little less than 9 inches is surface runoff or flows into the ocean and lakes. This 9 inches represents an average flow of about 1,800,000 cubic feet of water a second, or about eight times the annual outflow of the Great Lakes through the St. Lawrence River. Of this, incomplete data show that between one-third and two-fifths, or between 600,000 and 700,000 cubic feet a second, has passed through the ground before entering the streams. This forcefully emphasizes the vital role of ground water as a contributor to stream flow. It also underscores the importance of recognizing that ground water and surface water may be com- petitors for water not absorbed by the soil, and that withdrawal of large quantities of water from underground storage may result in depletion of stream flows in some areas during the season of low flow in the river, when competition between uses of its water is at a maximum. In the light of all these facts, we see that if we are to keep a balanced approach to the water sit- uation, this competition must always be consid- ered and that, in our water resources planning, we cannot talk about ground water or surface water. We must talk about water. Practically all ground water problems result from mismanagement, including excessive extrac- tion or careless contamination. Much of this mismanagement derives from a failure to foresee results of uncontrolled development. According to the Geological Survey:4 Without proper management we can look forward to nothing more than aggravation of existing prob- lems and creation of new ones. With it we can modify the natural regime to make the ground water reservoirs take in more water and waste less; we can utilize their storage function more effectively to reduce wasteful and destructive flood runoff in the wet season and in periods of wet years and make more water available in the dry season and in periods of dry years, when it is needed most; in short we can make ground water assume its rightful place in our economy, a place it must occupy if we are to continue to grow in strength and well-being. A common kind of mismanagement is that in which, through improper spacing of wells or ex- cessive pumping, ground water is being mined. To withdraw ground water at a greater rate than natural replenishment and increased recharge is simply to mine it out. On the southern High Plains in Texas, to name but one example among many, water is being cur- rently withdrawn at more than 20 times the esti- mated rate of replenishment. That region, in its irrigated parts, is actually drawing on a vast amount of stored water accumulated in the past, amounting to perhaps 150 million acre-feet. An approach at the start of the development of this region based on proper water management would first have determined the available water resources, the amounts of water that could be withdrawn under various conditions, and the lengths of time over which the withdrawal could 4 Id., p. 58. 911609-50------11 119 |
