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Several recently developed and two proposed methods for measuring the hydraulic conductivity of soil in place are described. Particular attention is given to the so-called auger hole, piezometer and tube methods. In the auger hole method an auger hole is bored to a depth below the water table and the water in it is pumped out. After the hole has been emptied, the ensuing rate of rise of water in it is determined and this rate is then converted to the hydraulic conductivity of the soil by use of a suitable formula. In the piezometer and tube methods the procedure is the same except that the auger hole is now effectively cased, and there is only a small cavity at the base of the cased hole into which the rate of water entry is noted. The latter methods have the advantage that they permit the measurement of the hydraulic conductivity at virtually a point in the soil. The auger hole method, on the other hand, gives an average conductivity for the whole length of the hole. Results from the auger hole method are less variable. The problem of soil anisotropy is discussed, and it is pointed out that the anisotropic components of the hydraulic conductivity may be determined by use of the methods.
Professor of Soils and Physics, Iowa State College, Ames, Iowa