摘要:

Streamflow from small watersheds on the western slopes of the Oregon Cascade Range is strongly influenced by a maritime climate (wet winters and dry summers). Although annual precipitation is high (94 inches in the study area), overland flow is almost unknown. Peak flows result largely from subsurface flow and under conditions in which both retention and detention reservoirs are almost filled during extended periods of low‐intensity rainfall. Under these conditions, vegetation appears to exert a minimum influence on high streamflow. Lowest Streamflow occurs from late August to mid‐November and may follow a 60− to 100‐day period with little or no rain. The dense vegetation of this part of the Douglas‐fir region appears to exert its major influence at such times. Removal of vegetation from only 30% of a 250‐acre watershed has caused a 12–28% increase in minimum streamflow. On a 237‐acre watershed on which 80% of the trees were cut, the increase in l

ISSN:0043-1397    

DOI:10.1029/WR001i001p00125

年代:1965

数据来源: WILEY

摘要:

The flow of water through a homogeneous anisotropic soil is governed by Darcy's equation in which the velocity is proportional to the imposed hydraulic gradient. The constant of proportionality (coefficient of permeability) is a symmetric tensor of second rank, reducing to a scalar only in the case of isotropic soils. It is shown that for determining the velocity vector from a known hydraulic gradient the permeability tensor ellipsoid should be constructed with semiaxes equal to the inverse of the square root of the permeability values. For determining the hydraulic gradient from a known velocity, the permeability tensor ellipsoid should have semiaxes equal to the square root of the principal permeability values. The fact that two different tensor ellipsoids can be constructed for a given anisotropic soil may produce confusion and give rise to a significant error. Special attention should therefore be given in evaluating the appropriate permeability value to be used in Darey's equation. It is recommended that the ellipsoid used always be the one with semiaxes equal to the inverse square root of the principal permeability values. Permeability tests were conducted on anisotropic sandstone. Cylindrical cores were taken at various directions with respect to a fixed coordinate system, and permeability values were determined in a constant‐head permeameter. The values obtained when plotted on polar coordinate paper result in a two‐dimensional permeability ellipse. The necessary graphical constructions for determining the direction of the velocity or the direction of the hydraulic gradient from the corresponding tensor ellipses are also gi

ISSN:0043-1397    

DOI:10.1029/WR001i001p00135

年代:1965

数据来源: WILEY

摘要:

The cost allocation method described here, which is for dual purposes or combined electricity water desalination plants, uses exclusively economic data. The method is based on the cost of power and water produced in single‐purpose plants and on the application of the cost relationship for a given net output of water and power to the total annual cost of a combined plan

ISSN:0043-1397    

DOI:10.1029/WR001i001p00143

年代:1965

数据来源: WILEY