DETERMINING SPECIFIC YIELD OF OGALLALA AQUIFER BY NEUTRON METHOD

The specific yield of the Ogallala formation, a water table aquifer, was determined with a neutron moisture meter. An access tube penetrated a 12‐foot section of the aquifer. This section was saturated by recharging water to the aquifer and then dewatered by pumping for 11 days. The specific yield of the aquifer was calculated from neutron moisture measurements made at saturation after most gravity drainage had occurred. The average specific yield for 25 measurements made at ½‐foot intervals was 052. This value compares favorably with the specific yields determined by tracer techniques and laboratory analysis of cores. However, the specific yield determined by the neutron method was 50% greater than the specific yield determined by pumping tests. Copyright 1969 by the American Geophysical Union.