Low streamflows are an increasing problem in central and western Kansas. Ground-water consumption by phreatophytes in riparian corridors in these areas is one factor contributing to the low streamflows. Knowledge of the amount of ground water consumed by phreatophytes is necessary to understand the importance of this mechanism relative to ground-water pumping for irrigation, and to assess the water savings that can be achieved through phreatophyte removal activities. The Kansas Geological Survey and Kansas State University are conducting studies to improve methods for quantifying ground-water consumption by phreatophytes and to determine the ground-water savings that could be achieved through their removal. The current study sites are in riparian areas along the Arkansas River near Larned, Pawnee County, and the Cimarron River near Ashland, Clark County. The primary trees at the Larned site are cottonwood, willow, and mulberry, whereas salt cedar (tamarisk) and Russian olive predominate at the Ashland site. The studies include measurements of ground-water levels, soil moisture, sap flow in trees, and meteorologic variables. The most promising method is based on analysis of diurnal fluctuations in ground-water levels through the growing season. In this paper we describe the major controls on phreatophyte-induced water table fluctuations and present initial estimates of ground-water consumption.