In recent years soil water sensors, based upon the heat dissipation principle, have been introduced commercially which respond relatively quickly to changes in soil water matric potentials in the -10 to -1500 kPa range. Over 100 of these soil heat dissipation sensors were installed at 13 SHAWMS (Soil Heat and Water Measurement Station) sites in the Little Washita River experimental watershed (LWRW), located in southwestern Oklahoma. An additional SHAWMS was installed at the Agricultural Research Service's Grazinglands Research Laboratory (GRL)located in El Reno, Oklahoma. The LWRW and GRL comprise two of the three main ground sampling areas of the Southern Great Plains 1997 Hydrology Experiment. The purpose of the SHAWMS is to provide measurements of the root zone component of the hydrologic budget as well as the spatial and temporal dynamics of soil water content. Eight heat dissipation sensors were installed at each SHAWMS: three at 5 cm below the soil surface and one each at 10, 15, 20, 25, and 60 cm below the soil surface. The operating principle, calibration and performance of the heat dissipation sensors is described, and data from the sensors are compared with independent, simultaneous measurements at selected sites