A method has been developed for continuous measurement of total soil moisture on a scale of hectares. The method is based on accurate measurement of groundwater pressures in thick clay formations and depends on the principle that changes of mechanical load result in changes of groundwater pressure. The resulting data are similar to those obtained by conventional weighing lysimeters, but on a much larger scale and with no significant hydrologic disturbance of the site. Several years of field testing show the method to be practicable.¿ 1997 American Geophysical Union