ABSTRACTIf there are gravity data and some geological information available from the region of an intermontane basin, then the volume of saturated sediments, volume of ground water available from storage, and the total volume of ground water can be determined from the gravitationally determined anomalous mass. The anomalous mass occurs because of a density contrast which exists between low density alluvium and high density bedrock which define the surface and subsurface boundaries of the basin. The gravity effect of the anomalous mass can be detected by a gravity survey of the basin after which it can be separated from other gravity effects by a regional‐residual separation. The anomalous mass is uniquely determined by applying Gauss's theorem to the residual gravity map.A model of an intermontane basin is developed which relates the anomalous mass to the total volume of saturated sediments. The total volume of saturated sediments is determined from the anomalous mass, the density contrasts between unsaturated and saturated alluvium and bedrock, the area of the basin, and the water table depth.The volume of water available from storage and the total volume of water in the basin are determined from the volume of saturated sediments and the storage coefficient and porosity of the sediments.The method is illustrated by a case history from Avra Valley, Arizona. It is concluded that the major advantage of this method occurs when well data are not available, because it eliminates the need for arbitrary assumptions about subsurface basin geometry to determine the volume of saturated sediment
展开▼
