Application of the gravity method to ground-water volume determinations of alluvial basins
AuthorGreenes, Kent A.
Sedimentary basins -- Mathematical models.
Groundwater flow -- Arizona -- Tohono O'odham Reservation -- Measurement.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractWhen gravity station coverage is sufficient and when information exists on the geology and hydrology of an alluvial basin, the amount of ground water available from storage can be determined from the gravitationally measured anomalous mass. Discrete gravity data reduction along with effective regional residual separation is applied to produce a Second Order Residual Gravity Anomaly Map. Two dimensional modeling of the residual gravity values is used to generate an accurate depth to bedrock map defining the hydrologic boundaries of the basin. Direct application of Gauss's Theorem to the residual gravity map gives the amount of anomalous mass. A density contrast model based on basin geometry and all available geologic information is constructed relating the amount of anomalous mass to the total volume of saturated sediments. The volume of ground water available from storage is estimated from the volume of saturated sediments and appropriate values of specific yield. Availability of shallow subsurface geologic information, coupled with improved gravity interpretation techniques, has resulted in improved estimates of ground-water volumes. This concept is illustrated by a case history from the Papago Farms area, Papago Indian Reservation, southern Arizona, where the amount of ground water available from storage is estimated to be 134 km^3.