Relationship of local water storage variations and superconducting gravimeter data at the Geodetic Observatory TIGO, Concepción, Chile

Abstract

Superconducting gravimeters SGs measure temporal variations of the Earth's gravity field with high precision. SGs have traditionally been used in geodetic applications. Recent studies, however, have shown that the disturbing signal component in SG time series can inversely be used as a hydrological sensor. Being sensitive to water mass changes in their surroundings, SGs provide unique measurements of total water storage variations, sum of storage variations in the snow cover, the unsaturated soil, and the groundwater, at local scales of several hundreds of meters. In this study, the relationship between local hydrology and gravity for the SG located at the Geodetic Observatory TIGO in Concepción, is investigated. SG time series are compared to the gravimetric response calculated by a geodetic model using soil moisture measurements to a depth of 2.6 m and a Digital Elevation Model for an area of 2 km around the SG. The results show that variations in moisture and gravimetric response are related to the topography and depth of analysis. Seasonal gravity variations of up to 12 μGal give indication of important water storage variations, which are related to the depth of unsaturated zones and groundwater.