Evaluating surface and subsurface water storage variations at small time and space scales from relative gravity measurements in semiarid Niger

Abstract

The acquisition of reliable data sets representative of hydrological regimes and their variations is a critical concern for water resource assessment. For the subsurface, traditional approaches based on probe measurements, core analysis, and well data can be laborious, expensive, and highly intrusive, while only yielding sparse data sets. For this study, an innovative field survey, merging relative microgravimetry, magnetic resonance soundings, and hydrological measurements, was conducted to evaluate both surface and subsurface water storage variations in a semiarid Sahelian area. The instrumental setup was implemented in the lower part of a typical hillslope feeding to a temporary pond. Weekly measurements were carried out using relative spring gravimeters during 3 months of the rainy season in 2009 over a 350 × 500 m2 network of 12 microgravity stations. Gravity variations of small to medium amplitude (≤220 nm s−2) were measured with accuracies better than 50 nm s−2, revealing significant variations of the water storage at small time (from 1 week up to 3 months) and space (from a couple of meters up to a few hundred meters) scales. Consistent spatial organization of the water storage variations were detected, suggesting high infiltration at the outlet of a small gully. The comparison with hydrological measurements and magnetic resonance soundings involved that most of the microgravity variations came from the heterogeneity in the vadose zone. The results highlight the potential of time lapse microgravity surveys for detecting intraseasonal water storage variations and providing rich space-time data sets for process investigation or hydrological model calibration/evaluatio

Characterizing rainfall-runoff signatures from micro-catchments with contrasting land cover characteristics in southern Amazonia

“…As outlined by Pfeffer et al . (), existing data and knowledge points out the central role of land use and confirms that land cover changes have a greater impact on runoff production than the rainfall amounts (Séguis et al ., ; Boulain et al .,; Massuel et al ., ). De Moraes et al .…”

Estimating epikarst water storage by time-lapse surface to depth gravity measurements

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Water storage changes as a marker for base flow generation processes in a tropical humid basement catchment (Benin): Insights from hybrid gravimetry

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“…A quick overview of the method can be found in Jacob et al [2010]. Following several authors, we added a 5 lGal threshold to the observed standard deviations before the adjustment, such that if an observed standard deviation is below this threshold, it is set to this value [Jacob et al, 2010;Christiansen et al, 2011c;Pfeffer et al, 2013]. This is done to account for systematic errors which are inherently not considered in CG5 standard deviation outputs.…”

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