The value of total water storage anomalies from GRACE for indicating and observing large-scale flood events

Andreas Güntner, Ben Gouweleeuw, Michal Mikolaj, Andreas Kvas, Philippa Higgins, Christian Gruber, Frank Flechtner, Torsten Mayer-Gürr, Adrian Jäggi

Research output: Contribution to conferenceAbstract


Time-variable data of the Earth’s gravity field provided by the satellite mission GRACE (until 2017) and GRACEFollowOn
(lauch in spring 2018) give information on mass changes on and below the Earth surface, notably
water storage changes. With a spatial resolution in the order of 300 km, GRACE provides unique large-scale and
integrative observations of variations in total water storage, i.e. the sum of all storage compartments that might
be relevant for the generation of flood events (groundwater, soil moisture, snow). Within the EGSIEM project
(European Gravity Service for Improved Emergency Management), funded by the Horizon 2020 Framework
Program of the European Union, a near real-time gravity field service was set up which delivered daily GRACE
data of water storage anomalies with a maximum latency of five days.
In this contribution, we assess the value of the daily GRACE-based water storage anomalies for (1) observing
large-scale flood events, and (2) as indicators of above-average wetness conditions in river basins prior to
the flood event. The analysis is based on several hundreds of large-scale flood events worldwide, recorded in the
Dartmouth Flood Observatory (DFO) within the GRACE operation period. We assess storage anomalies both for
the event area as given in DFO, as well as for the entire upstream river basin. For river basins with available river
discharge time series, the gravity-based pre-event wetness index is compared to other indices that are frequently
used as flood indicators, such as Antecedent Precipitation Index, satellite-based soil moisture indices or baseflow
before the event onset. We compare the correlation of these indices to flood characteristics such as peak discharge,
flood volume and runoff ratio. Results indicate the early-warning potential of the GRACE-based indices for
selected river basins such as the Danube, and in particular for flood events where snow storage and thus snowmelt
contribute to flood discharge.
Original languageEnglish
Publication statusPublished - 13 Apr 2018
EventEGU General Assembly 2018 - Wien, Austria
Duration: 9 Apr 201813 Apr 2018


ConferenceEGU General Assembly 2018


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