Hydrologie

REGHYDRO

Combined Hydrological Modelling and Regional Geodetic Estimation of Water Storage Variations in Large River Basins using GRACE Data (REGHYDRO):

REGHYDRO is a sub-project within the framework of the Deutsche Forschungsgemeinschaft (DFG) Priority Research Program Mass Transport and Mass Distribution in the Earth System (SPP 1257). REGHYDRO started in 2009 for a funding period of two years and has been currently successfull in getting a prolongation of further two years.

In March 2002, the GRACE satellite mission (Gravity Recovery and Climate Experiment) was launched as aUS– German joint partnership. GRACE is able to map the Earth's gravity field by making accurate measurements of the distance between two satellites orbiting the Earth in an altitude of 500 kilometres, using GPS and a microwave ranging system. It provides scientists from all over the world with an efficient way to map the Earth's static and dynamic gravity field with unprecedented accuracy.  The gravity variations that GRACE studies include changes due to surface and deep currents in the ocean, runoff and ground water storage on land masses, exchanges between ice sheets or glaciers and the oceans, and variations of mass within the Earth.

The overall goal of the REGHYDRO-project is to achieve an improved characterization of water storage (and flow) and of the gravity field in large river basins by combining global hydrological modelling and regional geodetic estimation using GRACE data. Regional gravity field features should be improved by using the WaterGAP Hydrological Model (WGHM) and global-scale hydrological modelling of water storage variations (and flow) in different storage compartments should benefit from information on the variation of the gravity field from GRACE.

In our working group on hydrology we focus on the hydrological component of gravity variations.Hydrological questions in this context are:

  • Under what conditions can human withdrawals be monitored using GRACE data, including the withdrawal of surface water, renewable groundwater resources and fossil groundwater resources?
  • What is the contribution of water storage in floodplains and wetlands to total water storage variations and variations in river discharge?
  • What is the contribution of continental glaciers to total water storage variations and variations in river discharge?
  • What are the (river basin-specific) reasons for the observed discrepancies between variations of total water storage as derived by GRACE and by thel WGHM?

WGHM results for water storage variations will be compared with available published data from soil- and groundwater monitoring networks in the U.S. (e.g. the Mississippi basin, the High Plains Aquifer, the state of Illinois).

In the last funding phase we implemented human water withdrawals also from groundwater (not only from surface water) in our model. This is the first time that water withdrawals from groundwater become part of a global hydrological model. In Döll et al. 2010 we showed that especially in semi-arid regions of the world, the seasonality of water storage variations is much better than in former model versions and closer to well observations and GRACE observations.

Results from both the hydrological and the gravity approach are used to compare, evaluate and calibrate the different applied models and methods. WGHM parameters will be calibrated against observed river discharge from different sources and against GRACE observations. In the end we will have basin-specific parameters as an input to WGHM as well as information about the most sensitive model parameters in each river basin. Generating global-scale hydrological information with a high temporal and spatial resolution will contribute to achieve a global geodetic-geodynamic observation system.

References:

Adam, L., Doell, P., Prigent, C. and F. Papa (2010): Global-scale analysis of satellite-derived time series of naturally inundated areas as a basis for floodplain modeling, Adv. Geosci., 27, 45–50, 2010.

Döll, P., Hoffmann-Dobrev, H., Portmann, F.T., Siebert, S., Eicker, A., Rodell, M., Strassberg, G., Scanlon, B.R. (2010): Impact of water withdrawals from groundwater and surface water on continental water storage variations, Journal of Geodynamics (accepted).

 

Keywords: global hydrological model, WGHM, water storage variations, GRACE, calibration

Participants: Heike Hoffmann-Dobrev, Linda Adam, PetraDöll

Cooperating institutions:

  • Universität Bonn, Institut für Geodäsie (Prof. Dr. Jürgen Kusche, Dr. Annette Eicker)

  • Universität Potsdam, Institut für Mathematik (Prof. Dr. Matthias Holschneider)

Duration: March 2009 – February 2013,

Funding entity: Deutsche Forschungsgemeinschaft DFG, SPP 1257 Massentransporte und Massenverteilungen im System Erde

Contact: hoffmann-dobrev@em.uni-frankfurt.de, l.adam@em.uni-frankfurt.de