Characterization of water storage dynamics in arid areas by satellite gravimetry

Johannes Riegger1, Mohammad Tourian2
1 Institute for Modelling Hydraulic and Environmental Systems, University of Stuttgart
2 Institute of Geodesy, University of Stuttgart

O 10.2 in Hydrogeologie arider Gebiete

30.05.2014, 17:40-18:00, H17, NW II

In arid areas there are tremendous difficulties to quantify water balances appropriately as actual evapotranspiration ETa and seepage from surface runoff during precipitation events cannot be measured directly and often river discharge does not occur. Modelling approaches for ETa are not suitable for a quantification as they show variations in a 30% range between the different models (PILPS/ AMIP Studies). Thus the knowledge of water storage characteristics and their dynamics is essential for the description of the short and long term system behaviour and the related water balance.

Groundbased observations of the storage components are not available on large spatial scales. Measurements of water storage changes by observations of changes in groundwater levels or soil water saturation (Rodell & Famiglietti 1999) are not reliable due to the inadequate density of monitoring points and the insufficiently knowledge of storage coefficients. However regional hydrogeological investigations based on large scale groundwater models (Kalbus et al. 2011) allow to constrain the water balance and thus storage dynamics even for arid areas.

Satellite gravimetry by GRACE provides monthly mass distributions on large spatial scales (>~250000km2) over the globe. For land masses monthly mass variations are interpreted as changes in total water storage of the considered area comprising all contributing storage compartments (snow/ice, surface water, soil, (un)saturated underground) in their vertical as well as in the horizontal distribution. A separation of the contributions from different storages is possible, if the related system dynamics i.e. the corresponding time constants differ sufficiently (Riegger & Güntner, 2005).

In this paper mass signals from GRACE gravimetry with quantified uncertainties (Riegger & Tourian 2012) are used to characterize the water storage dynamics in (semi)arid environments. For a selection of (semi)arid areas the short and long term behaviour of the total water storage is presented  Short term storage changes are used to determine and characterize actual evapotranspiration and compare it to precipitation events. Measurement uncertainties are discussed with respect to their implications on the determination of seasonal behaviour and long term trends.

Kalbus, E., Oswald, S., Wang, W., Kolditz, O., Engelhardt, I., Al Saud, M.I.,Rausch, R., 2011: Large-scale modeling of groundwater resources on the Arabian platform.  - International Journal of Water Resources and Arid Environment 1(1): 38-47

Riegger, J. & Güntner, A., 2005: Time variation in hydrology and gravity. – Earth, Moon, and Planets 94: 41-55

Riegger, J. & Tourian, M.J., 2012: Analysis of GRACE uncertainties by hydrological and hydro-meteorological observations. – Journal of Geodynamics, 5960(0), 16-27

Rodell, M. & Famigietti, J., 1999: Detectability of variations in continental water storage from satellite observation of time dependent gravity field. – Water resour. 35: 2705-2723.

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Letzte Änderung 17.10.2013