Druppel 15-2 - Dispuut Watermanagement

Hydrology
which simulates the terrestrial water
storage on a monthly basis. Next, these
results have been compared to the estimated
hydrological signal derived from
GRACE measurements.
Despite the large number of processes
influencing the gravity measurements, it
should be possible to filter out the
hydrological (= terrestrial water storage)
signal. To find the relation between the
gravity and the storage, first a hydrological
model was built, which simulates
the terrestrial water storage on a
monthly basis. Next, these results have
been compared to the estimated hydrological
signal derived from GRACE measurements.
Lukulu
Victoria Falls
Figure 2: Zambezi catchment in Southern
Africa.
The Zambezi catchment in Southern
Africa was chosen as study case, mainly
because of its large basin size and the
absence of tidal influences. Because the
quality of the precipitation input data is
very important for the performance of
the hydrological model, different rainfall
algorithms have been investigated in
this research.
The hydrological model consists of two
parts: a GIS based water balance model
and a Muskingum routing model. After
comparing the model results with
observed discharge data it can be concluded
that the model performance is
quite reasonable.
To obtain more knowledge about the
sensitivity of the model to parameter
and data uncertainty, the GLUE-procedure
has been used: firstly to determine
the uncertainty of four main model
parameters, and secondly to determine
the uncertainty in the precipitation and
potential evaporation input data of the
Zambezi model. From the GLUE results
it can be concluded, that no optimal
parameter set exists and that the uncertainty
in the model parameters is less
important then the uncertainty in the
input data.
As a first attempt GRACE data (spherical
harmonic coefficients provided by
GRACE) have been transformed into a
hydrological signal, which is called the
'direct estimation of hydrology from
GRACE data'-method. Comparing the
calculated hydrological signal obtained
from GRACE with the Zambezi-model
results, shows that in qualitative terms a
clear relation exists. Only the amplitude
from the GRACE-data is higher then the
amplitude of the Zambezi-model. This
could be due to various reasons: biomass
accumulation, more variation in
soil-vegetation interaction, and possibly
a model leakage error. By using averaging
kernel functions this latter error may
be reduced.
Miriam Gerrits
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