Abstract:
Accurate and up to date information on the status and trends of water balance is
needed to develop strategies for conservation and the sustainable management of water
resources. The purpose of this research is to estimate water balance in a semi-arid
environment with limited in-situ data by using a remote sensing approach. We 5 focus on
the Lake Manyara catchment, located within the East African Rift of northern Tanzania.
We use remote sensing and a semi-distributed hydrological model to study the spatial
and temporal variability of water balance parameters within Manyara catchment. Satellite
gravimetry GRACE data is used to verify the trend of the water balance result. The
10 results show high spatial and temporal variations and characteristics of a semi-arid climate
with high evaporation and low rainfall. We observe that the Lake Manyara water
balance and GRACE equivalent water depth show comparable trends a decrease after
2002 followed by a sharp increase in 2006–2007. Despite the small size of Lake
Manyara, GRACE data are useful and show great potential for hydrological research
15 on smaller un-gauged lakes and catchments in semi-arid environments. Our modelling
confirms the importance of the 2006–2007 Indian Ocean Dipole fluctuation in replenishing
the groundwater reservoirs of East Africa. The water balance information can
be used for further analysis of lake variations in relation to soil erosion, climate and
land cover/land use change as well as different lake management and conservation
20 scenarios. We demonstrate that water balance modelling can be performed accurately
using remote sensing data even in complex climatic settings.
