Division of Geodesy and Geoinformatics

The Mohorovičič discontinuity (Moho), which is the surface separating the Earth’s
crust from the mantle, is of great interest among geoscientists. The Moho depth can
be determined by seismic and gravimetric methods. The seismic methods are
expensive, time-consuming and suffer from lack of global coverage of data, while
the gravimetric methods use inexpensive and mostly already available global and
regional data based on an isostatic model. The main reasons for studying an isostatic
model are on one hand the gaps and uncertainties of the seismic models, and, on the
other hand, the generous availability of gravity data from global models for the
gravimetric-isostatic model. In this study, we present a new gravimetric-isostatic
Moho model, called the Vening Meinesz-Moritz (VMM) model. Also, a combined
Moho model based on seismic and gravimetric models is presented.
Classical isostatic hypotheses assume that the topographic potential is fully
compensated at all wavelengths, while is not the case in reality. We found that the
maximum degree of compensation for the topographic potential based on the new
Moho model is 60, corresponding to the resolution of about 330 km. Other (dynamic)
isostatic effects (such as temporal compensation, plate tectonics, post-glacial
rebound, etc) should be considered as well, which are disregarded in this thesis.
Numerical results imply that the dynamic phenomena affect mostly the longwavelengths.
The VMM model is applied for different purposes. The Moho density contrast is
an important parameter for estimating the Moho depth, and we present a technique to
simultaneously estimate Moho depth and density contrast by the VMM and seismic
models. Another application is the recovery of gravity anomaly from Satellite
Gravity Gradiometry (SGG) data by a smoothing technique, and we show that the
VMM model performs better than the Airy-Heiskanen isostatic model. We achieved
an rms difference of 4 mGal for the gravity anomaly estimated from simulated
GOCE data in comparison with EGM08, and this result is better than direct
downward continuation of the data without smoothing. We also present a direct
method to recover Moho depth from the SGG mission, and we show that the
recovered Moho is more or less of the same quality as that obtained from terrestrial
gravimetric data (with an rms error of 2 km). Moreover, a strategy is developed for
creating substitutes for missing GOCE data in Antarctica, where there is a polar gap
of such data.
The VMM model is further used for constructing a Synthetic Earth Gravity Model
(SEGM). The topographic-isostatic potential is simple to apply for the SEGM, and
the latter can be an excellent tool to fill data gaps, extending the EGMs to higher
degrees and validating a recovery technique of the gravity field from a satellite
mission. Regional and global tests of the SEGM yield a relative error of less than 3
% vs. EGM08 to degree 2160.

Land use/cover has shown significant changes during the past three decades in Ethiopia especially in the highlands of the country. That resulted in changes in streamflows and other hydrological processes. The existing land and water resources system of the area is adversely affected due the rapid growth of population, deforestation, surface erosion and sediment transport. The main objective of this study is to evaluate the impact of land use/cover changes in the hydrology of Beles Basin, Ethiopia. The physically based hydrologic model, SWAT, was developed for the Beles basin, Ethiopia by combining geospatial and climatic data. ArcGIS has been used to process geospatial data which includes the Digital Elevation Model (DEM) which has a resolution of 90 m, land use/cover and soil maps. A simple Interpolation technique has been used to fill in the missing precipitation data. The GIS interface version of SWAT (ArcSWAT) has the capability to utilize ArcGIS to facilitate input data preparation and output data generation. Idrisi Andes in cooperation with ArcGIS 9.2 used to generate landuse/cover maps from Landsat data of three different years. Three SWAT models were set up using the three generated land use/cover maps and used to evaluate the land use/cover change and its impacts on the streamflow of study basin. The primary hydrological model was evaluated through sensitivity analysis, model calibration, and model validation for realistic prediction of the different hydrological components in the basin. Out of twenty six flow parameters sixteen parameters were found to be sensitive. But the most sensitive ten parameters were selected and used for model calibration. The model calibration was carried out using observed streamflow data from 01 January 2001 to 31 December 2002 and a validation period from 01 January 2003 to 31 December 2004. The coefficient of determinations (R2) was 0.74 and the Nash-Sutcliffe simulation efficiency (NSE) was 0.62which indicated that the model was able to predict streamflow with reasonable accuracy. However, the hydrograph of the cumulative hydrographs of the calibration and validation periods showed significant discrepancies between the observed and the simulated data of each period. The average yearly flow volume of the observed streamflow on the cumulative hydrograph of the calibration period has exceeded the simulated streamflow. On the other hand on the cumulative hydrograph of the validation period the average yearly flow volume of the simulated streamflow was higher than the observed streamflow. The simulated result of the streamflow data from different land use/cover maps revealed that the change in the land use/cover classes of the basin throughout the study periods.

During the Bronze Age, bronze items were sacrificed to the gods by leaving them in the landscape. When making these sacrifices, known as deposits, the Bronze Age people followed certain landscape rules. These rules, and other similarities between the sites, can be rediscovered by analyzing the attributes of the sites. By understanding which attributes are relevant for the deposition sites, we can find more sites and contribute to the understanding of how Bronze Age depositions took place. This study aims to identify relevant attributes for the siting of Bronze Age Lake deposition sites near the lakes Mälaren and Hjälmaren in Sweden. 13 lake deposition sites were examined in ArcMap with respect to 6 attributes: Elevation, Soil Wetness, Aspect, Soil Type, Shore Distance, and Shore Direction. The attributes were studied independently of one another. The results revealed that a majority of deposits were the closest to a southern shore, there were no deposits in northern slopes, and no deposits were made between certain distances from the Bronze Age shoreline. Therefore, the attributes Shore Direction, Shore Distance, and Aspect appear to be relevant to lake deposition sites. The study briefly discusses how these results are related to archeological theories. As this study had a small sample size, the results cannot be assumed to apply to all lake deposit sites. Future studies should study more attributes, how attributes relate to one another, and examine the relevant attributes in other landscape features.

Background Rainfall variability exceedingly affects agriculture in Ethiopia, particularly in the eastern region where rainfall is relatively scarce. Hence, understanding the spatiotemporal variability of rainfall is indispensable for planning mitigation measures during high and low rainfall seasons. This study examined the spatiotemporal variability and trends of rainfall in the West Harerge Zone, eastern Ethiopia. Method The coefficient of variation (CV) and standardized anomaly index (SAI) were used to analyze rainfall variability while Mann-Kendall (MK) trend test and Sen’s slop estimator were employed to examine the trend and magnitude of the rainfall changes, respectively. The association between rainfall and Pacific Ocean Sea Surface Temperature (SST) was also evaluated by Pearson correlation coefficient (r). Results The annual rainfall CV during 1983–2019 periods is between 12 and 19.36% while the seasonal rainfall CV extends from 15–28.49%, 24–35.58%, and 38–75.9% for averag...