Papers by Tesfaalem Ghebreyohannes
Situational Use of Tigrinya on the Eve of Kudus Yohannes
Journal of Eritrean Studies, 2002
Managing the environmental impacts of war: What can be learned from conflict-vulnerable communities?
Science of the total environment, Jun 1, 2024
Zenodo (CERN European Organization for Nuclear Research), Feb 15, 2023
Tigray's wartime landscape -a regional geographical study in the Tembien highlands • We made harr... more Tigray's wartime landscape -a regional geographical study in the Tembien highlands • We made harrowing observations that are consistent with our past findings on failing crop yields, famine, and death toll in the Tigray war. • Many major findings hold true across the ten studied settlements and their surroundings. • In terms of rainfall, flooding, and deforestation rate, the results vary however per location. • Social bonds have become stronger in some communities, while weakening in others.
Downsides for downstream living communities : the case of the Tana-Beles hydropower project
The EGU General Assembly, 2019
Transhumance and landscape dynamics in northern Ethiopia
Transhumance between the Afar pastoralists and agro-pastoralist highlanders has been a common pra... more Transhumance between the Afar pastoralists and agro-pastoralist highlanders has been a common practice in northern Ethiopia. Despite its long history and direct effect on the interaction between the highlanders and lowlanders, no detail study has been undertaken on the impact of transhumance on landscape change in the marginal grabens of northern Ethiopia. Hence, this study has been carried out with the objective of examining the pattern and impact of transhumance on landscape change in the marginal grabens of northern Ethiopia. Spatio-temporal landscape change has been mapped and analyzed from aerial photographs of 1994 and Google Earth Imageries of 2011 and 2015 using ArcGIS 10.1. Perceptions of local communities on landscape change and the major driving factors have been collected using semi-structured interview and Focus Group Discussions (FGDs) and were analysed using Nvivo 10 software. Preliminary results reveal that transhumance has been increasing more in the Afar pastoralis...
The EGU General Assembly, 2019
Mountain stream dynamics as impacted by land cover/use change and rainfall variability in the northern Ethiopian highlands
Water budget variability in Aba’ala marginal graben of Northern Ethiopia
Marginal grabens are the major development corridors in northern Ethiopia. Despite the growing pr... more Marginal grabens are the major development corridors in northern Ethiopia. Despite the growing pressure on water resources, the hydrological budget of the grabens is inadequately understood to develop better management options. The study investigates the water balance of the Aba’ala graben (553 km2) along the western margin of the Danakil depression. We established rain gauges, divers, and staff gauges to collect the required data. Climate, crop and soil data were also collected to compute actual evapotranspiration. Rating curves and hydrographs were developed to analyze the runoff components of the graben. The study shows that seasonal rainfall (521.5 Mm3) has an erratic behavior that led to 29.2 Mm3 runoff volume entering the Aba’ala bottom. The average rate of water flow was varied between the escarpment and graben outlet (P<0.00). Furthermore, the western escarpment contributes 13.49 Mm3 baseflow to the graben bottom. However, 25.2 Mm3 volume of flood runoff is lost through t...
Exploration of a medieval African map (Aksum, Ethiopia) – How do historical maps fit with topography?
The EGU General Assembly, 2015
EthioTrees : ecosystem service valuation in the Tembien Highlands (North Ethiopia)
The North Ethiopian Highlands, located at the northernmost limit of the Intertropical Convergence... more The North Ethiopian Highlands, located at the northernmost limit of the Intertropical Convergence Zone, are a ‘hotspot’ of vulnerability to land degradation and climatic changes. The interplays between climatic vulnerability and forest cover changes in this region caused declining water availability and increased soil erosion, which strongly affects livelihood conditions. Therefore, integrated catchment management activities are implemented, such as the creation of exclosures, to mitigate ongoing land degradation. Exclosures are naturally regenerated areas from which livestock and uncontrolled wood cutting are excluded. Communal cost-benefit evaluation of exclosures shows highly positive outcomes, as they store green water, carbon, soil and nutrients. The aim of this project is to improve rural household income status for landless farmers in the Highlands of Dogua Tembien, by creating added value derived from woodland restoration and woodland ecosystem services development provided ...
Landscape Changes in the Semi-closed Raya Agricultural Graben Floor of Northern Ethiopia
Earth Systems and Environment, 2021
Over the last few decades, the need for landscape monitoring and assessment of changes in spatial... more Over the last few decades, the need for landscape monitoring and assessment of changes in spatial patterns over time has grown. Landscapes sustain changes of various aspects, such as their structure, in response to continuous modifications in land cover, land management regimes and policy decisions. This study investigates changes in the landscape structure along the Raya graben bottom in northern Ethiopia from 1986 to 2017. Landsat imageries were used to analyse land cover. The spatial structure of the landscape for 3 decades was evaluated using FRAGSTATS. The number of patches increased at the class and landscape levels. At the landscape level, the patches totalled 8,147 in 1986 and increased to 886,893 in 2017. Similarly, the patch density (PD) in 1986 was 3.4 and reached 372.7 in 2017. Therefore, high landscape fragmentation occurred within the study area. The value of the Shannon diversity index is close to 1.1, and the diversity of patch types within the landscape is regular. The Shannon Evenness Index value ranges from 0.6 to 0.7. Moreover, the diversity of patches has shown an increment across the study period. Each land cover reduces in size and proximity. Those changes were caused by population size, infrastructural development and commercial agriculture. Thus, proper land use planning must be practiced to reduce fragmentation and environmental impacts in landscapes that face increasing population pressure and continuous land cover changes.
Water, 2020
Due to renewed interest in hydropower dams in the face of climate change, it is important to asse... more Due to renewed interest in hydropower dams in the face of climate change, it is important to assess dam operations and management in combination with downstream impacts on rivers in (semi-)arid environments. In this study, the impacts of the Tekeze hydropower dam on downstream hydrology and river morphology were investigated, including impacts under normal and extreme reservoir operation conditions. Field observations, in-depth interviews, repeat terrestrial photographs, multi-year high-resolution satellite images, daily reservoir water levels and data on hourly to daily energy production were collected and studied. The results show that high flows (Q5) have declined (with factor 5), low flows (Q95) have increased (with factor 27), seasonal flow patterns have smoothened, river beds have incised (up to 4 m) and locally aggraded near tributary confluences. The active river bed has narrowed by 31%, which was accelerated by the gradual emergence of Tamarix nilotica and fruit plantations...
Small-scale irrigation expansion along the dam-regulated Tekeze River in Northern Ethiopia
International Journal of Water Resources Development, 2020
ABSTRACT Based on extensive field information, farmer-led small-scale irrigation systems along th... more ABSTRACT Based on extensive field information, farmer-led small-scale irrigation systems along the dam-regulated Tekeze River is investigated and the likelihood of future irrigation expansion within the area with modelled potential is discussed, considering facilitating and hampering factors. Due to dam-induced hydrologic alterations, downstream socio-ecological systems have strongly transformed as the irrigated area has quadrupled and the post-dam potential for perennial crop cultivation has attracted numerous migrant investors to the area, inducing inequalities but also providing opportunities. Future dam construction should involve tailored policy interventions to facilitate irrigation expansion, while safeguarding equal and sustainable access to water and land.
Spatial distribution and livelihood effects of debris cones at the western Afar Rift Valley margin, northern Ethiopia
Norsk Geografisk Tidsskrift - Norwegian Journal of Geography, 2020
ABSTRACT The objective of the study on which the article is based was to investigate the distribu... more ABSTRACT The objective of the study on which the article is based was to investigate the distribution, characteristics and livelihood effects of debris cones in the Aba’ala and Raya grabens in Ethiopia. The characteristics of the debris cones and their upper catchment areas were obtained from Google Earth Pro and Landsat images. Questionnaires were used to understand the livelihood effects of the debris cones. In addition, transect studies, interviews and observations were used to supplement the data. The data were analysed using descriptive statistics, a regression model and coupled criteria. The results showed that the debris cones differed in their physical characteristics and distribution, and their volumes were larger in the Raya graben than in the Aba’ala graben. The average flow lengths of the upper catchments was the major predictor of debris cone volume. The expansion of debris cones devastated farmlands, resulting in crop yield loss. Moreover, deposited debris damaged dwellings and pasture, and led to smallholder farmers’ displacement. However, the cones remained attractive for settlement and spate irrigation. The authors conclude that despite the benefits of debris cones, catchment rehabilitation measures should be implemented in the upper catchments to reduce the expansion of debris cones in the studied grabens.
Geotourism combines abiotic, biotic and cultural aspects. In Tigray in northern Ethiopia, the Ort... more Geotourism combines abiotic, biotic and cultural aspects. In Tigray in northern Ethiopia, the Orthodox Christian religion is a dominant component of culture, that highlights the importance of geology and the wider natural environment, and creates great visibility for it.
Geoheritage, 2020
Despite the high geoheritage value of caves and karsts, northern Ethiopia's largest cave at Zeyi ... more Despite the high geoheritage value of caves and karsts, northern Ethiopia's largest cave at Zeyi (13.5586°N, 39.1454°E) in the Dogu'a Tembien district has received little attention so far. We have studied its geological, geomorphic, socio-cultural and historical dimensions in a holistic way. The basal member of the Antalo Limestone, in which the Zeyi cave is located, consists of grainstone and wackestone with subordinate marly interlayers. Over a length of 364 m, the oval-shaped gallery displays stalagmites, stalactites, five columns, dissolution holes ("bell-holes") following joints, stalagmitic floors and other concretions or speleothems. In the absence of any dating of the cave, we contrasted its elevation above the current local base level with known average incision rates of the northern Ethiopian highlands to reconstruct its age, which was calculated as at least 2 to 4 million years. The palaeo-environmental information that is archived in the Zeyi cave sediment would hence cover the Pleistocene. The graves in the sediment at the bottom of the Zeyi cave further indicate that the place could be an ancient burial site, which gives scope for archaeological research. Zeyi boosts a unique combination of abiotic, biotic and cultural components: the nineteenth c. church under the overhanging cliff; the unique cave; the speleothems, cliffs and gorges; and the cave's bat colony which has been genetically confirmed to be composed of three syntopically roosting species. Accounting for a good balance between cave research, community-based geotourism, geoconservation and biodiversity conservation, the Zeyi cave has strong credentials to become a top geotouristic site in northern Ethiopia. However, major work needs to be done, including granting access for women and organising community-based geotourism.
Afrika Focus, 2019
The hydro-geomorphology of mountain catchments is mainly determined by vegetation cover. This stu... more The hydro-geomorphology of mountain catchments is mainly determined by vegetation cover. This study was carried out to analyse the impact of vegetation cover dynamics on flooding and water balance in 11 steep (0.27-0.65 m m-1) catchments of the western Rift Valley escarpment of Northern Ethiopia, an area that experienced severe deforestation and degradation until the first half of the 1980s and considerable reforestation thereafter. Land cover change analysis was carried out using aerial photos (1936,1965 and 1986) and Google Earth imaging (2005 and 2014). Peak discharge heights of 332 events and the median diameter of the 10 coarsest bedload particles (Max10) moved in each event in three rainy seasons (2012-2014) were monitored. The result indicates a strong reduction in flooding (R2 = 0.85, P<0.01) and bedload sediment supply (R2 = 0.58, P<0.05) with increasing vegetation cover. Overall, this study demonstrates that in reforesting steep tropical mountain catchments, magnitud...
Dynamics of ephemeral streams at the foot of degraded catchments in northern Ethiopia
Land Degradation & Development, 2019
The magnitudes of flash floods and their effect on channel width changes were investigated for Ha... more The magnitudes of flash floods and their effect on channel width changes were investigated for Hara River in the Raya graben (northern Ethiopia). Precipitation was measured using rain gauges evenly distributed over the study catchment. Event peak discharges were measured with crest‐stage gauges at a reference cross‐section. Changes in channel width were measured at six monitoring sites along a 1.5 km long reach. Decadal channel width change was analyzed over the period 1965–2014. The average rainfall depth of the rainy days was 14.2 ± 9.4 mm whereas the highest was 41.9 mm and the lowest, capable to generate some flow in the river, was only 1.8 mm. The maximum calculated discharge peaked at 408 m3/s whereas the lowest flow was 19.5 m3/s. An average widening of 0.11 ± 0.19 m per flood (for a total of 3.74 m) was measured. The cumulative precipitation and cumulative channel widening suggest that larger and longer lasting rains have substantial influence on channel width change. A mark...
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Papers by Tesfaalem Ghebreyohannes