Search

The absence of a basin-wide apportionment agreement on using the Nile River equitably has been a long-standing source of disagreement among Nile riparian states. This study introduces a new approach that the riparian states can consider that quantifies the Nile River's apportionment. The approach includes (1) developing a basin-wide database of indicators representative of the United Nations Watercourse Convention (UNWC) relevant factors and circumstances, (2) developing an ensemble of indicator weighting scenarios using various weighting methods, and (3) developing six water-sharing methods to obtain a range of apportionments for Egypt, Sudan, Ethiopia and the group of the White Nile Equatorial States for each weighting scenarios. The results illustrate a relatively narrow range of country-level water apportionments, even though some individual factor weights vary from 3% to 26%. Considering the entire Nile River, the water apportionment for Ethiopia ranges from 32% to 38%, Sudan and South Sudan from 25% to 33%, Egypt from 26% to 35%, and the Equatorial States from 5% to 7%. We trust that the six proposed equitable water-sharing methods may aid in fostering basin-wide negotiations toward a mutual agreement and address the dispute over water sharing. [ABSTRACT FROM AUTHOR]

Excess sediment and nutrient losses from intensifying agriculture degrade water quality and boost plant growth. The relationship between circulation patterns, spatial water quality degradation, and water hyacinth infestation is not adequately studied. The objective of this study is, therefore, to investigate the effect of lake circulation patterns on sediment and nutrient distribution and its implication on the spread of water hyacinth in a tropical lake. This study was carried out in Lake Tana, the largest freshwater lake in Ethiopia, where sediment and nutrient concentrations are increasing, and water hyacinths have become a challenge since 2011. The lake circulation pattern was simulated by the Delft3D model based on a bathymetry survey, discharge, and meteorological forcings. To predict the transport path of sediments and dissolved nutrients, an inert tracer was released in the four main river inlets of the lake. Observed lake water level measurements were used to validate the model. Our results show that the lake circulation pattern could explain the transport path of sediment and nutrients and the location of the water hyacinths found in the northeast of the lake. Sediments and nutrients from the largest river, Gilgel Abay, in the southeast of Lake Tana, flow through the two outlets nearby with little sediment deposition due to the relatively short retention time. The phosphorus-rich sediments of the 24 h at 105 °C remaining three main rivers joining the lake at the north and east are transported to the northeast. Thus, the management and control of water hyacinths should focus on the northern and eastern catchment areas of Lake Tana. [ABSTRACT FROM AUTHOR]

The highlands serve as water towers for the blue water in the surrounding area, with often insufficient rainfall for rainfed crops. The population is growing in the highlands, changing the hydrology and blue and green water availability. One of the changes that affect the highlands of Ethiopia is the rapidly expanding areas of small patches of eucalyptus on farmers fields. This manuscript aims to sort through the limited available literature and develop a water balance model as a starting point to discuss how hydrology is affected by increased acreage of eucalyptus in the highlands. We find some evidence in the literature that patches of eucalyptus during the dry phase may withdraw water from the subsoil up to twice the rate of evapotranspiration when the soil water is not limited. Since saturation excess generates surface runoff in the subhumid and humid highlands, water withdrawn during the dry phase should be made up before the area with eucalyptus becomes hydraulically active. The amount of water that can be removed from storage by eucalyptus is greater in areas with a long dry monsoon phase than in temperate climates for the same increase in trees. We also found, as expected, that the eucalyptus water balance model, as developed in this paper, was not valid for areas in semi-arid and arid regions. Soil crusting and water repellency might induce infiltration excess runoff. A tentative implication is that since most blue water is produced in the areas with the highest rainfall, eucalyptus in subhumid and humid monsoon regions will affect the blue water supply downstream but not the plant available green water although shading will decrease yield in the immediate surroundings of the eucalyptus trees. [ABSTRACT FROM AUTHOR]

Nitrate is globally the most widespread and widely studied groundwater contaminant. However, few studies have been conducted in sub-Saharan Africa, where the leaching potential is enhanced during the rainy monsoon phase. The few monitoring studies found concentrations over drinking water standards of 10 mg N-NO3− L−1 in the groundwater, the primary water supply in rural communities. Studies on nitrate movement are limited to the volcanic Ethiopian highlands. Therefore, this study aimed to evaluate the transport and fate of nitrate in groundwater and identify processes that control the concentrations. Water table height, nitrate, chloride, ammonium, reduced iron, and three other groundwater constituents were determined monthly in the groundwater in over 30 wells in two contrasting volcanic watersheds over two years in the Ethiopian highlands. The first watershed was Dangishta, with lava intrusion dikes that blocked the subsurface flow in the valley bottom. The water table remained within 3 m of the surface. The second watershed without volcanic barriers was Robit Bata. The water table dropped rapidly within three months of the end of the rain phase and disappeared except near faults. The average nitrate concentration in both watersheds was between 4 and 5 mg N-NO3− L−1. Hydrogeology influenced the transport and fate of nitrogen. In Dangishta, water was blocked by volcanic lava intrusion dikes, and residence time in the aquifer was larger than in Robit Bata. Consequently, nitrate remained high (in several wells, 10 mg N-NO3− L−1) and decreased slowly due to denitrification. In Robit Bata, the water residence time was lower, and peak concentrations were only observed in the month after fertilizer application; otherwise, it was near an average of 4 mg N-NO3− L−1. Nitrate concentrations were predicted using a multiple linear regression model. Hydrology explained the nitrate concentrations in Robit Bata. In Dangishta, biogeochemistry was also significant. [ABSTRACT FROM AUTHOR]

This study employed geomorphometric analysis to characterize the four major watersheds (Gilgel Abay, Gumara, Rib, and Megech) of Lake Tana sub-basin, Ethiopia, and prioritize the watersheds for the implementation of SWC practices using GIS and remote sensing techniques. Also, the study analyzed streamflow and sediment data recorded at the outlets of each watershed to associate the geomorphometric prioritization result with recordings of the watersheds. Geomorphometric analysis results indicated that the Rib watershed is the most susceptible watershed for soil erosion and should be prioritized for the implementation of SWC practices. The analysis of streamflow and suspended sediment concentration suggest that the Rib watershed had the second maximum sediment yield (14.3 t ha−1 yr−1) compared to the other three watersheds. This is because of the low streamflow response of the watershed compared with the Gumara watershed which had the highest sediment yield (18.9 t ha−1 yr−1). [ABSTRACT FROM AUTHOR]

Agricultural intensification in sub-Saharan African countries has significantly increased pesticide applications. Information on pesticide residues and their transport in groundwater and streams is needed to properly manage and reduce any harm to the ecosystem and environment. This information is lacking in the volcanic soils of Ethiopian highlands. Therefore, this study was conducted to assess pesticide concentrations in ground and surface water and their risk to humans and aquatic life. The 9 km2 rural watershed Robit Bata in the Lake Tana Basin was selected. Crops were grown under rainfed and irrigated conditions. Pesticide use was assessed, and groundwater samples were collected from eight wells and surface water samples at the outlet twice in the rain phase and once in the dry phase. Samples were analyzed for chlorpyrifos, dimethoate, (α and β) endosulfan, profenofos, NO 3 − , and pH. Chlorpyrifos and endosulfan, which are strongly adsorbed and slowly degrading pesticides, were found in nearly all surface and groundwater samples, with maximum concentrations in surface water of 8 µg L−1 for chlorpyrifos and 3 µg L−1 endosulfan. Maximum groundwater concentrations were only slightly lower. The weakly adsorbed and fast degrading pesticides, dimethoate, and profenofos were detected only in the rain phase after spraying in the groundwater, indicating preferential transport to groundwater at depths of up to 9 m. The average concentration was 0.38 μg L−1 for dimethoate in surface waters and 1.24 μg L−1 in groundwater. Profenofos was not detected in surface water. In the groundwater, the average concentration was 0.05 μg L−1. Surface water concentrations of chlorpyrifos and endosulfan were highly toxic to fish. The World Health Organization banned these pesticides worldwide. It should be phased out for use in Ethiopia to safeguard the ecological health of Lake Tana, which is rich in biodiversity and endemic fish species. [ABSTRACT FROM AUTHOR]

Poverty is multi-dimensional global challenge that impedes individual and community capacities to satisfy basic needs. These capacities are shaped by locally configured institutional and biophysical processes that are often hidden from external researchers and practitioners. To explore this worldwide aspect, we adopt participatory rural appraisal (PRA) methods to expose barriers to implementing livelihood strategies to address poverty in Ethiopia's upper Blue Nile basin, where 85 % of the population are subsistence farmers reliant on local ecosystem services (ES). We identify local barriers to poverty alleviation in three steps. First, we classify major ES-livelihood interrelationships among communities of Debre Mawi catchment in upper Blue Nile. Secondly we assess ongoing struggles in these interrelations using combined biophysical and social assessment criteria to evaluate how poverty relates to current patterns of ES management. The analysis identifies complex interdependencies between livelihoods and regulating (crop pest controls), provisioning (water, land, and feed availability, soil fertility) and cultural (top-down ES management, population growth) ES that create bottlenecks to effectively 'lock in' poverty. Thirdly, we identify potential new ES management strategies, focused on dry season water availability. We conduct participatory field experiments on rooftop water harvesting to show this is a promising approach for increasing water availability to enhance agricultural production. Depending on the rooftop area, our modelling suggests that farmers can improve household income by US$136– 14,876 from 5 months beef fattening and US$69–7704 from 4 months sheep fattening. Except these specific livelihood strategies, the findings are replicable to the world's ES-dependent regions. • A novel rigorous approach was developed to maximize poverty alleviation. • Water scarcity is most important bottleneck to move out of poverty. • Rooftop water harvesting avoids water scarcity and improves livelihood. • Unpredictable rainfall causes significant crop yield reduction. • Poverty alleviation needs to focus on the poorest segment of society. [ABSTRACT FROM AUTHOR]

Accelerated sediment concentration has become a pervasive feature in developing countries and has substantially impacted lake ecosystem functioning. Despite this, very few comprehensive studies have examined the changes in sedimentation over the time that agriculture intensified greatly with the increasing population. This study aims to fill this gap using historical and recent bathymetric surveys to determine sediment deposition and link these to watershed development. With its unique ecology, Lake Tana that was pristine less than 100 years ago, is one of these systems experiencing increasing sediment concentrations. A detailed bathymetric survey was conducted in late 2017 and compared with bathymetric surveys conducted in 1940, 1987, and 2006. The result shows that in the past 77 years, Lake Tana's depth decreased an average of 28 ± 11 cm, equivalent to nearly 0.9 ± 0.4 Tg (million tons). Sediment deposition was 2.8 ± 2.3 mm a−1 between 1940 and 1987, when the agricultural intensification started. It almost doubled to 5.0 ± 3.7 mm a−1 after that. Spatially, the sediment deposition was most significant in areas near the major river inlets where 2 to 10 km long peninsulas were formed. The increase in sediment deposition is primarily driven by newly formed valley bottom gullies formed after deforestation disturbed the hydrological equilibrium, and watershed outflow increased. [ABSTRACT FROM AUTHOR]

Land degradation in developing countries is exacerbating hardpan development that causes the formation of perched watertable, which in turn results in increased runoff and erosion. To reduce overland flow and erosion, percolation through the hardpan needs to be improved. One successful way to achieve this is ripping off the hardpan and plausibly liming. However, in the highlands of Ethiopia, there is little information available on these two techniques. The objectives of this study were, therefore, to determine the effects of ripping off degraded soils on runoff and erosion rates and whether liming would improve the effectiveness of ripping. A field study was conducted in the Anjeni watershed. Thirty‐two experimental runoff plots were installed across the watershed. Conventional tillage at 15 cm depth and ripping to 30, 45, and 60 cm depths were applied with and without lime amendments. Results showed that ripping to 60 cm depth resulted in a significant reduction of runoff. However, liming increased runoff response, on average by 10%. In contrast to the reduction in runoff amounts, an increase in ripping depth increased the amount of soil loss especially during the first storms at the beginning of the monsoon rainy season. Liming significantly decreased soil loss by up to 35%. Although plots with deep ripping plus liming had greater runoff production than other plots, soil loss was less. Overall, the findings suggest that deep ripping has promise but more research is needed before widely implemented. [ABSTRACT FROM AUTHOR]

Given the critical role of water in rural development, it is essential to quantify water use by various sectors. Reportedly, a significant water loss during the dry monsoon phase is by Eucalyptus trees in the Ethiopian highlands but few quantitative studies have been carried out. In our study in the Fogera plain near Lake Tana, consumptive water use of a small Eucalyptus patch was calculated from the fluctuating diurnal water table observations for two dry monsoon phases. During the dry monsoon phase in 2014, the groundwater table declined linearly at a rate of 2.6 cm d−1 and in 2015 the decline was 2.5 cm d−1. Daily fluctuations in groundwater were around 20 cm. Translating changing groundwater levels in precise evapotranspiration rates was cumbersome because of uncertainty in the value of drainable porosity. We concluded that the evapotranspiration over the small Eucalyptus patch was at a minimum 3.4 mm d−1 but more likely around 10 mm d−1 at the end of the dry phase. The 10 mm d−1 is twice the reference evaporation rate. This is in accordance with advection aridity approach where the actual evaporation of isolated patches with access to groundwater in dry environments can evaporate at twice the reference rate. The current and future extent of Eucalyptus patches and forests need, therefore, be considered in the management of the groundwater resource. [ABSTRACT FROM AUTHOR]

Feeding 9 billion people in 2050 will require sustainable development of all water resources, both surface and subsurface. Yet, little is known about the irrigation potential of hillside shallow aquifers in many highland settings in sub‐Saharan Africa that are being considered for providing irrigation water during the dry monsoon phase for smallholder farmers. Information on the shallow groundwater being available in space and time on sloping lands might aid in increasing food production in the dry monsoon phase. Therefore, the research objective of this work is to estimate potential groundwater storage as a potential source of irrigation water for hillside aquifers where lateral subsurface flow is dominant. The research was carried out in the Robit Bata experimental watershed in the Lake Tana basin which is typical of many undulating watersheds in the Ethiopian highlands. Farmers have excavated more than 300 hand dug wells for irrigation. We used 42 of these wells to monitor water table fluctuation from April 16, 2014 to December 2015. Precipitation and runoff data were recorded for the same period. The temporal groundwater storage was estimated using two methods: one based on the water balance with rainfall as input and baseflow and evaporative losses leaving the watershed as outputs; the second based on the observed rise and fall of water levels in wells. We found that maximum groundwater storage was at the end of the rain phase in September after which it decreased linearly until the middle of December due to short groundwater retention times. In the remaining part of the dry season period, only wells located close to faults contained water. Thus, without additional water sources, sloping lands can only be used for significant irrigation inputs during the first 3 months out of the 8 months long dry season. [ABSTRACT FROM AUTHOR]

Gullies that are expanding at alarming rate are responsible for the majority of soil losses in the (sub) humid highlands of Ethiopia. Few affordable and effective methods for gully erosion control are available in the highlands. The objective of the study was to develop cost-effective measures to halt gully expansion by determining stable-bank conditions under a variety of environmental situations using the Bank Stability and Toe Erosion Model (BSTEM). The study was carried out in the sub humid Debre Mawi watershed, located 30 km south of Lake Tana. Input data for the BSTEM model were collected using field surveys and soil sampling. After the BSTEM was tested on actual measured soil data, soil cohesion and internal friction angle were calibrated against observed gully bank retreat. Using the calibrated parameters, the model evaluated the stabilization of the existing gully bank under different scenarios in which groundwater table, bank angle and bank height, tension crack depth, vegetation, and toe protection were varied. Finally, the head-cut of the study gully was treated based on the model recommendation. The simulated results showed that a 5 m deep gully was stable under fully saturated conditions when the bank toe is protected, its upper surface is vegetated, and its bank angles do not exceed 45°. If the depth of the gully is less than 5 m or if its water table is deeper than 0.5 m, only regrading the gully bank to an angle of 45° can stabilize the gully. BSTEM showed to be an effective tool that can be used to evaluate gully control measures. [ABSTRACT FROM AUTHOR]

Abstract: Soil erosion, with significant contributions from gullies, is a serious problem in the Ethiopian highlands. The objective of this paper is to examine patterns of discharge and sediment transport in the Ethiopian highlands, and to provide an initial assessment of whether soil and water conservation practices (SWCP) can reduce sediment loads in watersheds with actively eroding gullies. The study was conducted in the 414‐ha Ene‐Chilala watershed with a unimodal sub‐humid monsoon climate and actively eroding gullies in the valley bottoms. In 2013 and 2014, the local community was mandated to install upland infiltration furrows and farmers voluntarily rehabilitated six gully heads and protected 16 m of eroding stream banks. Discharge and sediment concentration were measured in two upslope watersheds and at the outlet. Since median infiltration capacity in the uplands was always greater than the rainfall intensity, saturation excess and interflow were main runoff pathways. After 175 mm cumulative rainfall, the groundwater table reached the surface in the valley bottoms, restricting infiltration, and runoff was generated as saturation excess overland flow and flowed through active gullies out of the watershed. Upland rill erosion on ploughed land early in the rain phase, and gully erosion in saturated valley bottoms thereafter, were sources of sediment in the rivers. The mandated infiltration furrows installed on the contour overtopped and damaged cropland. The off‐contour furrows increased streamflow. Gully rehabilitation of an upland gully effectively reduced stream sediment concentration in the upland weir. However, there was little benefit at the watershed outlet since the stream picked up the unconsolidated sediment from the failing banks in the downstream porting of the watershed. Therefore, soil conservation programs that in addition to installing upland practices, rehabilitate the main sediment source (gullies) appear to be the most effective approach to reducing in‐stream suspended sediment concentrations. © 2018 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Land use changes in many landscapes result in gully formation, carving up agricultural land and playing a large role in filling up downstream reservoirs by connecting uplands with rivers. This includes the Ethiopian highlands. Our objective is to begin investigating the interaction of upland and gully erosion and to quantify the portion of eroded sediment originating from a gully to prioritize erosion control practices. For this purpose, a 5‐m deep valley bottom gully of the 13‐ha catchment in the Debre Mawi watershed in the subhumid Ethiopian highland near Lake Tana was selected. The upstream and downstream gully discharge and sediment concentrations were measured over a 2‐year period. The results show that the sediment concentration at the outlet was about 10 times greater than at the inlet. The sediment budget calculation showed that about over 90% of the sediment at the outlet originated from within the gully. Hysteresis analysis of the sediment concentration discharge relationship showed that sediment supply from the upland was limited, but sediment was always available to be eroded and transported in the gully because of bank failures and headcut retreat. Thus, to reduce sediment loads in rivers and consequent adverse downstream impacts, designing cost‐effective measures to treat gullies should be a priority in the subhumid Ethiopian highlands. [ABSTRACT FROM AUTHOR]

Landscape response to drivers of change is more visible and noticeable in deltas and floodplains than in upstream. Here, we address the changes of Lake Tana basin by investigating the delta development of Gumara River and sediment deposition in the Fogera floodplain over a 58-year period when agricultural land expanded, agriculture intensified, and flooding of the alluvial plain became more frequent. Old maps show that delta formation before the 1950s was minimal, indicating that the sediment contributed by the rivers to the lake was small. However, during the last 58 years, the delta has expanded continuously. When considering the same lake level (2·68 m) from 1984 to 2014, the delta has expanded an average of 5 ha annually, and by considering different lake levels and corresponding delta areas, the delta increased in height an average of 3 cm annually. While the growth of the delta was approximately linear, the sediment concentration in the river doubled in the last 30 years, indicating more efficient sediment trapping in the floodplain as a result of higher lake levels, rising river beds, and farmers intervening with the course of the river near the shore. Unless effective river restoration and catchment-based treatment measures are put in place, the capacity of the rivers will further reduce and aggravate the flooding of the floodplain, causing more sediment deposition in the river channel and on the floodplain. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Controlling soil erosion is important for maintaining land productivity and reducing sedimentation of reservoirs in the Ethiopian highlands. To gain insights on sediment loss patterns, magnitude of peak sediment events, and their contribution to annual loads, hydrometric and sediment concentration data were collected for five years (2010 - 2014) from the 95-ha Debre Mawi and four nested catchments (located 30 km south of Lake Tana). Soil and water conservation practices (SWCPs) consisting of soil bunds with 50-cm-deep furrows were implemented in the third year, which made it possible to examine the effects of SWCPs on peak sediment loads. The results show that a 10-min event causes soil loss of up to 11·4 Mg ha−1, which is 22% of the annual sediment yield. Thirty to seventy-five percent (up to 30 Mg ha−1day−1) of the sediment yield was contributed by the greatest daily flow in each year. The contribution increases to 86% for the two largest daily flows. SWCP interventions reduced sediment loss by half but did not affect the relative contribution of peak events to annual loads. Because of gully erosion, peak sediment loads at the outlet of the entire catchment were greater (up to 30 Mg ha−1day−1) as compared to the nested catchments without gullies (0·5 to 8 Mg ha−1day−1). Consequently, to reduce sediment loss, conservation measures should be designed to decrease runoff during large storms. This can be attained by deepening furrows on unsaturated hillsides and reducing the entrainment of unconsolidated sediment from failed gully banks. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Groundwater levels are declining at unsustainable levels in many areas of the world. To secure this resource for future generation, well-documented groundwater level observations are needed to derive recharge rates and sustainable withdrawal amounts. Although groundwater is routinely monitored in most of the world, relatively little information is available in sub-Saharan Africa including the Ethiopian highlands where groundwater irrigation could greatly increase food security. To obtain sustainable withdrawal rates for the wet Ethiopian highlands, we selected the Fogera plain in the Lake Tana basin with a sub-humid climate. Weekly groundwater levels were measured in 32 abandoned shallow wells over a 2-year period in 2014 and 2015. Our observations showed that in the 2 years, the groundwater level reached the surface during the rainy monsoon phase around first week of August. At the end of the dry monsoon phase in May, the average groundwater table was at 4 m depth. The amount of water removed by evaporation during the dry phase was 850 mm year−1. This is replenished through recharge during the wet phase. Rain in excess of the recharge and evaporation is stored on the surface or converted to overland flow. The groundwater flowed slowly towards the lake, but water passing the lakeshore was not a significant term in the water balance of the plain. Irrigation from groundwater seems to be sustainable especially when rivers flood periodically. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Increasing population and intensification of agriculture increase erosion rates and often result in severe land degradation and sedimentation of reservoirs. Finding effective management practices to counteract the increasing sediment load is becoming increasingly urgent especially in the Ethiopian highlands where the construction of the hydroelectric Grand Renaissance Dam on the Blue Nile is underway. In this paper, we examine the results of 9 years of a watershed experiment in which discharge and sediment losses were observed in the 113 ha Anjeni watershed of the Blue Nile Basin. The study period encompasses conditions before, during, and after the installation of graded Fanya- Juu ('throw uphill' bunds) soil and water conservation practices (SWCP), which had the ultimate goal of creating terraces. We use a saturation-excess runoff model named the parameter-efficient distributed model as a mathematical construct to relate rainfall with discharge and sediment losses at the outlet. The parameter-efficient distributed model is based on landscape units in which the excess rainfall becomes direct runoff or infiltrates based on topographic position or hardpan characteristics. Deviations in this rainfall-discharge-sediment loss relationship are ascribed to the changes in infiltration characteristics caused by SWCPs on the hillslopes. With this technique, we found that in the Anjeni basin, the Fanya-Juu SWCPs are only effective in increasing the infiltration and thereby reducing the direct runoff and sediment concentrations in the first 5 years. At the end of the 9-year observation period, the direct runoff and sediment concentrations were barely reduced compared to the levels before SWCP were installed. In addition, we found that the model structure based on landscape units was able to represent the varying runoff and erosion processes during the 9 years well by varying mainly the portion of degraded land (and thereby representing the effectiveness of the Fanya-Juu to reduce runoff by increasing infiltration). [ABSTRACT FROM AUTHOR]

Drainage of paved and unpaved roads has been implicated as a major contributor of overland flow and erosion in mountainous landscapes. Despite this, few watershed models include or have tested for the effect roads have on discharge and sediment loads. Though having a model is an important step, its proper application and attention to distinct landscape features is even more important. This study focuses on developing a module for drainage from a road and tests it on a nested watershed (Shanko Bahir) within a larger previously studied site (Debre Mawi) that receives overland flow contributions from a highly compacted layer of soil on an unpaved road surface. Shanko Bahir experiences a sub-humid monsoonal climate and was assessed for the rainy seasons of 2010, 2011, and 2012. The model chosen is the Parameter Efficient Distributed (PED) model, previously used where saturation-excess overland flow heavily influences discharge and sediment concentration variation, though infiltration-excess occasionally occurs. Since overland flow on unpaved surfaces emulates Hortonian flow, an adjustment to the PED model (the developed module) advances possible incorporation of both flow regimes. The modification resulted in similar modeling performance as previous studies in the Blue Nile Basin on a daily basis (NSE = 0.67 for discharge and 0.71 for sediment concentrations). Furthermore, the road while occupying a small proportion of the sub-watershed (11%) contributed importantly to the early discharge and sediment transport events demonstrating the effect of roads especially on sediment concentrations. Considerations for the dynamic erodibility of the road improved sediment concentration simulation further (NSE = 0.75). The results show that this PED modeling framework can be adjusted to include unpaved compacted surfaces to give reasonable results, but more work is needed to account for contributions from gullies, which can cause high influxes of sediment. [ABSTRACT FROM AUTHOR]

Intensifying agriculture in Africa is degrading the water quality of rivers and lakes, thereby, threatening the sustainable use of water resources. In Lake Tana in the Ethiopian highlands, the first signs of eutrophication were recently observed. Since relatively little is known about the non-point source pollution in sub-Saharan Africa, the objective was to examine non-point sources phosphorus contribution of an agricultural watershed near Lake Tana. The 7-km2 Awramba watershed was selected. Dissolved phosphorus concentration (DPC) in groundwater and soil-available phosphorus was measured at three landscape positions and discharge, sediment, and DPC at the outlet. The results indicated that DPC in groundwater was most elevated in the periodically saturated valley bottoms while available P was the greatest in the cropped fields at mid-slope. The DPC increased with discharge. During base flow the concentration in the stream was similar to that in ground water. The results were consistent with other hydrological watershed studies in which the major source of runoff, erosion, and phosphorus originated from valley bottom lands. Hence, converting the periodically saturated areas in the stream corridor to buffer zones with reduced P input can be an important tool in reducing P from rural watersheds in the Ethiopian highlands. [ABSTRACT FROM AUTHOR]

Experimental research in the Ethiopian highlands found that saturation excess induced runoff and erosion are common in the sub-humid conditions. Because most erosion simulation models applied in the highlands are based on infiltration excess, we, as an alternative, developed the Parameter Efficient Distributed (PED) model, which can simulate water and sediment fluxes in landscapes with saturation excess runoff. The PED model has previously only been tested at the outlet of a watershed and not for distributed runoff and sediment concentration within the watershed. In this study, we compare the distributed storm runoff and sediment concentration of the PED model against collected data in the 95-ha Debre Mawi watershed and three of its nested sub-watersheds for the 2010 and 2011 rainy seasons. In the PED model framework, the hydrology of the watershed is divided between infiltrating and runoff zones, with erosion only taking place from two surface runoff zones. Daily storm runoff and sediment concentration values, ranging from 0.5 to over 30 mm and from 0.1 to 35 g l−1, respectively, were well simulated. The Nash Sutcliffe efficiency values for the daily storm runoff for outlet and sub-watersheds ranged from 0.66 to 0.82, and the Nash-Sutcliffe efficiency for daily sediment concentrations were greater than 0.78. Furthermore, the model uses realistic fractional areas for surface and subsurface flow contributions, for example between saturated areas (15%), degraded areas (30%) and permeable areas (55%) at the main outlet, while close similarity was found for the remaining hydrology and erosion parameter values. One exception occurred for the distinctly greater transport limited parameter at the actively gullying lower part of the watershed. The results suggest that the model based on saturation excess provides a good representation of the observed spatially distributed runoff and sediment concentrations within a watershed by modelling the bottom lands (as opposed to the uplands) as the dominant contributor of the runoff and sediment load. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding the relationship between topography, hydrological processes, and runoff source areas is essential in engineering design, such as predicting floods and implementing effective watershed management practices. This relationship is not well defined in the highlands with a monsoon climate and needs further study. The objective of this study is to relate topographic position and hydrological response in tropical highlands. The research was conducted in the Debre Mawi watershed in the northwest sub-humid Ethiopian highlands. In the monsoon rain phase of 2017 and 2018, groundwater depth, infiltration rate, and surface runoff were monitored at the upslope, midslope, and downslope positions. Surface runoff rates were measured in farmer fields through distributed V-notch weirs as estimates of positional runoff. Average water table depths were 30 cm deep in the downslope regions and 95 cm in the upslope position. The water table depth affected the steady-state infiltration rate in the rain phase. It was high upslope (350 mm h−1), low midslope (49 mm h−1), and zero downslope. In 2017, the average runoff coefficients were 0.29 for the upslope and midslope and 0.73 downslope. Thus, topographic position affects all aspects of the watershed hydrology in the humid highlands and is critical in determining runoff response. [ABSTRACT FROM AUTHOR]

Land use and land cover changes are driven by human actions and, in turn, drive changes that alter the availability of products and services for people and livestock. For proper planning, these cause-and-effect interrelations need to be understood. This is especially important for Ethiopia where the resource base is declining and should be improved in order to feed the growing population. To better understand these interrelations, we studied trends in the natural resource base over a 35-year period for two contrasting sites in the Ethiopian Highlands: semi-arid and water-short Lenche Dima, and sub-humid and moisture-sufficient Kuhar Michael. Information was obtained using time-series satellite images, geographical positioning system, a socio-economic survey and a document review. Results showed that for sub-arid Lenche Dima there were minimal changes in land use and land cover patterns, while in water-sufficient Kuhar Michael cropland greatly increased at the expense of the grazing land and bare soil. At the same time land holding size and cattle numbers decreased in Lenche Dima while they remained the same in Kuhar Michael, although overall land holdings remained larger in Lenche Dima than in Kuhar Michael. This study thus found large differences in development of agriculture since the 1970s: intensification of agriculture is possible in the water-sufficient sub-humid climate by displacing animal husbandry with high value crops that need irrigation during the dry monsoon season. This is not possible for the semi-arid area where water is the limiting factor in production even if a market is close by. Agriculture in the semi-arid areas also requires larger land holdings because of the risk of droughts and low yields during some years. This comparative analysis suggests that without sufficient water, the shift from subsistent to commercial market-driven agriculture cannot be easily accomplished. [ABSTRACT FROM PUBLISHER]

The article presents a study that discusses the historical trends of rainfall and runoff in the Blue Nile Basin in Ethiopia and Sudan from 1964 to 2003. The study is undertaken through a rainfall-runoff model that analyzed the causes of the observed trends. Results show that despite no significant trend in the average rainfall both seasonal and basin-wide, significant increases in discharge during rainy season from June to September were observed at all three stations.

The article discusses a study in Ethiopia which discovers the development of a realistic model which is a useful tool for planning watershed management and conservation activities. It is noted that the model divides the watershed into different regions which become hydrologically active given various amounts of effective cumulative rainfall. It further states that rainfall and potential evaporation are used as major inputs in running separate water balance for each of the hydrologic regions.

The article focuses on a study in Blue Nile River which examines the development of simple hydrology and erosion models through the use of saturation excess runoff principles and interflow processes. It states that a water balance approach is used by dividing the landscape into variable saturated areas, exposed rock and hillslopes. It notes that available precipitation and potential evaporation data and a minimum of calibration parameters are used to couple the model with erosion model.

The article provides information on a study that presented a simple rainfall-discharge analysis for the Andit Tid, Anjeni, and Maybar watersheds of northern Ethiopia. A hydrologic data collected from the three research stations in the Amhara National Regional State was used in the study. It was found that temporal dynamics play an important role in the hydrologic behaviour of the watersheds. It shows that the saturation excess mechanism, despite the different rainfall patterns between the three watersheds, is the main reason that the runoff behaviour is similar.

There is an increasing need globally to establish relationships among flow, ecology, and livelihoods to make informed decisions about environmental flows. This paper aimed to establish the ecological foundation for a holistic environmental flow assessment method in the Gumara River that flows into Lake Tana in Ethiopia and the Blue Nile River. First, the ecological conditions (fish, macro-invertebrate, riparian vegetation, and physicochemical) of the river system were characterized, followed by determining the hydrological condition and finally linking the ecological and hydrological components. The ecological data were collected at 30 sites along the Gumara River on March 2016 and 2020. River hydrology was estimated using the SWAT model and showed that the low flow decreased over time. Both physico-chemical and macroinvertebrate scores showed that water quality was moderate in most locations. The highest fish diversity index was in the lower reach at Wanzaye. Macroinvertebrate diversity was observed to decrease downstream. Both the fish and macroinvertebrate diversity indices were less than the expected maximum, being 3.29 and 4.5, respectively. The normalized difference vegetation index (NDVI) for 30 m and 60 m buffer distances from the river decreased during the dry season (March–May). Hence, flow conditions, water quality, and land-use change substantially influenced the abundance and diversity of fish, vegetation, and macroinvertebrate species. The pressure on the ecology is expected to increase because the construction of the proposed dam is expected to alter the flow regime. Thus, as demand for human water consumption grows, measures are needed, including quantification of environmental flow requirements and regulating river water uses to conserve the ecological status of the Gumara River and Lake Tana sub-basin. [ABSTRACT FROM AUTHOR]

Lakes hold most of the freshwater resources in the world. Safeguarding these in a changing environment is a major challenge. The 3000 km2 Lake Tana in the headwaters of the Blue Nile in Ethiopia is one of these lakes. It is situated in a zone destined for rapid development including hydropower and irrigation. Future lake management requires detailed knowledge of the water balance of Lake Tana. Since previous water balances varied greatly this paper takes a fresh look by calculating the inflow and losses of the lake. To improve the accuracy of the amount of precipitation falling on the lake, two new rainfall stations were installed in 2013. The Climate Hazards Group Infrared Precipitation Version two (CHIRPS-v2) dataset was used to extend the data. After reviewing all the previous studies and together with our measurements, it was found that the period of 1990–1995 likely had the most accurate gauged discharge data. During some months in this period, the lake water balance was negative. Since the river inflow to the lake cannot be negative, water was either lost from the lake via the subsurface through faults, or the outflow measurements were systematically underestimated. Based on the evaporation rate of 1650 mm, we found that unaccounted loss was 0.6 km3 a−1, equivalent to 20 cm of water over the lake area each year. This implies the need for reliable rainfall data and improved river discharge measurements over a greater portion of the basin both entering and exiting the lake. Also, integrated hydrological and geologic investigations are needed for a better understanding of the unaccounted water losses and quantifying the amount of subsurface flow leaving the lake. [ABSTRACT FROM AUTHOR]

Volcanic highlands supply water to 40% of the world's population. Soil degradation threatens this water supply. Studies on geohydrology that affect the effectiveness of land and water management (LWM) practices in reducing soil degradations are limited. To aid in the effectiveness of LWM practices, we conducted a field experiment in the Gomit watershed in the semihumid Ethiopian Highlands on the interaction of hydrogeology and LWM practices. We found that in a watershed with strongly faulted tertiary basalt, 30% of the rainfall was drained through faults to another basin. Consequently, the discharge at the outlet was less than half of that of other watersheds with quaternary basalts. Despite the high sediment concentration, i.e., around 15 g L−1, in the Gomit watershed, the sediment yield of less than 4 Mg ha−1 a−1 was below average for the agricultural watershed in Ethiopia because of the low runoff response. While some faults facilitated drainage, others acted as a barrier. Groundwater stored behind the barriers was used as a municipal potable water source. Since the effectiveness of LWM practices depends on the amount of erosion that can be prevented, considerations of country-wide prioritizing of investments in land and water management practices should include the geology of the watersheds. [ABSTRACT FROM AUTHOR]

Minasny et al. (2020) proposed enhancing future global soil science research by examining the role of soils in global ecosystem functioning. They argued in particular that meaningful collaboration between high- and low-income countries is essential to generate new knowledge and facilitate capacity building. In this commentary, we provide an account of our experience with an effective cooperative research and training partnership between Cornell University and Bahir Dar University in Ethiopia. We note that, in addition to the willingness and commitment of the scientists to cooperate, support and flexibility of senior university administrators is essential for international cooperation to succeed. We illustrate these points describing our experience and show that these cooperative efforts are evolving incrementally and in many cases do not follow well-laid-out programs. [ABSTRACT FROM AUTHOR]

Lakes hold most of the world's fresh surface water resources. Safeguarding these resources from water quality degradation requires knowledge of the relationship between lake morphometry and water quality. The 3046-km2 Lake Tana in Ethiopia is one of the water resources in which the water quality is decreasing and water hyacinths have invaded. The objective of this study is to understand the interaction between the lake morphometry and water quality and specifically the phosphorus dynamics and their effect on the water hyacinths. A bathymetric survey was conducted in late 2017. Various morphometric parameters were derived, and both these parameters and sediment available phosphorus were regressed with the dissolved phosphorus. The results show that, with a wave base depth that is nearly equal to a maximum depth of 14.8 m, the bottom sediments were continuously suspended in the water column. As a result of the resuspension mixing, we found that the dissolved phosphorus in the water column decreased with lake depth and increased with sediment available phosphorus (R2 = 0.84) in the northern half of the lake. This relationship is not as strong in the south due to a large flow of Gilgel Abay to the outlets. Water hyacinths were found where the lake was shallow and the available phosphorus was elevated. The large reservoir of sediment phosphorus will hamper any remedial efforts in removing the water hyacinths. [ABSTRACT FROM AUTHOR]

The sustainable development of water resources includes retaining some amount of the natural flow regime in water bodies to protect and maintain aquatic ecosystem health and the human livelihoods and wellbeing dependent upon them. Although assessment of environmental flows is now occurring globally, limited studies have been carried out in the Ethiopian highlands, especially studies to understand flow-ecological response relationships. This paper establishes a hydrological foundation of Gumara River from an ecological perspective. The data analysis followed three steps: first, determination of the current flow regime—flow indices and ecologically relevant flow regime; second, naturalization of the current flow regime—looking at how flow regime is changing; and, finally, an initial exploration of flow linkages with ecological processes. Flow data of Gumara River from 1973 to 2018 are used for the analysis. Monthly low flow occurred from December to June; the lowest being in March, with a median flow of 4.0 m3 s−1. Monthly high flow occurred from July to November; the highest being in August, with a median flow of 236 m3 s−1. 1-Day low flows decreased from 1.55 m3 s−1 in 1973 to 0.16 m3 s−1 in 2018, and 90-Day (seasonal) low flow decreased from 4.9 m3 s−1 in 1973 to 2.04 m3 s−1 in 2018. The Mann–Kendall trend test indicated that the decrease in low flow was significant for both durations at α = 0.05. A similar trend is indicated for both durations of high flow. The decrease in both low flows and high flows is attributed to the expansion of pump irrigation by 29 km2 and expansion of plantations, which resulted in an increase of NDVI from 0.25 in 2000 to 0.29 in 2019. In addition, an analysis of environmental flow components revealed that only four "large floods" appeared in the last 46 years; no "large flood" occurred after 1988. Lacking "large floods" which inundate floodplain wetlands has resulted in early disconnection of floodplain wetlands from the river and the lake; which has impacts on breeding and nursery habitat shrinkage for migratory fish species in Lake Tana. On the other hand, the extreme decrease in "low flow" components has impacts on predators, reducing their mobility and ability to access prey concentrated in smaller pools. These results serve as the hydrological foundation for continued studies in the Gumara catchment, with the eventual goal of quantifying environmental flow requirements. [ABSTRACT FROM AUTHOR]

Anthropogenic landscape conversion from forest to agricultural land affects baseflow. Baseflow is a source of potable water and can be used for the irrigation of high value crops. Finding ways to increase base and inter flow (i.e., groundwater flow) is, therefore, essential for the improvement of the livelihood of rural inhabitants. Therefore, the objective is to investigate the effect of landscape interventions on stream discharge and, in particular, on groundwater flow. The Tikur-Wuha experimental watershed in the upper reaches of the Blue Nile was selected because discharge data were available before and after implementation of a suite of land management practices that, among others, enhanced the percolation of water to below the rootzone. The parameter efficient distributed (PED) model was used to separate overland flow from total flow. The groundwater flow index (GWFI), defined as the quotient of the annual groundwater flow to the total stream discharge at the outlet of the watershed, was calculated. Our analysis with the PED model showed that at similar annual rainfall amounts, more baseflow and less surface runoff was generated after the landscape intervention, which promoted deep infiltration of the rainwater. The decrease in surface runoff shortly after the implementation of the land management practices is similar to observations in other watersheds in the Ethiopian highlands. [ABSTRACT FROM AUTHOR]

Planning and decision making for new irrigation development projects requires the systematic assessment of irrigable land together with available water resources. The data required are usually not available in developing countries, and therefore a method was developed for quantifying surface water resources and potentially irrigable land in ungauged watersheds in the Upper Blue Nile Basin using Soil and Water Assessment Tool (SWAT) model and Multi-Criterion Decision Evaluation (MCDE). The method was tested using the Lah river basin in the Jabitenan district and then applied in the whole area, including ungauged areas. In MCDE, soil type, slope, land use, and river proximity were considered. Onion, Cabbage and Tomato were grown on the identified irrigable areas. The predicted monthly stream discharge agreed well with observed values, with Nash and Sutcliffe efficiencies of 0.87 during calibration and 0.68 for validation. The SWAT model calibrated parameters from the gauged catchment were used to simulate the discharge of the ungauged catchments. The potential irrigable land was determined in Jabitenan woreda and included the Rivers like Birr, Tikurwuha, Gunagun, Leza Lah, Geray,Arara, Debolah, Guysa, and Silala, with an area of 460 km2. By evaluating gross irrigation demand of irrigable land with available flow in rivers (both observed and simulated), the actual surface irrigation potential was 47 km2. The main limitation for surface irrigation in all districts was the available water and not the land suitable for irrigation. Therefore, the study suggests that in order to irrigate a greater portion of the irrigable land, water should be stored during the monsoon rain phase for use in the last part of the dry phase. [ABSTRACT FROM AUTHOR]

In many developing countries and remote areas of important ecosystems, good quality precipitation data are neither available nor readily accessible. Satellite observations and processing algorithms are being extensively used to produce satellite rainfall products (SREs). Nevertheless, these products are prone to systematic errors and need extensive validation before to be usable for streamflow simulations. In this study, we investigated and corrected the bias of Multi-Sensor Precipitation Estimate–Geostationary (MPEG) data. The corrected MPEG dataset was used as input to a semi-distributed hydrological model Hydrologiska Byråns Vattenbalansavdelning (HBV) for simulation of discharge of the Gilgel Abay and Gumara watersheds in the Upper Blue Nile basin, Ethiopia. The result indicated that the MPEG satellite rainfall captured 81% and 78% of the gauged rainfall variability with a consistent bias of underestimating the gauged rainfall by 60%. A linear bias correction applied significantly reduced the bias while maintaining the coefficient of correlation. The simulated flow using bias corrected MPEG SRE resulted in a simulated flow comparable to the gauge rainfall for both watersheds. The study indicated the potential of MPEG SRE in water budget studies after applying a linear bias correction. [ABSTRACT FROM AUTHOR]

• Use of Berken plow and intercropping with pigeon pea improves soil characteristics. • Root penetration resistance increased with maize roots penetrating 1.2–1.5 times deeper. • Berken plow had the greatest available storage of 56 cm and smallest runoff in both years. • Increases in infiltration resulted in increased soil moisture retention up to 60 cm depth. • Increases in maize productivity resulted in a positive net benefit. Closing the yield gap and enhancing efficiency in rainfed maize production systems in Ethiopia requires urgent action in increasing the productivity of degraded agricultural land. The degradation of land through continuous compaction and decline in the organic matter has resulted in a wide-spread formation of a hardpan that restricts deep percolation, prevents plant root development, and, ultimately can lead to increased erosion. Studies exploring practical low-cost solutions to break the hardpan are limited in Ethiopia. The main objective was to evaluate soil mechanical (i.e. modified plow or Berken plow) or biological intervention (i.e. intercropping with pigeon pea) effectiveness to enhance soil water management and crop yield of rainfed maize systems whilst reducing soil erosion and runoff. Five farm fields, each including four plots with different tillage treatments, were monitored during two rainy seasons in 2016 and 2017. The treatments were: (i) farmers practice under conventional (CT) tillage; plots tilled three times using an oxen driven local plow Maresha , (ii) no-till (NT), (iii) Berken tillage (BT), plots tilled three times using an oxen pulled Berken plow, and (iv) biological (CT + Bio), tap-rooted pigeon pea intercropped with maize on plots conventionally tilled. Results showed that mean tillage depth was significantly deeper in the BT (28 cm) treatment compared to CT and CT + Bio (18 cm) treatments. Measured soil penetration resistance significantly decreased up to 40 cm depth under BT and maize roots reached 1.5 times deeper compared to roots measured in the CT treatment. Under BT, the estimated water storage in the root zone was estimated at 556 mm, 1.86 times higher compared to CT, 3.11 times higher compared to NT and 0.89 times higher compared to CT + Bio. The positive effects on increased water storage and root development resulted in an average increase in maize grain (i.e. 15%, 0.95 t ha−1) and residual above ground biomass (0.3%, 6.4 t ha−1) leading to a positive net benefit of 138 USD ha−1 for the BT treatment compared to the CT treatment. The negative net benefit obtained under CT and CT+Bio was mainly related to the high labor cost related to plowing, weeding, planting, and fertilizer application whilst in the NT this was related to the significantly lower maize yields. The positive effects in the BT treatment, and to some extent the CT+Bio treatment show great potential for smallholder rainfed maize systems where degraded soils with hardpans and high variability in rainfall prevail. [ABSTRACT FROM AUTHOR]

A nine-year (2010–2018) field study in the Debre Mawi watershed was conducted to understand the effect of governmentally-imposed and farmer-initiated conservation practices. The watershed is in the sub-humid Ethiopian Highlands which experience high and increasing erosion rates despite years of conservation efforts. Consequently, reservoirs are filling up with sediment and soil degradation is enhanced, calling for the evaluation of conservation practices currently in use. The few past long-term experimental studies on structural practices are inconclusive. In addition, only anecdotal information is available for streamflow and sediment loss. Precipitation, stream discharge, and suspended sediment concentrations were recorded manually in the Debre Mawi watershed during the nine-year period. Groundwater depth and total saturated area measurements were taken for selected periods. From 2012 to 2014, government-mandated conservation practices were constructed, which consisted of 50-cm-deep infiltration furrows with bunds downslope. These furrows were filled in with sediment by 2018. At the same time, the acreage of eucalyptus trees planted by farmers on the most vulnerable lands tripled to 5% of the total area with most trees fully grown in 2018. Runoff coefficients and sediment concentrations decreased steadily throughout the nine years. In the saturated bottomlands, the observations suggested that government-sponsored infiltration furrows in the saturated bottomlands were ineffective and may concentrate flows and enhance gully erosion, while eucalyptus trees appear effective. The results of this observational study point to both the potential benefits of conservation practices in this sub-humid tropical highland region and to emerging long-term risks. If structural conservation is to be pursued in watersheds like Debre Mawi, due attention must be given to the safe removal of excess water from the valley bottoms. The vegetative farmer-initiated practice of planting eucalyptus trees effectively reduced streamflow and erosion, but at the same time, might dry up wells during the dry monsoon phase which should be investigated further. Image 1 • Acreage of eucalyptus planted by farmers increased three-fold in nine years. • Observed runoff and sediment yield declined with increased acreage of eucalytus. • Dry phase eucalyptus evaporation delayed saturation excess runoff in rain phase. • Infiltration furrows were not maintained, filled up, and appeared ineffective. • Groundwater irrigation is feasible when lava dikes block subsurface downhill flow. [ABSTRACT FROM AUTHOR]

Land resources in developing countries are facing intense degradation due to deforestation and subsequent loss of organic matter from continuous tillage that causes soil erosion and gulley formation. The Ethiopian highlands are especially and severely affected. One of the land and water management practices to counteract this problem, fenced areas to prevent livestock access (called exclosures), has been in practice for the last few decades in the semi-arid highlands of Ethiopia but its effect on degraded landscapes has not been well researched -- especially in the sub-humid and humid highlands. The aim of this study is to evaluate the effects of exclosures on improving degraded landscapes in the sub-humid highlands. The research was carried out in the Ferenj Wuha watershed, in the northwestern sub-humid Ethiopian highlands, where land and water management practices were implemented starting in 2011. Vegetation was inventoried and aboveground biomass, carbon and nutrient stock determined for communal grazing land, exclosures and for other uses. In addition, soil samples were collected for nutrient analysis. Our results show that exclosures have a richer and more diverse set of plant species compared to communal grazing land. Establishment of an exclosure also enhanced organic carbon, total nitrogen and available phosphorus. Over a six-year period, aboveground biomass increased by 54 Mg ha−1 (or 81%) at the watershed scale because of the conversion of communal grazing land to exclosures. The improvement in soil nutrients due to exclosures, in turn, increased carbon and nutrient stock. The results support regeneration of degraded landscapes by restoring vegetation, soil fertility, carbon and nutrient stocks in the Northwestern highlands of Ethiopia. However, additional research is required to more accurately quantify these improvements because current research efforts that sample only the surface soils seem to indicate that the capacity of exclosures to increase soil carbon storage is decreasing when annual rainfall is increasing. Image 1 • Ethiopian Highlands are degraded due to continuous cultivation after deforestation. • Exclosures that keep cattle out, improve degraded soils. • Exclosures increase soil organic carbon and nitrogen but not available phosphorus. • Increasing rainfall decreases effectiveness of soil carbon storage in surface 20 cm of soil. • Exclosures should be sampled over entire rooting depth for proper evaluation. [ABSTRACT FROM AUTHOR]