Blue Nile Research Articles

Temporal Dynamics and Trend Analysis of Areal Rainfall in Muger Subwatershed, Upper Blue Nile, Ethiopia

This study was employed to investigate the temporal variability and trend analysis of areal rainfall in the Muger subwatershed, Upper Blue Nile, Ethiopia. The study was run over the following procedures to handle the main objective: (1) determining the areal rainfall from gauged point rainfall using the Thiessen polygon method, (2) grouping the months in the season according to the study area, (3) evaluating the temporal dynamics of annual and seasonal areal rainfall using the coefficient of variation (CV), standard anomaly index (SAI), and precipitation concentration index (PCI), and (4) analyzing the trend of annual and seasonal areal rainfall using modified Mann–Kendall’s (modifiedmk) test in RStudio. Based on the temporal variability analysis, CV results depict that annual and summer areal rainfall had low variability with values of 13.43% and 13.7%, respectively. Winter and spring areal rainfall shows high variation with a CV value of 50.5% and 36%, respectively. According to the SAI output, around 70% of the considered year was in the normal condition of wetness. On the other hand, the seasonal (winter, spring, and summer) rainfall distribution of the study area shows strong irregularity distribution throughout the considered years as a result of PCI with a value of 57.5%. The trend of the areal rainfall was shown to be both increasing and decreasing. However, the trend was insignificant with a 10% confidence level.

Effect of land use land cover change on stream flow in Azuari watershed of the Upper Blue Nile Basin, Ethiopia

Effect of land use land cover change on stream flow in Azuari watershed of the Upper Blue Nile Basin, Ethiopia

Operational analysis of lake Tana under climate change, Upper Blue Nile Basin, Ethiopia

The excessive abstraction of lake water affects its sustainability and is common in Lake Tana. Hence this study aims to develop operation rule curves for optimum operation of Lake Tana reservoir by considering the effects of small and large-scale irrigation water abstraction, Hydropower demand, and climate change. The data used in this study were produced by two Global Circulation Models (GCMs) (MIROC5 and MPI) under two Representative Concentration Pathways (RCP4.5 and RCP8.5) in the 2040s (2020–2049) and 2070s (2050–2079). For RCP4.5 and RCP 8.5 scenarios of the 2040s- and 2070s-time domains, lake temperature exhibits an upward trend. The lake rainfall also will show an increase for the 2040s and 2070s under both RCP scenarios. The outcome showed that in all future scenarios, lake evaporation under RCP4.5 of 2040s and 2070s rise between 3.6 % to 7 % and 4.6 % to 19, respectively, while for RCP8.5 of 2040s and 2070s increases between 4.6 % to 9.9 % and 9.2 % to 24.7 %. The surface water inflow increased for RCP4.5 (2070s) and RCP8.5 (2040s), whereas it declined for RCP4.5 (the 2040s) and RCP8.5 (2070s. Under both scenarios, the average value of the time-based and volumetric reliability in the 2040s and 2070s is less than 80 %. The reservoir will take a very long time to recover from the shortfall as the resilience levels are below 50 %. Additionally, the dimensionless vulnerability was less than 50 %, indicating that there won't be a shortage of inflow to meet demand at the reservoir. Based on evaluation, the reservoir will not probably perform well in any way because of the rise in upstream abstractions. To guide the operation of the reservoir, operation rule curves were developed using the Hec-ResSim model. Generally, the government, decisions, and policymakers should set a water resources management plan not trigger normal functioning of the Lake system.

Physical and chemical features of hydro-geologically connected wetlands in the Abbay River basin, Ethiopia

Physico-chemical water quality assessment is vital for wetland characterization, detecting environmental stress affecting the ecosystem and wetland management interventions. Therefore, this study aimed at comprehensive analysis of water quality parameters of six hydro-geologically connected wetlands in West Gojjam zone, Amhara region, Ethiopia. Water quality data was collected for one year (from June 2022 to April 2023) during four sampling seasons (pre-rainy, main-rainy, post-rainy and dry seasons) from twelve purposively selected sampling sites. In-situ measurements and nutrient analysis were carried out following standard procedures. Water quality index (WQI) was also computed by the weighted arithmetic water quality index method (WAWQI) based on selected parameters. Phosphate ranged from 0.24 mg/l (Kurt Bahir) to 1.80 mg/l (Zindib) and nitrate ranged from 2.12 mg/l (at Gudera) to 3.25 mg/l (at Geray). This increased nutrient concentration and the decreasing trend in DO level clearly indicates their ecological degradation. There was a statistically significant difference (P < 0.05, One-way ANOVA) in the mean measurements of some of the parameters among the study wetlands and among the study seasons. The PCA also clearly shows the most influential variables responsible for the variation among the wetlands. The study concluded that the wetlands water quality has been degraded. Therefore, regular water quality monitoring is recommended to reduce further deterioration.

Alterations in Hydrological Responses under Changing Climate and Land Use/Land Cover across Contrasting Agroecological Environments: A Case Study on the Chemoga Watershed in the Upper Blue Nile Basin, Ethiopia

We analyzed hydrological responses to changing climate and land use/land cover (LULC) for the past (1985–2020) and future (2021–2080) in the Chemoga watershed of the Upper Blue Nile Basin. The watershed comprises four agroecological environments: Moist Kolla, Moist Weyna Dega, Moist Dega, and Wet Wurch. Past and projected LULC changes under business-as-usual (BAU) and land conservation (LC) scenarios were utilized. Climate projections from 2021 to 2080, under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), were downscaled from Global Climate Models. Utilizing the Soil and Water Analysis Tool, we assessed impacts on mean annual surface runoff (SR) and evapotranspiration (ET). Maximum and minimum temperatures increased significantly in the past and future climate scenarios, with a significant rainfall increase observed under SSP5-8.5. Historical trends revealed a 16.6% increase in SR and 7% in ET from 1983–2002 to 2003–2020. Under BAU LULC with the SSP2-4.5 (SSP5-8.5) climate scenario, SR increased by 24% (26.1%) and ET by 3.1% (4.4%) from 2003–2020 to 2021–2050, followed by a subsequent SR rise of 13.7% (14.0%) and ET increase of 6.0% (5.7%) from 2021–2050 to 2051–2080. Conversely, the LC LULC with SSP2-4.5 (SSP5-8.5) resulted in a 5.3% (4.2%) SR decrease and ET increase of 9.7% (11.3%) from 2003–2020 to 2021–2050 and a further SR decrease of 1% (0.7%) and 6.1% (6.9%) ET increase from 2021–2050 to 2051–2080. The Moist Kolla agroecology experienced the highest SR increase due to vegetation clearances for commercial farming. Meanwhile, the LC scenario indicated substantial decreases in SR and marginal increases in ET in the Moist Weyna Dega agroecology due to forest restoration on steep slopes. Overall, SR showed greater sensitivity to LULC changes, while ET was more responsive to climate changes. The results emphasize considering diverse agroecological contexts for effective water resource management under changing climate and LULC scenarios.

Review on Epidemiology and Economic Impact of Tsetse Transmitted Bovine Trypanosomiasis in Ethiopia

Most vector-borne human diseases worldwide are spread by arthropod disease vectors, including mosquitoes, ticks, tsetse flies, and sandflies, which are greatly impacted by environmental factors. The tsetse-transmitted animal Trypanosomiasis severely hampers animal production and agricultural development in Ethiopia. The southern portion of the Rift Valley, the southwest corner of the nation, the western lowlands and escarpments, and the Blue Nile are the only areas in Ethiopia where tsetse flies are found. These areas are limited to longitudes 33° and 38° E and latitudes 5° and 12° N. The three Trypanosoma species that have the most impact on cattle in Ethiopia are Trypanosoma brucei, Trypanosoma vivax, and Trypanosoma congolense. Particularly in the "tsetse belt," which includes the Omo, Borena, and Metekel zones of the Benishangul Gumuz region, the illness is extensively spread throughout the western and southwest regions of the nation. Ethiopia’s main river systems, including the Abay/Didessa, Omo/Gibe, Baro/Akobo, and southern Rift Valley, are linked to the prevalence of tsetse fly infestations and the Trypanosomiasis they cause. Mixed livestock and crop production is the major farming style in Ethiopia’s highlands and plays a crucial role in agricultural activity. The bioclimatic threshold for tsetse flies in Ethiopia has not been met. Since it has long been typical for the peasantry in general and livestock owners, in particular, to avoid tsetse-infested areas to reduce their chance of contracting Trypanosomiasis, the impact of tsetse-borne Trypanosomiasis on development efforts in rural Ethiopia is becoming increasingly significant. This review examines the economic impact and epidemiology of tsetse-transmitted bovine trypanosomiasis in Ethiopia.

Composition and seasonality of rodent diet in Chimit Kola, Blue Nile Gorge, Ethiopia

A study on the composition and seasonality of rodent diet was carried out during 2020–2022 years in Chimit Kola to determine the type, relative proportion and seasonality of food items consumed. A total of 166 stomach contents that belong to six rodent species (Mastomys awashensis, Acomys louisae, Arvicanthis raffertyi, Lophuromys simensis, Gerbilliscus sp. and Lemniscomys macculus) were investigated. Parametric and non-parametric analyses of variance were used to test the difference. Leaves and stems, seeds, invertebrates, fruits and unidentified food matters were the food items identified in the stomach contents of rodents. There was a significant variation in food items consumed among rodent species. Arvicanthis raffertyi and L. macculus consumed more leaves and stems whereas L. simensis, A. louisae and Gerbilliscus sp. mostly fed on invertebrates. Mastomys awashensis consumed relatively more seeds (30%) than any other rodent species (ranging from 14 to 28%). Acomys louisae, L. simensis and Gerbilliscus sp. consumed more leaves and stems during the dry season and invertebrates during the wet season. Similarly, A. raffertyi consumed more leaves and stems during the wet season and seeds during the dry season. However, the diet of M. awashensis and L. macculus and some food items (fruits and unidentified food matters) of most rodent species were similar between seasons. Mastomys awashensis significantly consumed a higher proportion of seeds in the fallowland (44%) than in other habitats (ranging from 19 to 31%). Similarly, A. louisae and L. macculus consumed a significantly higher proportion of invertebrates in bushland (53%) and riverine forests (48%) than in other habitats (ranging from 16 to 47%), respectively. The present finding concluded that these rodent species are diet generalists, feeding on a variety of available resources depending on seasons and habitats. The study documents the diet composition of these rodent species for the first time. Thus, the management and conservation of these rodents should be in consideration of their feeding habits and factors that influence their diets.

Smallholder farmers' vulnerability to climate change and variability: Evidence from three agroecologies in the Upper Blue Nile, Ethiopia

This study delves into the profound impact of climate change on agriculture in Ethiopia, particularly the vulnerabilities faced by smallholder farmers and the resulting implications for poverty. Focusing on three distinct agroecologies, namely: highland, midland, and lowland zones. The study employed a robust methodology, combining a cross-sectional survey, spatial-temporal trend analysis using GIS, and the development of an overall vulnerability index through the balanced weighted average method. The study, encompassing 646 households, combines data from a variety of sources and analytical tools like the vulnerability index, ArcGIS 10.8, and ERDA's IMAGINE 2015. Utilizing the LVI-IPCC scale, the study shows that climate change is an immediate vulnerability in all agroecological zones. It identifies highland areas as the most sensitive and exposed regions, while lowland households are found to be the most vulnerable in terms of overall vulnerabilities. The research reveals specific challenges faced by communities, such as inadequate health facilities and insufficient food and water supplies in both highland and lowland agroecosystems. Additionally, our investigation has observed a significant alteration in land use practices, specifically the shift from communal grazing land to private cultivation and plantations, emphasizing eucalyptus. This alteration enhances the ecosystem's vulnerability to climate disturbances. The study suggests targeted interventions, such as advocating for sustainable land-use practices, afforestation, and adopting climate-smart agriculture practices. It is important to implement policy measures that prioritize conserving and restoring shrubland, grazing land, and natural forests to ensure both long-term socio-economic and ecosystem resilience. The study's nuanced insights are instrumental in understanding the diverse challenges posed by climate change in Ethiopian agriculture, supporting informed policymaking and sustainable interventions.

Comparative transcriptomic and epigenomic analyses to identify the cold resistance-associated genes and disclose the regulatory mechanisms in tilapias

Dissecting the genetic basis of cold resistance in fish has great theoretic and economic significance. Despite large numbers of cold-responsive genes have been identified from the tilapia tissues, the core cold resistance-associated genes (CRAGs) and their regulatory mechanisms remain to be explored. In this study, the blue tilapia (BT, Oreochromis aureus) and Nile tilapia (NT, O. niloticus) were exposed to a gradually intensified cold stress. Brain samples were collected from the fish during cold exposure and subjected to total RNA isolation. Isoform sequencing was performed using the pooled total RNA samples of each species to improve the transcriptome assemblies. Gene expression profiles upon cold exposure was characterized by RNA sequencing (RNA-seq). The core CRAGs were identified by a comparative analysis for the transcriptomic data represented here and that of zebrafish (Danio rerio) in one previous study. A total of 513 core CRAGs were identified, which demonstrated consistent cold-induced expression among BT, NT and zebrafish. The genes underwent cold-induced alternative splicing at each time point were also identified and compared with the corresponding differentially expressed genes. The samples matched to those for RNA-seq were subjected to assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) to profile the chromatin accessibility dynamics. The genes associated with at least one open chromatin region (OCR) had significantly higher transcriptional abundance than those without an OCR. ATF3, FOS::JUN dimer and JDP2 were among the top transcription factors (TFs) that may play crucial roles in regulating the cold-elicited transcriptional responses. Furthermore, the genetic variations between BT and NT were mined from the RNA-seq and ATAC-seq reads and mapped to the TF binding sites and splicing regions. The function of a G/A variant in regulating the cold-induced alternative splicing of the dennd5a gene was confirmed by a minigene splicing assay. Our data provide new insights into the genetic mechanisms determining cold resistance of tilapias and are meaningful for the breeding of cold-tolerant tilapia varieties.

Effect of Eucalyptus globulus Plantations on Soil Physicochemical Properties in the Upper Blue Nile, Ethiopia

In recent years, there has been a substantial conversion of croplands and grasslands to short rotation Eucalyptus globulus plantations in the northern highlands of Ethiopia. This has raised concerns among researchers, policymakers, and environmentalists regarding potential adverse effects on soil fertility. To address these concerns, a study was conducted to evaluate the impact of Eucalyptus globulus plantations on selected soil physicochemical properties in the region. The study involved four land-use types, comprising two age groups of Eucalyptus globulus plantations (4-year-old and 9-year-old), as well as areas designated for grasslands and croplands. Soil sampling was carried out in 10 m × 10 m subplots within each experimental plot, and standard methods were employed for soil analysis. The soil laboratory results were statistically analyzed using Two-way ANOVA and Pearson’s correlation coefficients in R software version 4.1.0. The findings revealed significant variations (p&lt;0.05) in soil bulk density, soil organic carbon, and soil pH between the 4-year-old and 9-year-old Eucalyptus globulus plantations and the grasslands. A notable difference (p&lt;0.05) in exchangeable acidity was observed between the 4-year-old and 9-year-old E. globulus plantations, with the latter exhibiting the highest mean exchangeable acidity (6.20 ± 0.76). However, no significant differences (p&lt;0.05) were observed between the Eucalyptus plantations and the grasslands in available phosphorus (Av.P), exchangeable calcium (Ca2+), sodium (Na+), and magnesium (Mg2+) concentrations, as well as cation exchange capacity (CEC). The study results has, therefore, implied that Eucalyptus globulus plantations induced changes in specific soil properties with varying stand ages in the study area. Nonetheless, it was emphasized that further long-term research is necessary to comprehend the effects of these plantations on soil properties.

Scenario-Based Land Use and Land Cover Change Detection and Prediction Using the Cellular Automata–Markov Model in the Gumara Watershed, Upper Blue Nile Basin, Ethiopia

Land use and land cover (LULC) change detection and prediction studies are crucial for supporting sustainable watershed planning and management. Hence, this study aimed to detect historical LULC changes from 1985 to 2019 and predict future changes for 2035 (near future) and 2065 (far future) in the Gumara watershed, Upper Blue Nile (UBN) Basin, Ethiopia. LULC classification for the years 1985, 2000, 2010, and 2019 was performed using Landsat images along with vegetation indices and topographic factors. The random forest (RF) machine learning algorithm built into the cloud-based platform Google Earth Engine (GEE) was used for classification. The results of the classification accuracy assessment indicated perfect agreement between the classified maps and the validation dataset, with kappa coefficients (K) of 0.92, 0.94, 0.90, and 0.88 for the LULC maps of 1985, 2000, 2010, and 2019, respectively. Based on the classified maps, cultivated land and settlement increased from 58.60 to 83.08% and 0.06 to 0.18%, respectively, from 1985 to 2019 at the expense of decreasing forest, shrubland and grassland. Future LULC prediction was performed using the cellular automata–Markov (CA–Markov) model under (1) the business-as-usual (BAU) scenario, which is based on the current trend of socioeconomic development, and (2) the governance (GOV) scenario, which is based on the Green Legacy Initiative (GLI) program of Ethiopia. Under the BAU scenario, significant expansions of cultivated land and settlement were predicted from 83.08 to 89.01% and 0.18 to 0.83%, respectively, from 2019 to 2065. Conversely, under the GOV scenario, the increase in forest area was predicted to increase from 2.59% (2019) to 4.71% (2065). For this reason, this study recommends following the GOV scenario to prevent flooding and soil degradation in the Gumara watershed. Finally, the results of this study provide information for government policymakers, land use planners, and watershed managers to develop sustainable land use management plans and policies.

Media, Communication, and the Water Security Crisis

Abstract The Middle East region is facing several problems related to local issues, including the Blue Nile Dam crisis that threatens Egypt’s water security. The crisis arose when Ethiopia announced its intention to build a dam on the Blue Nile for economic purposes. Despite ongoing negotiations between Egypt and Ethiopia, the dispute has escalated in the past three years and the parties have failed to reach an agreement. The media has played an active role in highlighting the positions of the parties to the Blue Nile Dam crisis. This article focuses on monitoring and analyzing the media discourse about the Blue Nile Dam crisis in the Egyptian, Sudanese, and Ethiopian press and the interpretation of its trends in light of its connection with what the media discourse presents to countries in the surrounding political and media context.

Integrated approach for groundwater potential exploration in Abbay River Basin, East Africa

This paper presents and examines groundwater potential zones with the help of remote sensing and GIS methods for controlling and investigating the geospatial data of each parameter. Groundwater is a very important source for water supply and others, considering its availability, quality, cost, and time-effectiveness to develop. It is virtually everywhere and yet variable in quantity. Because of several conditions, such as rapid population growth, urbanization, industrialization, and agricultural development, groundwater sources are under severe threat. Climate change plays an important role in the quality and quantity of groundwater potential. In addition, climate change severely affects parameters that influence groundwater recharge. Unreliable exploitation and poor quality of surface water resources tend to increase the decline in groundwater levels. Hence, it is necessary to identify groundwater potential zones that can be used to optimize and monitor groundwater resources. This study was conducted in the Abbay River Basin and identifies the location of groundwater potential for developing new supplies that could be used for a range of purposes in the study area, where groundwater serves as the main source for agricultural purposes rather than surface water. Seven selected parameters—lineament density, precipitation, geology, drainage density, land use, slope, and soil data—were collected, processed, resampled, projected, and reclassified for hydrological analysis. For the generation of groundwater zones, weightage was calculated using an analytical hierarchy method, reclassified, ranked, and overlaid with GIS. The obtained results of weightage were lineament density (37%), precipitation (30%), geology (14%), drainage density (7%), land use land cover (5%), slope (4%), and soil (3%). The consistency ratio estimated for this study was 0.089, which was acceptable for further analysis. Based on the integration of all thematic layers and the generated groundwater potential zones, the map was reclassified into five different classes, namely very good, good, moderate, poor, and very poor. The results of this study reveal that 1295.33 km2 of the study area can be considered very poor, 58,913.1 km2 is poor, 131,323 km2 is moderate, 18,557 km2 is good, and 311.5 km2 is very good. Any groundwater management project performed in the better regions would offer the greatest value. A similar study would be valuable before planning any water resource development activity, as this would save the expense of comprehensive field investigations. This study also demonstrates the importance of remote sensing and GIS techniques in mapping groundwater potential at the basin scale and suggests that similar methods could be applied across other river basins.

Drought Dynamics in the Nile River Basin: Meteorological, Agricultural, and Groundwater Drought Propagation

The Nile River Basin (NRB) has experienced a notable rise in drought episodes in recent decades. The propagation of meteorological, agricultural, and groundwater drought dynamics in the NRB was investigated in this study. The following drought indices examined the correlation and propagation among meteorological, agricultural, and groundwater droughts. These are the standardized precipitation evapotranspiration index (SPEI), soil moisture index, Gravity Recovery and Climate Experiment, and GRACE Follow-On (GRACE/GRACE-FO)-derived groundwater drought index (GGDI). These droughts were comprehensively evaluated in the NRB from 2003 to 2022. The cross-wavelet transform approach highlighted the links between droughts. The following are the key findings: (1) In the NRB, the cross-wavelet energy spectrum of wavelet coherence can indicate the internal connection between meteorological versus (vs.) agricultural and agricultural versus (vs.) groundwater drought. The time scale with the most significant correlation coefficient is the drought propagation time. (2) The El Niño–Southern Oscillation (ENSO) correlated with agricultural and groundwater drought much more than the Indian Ocean Dipole (IOD), demonstrating that ENSO has an important impact on drought advancement. (3) The R2 values were 0.68 for GGDI vs. standardized soil moisture index (SSI), 0.71 for Blue Nile Region (BNR) GGDI vs. SSI, and 0.55 for SSI vs. Standardized Precipitation Evapotranspiration Index (SPEI). Similarly, in the Lake Victoria Region (LVR), GGDI vs. SSI was 0.51 and SSI vs. SPEI was 0.55, but in the Bahr-el-Ghazal Region (BER), GGDI vs. SSI was 0.61 and SSI vs. SPEI was 0.27 during the whole research period with varied lag durations ranging from 1 to 6 months. Thus, the propagation of drought (i.e., meteorological, agricultural, and groundwater drought) dynamics has the potential to reshape our understanding of drought evolution, which could lead to early drought forecasting across the NRB and similar climatic regions.

Trade-off and synergy analysis between hydropower generation and irrigation development in the Abbay River Basin, Ethiopia

Study region: Abbay River Basin, EthiopiaStudy Focus: This research focused on evaluating the trade-off and synergy between hydropower and irrigation under various development scenarios. The hydro-economic analysis was undertaken to provide insight regarding the benefits received from hydropower and irrigation development scenarios. New hydrological insights for the regionThe research demonstrated the holistic development of water resources for both energy generation and irrigation purposes, thereby maximizing economic benefits while ensuring sustainable water resource management. HEC-ResSim model was found to be adequate for evaluating the power generating capacity of multiple hydropower cascade systems under various irrigation water diversion scenarios. The findings revealed that by focusing solely on hydropower projects without incorporating irrigation development, Abbay river basin would generate up to 38 TWh of annual energy from GERD, Karadobi, Bekoabo and Mandaya cascades, with GERD accounting for 39% of the total output. Under full integration of irrigation development with four hydropower cascades, annual system energy generation was reduced by 12%. Despite the trade-off, the hydro-economic analysis revealed that the combined benefit from hydropower and irrigation surpass the benefits derived exclusively from hydropower only. Under full irrigation development the combined benefit exceeded the benefit obtained solely from four cascade hydropower without irrigation by 94%. The result revealed that simultaneous development of hydropower and irrigation is advisable, rather than prioritizing hydropower projects exclusively over Abbay river basin.

Comparison of Google Earth Engine Machine Learning Algorithms for Mapping Smallholder Irrigated Areas in a Mountainous Watershed, Upper Blue Nile Basin, Ethiopia

Comparison of Google Earth Engine Machine Learning Algorithms for Mapping Smallholder Irrigated Areas in a Mountainous Watershed, Upper Blue Nile Basin, Ethiopia

Impacts of the Grand Ethiopian Renaissance Dam on the Nile River’s downstream reservoirs

The Nile River Basin’s (NRB’s) water resources are vulnerable to hydrologic alteration projects. Construction of the Grand Ethiopian Renaissance Dam (GERD), a hydroelectric power project on the Blue Nile, is expected to improve living standards in Ethiopia and contribute to the country's sustainable development. However, the effects of the GERD on water resources of downstream countries (Sudan and Egypt) have been a source of concern. In this study, eight types of remote sensing data and products were used to assess the impacts of the GERD reservoir’s filling process on Ethiopia’s, Sudan’s, and Egypt’s surface water resources. Specifically, spatiotemporal variability in surface area, volume, rainfall, and water storage for five reservoirs located in Ethiopia (GERD), Sudan (Roseires and Merowe), and Egypt (Lake Nasser and Toshka) for the period 2013–2022 were examined. Results indicate that (1) the GERD reservoir’s three filling phases started in July 2020, July 2021, and August 2022, respectively, (2) at the onset of these three phases, the GERD reservoir covered an area (volume) of 110 ± 7 km2 (1.87 ± 0.07 km3), 233 ± 31 km2 (4.30 ± 0.48 km3), and 544 ± 126 km2 (11.79 ± 2.18 km3), respectively, (3) a reduction in the GERD reservoir’s area (24–49 %) observed at the end of the first two fillings is attributed to enhanced infiltration and evaporation rates at the GERD site, (4) no significant changes were observed in the Roseires and Merowe reservoir’s surface areas, although both Nasser and Toshka reservoirs saw a slight increase in surface area during the investigated period, (5) the observed increase in water storage over the five reservoirs is attributed mainly to increased rainfall rates (6–10 %) and heavy flooding during the GERD filling period, and (6) if the GERD filling continues at the similar rates for an additional four years during drought periods, Egypt's Nile water allocation might be reduced by 35.47 ± 2.29 % (16.57 ± 1.07 km3), which could translate into an agricultural land loss of 33.14 ± 1.81 % each year. This study emphasizes the critical need for Ethiopia, Sudan, and Egypt to work together to effectively and equitably manage the water resources of the NRB.

Historical climate impact attribution of changes in river flow and sediment loads at selected gauging stations in the Nile basin

The Nile basin is the second largest basin in Africa and one of the regions experiencing high climatic diversity with variability of precipitation and deteriorating water resources. As climate change is affecting most of the hydroclimatic variables across the world, this study assesses whether historical changes in river flow and sediment loads at selected gauges in the Nile basin can be attributed to climate change. An impact attribution approach is employed by constraining a process-based model with a set of factual and counterfactual climate forcing data for 69 years (1951–2019), from the impact attribution setup of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3a). To quantify the role of climate change, we use the non-parametric Mann-Kendall test to identify trends and calculate the differences in long-term mean annual river flow and sediment load simulations between a model setup using factual and counterfactual climate forcing data. Results for selected river stations in the Lake Victoria basin show reasonable evidence of a long-term historical increase in river flows (two stations) and sediment load (one station), largely attributed to changes in climate. In contrast, within the Blue Nile and Main Nile basins, there is a slight decrease of river flows at four selected stations under factual climate, which can be attributed to climate change, but no significant changes in sediment load (one station). These findings show spatial differences in the impacts of climate change on river flows and sediment load in the study area for the historical period.

Modeling the impact of land use land cover change on the estimation of soil loss and sediment export using InVEST model at the Rib watershed of Upper Blue Nile Basin, Ethiopia

Information on soil loss and sediment export is essential to identify vulnerable area of soil erosion and to inform conservation interventions in a given watershed. The goal of this study was to analyze the changes in soil loss and sediment exports in the Rib watershed of Ethiopia's Upper Blue Nile Basin. The study used spatial data by using a variety of data sources, including topographic maps, soil maps, meteorological data, and satellite images. Cultivated land, forests, grazing areas, shrubs, water bodies, and settlements were all identified in the study watershed. Soil loss and sediment export were calculated using the Integrated Valuation of Ecosystem Services and Tradeoff (In-VEST) model. The model was calibrated using the sediment yield data gathered in the sample watersheds. The results reveal that while the equivalent sediment export grew from 6.54 t/ha/year to 11.05 t/ha/year in 2000 and 2020, respectively, the average soil loss increased from 22.37 t/ha/year in 2000 to 33.38 t/ha/year in 2020. The largest rate of soil erosion was seen on cultivated land, which increased from 40.86 t/ha/year in 2000 to 53.9 t/ha/year in 2020. This relates to the expansion of the agricultural land. The soil loss and sediment export rates in sub-watersheds three (SW-3) and five (SW-5) were the highest, at 61.80 and 63.48 t/ha/year and 18.75 and 19.35 t/ha/year, respectively. The least amount of soil loss occurs in sub-watershed twelve (SW-12) (2.56 t/ha/year). This is because SW-12 is situated in the watershed's lower reaches fogera plain parts of the watershed experiencing less erosion. The result concluded that prioritizing those sub-watersheds is important for informed decision-making processes.

Agroecology-based land use/land cover change detection, prediction and its implications for land degradation: A case study in the Upper Blue Nile Basin

This study examined land use/land cover (LULC) changes in Chemoga watershed of the Upper Blue Nile Basin, comprising four distinct agroecological regions: Wet Wurch, Moist Dega, Moist Weyna Dega, and Moist Kolla. We used multi-temporal Landsat images from 1985 to 2020, a hybrid classification method and the Cellular Automata-Markov model to analyze historical and predict future (2020–2060) LULC changes under business-as-usual (BAU) and land conservation (LC) scenarios. Magnitudes and patterns of spaciotemporal LULC changes were analyzed using intensity analysis. Cropland expanded across all agroecologies from 1985 to 2020, with Moist Kolla experiencing the highest increase at the expense of woodland, due the introduction of commercial farming to this hotter, less populated and inaccessible area. Moist Dega exhibited the highest allocation changes within cropland and forest, attributable to farmers’ adoption of rotational land use to rehabilitate extensively degraded cultivated lands. Under the BAU scenario, projections suggest further cropland expansion at expense of woodland in Moist Kolla and built-up areas at the expense of cropland and grassland in Moist Dega. Under the LC scenario, forest cover is expected to increase at the expense of cropland across all agroecologies. The historical and projected BAU LULC change scenario substantially increased soil erosion and reduced ecosystem services. These effects can be minimized if LC scenario is properly implemented. The agroecology-based LULC intensity analysis reveals local drivers of change and associated impacts, providing vital insights for targeted land use planning in this study watershed and other watersheds facing similar challenges.