ABSTRACT
Climate change poses significant challenges to water resources and streamflow in Ethiopia, a country highly dependent on agriculture and vulnerable to environmental shifts. This paper reviews the current state of knowledge on climate change impacts on streamflow in Ethiopia, emphasizing factors driving these changes and drawing insights from relevant studies. The analysis encompasses hydrological responses to climate change, including alterations in precipitation patterns, temperature fluctuations, and changes in water availability. Additionally, the study examines the impact of land use changes on streamflow dynamics. Comparative insights from neighboring countries and river basins further illuminate the broader regional implications of climate change on water resources. According to the previous research reviewed in this paper, climate change, land use change, and increment in extreme events (drought) have affected the stream flow over the last decades. The findings underscore the urgent need for adaptive strategies and sustainable water management practices to mitigate the adverse effects of climate change on streamflow and ensure water security in Ethiopia and beyond.
HIGHLIGHTS
The review paper provides localized insights into climate change impacts.
It contributes valuable information for water resource managers and policymakers.
It assesses the risks posed by climate change to Ethiopia's hydro-meteorological conditions.
It explores the socioeconomic consequences of hydro-meteorological changes induced by climate change.
The review contributes to the scientific knowledge base.
INTRODUCTION
Climate change is a global phenomenon that affects various aspects of the environment, including stream flow. The impact is higher in low-income countries like Ethiopia (Bezu 2020). Ethiopia is one of the countries that is highly vulnerable to the impacts of climate change due to its dependence on agriculture and limited water resources. Climate change has become a significant challenge for Ethiopia, as the country is experiencing a variety of impacts, including changes in precipitation patterns, increasing temperatures, and a reduction in water availability (Kuma 2012; Tadese et al. 2019b; Mengistu et al. 2021; Tigabu et al. 2021). These changes are having a significant impact on the country's water resources, particularly its streams and rivers (Daba & You 2020; Getahun et al. 2020). The impact of climate change on stream flow in Ethiopia is not limited to the reduction in water availability but also includes an increase in the frequency and intensity of extreme weather events such as floods and droughts (Getahun et al. 2020; Orke & Li 2022; Tareke & Awoke 2022; Tareke & Awoke 2023). This led to significant economic and social impacts, including crop failure, displacement, and loss of life and property. Climate change is having a significant impact on streamflow in Ethiopia, and this is a major concern for both the country's economy and the well-being of its people (Gelete et al. 2020; Gonfa et al. 2022). Ethiopia is heavily reliant on its rivers for irrigation, hydroelectric power, and drinking water, so any changes in the stream flow can have far-reaching consequences. Climate change can alter the spatial and temporal availability of water resources (Melaku Melese 2016). As a result, the hydrological processes and the ecosystem functions are altered (Getahun et al. 2020).
The purpose of this review is to examine the current state of knowledge on climate change impacts on stream flow in Ethiopia, focusing on the factors driving these changes, and drawing on relevant studies and reports.
HYDROLOGICAL RESPONSE TO CLIMATE CHANGE IMPACT IN ETHIOPIA
Climate change on stream flow in Ethiopia
Climate change is having a significant impact on stream flow in Ethiopia. As indicated by Roth et al. (2018), the projected temperature and precipitation changes, in turn, have noticeable impacts on modeled streamflows. Several studies have examined the impacts of climate change on stream flow in the country, and the findings are consistent. The following are some of the impacts of climate change on stream flow in Ethiopia:
- 1.
Mengistu et al. (2021) and Roth et al. (2018) studied the impact of climate change on the stream flow of the Upper Blue Nile River Basin in Ethiopia. They found that under future climate scenarios, stream flow is likely to decrease significantly, which could have significant impacts on water availability for agriculture and hydropower production. They conclude that by the end of the 21st century, annual precipitation in the basin is projected to decrease by up to −10.8% under RCP4.5 and −19.0% under RCP8.5 scenarios, and PET is estimated to increase by up to 27.1% compared to the 1981–2010 baseline period mainly due to the projected temperature increase.
- 2.
Daba & You (2020) and Tadese et al. (2019b) analyzed the impact of climate change on the stream flow of the Awash River Basin in Ethiopia. They found that annual stream flow is likely to decrease which could have significant impacts on water availability for irrigation, hydropower generation, and other uses. However, the declining trend might be related to irrigation expansion in the Upper and Middle Awash, improper water abstraction and poor water management, climatic factors, and environmental changes in the basin.
- 3.
Anose et al. (2022) studied the substantial warming and erratic rainfall that has made the Omo-Ghibe River Basin vulnerable to drought events. They conclude that the observed drought intensity can increase the water deficit and other natural resources degradation which could have significant impacts on water availability for irrigation, hydropower generation, and ecosystem services.
- 4.
Tigabu et al. (2021) analyzed the impact of climate change on the groundwater contribution to the streamflow of the Tekeze River Basin in Ethiopia. They found that declines in groundwater contribution to streamflow will be higher in lowland portions which could have significant impacts on water availability for agriculture, hydropower generation, and other uses.
In addition, some of the impacts of climate impact on the stream flow are summarized in Table 1. For example, a recent study by Assfaw et al. (2023) showed that yearly mean rainfall (streamflow) in the Kessem watershed (Awash Sub-basin) is anticipated to increase by 12.5 and 48.8% in the 2040s and 2070s, under the SSP5-8.5 emissions scenario, respectively.
Previous studies of the impact of climate change on stream flow in Ethiopia
Study catchments . | Location . | Area (km2) . | Study period . | Model used . | Major flow change within the study period . | References . |
---|---|---|---|---|---|---|
Kessem watershed | Middle Awash Sub-Basin | 2,908.4 | 1992–2020 and 2031–2090 | SWAT | Streamflow increases by 12.5 and 48.8% in the 2040s and 2070s, respectively, under the SSP5-8.5 emission scenario. | Assfaw et al. (2023) |
Rift Valley Lakes Basin | Rift Valley Lakes Basin | 55,050 | 1981–2018 | SWAT + | Surface runoff, lateral flow, and percolation differed over the basin by 7.8 to 13.14%, −4.47 to −16.51%, and −3.28 to −10.19%, respectively. | Ayalew et al. (2023) |
Mojo catchment | Awash Basin | 1,601.84 | 1985–2005 and 2006–2080 | CMIP5 | Drought variability of up to −3.7 mm was observed during RCP8.5, indicating a 22% risk of drought occurring in the watershed in the distant future. | Alemu et al. (2023) |
Awash Basin | Awash Basin | 112,000 | 1986–2005 and two future scenarios (2050 and 2070s) | GRCM | A decrease in precipitation in 4 months (February/March to May), with a rate of 34.7% under RCP8.5 and a maximum temperature increase of 3.4 and 4.1 °C in the 2050s and 2070s, respectively, under RCP8.5. | Tadese et al. (2019a) |
Katar and Meki watersheds | Rift Valley Basin | – | 1997–2017 and 2021–2080 | SWAT | Annual water yields in the Katar and Meki sub-basins will increase by 0.38–57.1% and 6.57–49.9%, respectively. | Balcha et al. (2023) |
Deme watershed, | Omo-Gibe Basin | 1,287.9 | 1989–2010 and 2031–2070 | SWAT | Under the RCP8.5 scenario, surface runoff will decrease by 15.10%, groundwater by 14.78%, and total water yield by 26.10% between 2031 and 2050. | Daniel (2023) |
Guder Catchment, | Upper Abbay Basin | – | 1986–2016 | SWAT | Under RCP 8.5, the precipitation and temperature will decrease by up to 14.4% and +4.4 °C, respectively, in the period from 2057 to 2086, and total water yield from 2024 to 2086 may be reduced by 3.2 mm per year. | Gemechu et al. (2021) |
Upper Wabe Bridge watershed | Wabe Shebele Basin | 202,220 | Mean seasonal streamflow decreases in the Belg (short rainy) season by −10.91% and increases in the Kiremt (rainy) season by 17.4%. | Gurara et al. (2021) | ||
Omo-Gibe Basin | Omo-Gibe Basin | 79,000 | 1989–2019 and 2025–2100 | SWAT | The estimated annual average streamflow decline ranges from 7.08–10.99% under the RCP 4.5 emission scenarios to 10.98–12.88% under the RCP 8.5 emission scenarios. | Orkodjo et al. (2022) |
Andasa watershed | Upper Blue Nile Basin | 576 | 2013–2099 | SWAT | Increasing potential evapotranspiration (PET) by 4.4–17.3% and decreasing streamflow and soil water by 48.8–95.6% and 12.7–76.8%, respectively. | Tarekegn et al. (2021) |
Bilate | Southern Ethiopia | 562.560 | 1981–2010 | SWAT | A 30.87% reduction in rainfall resulted in a 4.09, 1.43, and 3.57% decrease in runoff, groundwater, and water yield, respectively. An increase in mean temperature by 1.3 °C resulted in a 7 and 0.8% increase in potential and actual evapotranspiration, respectively. Runoff, groundwater, and water production are expected to decline by 11.24, 12.54, and 11.54%, respectively. | Kuma et al. (2021) |
Study catchments . | Location . | Area (km2) . | Study period . | Model used . | Major flow change within the study period . | References . |
---|---|---|---|---|---|---|
Kessem watershed | Middle Awash Sub-Basin | 2,908.4 | 1992–2020 and 2031–2090 | SWAT | Streamflow increases by 12.5 and 48.8% in the 2040s and 2070s, respectively, under the SSP5-8.5 emission scenario. | Assfaw et al. (2023) |
Rift Valley Lakes Basin | Rift Valley Lakes Basin | 55,050 | 1981–2018 | SWAT + | Surface runoff, lateral flow, and percolation differed over the basin by 7.8 to 13.14%, −4.47 to −16.51%, and −3.28 to −10.19%, respectively. | Ayalew et al. (2023) |
Mojo catchment | Awash Basin | 1,601.84 | 1985–2005 and 2006–2080 | CMIP5 | Drought variability of up to −3.7 mm was observed during RCP8.5, indicating a 22% risk of drought occurring in the watershed in the distant future. | Alemu et al. (2023) |
Awash Basin | Awash Basin | 112,000 | 1986–2005 and two future scenarios (2050 and 2070s) | GRCM | A decrease in precipitation in 4 months (February/March to May), with a rate of 34.7% under RCP8.5 and a maximum temperature increase of 3.4 and 4.1 °C in the 2050s and 2070s, respectively, under RCP8.5. | Tadese et al. (2019a) |
Katar and Meki watersheds | Rift Valley Basin | – | 1997–2017 and 2021–2080 | SWAT | Annual water yields in the Katar and Meki sub-basins will increase by 0.38–57.1% and 6.57–49.9%, respectively. | Balcha et al. (2023) |
Deme watershed, | Omo-Gibe Basin | 1,287.9 | 1989–2010 and 2031–2070 | SWAT | Under the RCP8.5 scenario, surface runoff will decrease by 15.10%, groundwater by 14.78%, and total water yield by 26.10% between 2031 and 2050. | Daniel (2023) |
Guder Catchment, | Upper Abbay Basin | – | 1986–2016 | SWAT | Under RCP 8.5, the precipitation and temperature will decrease by up to 14.4% and +4.4 °C, respectively, in the period from 2057 to 2086, and total water yield from 2024 to 2086 may be reduced by 3.2 mm per year. | Gemechu et al. (2021) |
Upper Wabe Bridge watershed | Wabe Shebele Basin | 202,220 | Mean seasonal streamflow decreases in the Belg (short rainy) season by −10.91% and increases in the Kiremt (rainy) season by 17.4%. | Gurara et al. (2021) | ||
Omo-Gibe Basin | Omo-Gibe Basin | 79,000 | 1989–2019 and 2025–2100 | SWAT | The estimated annual average streamflow decline ranges from 7.08–10.99% under the RCP 4.5 emission scenarios to 10.98–12.88% under the RCP 8.5 emission scenarios. | Orkodjo et al. (2022) |
Andasa watershed | Upper Blue Nile Basin | 576 | 2013–2099 | SWAT | Increasing potential evapotranspiration (PET) by 4.4–17.3% and decreasing streamflow and soil water by 48.8–95.6% and 12.7–76.8%, respectively. | Tarekegn et al. (2021) |
Bilate | Southern Ethiopia | 562.560 | 1981–2010 | SWAT | A 30.87% reduction in rainfall resulted in a 4.09, 1.43, and 3.57% decrease in runoff, groundwater, and water yield, respectively. An increase in mean temperature by 1.3 °C resulted in a 7 and 0.8% increase in potential and actual evapotranspiration, respectively. Runoff, groundwater, and water production are expected to decline by 11.24, 12.54, and 11.54%, respectively. | Kuma et al. (2021) |
The shift in water balance components suggested a significant regional variance in water fluxes in watersheds with rainfall (40–10%), evapotranspiration (20–5%), surface runoff (7.8–13.1%), lateral flow (4.47–16.5%), and percolation (3.3–10.2%) distributed differently (Ayalew et al. 2023).
Similarly, Gemechu et al. (2021) also indicated that the overall water yield in the Guder Catchment, Upper Abbay Basin from 2024 to 2086 could be reduced by 3.2 mm per year. In addition, the surface runoff in the Deme watershed, Omo-Gibe Basin, will decrease by 15.10%, groundwater by 14.78%, and total water production by 26.10% between 2031 and 2050 under the RCP8.5 scenario (Daniel 2023).
On the contrary, Balcha et al. (2023) indicated that the annual water yield in the Katar and Meki sub-basins (Central Rift Valley Lakes Basin) will rise by 0.38–57.1% and 6.57–49.9%, respectively. Gurara et al. (2021) also showed that the streamflow in the Upper Wabe Bridge watershed in the Wabe Shebele River Basin reduces by 10.91% during the Belg (short rainy) season, whereas it increases by 17.4% during the Kiremt season.
Reduction in water availability
One of the most significant impacts of climate change on stream flow in Ethiopia is a reduction in water availability. This reduction is due to a combination of factors, including changes in precipitation patterns and higher rates of evaporation (Gebrechorkos et al. 2020; Muluneh 2020). Climate change's effects on water, such as floods, droughts, ocean acidification, and rising sea levels, are anticipated to intensify in the coming years (Alemu et al. 2023). Water availability varies in space and time. At various places, its availability is either too much or too little. The severity of water shortage is pronounced in sub-saharan regions and mild in other parts of Africa. Ethiopia, a country of ancient culture, is located in the north-eastern part of the Horn of Africa. The water resources development and management conditions in Ethiopia are no better than any other Sub-Saharan African region, if not worse. Less than half of the population has access to safe and adequate drinking water. Only one-third (approximately) of the population has access to adequate sanitation services.
Climate change is a significant driver of the reduction in water availability in many regions around the world. As global temperatures rise, changes in precipitation patterns and increased evaporation rates contribute to decreased water availability for human and ecological needs (IPCC 2014; Orke & Li 2022).
According to Belay et al. (2021), the increasing temperature in southern Ethiopia creates severe water loss due to evaporation and affects agriculture and livestock production, domestic water supply, and municipal services. Climate change is expected to exacerbate water scarcity in Ethiopia, particularly in rural areas. Climate change distorts the water supply–demand balance, which increases the demand for water while diminishing the supply (availability) (Gelete et al. 2020).
Changes in precipitation patterns and trends
Climate change has a direct influence on precipitation. The increased heating leads to greater evaporation and thus surface drying, thereby increasing the intensity and duration of drought (Trenberth 2011). Climate change can have profound effects on the hydrologic cycle through precipitation, evapotranspiration, and soil moisture with increasing temperature. However, the extra precipitation will be unequally distributed around the globe. Some parts of the world may see significant reductions in precipitation or major alterations in the timing of wet and dry seasons (Kuma 2012).
A study by Belay et al. (2021) found that there was a decreasing rainfall trend from 1995 to 2016, which was about 60.86 mm per year in southern Ethiopia. This reduction of rainfall in the study area could harm crop production, forage production for livestock feed, and food security.
Climate change is causing changes in precipitation patterns in Ethiopia, with many areas experiencing more frequent and severe droughts. These droughts are having a significant impact on stream flow in the country, as they reduce the amount of water that is available in the rivers and streams. Several studies have shown that changes in precipitation patterns are already having a significant impact on stream flow in Ethiopia. A study by Tessema et al. (2021) indicates that climate change has been significantly affecting the trends and patterns of seasonal rainfall in the Awash Basin.
In another study by Belay et al. (2019), the annual spatiotemporal analysis in the Beles Basin (sub-basins of the Upper Blue Nile Basin) revealed: a mean annual rainfall of 1,490 mm (1,050–2,090 mm), a 50 mm increase in mean annual rainfall per 100 m elevation rise, periodical and persistent drought occurrence every 8–10 years, a significant increasing trend of rainfall (∼5 mm/year), high rainfall variability observed at the lowland and drier parts of the basin, and a high coefficient of variation of monthly rainfall in March and April.
The results of the trend analysis in the Amhara region, northern Ethiopia, showed an overall rise in the annual and seasonal rainfall (excluding winter) from 1981 to 2017 (Alemu & Bawoke 2020). The expected changes in temperature and precipitation extremes are likely to have significant adverse effects on many socioeconomic activities throughout Ethiopia (Teshome & Zhang 2019).
Generally, several previous studies indicate that there were changes in temperature and precipitation patterns and trends in Ethiopia (Table 2).
Previous studies of the impact of climate change on precipitation patterns and trends in Ethiopia
Study catchment/basins . | Area (ha) . | Study period . | Model used . | Majo change within the study period . | References . |
---|---|---|---|---|---|
Great Rift Valley Basins | 18,219,000 | 1981–2010 | – | During the main season, there is a 14–35% fluctuation in rainfall, 20–256 days of length of growing period (LGP), and a 50–100% chance of a dry spell. | Ademe et al. (2020) |
Amhara region | – | 1981–2017 | CHIRPS | Inter-annual variability in rainfall with negative and positive anomalies in 59.46 and 40.54% of the examined years, respectively. | Alemu & Bawoke (2020) |
Central Ethiopia | 92,800 | 1988–2017 | ClimPACT2 | Average annual temperature has increased by 0.4 and 0.3 °C every decade in the lowland and midland regions, respectively, and average annual rainfall in the midland has increased by 178 mm over the last decade. | Etana et al. (2020) |
Upper Blue Nile Basin | 17,600,000 | 1953–2014 | – | A substantial increasing trend of 12.85 mm per year occurred in the central-eastern and a considerable drop of 17.78 mm per year in southwestern. | Samy et al. (2019) |
Study catchment/basins . | Area (ha) . | Study period . | Model used . | Majo change within the study period . | References . |
---|---|---|---|---|---|
Great Rift Valley Basins | 18,219,000 | 1981–2010 | – | During the main season, there is a 14–35% fluctuation in rainfall, 20–256 days of length of growing period (LGP), and a 50–100% chance of a dry spell. | Ademe et al. (2020) |
Amhara region | – | 1981–2017 | CHIRPS | Inter-annual variability in rainfall with negative and positive anomalies in 59.46 and 40.54% of the examined years, respectively. | Alemu & Bawoke (2020) |
Central Ethiopia | 92,800 | 1988–2017 | ClimPACT2 | Average annual temperature has increased by 0.4 and 0.3 °C every decade in the lowland and midland regions, respectively, and average annual rainfall in the midland has increased by 178 mm over the last decade. | Etana et al. (2020) |
Upper Blue Nile Basin | 17,600,000 | 1953–2014 | – | A substantial increasing trend of 12.85 mm per year occurred in the central-eastern and a considerable drop of 17.78 mm per year in southwestern. | Samy et al. (2019) |
For example, Etana et al. (2020) showed that in Central Ethiopia, the average annual temperature has increased by 0.4 and 0.3 °C every decade in the lowland and midland regions, respectively. And average annual rainfall in the midland has increased by 178 mm over the last decade. Another study by Alemu & Bawoke (2020) indicated that in the Amhara region, northern Ethiopia, there was inter-annual variability in rainfall with negative and positive anomalies of 59.46 and 40.54% in (1981–2017), respectively.
In addition, Samy et al. (2019) also indicated a substantial increasing trend of 12.85 mm per year occurred in the central-eastern and a considerable drop of 17.78 mm per year in the southwestern Upper Blue Nile Basin.
Increased frequency of extreme events
Climate change is also causing an increase in the frequency of extreme events, such as floods and droughts (Gezie & Tejada Moral 2019; Orke & Li 2022; Tareke & Awoke 2022, 2023). These extreme events are having a significant impact not only on agriculture but also on stream flow in Ethiopia (Nasir et al. 2021; Tessema et al. 2021). Ethiopia has been facing severe droughts at least twice per decade and several severe flood hazards (Mulugeta et al. 2019; Bezu 2020). For example, a study by Alemayehu & Bewket (2017) found that extreme floods in the Upper Blue Nile River Basin had caused significant damage to infrastructure, including bridges and roads, which had a significant impact on stream flow.
Following the 2015 El Niño drought, certain parts of the Horn of Africa saw floods in 2016. In Ethiopia, the 2016 flood event occurred with strong Kiremt rains and caused many localized flash floods, landslides, and overflowing rivers in Lower Omo Valley, Dire Dawa, Amhara, Afar, Somali, Tigray, Gambella, Oromia, and Harari districts (Mamo et al. 2019).
Flooding and droughts have been two of the most destructive repercussions of the climate catastrophe, affecting billions of people throughout the world (Mekonnen et al. 2023).
According to Bezu (2020), the drought from 1900 to 2010 killed over 400,000 people and put 54 million people at risk of starvation, and in 2004, 2005, 2008, 2016, and 2017, about 8, 6.3, 11.6, 18, and 8.5 million people, respectively, require food aid. The flood of 2006 destroyed crops on 1907 ha and reduced production by 20%; around 15,600 cattle died, and 199,902 people required humanitarian assistance. The massive floods resulted in a loss of 1.5 billion tonnes of topsoil, which was estimated to be worth US$106 million (Table 3). In addition, Edamo et al. (2022) showed that, in the Boyo watershed, southern Ethiopia, under the RCP8.5 scenario, 193 ha of the study could be flooded with flood events that have a recurrence time of 100 years in the long run. As a result, Ethiopia is frequently faced with climate-related hazards, commonly drought and floods, and its agricultural products decrease from time to time leading to more economic loss (Gidey et al. 2018; Teshome & Zhang 2019; Shitu 2021).
Previous studies of the impact of extreme events in Ethiopia
Study catchments . | Location . | Area (km2) . | Study period . | Model used . | Major loss within the study period . | References . |
---|---|---|---|---|---|---|
Boyo watershed | Southern Ethiopia | – | 1976–2005 and 2041–2100 | (Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS)) and (HEC-RAS) | Under the RCP8.5 scenario, 193 ha of the study could be flooded with flood events that have a recurrence time of 100 years in the long run. | Edamo et al. (2022) |
Ethiopia | Ethiopia | 1.13 million Km2 | 1900–2017 | Review | Between 1900 and 2010, the drought killed more than 400,000 people and put 54 million people at risk of hunger. In 2004, 2005, 2008, 2016, and 2017, around 8, 6.3, 11.6, 18, and 8.5 million individuals require food assistance. The 2006 flood damaged crops on 1907 hectares, killed approximately 15,600 cattle, and left 199,902 people in need of humanitarian assistance. The high floods resulted in a loss of 1.5 billion tonnes of topsoil, which is estimated to be worth US$106 million. | Bezu (2020) |
Study catchments . | Location . | Area (km2) . | Study period . | Model used . | Major loss within the study period . | References . |
---|---|---|---|---|---|---|
Boyo watershed | Southern Ethiopia | – | 1976–2005 and 2041–2100 | (Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS)) and (HEC-RAS) | Under the RCP8.5 scenario, 193 ha of the study could be flooded with flood events that have a recurrence time of 100 years in the long run. | Edamo et al. (2022) |
Ethiopia | Ethiopia | 1.13 million Km2 | 1900–2017 | Review | Between 1900 and 2010, the drought killed more than 400,000 people and put 54 million people at risk of hunger. In 2004, 2005, 2008, 2016, and 2017, around 8, 6.3, 11.6, 18, and 8.5 million individuals require food assistance. The 2006 flood damaged crops on 1907 hectares, killed approximately 15,600 cattle, and left 199,902 people in need of humanitarian assistance. The high floods resulted in a loss of 1.5 billion tonnes of topsoil, which is estimated to be worth US$106 million. | Bezu (2020) |
Land use change
Land use change is another factor that is driving climate change impacts on streamflow by affecting the hydrological processes of a watershed in Ethiopia and these changes have an important influence and are the main factor for monitoring the water balances (Leta et al. 2021b). Agricultural expansion, deforestation, and urbanization have led to significant changes in land cover and land use (LULC) in Ethiopia. This has resulted in reduced vegetation cover, increased soil erosion, and decreased infiltration rates, leading to reduced groundwater recharge and streamflow. Moreover, land use change has led to changes in the timing and amount of water available in streams, as well as changes in water quality due to increased sedimentation and pollution (Muluneh 2020).
The predicted increase of agricultural and urban land by decreasing mainly forest land will lead 2035 to an increase of 2.33% in surface runoff and a decline in groundwater flow, lateral flow, and evapotranspiration (Leta et al. 2021b).
Ethiopia's forest cover decreased from 13.3% (14.69 million ha) in 1993 to 11.4% (12.54 million ha) in 2016, with an estimated annual rate of change of 0.8% (104,600 ha/year). Meanwhile, agricultural land increased from 27.66% (30.54 million ha) in 1993 to 32.83% (36.26 million ha) in 2016 (Negese & Miano 2021).
Changes in LULC can also affect stream flow in Ethiopia. A study by Teklay et al. (2021) found that land use changes in the Gumara Watershed Tana Sub-basin have reduced the stream flow, due to an increase in vegetation cover and a decrease in soil infiltration.
The assessment of LULC change is indispensable for the sustainable development of land and water resources (Leta et al. 2021b).
LULC dynamics, in general, and the conversion of natural vegetation cover into cultivated land, in particular, are major human-caused problems in Ethiopia, contributing significantly to increased soil erosion and altering the country's hydrological balance (Negese & Miano 2021). For example, Leta et al. (2021a) indicated in the Nashe watershed, Upper Blue Nile, the agricultural land increased by 39.15%. Forest land, range land, and grassland all declined at rates of 48.38, 19.58, and 26.23% each year, respectively. Forest land will be reduced from 16.94% in 2019 to 8.07% by 2050. The agricultural land area increased from 57,868.95 ha in 2019, to 69,021.20 ha in 2035 and 69,264.44 ha by 2050 (Table 4).
Previous studies on LULC change (the driving climate change impacts) in Ethiopia
Study catchments . | Location . | Area (ha) . | Study period . | Model used . | Major LULC change within the study period . | References . |
---|---|---|---|---|---|---|
Shenkolla | Central Ethiopia | 1,457 | 1973–2017 | ArcGIS 10.3 | Forest reduced by 8.99% and agricultural land expanded by 8.99%. | Bufebo & Elias (2021) |
Erer Sub-Basin | Wabi Shebelle Basin | 3,860 | 1998–2018 | RUSLE | Cropland increased by 16.44%, and forest area and shrubland decreased by 1.57 and 16.8%, respectively. | Weldu Woldemariam & Edo Harka (2020) |
Nashe watershed | Upper Blue Nile | 94,578 | 1992–2019, 2035, and 2050 | Landsat images and Change Modeller | Agricultural land rose by 39.15%. Forest land, range land, and grassland all fell at rates of 48.38, 19.58, and 26.23% each year, respectively. Reduction of frost land from 16.94% in 2019 to 8.07% in 2050. Expansion of agricultural land from 57,868.95 ha in 2019. To 69,021.20 ha in 2035 and 69,264.44 ha in 2050. | Leta et al. (2021a) |
Ethiopia | Ethiopia | 1.13 million km2 | 1985–2015 | Review | The country's forest and woodland coverage dropped from 40% in the early 20th century to 15%. | Genet (2020) |
Study catchments . | Location . | Area (ha) . | Study period . | Model used . | Major LULC change within the study period . | References . |
---|---|---|---|---|---|---|
Shenkolla | Central Ethiopia | 1,457 | 1973–2017 | ArcGIS 10.3 | Forest reduced by 8.99% and agricultural land expanded by 8.99%. | Bufebo & Elias (2021) |
Erer Sub-Basin | Wabi Shebelle Basin | 3,860 | 1998–2018 | RUSLE | Cropland increased by 16.44%, and forest area and shrubland decreased by 1.57 and 16.8%, respectively. | Weldu Woldemariam & Edo Harka (2020) |
Nashe watershed | Upper Blue Nile | 94,578 | 1992–2019, 2035, and 2050 | Landsat images and Change Modeller | Agricultural land rose by 39.15%. Forest land, range land, and grassland all fell at rates of 48.38, 19.58, and 26.23% each year, respectively. Reduction of frost land from 16.94% in 2019 to 8.07% in 2050. Expansion of agricultural land from 57,868.95 ha in 2019. To 69,021.20 ha in 2035 and 69,264.44 ha in 2050. | Leta et al. (2021a) |
Ethiopia | Ethiopia | 1.13 million km2 | 1985–2015 | Review | The country's forest and woodland coverage dropped from 40% in the early 20th century to 15%. | Genet (2020) |
In the Erer Sub-Basin, Wabi Shebelle Basin, cropland increased by 16.44%, and forest area and shrubland decreased by 1.57 and 16.8%, respectively (Weldu Woldemariam & Edo Harka 2020) (Table 4). Genet (2020) also showed that the country's forest and woodland coverage dropped from 40% in the early 20th century to 15%.
COMPARATIVE REVIEW OF CLIMATE CHANGE IMPACT ON NEIGHBORING COUNTRIES AND BASINS OF ETHIOPIA
Based on countries
Sudan
Sudan is vulnerable to climate change due to its hot climate, with mean annual temperatures ranging from 26 to 32 °C across the country. An increase in local temperature will affect the entire Sudan. Rainfed agriculture, aquaculture, natural ecology systems and biodiversity, water resources, and energy (production and consumption) are the sectors most sensitive to rising temperatures. This increases the vulnerability of particular communities, including poor farmers, pastoralists, and general populations that rely on rainfed agriculture. However, Sudan's climatic changes will not be restricted to mere temperature (which is anticipated to climb in the range of 0.5° to 3 °C by 2050) and precipitation (which is projected to increase by 4% every decade) (Siddig et al. 2020). Sudan will also face increased rainfall variability, increasing the frequency of droughts and floods. Currently, floods, flashfloods, and perhaps landslides afflict the southern, southeastern, and hilly areas in the northeast of the country, and droughts harm the northern and sections of the middle and middle west of the country. Pastoralists, impoverished farmers, and usually poor households with elderly members, children, and women are the most vulnerable communities to droughts and floods (Sayed & Abdala 2013).
Sayed & Abdala (2013) and Siddig et al. (2020) investigated reactions to climate risk and climate change risks in the agricultural and rural sectors. This is not only because agriculture is a vital industry for the life of the majority of Sudanese people and the Sudanese economy, but it is also the sector of the economy that is most affected by climate change. The proposed interventions include:
- 1.
Investing in infrastructure to defend against flooding;
- 2.
Creating programs and projects to mitigate and adapt to the effects of climate change in the agricultural and rural sectors;
- 3.
Improving land ownership, particularly for animal producers, so that they can legally use land like crop producers, as well as demarcating and charting livestock routes and enforcing their use to enhance access to natural productive assets;
- 4.
Addressing water shortages by encouraging water harvesting and full use of rainfall and seasonal streams beyond the Nile Basin, exploiting groundwater, and producing drought-resistant crop varieties; and
- 5.
Treating water as a precious resource and improving its effective use.
Egypt
Egypt's key crops lack self-sufficiency due to rapid population increase, limited water resources, and weather variability. Climate change is exerting more pressure, both directly and indirectly, on achieving self-sufficiency, food security, and safety (Mostafa et al. 2021).
Climate change may have an impact on both water resources and demand. Many places rely on groundwater for agriculture. These areas are primarily arid and semi-arid. Groundwater recharge is viewed as a byproduct of irrigation return flow. Climate change could have a big impact on aquifer storage (Zhou et al. 2010).
The Nile River serves as the primary supply of water in Egypt. As a result, any modifications to its flow are extremely crucial. According to Khir-Eldien & Zahran (2017), the Nile River loses a significant amount of water to evaporation during its 3,000-km length through arid northern Sudan and Egypt. Thus, temperature and precipitation fluctuations have a significant impact on water supply. Their study indicated that the availability of groundwater in Egypt's Nile Valley and Delta may be diminished as a result of the influence of climate change on water demand and groundwater withdrawals. Surface and groundwater supplies in many locations have been diminished due to changes in precipitation and runoff, as well as changes in use and withdrawal.
The recommended adaptation scenarios to climate change by Siddig et al. (2020) include (i) changing sowing date, (ii) increasing the amount of irrigation water added, and (iii) use of modern irrigation systems.
Based on the River Basin
Congo River Basin
Eleven nations share the Congo Basin (Angola, Burundi, Cameron, Central African Republic, DR Congo, Gabon, Republic of Congo, Rwanda, South Sudan, Sudan, and Zambia). The Congo River, Africa's second-longest river, is a tropical river with little variability in flows (Coefficient of Variance (CV) = 13%), temperature (23–25 °C), and ETo (1,100–1,200 mm/year) (Alsdorf et al. 2016); the basin is enriched with the second worldwide rainfed forests (45% of the area) which are expected to play a substantial role in balancing carbon dioxide emissions (Haensler et al. 2013).
Limpopo River Basin
The Limpopo River begins in South Africa and flows 1,750 km into the Indian Ocean in Mozambique. Botswana, Mozambique, South Africa, and Zimbabwe are all riparian states. Repeated drought cycles remained a significant concern in the region.
Niger River Basin
The Niger Basin comprises the longest river in West Africa and the third longest river in Africa, measuring 4,200 km with an average annual flow of 180 km3. Its basin covers nine countries: Benin, Burkina Faso, Cameroon, Chad, Côte d'Ivoire, Guinea, Mali, Niger, and Nigeria. For more than 30 years, the region has experienced a 20–30% rainfall deficit. This shortfall, combined with anthropogenic influences, had passive consequences, such as hydrological droughts (reduced runoff by 20–55% at the expense of most ecosystems), and the emergence and/or exacerbation of specific environmental events that posed a threat to human survival (Shamseddin & Chaibi 2019).
Nile River Basin
The Nile River Basin covers around 10% of the African continent. It is Africa's longest river, flowing from two main sources: the Equatorial Lakes and Ethiopia's highlands. Its waters are shared by 11 countries: Kenya, Uganda, Tanzania, Rwanda, Burundi, DR Congo, Ethiopia, Sudan, South Sudan, Eritrea, and Egypt. The flow variability reflects the seasonal trend in rainfall in Ethiopia and the big lakes. According to Siam & Eltahir (2017), projected increases in El Niño and La Niña occurrences in the 21st century may cause a 50% (±35%) increase in inter-annual variability of total Nile flow.
Senegal River Basin
The Senegal River is West Africa's second-longest river, which runs 1,800 km. The river's flow regime is mostly determined by rainfall in Guinea's Upper Basin (about 2,000 mm/year). Senegal Basin is shared by four western African countries (Guinea, Mali, Mauritania, and Senegal). The repeated drought cycles throughout the last 100 years have resulted in a dramatic decline of 70% in the river's annual flow, which normally ranges between 6.9 and 41.5 km3 (Mbaye et al. 2015).
Zambezi River Basin
The Zambezi Basin is Africa's fourth largest river basin (after Congo, Nile, and Niger), covering 1.4 million km2 (Kling et al. 2014). It is shared by eight countries: Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia, and Zimbabwe. Since 1980, the region has been experiencing a 26-year drought cycle (World Bank 2010).
CONCLUSION
In Ethiopia, anthropogenic causes are hastening the effect of climate changes, which have an impact on humans and natural resources in general, as well as water resources in particular. This paper investigates the repercussions of climate change on streamflow in Ethiopia, focusing on its implications for water resources management. Ethiopia's vulnerability to climate change, compounded by its reliance on agriculture and limited water resources, underscores the urgency of understanding how climate shifts affect streamflow dynamics. The primary goal of this review paper was to examine the effects of climate change on the hydro-meteorological processes in the country. The review synthesizes findings from various studies, highlighting the adverse impacts of climate change on streamflow, including reduced water availability, alterations in precipitation patterns, and increased frequency of extreme events like floods and droughts. Additionally, it examines the role of land use changes in exacerbating these challenges. The country's forest and woodland coverage dropped from 40% in the early 20th century to 15% due to the increments of agricultural land. Comparative insights from neighboring countries and river basins provide a broader regional perspective on the climate-water nexus. Overall, the study emphasizes the critical need for adaptive measures and sustainable water management strategies to safeguard water security in Ethiopia amidst escalating climate pressures.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.