Recently there are signs of water quality impairment in Lake Tana, the largest fresh water in Ethiopia. The lake is the growth corridor of the government and supports millions of livelihood around. In order to sustain...Recently there are signs of water quality impairment in Lake Tana, the largest fresh water in Ethiopia. The lake is the growth corridor of the government and supports millions of livelihood around. In order to sustain the benefit and maintain the ecosystem of the lake, the lake health has to be kept safe. Therefore monitoring and evaluation of the water quality of lake is very vital. This study focuses on current and previous trends water quality of the lake through measurements and Landsat Images near entry of Gumera River. Statistical analysis of the physical (Turbidity and STD and biological (Cha-a,) and chemical (DPC) water quality parameters were done. Linear and non-linear regression models between water quality parameter and reflectance of Landsat 7 ETM+ images were fitted based on band combinations. Pervious trend in turbidity was analyzed based on the regression models. The results showed that reflectance and turbidity satisfactorily result with an R2 ranging from 0.61 - 0.68. Form 1999-2014 the turbidity of the lake has indicated an increasing trend. Delta development near the entry of Gumera River has been enlarged by 48% because of an increase sediment inflow. The sign in the decreasing water quality of the lake was attributed to the non-point source sediment and nutrient inflow to the lake with high erosion rate from the watersheds. Measures to reduce the non-point source sediment and nutrient inflow by targeting the source areas (hot spots) in the agricultural watersheds need to be priority for stakeholders working on the soil and water conservation. Moreover, reducing the recession agriculture around the lake and wetland management could be crucial for improving lake water quality.展开更多
Low flow analysis provides crucial information for the planning and design water resource development, risk assessment and environmental flow management. Understanding the low flow regimes and evaluating the magnitude...Low flow analysis provides crucial information for the planning and design water resource development, risk assessment and environmental flow management. Understanding the low flow regimes and evaluating the magnitudes for incorporating in water resources management is vital for the countries like Ethiopia where demand for water is increasing. However, there were hardly enough studies in understanding the trends of low flow and frequency analysis. Therefore, this study focuses on evaluation of the trends in low flows and regional low flow analysis in the Blue Nile Basin, Ethiopia. In order to carry out the study, 15 river sub-basins in the Blue Nile Basin were selected based on the long term data availability and presence of quality of data. The 3-day sustained low flow (3d-slf), the 7-day sustained low flow (7d-slf) and the 14-day sustained low flow (14d-slf) models were used to extract the data from the daily time series stream data obtained from MoWIE. Trends in low flow were analyzed separately by using Mann-Kendall (MK) trend test. Low flow frequency analysis was used to estimate the long term low flow quantiles. In addition, regional analysis for estimating the quantiles for ungaged catchments was also developed based on the regional growth curve and catchment characteristic of drainage basins. The results indicated that 3d-slf, 7d-slf and 14d-slf models of low flow series indicated no significant difference for each station at 95% CI. Out of the 15 selected stations, 12 of stations have indicated decreasing;two stations indicated increasing and remaining one station with no trend. Mainly decreasing trend was associated with the land cover and climate change which results in increasing runoff and evapotranspiration respectively. Weibull distribution—GEV and LGN was found best fit based on the L-Moment Ratio Diagram (L-MRD). Hence quantile estimations have indicated diminishing magnitudes of low flow quintiles for 2 - 500 years return periods. Regional low frequency analysis has provided a very good relationship between discharge and catchment characteristics with an R2 of 0.72. Where area (A) and rainfall (R) followed by slope were found sensitive to compute in developing the regional region equations between mean low flows and the physiographic data. This study indicated that there needs to be a new water management scenario and adaptation mechanism of climate change and land use land cover dynamics for utilizing water resource in the Blue Nile Basin.展开更多
Water is likely the most limiting factor in increasing agricultural production in large parts of Africa. Reference evaporation (ET0) is a key hydrological parameter to use efficiently the scarce supply. Several method...Water is likely the most limiting factor in increasing agricultural production in large parts of Africa. Reference evaporation (ET0) is a key hydrological parameter to use efficiently the scarce supply. Several methods are available for predicting reference evaporation, but the accuracy of any of the methods has not been established for the Ethiopian highlands. The objective of this study is, therefore, to select the best methods for calculating the reference evaporation ET0. For the section, meteorological data of the Bahir Dar station were used, because all data needed for this study including the Class A pan Evaporation were recorded on a daily basis. Pan evaporation was considered as the best estimator of the reference evaporation. The results showed that the FAO-Penman Monteith (using solar radiation, wind speed, temperature and relative humidity) and Enku method (using only maximum daily temperatures) have acceptable daily ET0 ranges and predicted to Class A pan evaporation with correlation coefficients greater than 90% in a monthly basis. Next best was the Thornthwaite’s method with correlation coefficient of 89% with pan evaporation. Piche methods performed relatively well with correlation coefficient of greater than 70%. Blaney-Criddle, Priestley & Taylor, and Hargreaves performed the poorest in predicting pan evaporation. These methods should be recalibrated for local condition and therefore not recommended for use in the Ethiopian highlands. In summary, the FAO-Penman Monteith is recommended for locations where the input data are available;otherwise, the Enku method using maximum daily temperature is best for estimating the reference evaporation.展开更多
Cover management and support practices largely control the magnitude and variability of soil erosion.Although soil erosion models account for their importance(particularly by C-and P-factors in the Revised Universal S...Cover management and support practices largely control the magnitude and variability of soil erosion.Although soil erosion models account for their importance(particularly by C-and P-factors in the Revised Universal Soil Loss Equation),obtaining spatially explicit quantitative field data on these factors remains challenging.Hence,also our insight into the effects of soil conservation measures at larger spatial scales remains limited.We analyzed the variation in C-and P-factors caused by human activities and climatic variables by reviewing 255 published articles reporting measured or calculated C-and P-factor values.We found a wide variation in both factor values across climatic zones,land use or cover types,and support practices.The average C-factor values decreased from arid(0.26)to humid(0.15)climates,whereas the average P-factor values increased(from 0.33 to 0.47,respectively).Thus,support practices reduce soil loss more effectively in drylands and drought-prone areas.The global average C-factor varies by one order of magnitude from cropland(0.34)to forest(0.03).Among the major crops,the average C-factor was highest for maize(0.42)followed by potato(0.40),among the major orchard crops,it was highest for olive(0.31),followed by vineyards(0.26).The P-factor ranged from 0.62 for contouring in cropland plots to 0.19 for trenches in uncultivated land.The C-factor results indicate that cultivated lands requiring intensive site preparation and weeding are most vulnerable to soil loss by sheet and rill erosion.The low P-factor for trenches,reduced tillage cultivation,and terraces suggests that significantly decreased soil loss is possible by implementing more efficient management practices.These results improve our understanding of the variation in C-and P-factors and support large-scale integrated catchment management interventions by applying soil erosion models where it is difficult to empirically determine the impact of particular land use or cover types and support practices:the datasets compiled in this study can support further modeling and land management attempts in different countries and geographic regions.展开更多
Globally,grasslands,covering about 40%of the Earth’s land area,are vital for supporting important ecosystem functions,services,and livelihoods of millions of humans.Currently,grassland degradation is a major threat t...Globally,grasslands,covering about 40%of the Earth’s land area,are vital for supporting important ecosystem functions,services,and livelihoods of millions of humans.Currently,grassland degradation is a major threat to the maintenance of ecological services,1 food security,and sustainable development,and directly hinders the global efforts with meeting goals and targets such as the The UN Decade on Ecosystem Restoration and Sustainable Development Goals(SDGs).Remote sensing approaches have the advantages of spanning large geographical areas withmultiple spatial,spectral,and temporal resolutions.In global scale,remote sensing methods used normalized difference vegetation index to determine net primary productivity(NPP),which still is the effectivemethod to indicate grassland conditions.To master the general situation of grassland,we analyzed the global spatial-temporal variation of NPP from 2001 to 2019 at the pixel level across the globe.As presented in Figure 1A,the NPP values of global grasslands showed an obvious variation trend,which indicated a considerable distribution pattern of spatial heterogeneity.The decreasing and increasing trend in grassland NPP covered approximately 25.3%and 74.5%of the total grassland area,respectively.展开更多
Lack of appropriate agronomic practices is one of the major causes for soil erosion and low yields in teff(Eragrostis tef[Zucc.])production in Ethiopia.A 3-yr study was conducted at the Aba Gerima watershed in northwe...Lack of appropriate agronomic practices is one of the major causes for soil erosion and low yields in teff(Eragrostis tef[Zucc.])production in Ethiopia.A 3-yr study was conducted at the Aba Gerima watershed in northwestern Ethiopia,to investigate the effects of two tillage practices(reduced tillage[RT]and conventional tillage[CT]),two planting methods(row planting[RP]and broadcast planting[BP]),and two compaction options(with[+T]and without[-T]trampling)on soil loss and teff yields in a split-split plot arrangement.Sediment concentration ranged from 0.01 to 5.37 g L^(-1)(mean,0.25 g L^(-1))in our study.Accordingly,the estimated total(August-October)soil loss ranged from 0.2 to 0.5 t ha^(-1)(mean,0.3 t ha^(-1)).The sediment concentration and total soil loss were significantly influenced(P<0.05)by tillage,planting methods,and trampling only in the third monitoring year.RT reduced soil loss by 19% relative to that of CT,whereas RP resulted in a 13%reduction in soil loss over BP.The-T plots showed a 15%reduction in soil loss as compared to+T plots.Results revealed significant increase in soil total carbon and nitrogen in RT and-T.Less soil loss and greater teff grain yield were obtained in plots with improved agronomic practices(RT and RP)compared to conventional ones(CT and BP).Based on our findings we conclude that the use of RT,RP,and-T practices can effectively minimize soil loss without any crop yield penalty.展开更多
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 mult...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.展开更多
Background:Evaluating the impacts of land-use/land-cover(LULC)changes on ecosystem service values(ESVs)is essential for sustainable use and management of ecosystems.In this study,we evaluated the impact of human activ...Background:Evaluating the impacts of land-use/land-cover(LULC)changes on ecosystem service values(ESVs)is essential for sustainable use and management of ecosystems.In this study,we evaluated the impact of human activity driven LULC changes on ESVs over the period 1982–2016/17 in contrasting agro-ecological environments:Guder(highland),Aba Gerima(midland),and Debatie(lowland)watersheds of the Upper Blue Nile basin,Ethiopia.Results:During the study period,the continuous expansion of cultivated land at the expense of natural vegetation(bushland,forest,and grazing land)severely reduced the total ESV by about US$58 thousand(35%)in Aba Gerima and US$31 thousand(29%)in Debatie watersheds.In contrast,the unprecedented expansion of plantations,mainly through the planting of Acacia decurrens,led,from 2006,to a ESV rebound by about US$71 thousand(54%)in Guder watershed,after it had decreased by about US$61 thousand(32%)between 1982 and 2006.The reduction in natural forest area was the major contributor to the loss of total ESV in the study watersheds,ranging from US$31 thousand(63%)in Debatie to US$96.9 thousand(70%)in Guder between 1982 and 2016/17.On an areaspecific basis,LULC changes reduced the average ESV from US$560 ha^(−1) year^(−1)(1982)in Guder to US$306 ha^(−1) year^(−1)(2017)in Debatie watersheds.Specific ESVs such as provisioning(mainly as food production)and regulating services(mainly as erosion control and climate regulation)accounted for most of the total ESVs estimated for the study watersheds.Conclusions:In most cases,the total and specific ESVs of the watersheds were negatively associated with the population growth,which in turn was positively associated with the expansion of cultivated land over the study period.In Guder,however,ESVs were positively associated with population growth,especially after 2012.This is mainly due to the expansion of Acacia decurrens plantations.Our results suggest,therefore,that future policy measures and directions should focus on improving vegetation cover through planting multipurpose trees such as Acacia decurrens to prevent future loss of ESV in the midland and lowland regions of the Upper Blue Nile basin and beyond.However,caution must be taken during plantation of invasive species as they may have undesirable consequences.展开更多
文摘Recently there are signs of water quality impairment in Lake Tana, the largest fresh water in Ethiopia. The lake is the growth corridor of the government and supports millions of livelihood around. In order to sustain the benefit and maintain the ecosystem of the lake, the lake health has to be kept safe. Therefore monitoring and evaluation of the water quality of lake is very vital. This study focuses on current and previous trends water quality of the lake through measurements and Landsat Images near entry of Gumera River. Statistical analysis of the physical (Turbidity and STD and biological (Cha-a,) and chemical (DPC) water quality parameters were done. Linear and non-linear regression models between water quality parameter and reflectance of Landsat 7 ETM+ images were fitted based on band combinations. Pervious trend in turbidity was analyzed based on the regression models. The results showed that reflectance and turbidity satisfactorily result with an R2 ranging from 0.61 - 0.68. Form 1999-2014 the turbidity of the lake has indicated an increasing trend. Delta development near the entry of Gumera River has been enlarged by 48% because of an increase sediment inflow. The sign in the decreasing water quality of the lake was attributed to the non-point source sediment and nutrient inflow to the lake with high erosion rate from the watersheds. Measures to reduce the non-point source sediment and nutrient inflow by targeting the source areas (hot spots) in the agricultural watersheds need to be priority for stakeholders working on the soil and water conservation. Moreover, reducing the recession agriculture around the lake and wetland management could be crucial for improving lake water quality.
文摘Low flow analysis provides crucial information for the planning and design water resource development, risk assessment and environmental flow management. Understanding the low flow regimes and evaluating the magnitudes for incorporating in water resources management is vital for the countries like Ethiopia where demand for water is increasing. However, there were hardly enough studies in understanding the trends of low flow and frequency analysis. Therefore, this study focuses on evaluation of the trends in low flows and regional low flow analysis in the Blue Nile Basin, Ethiopia. In order to carry out the study, 15 river sub-basins in the Blue Nile Basin were selected based on the long term data availability and presence of quality of data. The 3-day sustained low flow (3d-slf), the 7-day sustained low flow (7d-slf) and the 14-day sustained low flow (14d-slf) models were used to extract the data from the daily time series stream data obtained from MoWIE. Trends in low flow were analyzed separately by using Mann-Kendall (MK) trend test. Low flow frequency analysis was used to estimate the long term low flow quantiles. In addition, regional analysis for estimating the quantiles for ungaged catchments was also developed based on the regional growth curve and catchment characteristic of drainage basins. The results indicated that 3d-slf, 7d-slf and 14d-slf models of low flow series indicated no significant difference for each station at 95% CI. Out of the 15 selected stations, 12 of stations have indicated decreasing;two stations indicated increasing and remaining one station with no trend. Mainly decreasing trend was associated with the land cover and climate change which results in increasing runoff and evapotranspiration respectively. Weibull distribution—GEV and LGN was found best fit based on the L-Moment Ratio Diagram (L-MRD). Hence quantile estimations have indicated diminishing magnitudes of low flow quintiles for 2 - 500 years return periods. Regional low frequency analysis has provided a very good relationship between discharge and catchment characteristics with an R2 of 0.72. Where area (A) and rainfall (R) followed by slope were found sensitive to compute in developing the regional region equations between mean low flows and the physiographic data. This study indicated that there needs to be a new water management scenario and adaptation mechanism of climate change and land use land cover dynamics for utilizing water resource in the Blue Nile Basin.
文摘Water is likely the most limiting factor in increasing agricultural production in large parts of Africa. Reference evaporation (ET0) is a key hydrological parameter to use efficiently the scarce supply. Several methods are available for predicting reference evaporation, but the accuracy of any of the methods has not been established for the Ethiopian highlands. The objective of this study is, therefore, to select the best methods for calculating the reference evaporation ET0. For the section, meteorological data of the Bahir Dar station were used, because all data needed for this study including the Class A pan Evaporation were recorded on a daily basis. Pan evaporation was considered as the best estimator of the reference evaporation. The results showed that the FAO-Penman Monteith (using solar radiation, wind speed, temperature and relative humidity) and Enku method (using only maximum daily temperatures) have acceptable daily ET0 ranges and predicted to Class A pan evaporation with correlation coefficients greater than 90% in a monthly basis. Next best was the Thornthwaite’s method with correlation coefficient of 89% with pan evaporation. Piche methods performed relatively well with correlation coefficient of greater than 70%. Blaney-Criddle, Priestley & Taylor, and Hargreaves performed the poorest in predicting pan evaporation. These methods should be recalibrated for local condition and therefore not recommended for use in the Ethiopian highlands. In summary, the FAO-Penman Monteith is recommended for locations where the input data are available;otherwise, the Enku method using maximum daily temperature is best for estimating the reference evaporation.
基金the Science and Technology Research Partnership for Sustainable Development(SATREPS,Grant Number JPMJSA1601)the Japan Science and Technology Agency(JST)/Japan International Cooperation Agency(JICA).
文摘Cover management and support practices largely control the magnitude and variability of soil erosion.Although soil erosion models account for their importance(particularly by C-and P-factors in the Revised Universal Soil Loss Equation),obtaining spatially explicit quantitative field data on these factors remains challenging.Hence,also our insight into the effects of soil conservation measures at larger spatial scales remains limited.We analyzed the variation in C-and P-factors caused by human activities and climatic variables by reviewing 255 published articles reporting measured or calculated C-and P-factor values.We found a wide variation in both factor values across climatic zones,land use or cover types,and support practices.The average C-factor values decreased from arid(0.26)to humid(0.15)climates,whereas the average P-factor values increased(from 0.33 to 0.47,respectively).Thus,support practices reduce soil loss more effectively in drylands and drought-prone areas.The global average C-factor varies by one order of magnitude from cropland(0.34)to forest(0.03).Among the major crops,the average C-factor was highest for maize(0.42)followed by potato(0.40),among the major orchard crops,it was highest for olive(0.31),followed by vineyards(0.26).The P-factor ranged from 0.62 for contouring in cropland plots to 0.19 for trenches in uncultivated land.The C-factor results indicate that cultivated lands requiring intensive site preparation and weeding are most vulnerable to soil loss by sheet and rill erosion.The low P-factor for trenches,reduced tillage cultivation,and terraces suggests that significantly decreased soil loss is possible by implementing more efficient management practices.These results improve our understanding of the variation in C-and P-factors and support large-scale integrated catchment management interventions by applying soil erosion models where it is difficult to empirically determine the impact of particular land use or cover types and support practices:the datasets compiled in this study can support further modeling and land management attempts in different countries and geographic regions.
基金funded by the Second Scientific Expedition to the Qinghai-Tibet Plateau(grant no.2019QZKK0405)the Innovative Team of Grassland Resources from the Ministry of Education of China(IRT_17R59)and the Inner Mongolia Key Project(ZDZX2018020).
文摘Globally,grasslands,covering about 40%of the Earth’s land area,are vital for supporting important ecosystem functions,services,and livelihoods of millions of humans.Currently,grassland degradation is a major threat to the maintenance of ecological services,1 food security,and sustainable development,and directly hinders the global efforts with meeting goals and targets such as the The UN Decade on Ecosystem Restoration and Sustainable Development Goals(SDGs).Remote sensing approaches have the advantages of spanning large geographical areas withmultiple spatial,spectral,and temporal resolutions.In global scale,remote sensing methods used normalized difference vegetation index to determine net primary productivity(NPP),which still is the effectivemethod to indicate grassland conditions.To master the general situation of grassland,we analyzed the global spatial-temporal variation of NPP from 2001 to 2019 at the pixel level across the globe.As presented in Figure 1A,the NPP values of global grasslands showed an obvious variation trend,which indicated a considerable distribution pattern of spatial heterogeneity.The decreasing and increasing trend in grassland NPP covered approximately 25.3%and 74.5%of the total grassland area,respectively.
基金This research was supported by the Science and Technology Research Partnership for Sustainable Development(grant no.JPMJSA 1601)Japan Science and Technology Agency,and Japan International Cooperation Agency.
文摘Lack of appropriate agronomic practices is one of the major causes for soil erosion and low yields in teff(Eragrostis tef[Zucc.])production in Ethiopia.A 3-yr study was conducted at the Aba Gerima watershed in northwestern Ethiopia,to investigate the effects of two tillage practices(reduced tillage[RT]and conventional tillage[CT]),two planting methods(row planting[RP]and broadcast planting[BP]),and two compaction options(with[+T]and without[-T]trampling)on soil loss and teff yields in a split-split plot arrangement.Sediment concentration ranged from 0.01 to 5.37 g L^(-1)(mean,0.25 g L^(-1))in our study.Accordingly,the estimated total(August-October)soil loss ranged from 0.2 to 0.5 t ha^(-1)(mean,0.3 t ha^(-1)).The sediment concentration and total soil loss were significantly influenced(P<0.05)by tillage,planting methods,and trampling only in the third monitoring year.RT reduced soil loss by 19% relative to that of CT,whereas RP resulted in a 13%reduction in soil loss over BP.The-T plots showed a 15%reduction in soil loss as compared to+T plots.Results revealed significant increase in soil total carbon and nitrogen in RT and-T.Less soil loss and greater teff grain yield were obtained in plots with improved agronomic practices(RT and RP)compared to conventional ones(CT and BP).Based on our findings we conclude that the use of RT,RP,and-T practices can effectively minimize soil loss without any crop yield penalty.
基金supported by the Science and Technology Research Partnership for Sustainable Development(SATREPS,grant number JPMJSA1601)from the Japan Science and Technology Agency/Japan International Cooperation Agency。
文摘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.
基金funded by Science and Technology Research Partnership for Sustainable Development(SATREPS,grant number JPMJSA1601)Japan Science and Technology Agency(JST)/Japan International Cooperation Agency(JICA).
文摘Background:Evaluating the impacts of land-use/land-cover(LULC)changes on ecosystem service values(ESVs)is essential for sustainable use and management of ecosystems.In this study,we evaluated the impact of human activity driven LULC changes on ESVs over the period 1982–2016/17 in contrasting agro-ecological environments:Guder(highland),Aba Gerima(midland),and Debatie(lowland)watersheds of the Upper Blue Nile basin,Ethiopia.Results:During the study period,the continuous expansion of cultivated land at the expense of natural vegetation(bushland,forest,and grazing land)severely reduced the total ESV by about US$58 thousand(35%)in Aba Gerima and US$31 thousand(29%)in Debatie watersheds.In contrast,the unprecedented expansion of plantations,mainly through the planting of Acacia decurrens,led,from 2006,to a ESV rebound by about US$71 thousand(54%)in Guder watershed,after it had decreased by about US$61 thousand(32%)between 1982 and 2006.The reduction in natural forest area was the major contributor to the loss of total ESV in the study watersheds,ranging from US$31 thousand(63%)in Debatie to US$96.9 thousand(70%)in Guder between 1982 and 2016/17.On an areaspecific basis,LULC changes reduced the average ESV from US$560 ha^(−1) year^(−1)(1982)in Guder to US$306 ha^(−1) year^(−1)(2017)in Debatie watersheds.Specific ESVs such as provisioning(mainly as food production)and regulating services(mainly as erosion control and climate regulation)accounted for most of the total ESVs estimated for the study watersheds.Conclusions:In most cases,the total and specific ESVs of the watersheds were negatively associated with the population growth,which in turn was positively associated with the expansion of cultivated land over the study period.In Guder,however,ESVs were positively associated with population growth,especially after 2012.This is mainly due to the expansion of Acacia decurrens plantations.Our results suggest,therefore,that future policy measures and directions should focus on improving vegetation cover through planting multipurpose trees such as Acacia decurrens to prevent future loss of ESV in the midland and lowland regions of the Upper Blue Nile basin and beyond.However,caution must be taken during plantation of invasive species as they may have undesirable consequences.
