Your search found 15 records
1 Gieske, A.; Abeyou, W. W.; Getachew, H. A.; Alemseged, T. H.; Rientjes, T.. 2008. Non-linear parameterization of Lake Tana's flow system. In Abtew, W.; Melesse, A. M. (Eds.). Proceedings of the Workshop on Hydrology and Ecology of the Nile River Basin under Extreme Conditions, Addis Ababa, Ethiopia, 16-19 June 2008. Sandy, UT, USA: Aardvark Global Publishing. pp.128-145.
(Location: IWMI HQ Call no: 551.48 G136 ABT Record No: H044319)
(1.11 MB)
2 Habib, E.; Haile, Alemseged Tamiru; Sazib, N.; Zhang, Y.; Rientjes, T.. 2014. Effect of bias correction of satellite-rainfall estimates on runoff simulations at the source of the Upper Blue Nile. Remote Sensing, 6(7):6688-6708. [doi: https://doi.org/10.3390/rs6076688]
Rain ; Runoff ; Satellites ; River basins ; Hydrology ; Simulation models ; Calibration ; Catchment areas ; Stream flow / Africa / Ethiopia / Upper Blue Nile Basin
(Location: IWMI HQ Call no: e-copy only Record No: H046873)
(608 KB)
Results of numerous evaluation studies indicated that satellite-rainfall products are contaminated with significant systematic and random errors. Therefore, such products may require refinement and correction before being used for hydrologic applications. In the present study, we explore a rainfall-runoff modeling application using the Climate Prediction Center-MORPHing (CMORPH) satellite rainfall product. The study area is the Gilgel Abbay catchment situated at the source basin of the Upper Blue Nile basin in Ethiopia, Eastern Africa. Rain gauge networks in such area are typically sparse. We examine different bias correction schemes applied locally to the CMORPH product. These schemes vary in the degree to which spatial and temporal variability in the CMORPH bias fields are accounted for. Three schemes are tested: space and time-invariant, time-variant and spatially invariant, and space and time variant. Bias-corrected CMORPH products were used to calibrate and drive the Hydrologiska Byråns Vattenbalansavdelning (HBV) rainfall-runoff model. Applying the space and time-fixed bias correction scheme resulted in slight improvement of the CMORPH-driven runoff simulations, but in some instances caused deterioration. Accounting for temporal variation in the bias reduced the rainfall bias by up to 50%. Additional improvements were observed when both the spatial and temporal variability in the bias was accounted for. The rainfall bias was found to have a pronounced effect on model calibration. The calibrated model parameters changed significantly when using rainfall input from gauges alone, uncorrected, and bias-corrected CMORPH estimates. Changes of up to 81% were obtained for model parameters controlling the stream flow volume.
3 Gumindoga, W.; Rientjes, T.; Shekede, M. D.; Rwasoka, D. T.; Nhapi, I.; Haile, Alemseged Tamiru. 2014. Hydrological impacts of urbanization of two catchments in Harare, Zimbabwe. Remote Sensing, 6(12):12544-12574. [doi: https://doi.org/10.3390/rs61212544]
Hydrological factors ; Urbanization ; Impact assessment ; Catchment areas ; Water management ; Water resources ; Water table ; Land cover change ; Remote sensing ; Satellite imagery ; Rain ; Runoff ; Models ; Woodlands ; Deforestation ; Stream flow ; Soils ; Infiltration / Zimbabwe / Harare / Mukuvisi Catchment / Marimba Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H046874)
(9.22 MB)
By increased rural-urban migration in many African countries, the assessment of changes in catchment hydrologic responses due to urbanization is critical for water resource planning and management. This paper assesses hydrological impacts of urbanization on two medium-sized Zimbabwean catchments (Mukuvisi and Marimba) for which changes in land cover by urbanization were determined through Landsat Thematic Mapper (TM) images for the years 1986, 1994 and 2008. Impact assessments were done through hydrological modeling by a topographically driven rainfall-runoff model (TOPMODEL). A satellite remote sensing based ASTER 30 metre Digital Elevation Model (DEM) was used to compute the Topographic Index distribution, which is a key input to the model. Results of land cover classification indicated that urban areas increased by more than 600 % in the Mukuvisi catchment and by more than 200 % in the Marimba catchment between 1986 and 2008. Woodlands decreased by more than 40% with a greater decrease in Marimba than Mukuvisi catchment. Simulations using TOPMODEL in Marimba and Mukuvisi catchments indicated streamflow increases of 84.8 % and 73.6 %, respectively, from 1980 to 2010. These increases coincided with decreases in woodlands and increases in urban areas for the same period. The use of satellite remote sensing data to observe urbanization trends in semi-arid catchments and to represent catchment land surface characteristics proved to be effective for rainfall-runoff modeling. Findings of this study are of relevance for many African cities, which are experiencing rapid urbanization but often lack planning and design.
4 Fenta, A. A.; Rientjes, T.; Haile, Alemseged Tamiru; Reggiani, P. 2014. Satellite rainfall products and their reliability in the Blue Nile Basin. In Melesse, A. M.; Abtew, W.; Setegn, S. G. (Eds.). Nile river basin: ecohydrological challenges, climate change and hydropolitics. Dordrecht, Netherlands: Springer. pp.51-67.
Satellite observation ; Radar satellite ; Satellite imagery ; Meteorological stations ; River basins ; Rain ; Measurement ; Remote sensing ; GIS ; Precipitation ; Case studies / Ethiopia / Blue Nile Basin
(Location: IWMI HQ Call no: e-copy only Record No: H046898)
(0.37 MB)
In the Upper Blue Nile (UBN) basin, there is very sparse and uneven distribution of ground-based meteorological stations which constrain assessments on rainfall distributions and representation. To assess the diurnal cycle of rainfall across the UBN basin, satellite observations from Tropical Rainfall Measuring Mission (TRMM) were used in this study. Data of 7 years (2002–2008) of Precipitation Radar (PR) and TRMM Microwave Imager (TMI) were processed, with analyses based on geographic information system (GIS) operations, statistical techniques, and harmonic analysis. Diurnal cycle patterns of rainfall occurrence and rain rate from three in-situ weather stations are well represented by the satellite observations. Harmonic analysis depicts large differences in the mean of the diurnal cycle, amplitude, and time of the amplitude across the study area. Diurnal cycle of rainfall occurrence has a single peak in Lake Tana, Gilgel Abbay, and Jemma subbasins and double peaks in Belles, Dabus, and Muger subbasins. Maximum rain rate occurs in the morning (Gilgel Abbay, Dabus, and Jemma), afternoon (Belles, Beshilo, and Muger), and evening (Lake Tana and along the river gorges). Results of this study indicate that satellite observations provide an alternative source of data to characterize diurnal cycle of rainfall in data-scarce regions. We noticed, however, that there are a number of constraints to the use of satellite observations. For more accurate assessments, satellite products require validation by a network of well-distributed ground stations. Also, we advocate bias correction.
5 Haile, Alemseged Tamiru; Tefera, F. T.; Rientjes, T.. 2016. Flood forecasting in Niger-Benue basin using satellite and quantitative precipitation forecast data. International Journal of Applied Earth Observation and Geoinformation, 52:475-484. [doi: https://doi.org/10.1016/j.jag.2016.06.021]
Weather forecasting ; Weather data ; River basins ; Precipitation ; Satellite observation ; Flooding ; Rainfall-runoff relationships ; Early warning systems ; International waters ; Tributaries ; Calibration ; Models / Nigeria / Cameroon / Makurdi / Niger River / Benue River / Chadda River / Tchadda
(Location: IWMI HQ Call no: e-copy only Record No: H047675)
Availability of reliable, timely and accurate rainfall data is constraining the establishment of flood forecasting and early warning systems in many parts of Africa. We evaluated the potential of satellite and weather forecast data as input to a parsimonious flood forecasting model to provide information for flood early warning in the central part of Nigeria. We calibrated the HEC-HMS rainfall-runoff model using rainfall data from post real time Tropical Rainfall Measuring Mission (TRMM) Multi satellite Precipitation Analysis product (TMPA). Real time TMPA satellite rainfall estimates and European Centre for MediumRange Weather Forecasts (ECMWF) rainfall products were tested for flood forecasting. The implication of removing the systematic errors of the satellite rainfall estimates (SREs) was explored. Performance of the rainfall-runoff model was assessed using visual inspection of simulated and observed hydrographs and a set of performance indicators. The forecast skill was assessed for 1–6 days lead time using categorical verification statistics such as Probability Of Detection (POD), Frequency Of Hit (FOH) and Frequency Of Miss (FOM). The model performance satisfactorily reproduced the pattern and volume of the observed stream flow hydrograph of Benue River. Overall, our results show that SREs and rainfall forecasts from weather models have great potential to serve as model inputs for real-time flood forecasting in data scarce areas. For these data to receive application in African transboundary basins, we suggest (i) removing their systematic error to further improve flood forecast skill; (ii) improving rainfall forecasts; and (iii) improving data sharing between riparian countries.
6 Nigatu, Z. M.; Rientjes, T.; Haile, Alemseged Tamiru. 2016. Hydrological impact assessment of climate change on Lake Tana’s water balance, Ethiopia. American Journal of Climate Change, 5:27-37. [doi: https://doi.org/10.4236/ajcc.2016.51005]
Hydrology ; Impact assessment ; Climate change ; Lakes ; Water balance ; Statistical methods ; Models ; Emission ; Precipitation ; Temperature ; Evaporation ; Catchment areas ; Surface water ; Flow discharge / Ethiopia / Tana Lake
(Location: IWMI HQ Call no: e-copy only Record No: H047947)
The aim of this study is to evaluate the hydrological impacts of climate change on the water balance of Lake Tana in Ethiopia. Impact assessments are by downscaled General Circulation Model (GCM) output and hydrological modeling. For A2 and B2 emission scenarios, precipitation, maximum and minimum temperature estimates from the HadCM3 GCM were used. GCM output was downscaled using the Statistical DownScaling Model (SDSM 4.2). Impact analyses were applied for three future time periods: early, mid and late 21st century. Over-lake evaporation is estimated by Hardgrave’s method, and over-lake precipitation is estimated by inverse distance weighing interpolation, whereas inflows from gauged and ungauged catchments are simulated by the HBV hydrological model. Findings indicate increases in maximum and minimum temperature on annual base for both emission scenarios. The projection of mean annual over lake precipitation for both A2 and B2 emission scenarios shows increasing pattern for 21st century in comparison to the baseline period. The increase of mean annual precipitation for A2 emission scenario is 9% (112 mm/year), 10% (125 mm/year) and 11% (137 mm/year) for the three future periods respectively. B2 emission scenario mean annual precipitation shows increase by 9% (111 mm/year), 10% (122 mm/year) and 10% (130 mm/year) respectively for the three future periods. Findings indicate consistent increases of lake storage for all three future periods for both A2 and B2 emission scenarios.
7 Bhatti, H. A.; Rientjes, T.; Haile, Alemseged Tamiru; Habib, E.; Verhoef, W. 2016. Evaluation of bias correction method for satellite-based rainfall data. Sensors, 16(6):1-16. [doi: https://doi.org/10.3390/s16060884]
Satellite observation ; Rain ; Remote sensing ; Catchment areas ; Runoff water ; Hydrology ; Precipitation ; Meteorology ; Spatial distribution / Ethiopia / Gilgel Abbey Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H047948)
(3.11 MB)
With the advances in remote sensing technology, satellite-based rainfall estimates are gaining attraction in the eld of hydrology, particularly in rainfall-runoff modeling. Since estimates are affected by errors correction is required. In this study, we tested the high resolution National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Centre (CPC) morphing technique (CMORPH) satellite rainfall product (CMORPH) in the Gilgel Abbey catchment, Ethiopia. CMORPH data at 8 km-30 min resolution is aggregated to daily to match in-situ observations for the period 2003–2010. Study objectives are to assess bias of the satellite estimates, to identify optimum window size for application of bias correction and to test effectiveness of bias correction. Bias correction factors are calculated for moving window (MW) sizes and for sequential windows (SW’s) of 3, 5, 7, 9, ... , 31 days with the aim to assess error distribution between the in-situ observations and CMORPH estimates. We tested forward, central and backward window (FW, CW and BW) schemes to assess the effect of time integration on accumulated rainfall. Accuracy of cumulative rainfall depth is assessed by Root Mean Squared Error (RMSE). To systematically correct all CMORPH estimates, station based bias factors are spatially interpolated to yield a bias factor map. Reliability of interpolation is assessed by cross validation. The uncorrected CMORPH rainfall images are multiplied by the interpolated bias map to result in bias corrected CMORPH estimates. Findings are evaluated by RMSE, correlation coef cient (r) and standard deviation (SD). Results showed existence of bias in the CMORPH rainfall. It is found that the 7 days SW approach performs best for bias correction of CMORPH rainfall. The outcome of this study showed the ef ciency of our bias correction approach.
8 Haile, Alemseged Tamiru; Akawka, A. L.; Berhanu, B.; Rientjes, T.. 2017. Changes in water availability in the Upper Blue Nile basin under the representative concentration pathways scenario. Hydrological Sciences Journal, 62(13):2139-2149.
Water availability ; Water resources ; Climate change ; Temperature ; Drought ; Hydrogeology ; Intensification ; Rainfall-runoff relationships ; Evapotranspiration ; Catchment areas ; Stream flow ; Soil moisture ; Meteorological stations ; Calibration ; Land cover / Ethiopia / Upper Blue Nile Basin
(Location: IWMI HQ Call no: e-copy only Record No: H048259)
http://www.tandfonline.com/doi/pdf/10.1080/02626667.2017.1365149?needAccess=true
https://vlibrary.iwmi.org/pdf/H048259.pdf
https://vlibrary.iwmi.org/pdf/H048259.pdf
limatic and hydrological changes will likely be intensified in the Upper Blue Nile (UBN) basin by the effects of global warming. The extent of such effects for representative concentration pathways (RCP) climate scenarios is unknown. We evaluated projected changes in rainfall and evapotranspiration and related impacts on water availability in the UBN under the RCP4.5 scenario. We used dynamically downscaled outputs from six global circulation models (GCMs) with unprecedented spatial resolution for the UBN. Systematic errors of these outputs were corrected and followed by runoff modelling by the HBV (Hydrologiska ByrånsVattenbalansavdelning) model, which was successfully validated for 17 catchments. Results show that the UBN annual rainfall amount will change by -2.8 to 2.7% with a likely increase in annual potential evapotranspiration (in 2041–2070) for the RCP4.5 scenario. These changes are season dependent and will result in a likely decline in streamflow and an increase in soil moisture deficit in the basin.
9 Asfaw, W.; Haile, Alemseged Tamiru; Rientjes, T.. 2020. Combining multisource satellite data to estimate storage variation of a lake in the Rift Valley Basin, Ethiopia. International Journal of Applied Earth Observation and Geoinformation, 89:102095. [doi: https://doi.org/10.1016/j.jag.2020.102095]
Water storage ; Estimation ; Lakes ; Surface area ; Satellite imagery ; Landsat ; Radar ; Remote sensing ; Water levels ; Water extraction ; Rivers / Ethiopia / Rift Valley Basin / Lake Ziway
(Location: IWMI HQ Call no: e-copy only Record No: H049749)
https://www.sciencedirect.com/science/article/pii/S0303243419311997/pdfft?md5=640ffced1d934faff7ef42e894ee9542&pid=1-s2.0-S0303243419311997-main.pdf
https://vlibrary.iwmi.org/pdf/H049749.pdf
https://vlibrary.iwmi.org/pdf/H049749.pdf
(2.11 MB) (2.11 MB)
Integration of remote sensing data sets from multiple satellites is tested to simulate water storage variation of Lake Ziway, Ethiopia for the period 2009-2018. Sixty Landsat ETM+/OLI images served to trace temporal variation of lake surface area using a water extraction index. Time series of lake levels were acquired from two altimetry databases that were validated by in-situ lake level measurements. Coinciding pairs of optical satellite based lake surface area and radar altimetry based lake levels were related through regression and served for simulating lake storage variation. Indices for extracting lake surface area from images showed 91–99 % overall accuracy. Lake water levels from the altimetry products well agreed to in-situ lake level measurements with R2 = 0.92 and root mean square error of 11.9 cm. Based on this study we conclude that integrating satellite imagery and radar altimetry is a viable approach for frequent and accurate monitoring of lake water volume variation and for long-term change detection. Findings indicate water level reduction (4 cm/annum), surface area shrinkage (0.08km2 /annum) and water storage loss (20.4Mm3 /annum) of Lake Ziway (2009–2018).
10 Goshime, D. W.; Absi, R.; Haile, Alemseged Tamiru; Ledesert, B.; Rientjes, T.. 2020. Bias-corrected CHIRP [Climate Hazards Group InfraRed Precipitation] satellite rainfall for water level simulation, Lake Ziway, Ethiopia. Journal of Hydrologic Engineering, 25(9):05020024. [doi: https://doi.org/10.1061/(ASCE)HE.1943-5584.0001965]
Lakes ; Water levels ; Simulation ; Water balance ; Estimation ; Rainfall-runoff relationships ; Rivers ; Flow discharge ; Models ; Rain gauges ; Precipitation ; Catchment areas ; Evapotranspiration / Ethiopia / Lake Ziway / Meki Catchment / Katar Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H049933)
(2.50 MB)
Applicability of satellite rainfall products must be explored since rain gauge networks have limitations to provide adequate spatial coverage. In this study, Climate Hazards InfraRed Precipitation (CHIRP) satellite-only product was evaluated for rainfall-runoff modeling whereas the simulated runoff served as input to simulate the water levels of Lake Ziway from 1986 to 2014. CHIRP dataset was bias-corrected using power transformation and used as input to Hydrologiska Byråns Vattenbalansavdelning (HBV) model to simulate streamflow of Meki and Katar catchments. Results showed that gauged catchments of Meki and Katar contributed 524 and 855 mm to the annual lake inflow, respectively. The estimated runoff from ungauged catchments is 182 mm that amounts to approximately 8.5% of the total lake inflow over the period 1986–2000. The results of lake level simulation show good agreement from 1986 to 2000, but deteriorating agreement after 2000, which is mainly attributed to errors in water balance terms and human-induced impacts. For the period 1986–2000, the water balance closure error for the lake was 67.5 mm per year, which accounts for 2.9% of the total lake inflow from rainfall and river inflow. This study shows bias correction increases the applicability of CHIRP satellite product for lake water balance studies.
11 Bekele, W. T.; Haile, Alemseged Tamiru; Rientjes, T.. 2021. Impact of climate change on the streamflow of the Arjo-Didessa Catchment under RCP scenarios. Journal of Water and Climate Change, 12(6):2325-2337. [doi: https://doi.org/10.2166/wcc.2021.307]
Climate change ; Forecasting ; Catchment areas ; Stream flow ; Estimation ; Runoff ; Temperature ; Rain ; Evapotranspiration ; Hydrology ; Models ; Performance evaluation / Ethiopia / Upper Blue Nile Basin / Arjo-Didessa Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H050318)
https://iwaponline.com/jwcc/article-pdf/12/6/2325/934604/jwc0122325.pdf
https://vlibrary.iwmi.org/pdf/H050318.pdf
https://vlibrary.iwmi.org/pdf/H050318.pdf
(0.54 MB) (553 KB)
In this study, the impact of climate change on the streamflow of the Arjo-Didessa catchment, Upper Blue Nile basin, is evaluated. We used the outputs of four climate models for two representative concentration pathway (RCP) climate scenarios, which are RCP 4.5 and RCP 8.5. Streamflow simulation was done by using the HEC-HMS rainfall-runoff model, which was satisfactorily calibrated and validated for the study area. For the historic period (1971–2000), all climate models significantly underestimated the observed rainfall amount for the rainy season. We therefore bias-corrected the climate data before using them as input for the rainfall-runoff model. The results of the four climate models for the period 2041 to 2070 show that annual rainfall is likely to decrease by 0.36 to 21% under RCP 4.5. The projected increases in minimum and maximum temperature will lead to an increase in annual evapotranspiration by 3 to 7%, which will likely contribute to decreasing the annual flows of Arjo-Didessa by 1 to 3%. Our results show that the impact is season dependent, with an increased streamflow in the main rainy season but a decreased flow in the short rainy season and the dry seasons. The magnitudes of projected changes are more pronounced under RCP 8.5 than under RCP 4.5.
12 Goshime, D. W.; Haile, Alemseged Tamiru; Rientjes, T.; Absi, R.; Ledesert, B.; Siegfried, T. 2021. Implications of water abstraction on the interconnected Central Rift Valley Lakes Sub-Basin of Ethiopia using WEAP. Journal of Hydrology: Regional Studies, 38:100969. [doi: https://doi.org/10.1016/j.ejrh.2021.100969]
Water extraction ; Water demand ; Water supply ; Water resources development ; Lakes ; Catchment areas ; Stream flow ; Water balance ; Environmental flows ; Models / Ethiopia / Central Rift Valley Lakes Sub-Basin
(Location: IWMI HQ Call no: e-copy only Record No: H050844)
https://www.sciencedirect.com/science/article/pii/S2214581821001981/pdfft?md5=840d781070bf0befcda70ba6e2881493&pid=1-s2.0-S2214581821001981-main.pdf
https://vlibrary.iwmi.org/pdf/H050844.pdf
https://vlibrary.iwmi.org/pdf/H050844.pdf
(5.31 MB) (5.31 MB)
Study region: Central Rift Valley Lakes sub-basin, Ethiopia.
Study focus: The competition for water is rapidly increasing in Central Rift Valley lakes sub-basin due to the combined effect of various water resources developments. However, the impacts of recent and future water resources development pathways on the water balance of the three interconnected lakes (i.e. Lake Ziway, Langano and Abiyata) are unknown. The Water Evaluation And Planning (WEAP) model was used to assess the development impacts on water resources of the interconnected lakes. We considered three development pathways that are, recent (2009–2018), short-term (2019–2028) and long-term development (2029–2038). Lake Ziway water inflows from six catchments were estimated using the Hydrologiska Byråns Vattenbalansavdelning (HBV) rainfall-runoff model. Crop water requirements for irrigation schemes were estimated by the CROPWAT model.
New hydrological insights for the region: WEAP simulations show a total water demand of 102.3 Mm3 under the recent development pathway that increases by 46% and 118% for short-term and long-term development pathways, respectively. This will notably affect the water balance of the interconnected lakes and cause an unmet water demand of 47.9 Mm3 for the long-term (2028–2038). For Lake Ziway and Abiyata, water levels will decrease substantially to cause water scarcity in the long-term, and developments in Lake Ziway will significantly affect water storage in Lake Abiyata storages in Lake Abiyata. Overall, future developments will threaten the water resource of the interconnected lake system.
Study focus: The competition for water is rapidly increasing in Central Rift Valley lakes sub-basin due to the combined effect of various water resources developments. However, the impacts of recent and future water resources development pathways on the water balance of the three interconnected lakes (i.e. Lake Ziway, Langano and Abiyata) are unknown. The Water Evaluation And Planning (WEAP) model was used to assess the development impacts on water resources of the interconnected lakes. We considered three development pathways that are, recent (2009–2018), short-term (2019–2028) and long-term development (2029–2038). Lake Ziway water inflows from six catchments were estimated using the Hydrologiska Byråns Vattenbalansavdelning (HBV) rainfall-runoff model. Crop water requirements for irrigation schemes were estimated by the CROPWAT model.
New hydrological insights for the region: WEAP simulations show a total water demand of 102.3 Mm3 under the recent development pathway that increases by 46% and 118% for short-term and long-term development pathways, respectively. This will notably affect the water balance of the interconnected lakes and cause an unmet water demand of 47.9 Mm3 for the long-term (2028–2038). For Lake Ziway and Abiyata, water levels will decrease substantially to cause water scarcity in the long-term, and developments in Lake Ziway will significantly affect water storage in Lake Abiyata storages in Lake Abiyata. Overall, future developments will threaten the water resource of the interconnected lake system.
13 Haile, Alemseged Tamiru; Asfaw, Wegayehu; Rientjes, T.; Worako, A. W. 2022. Deterioration of streamflow monitoring in Omo-Gibe Basin in Ethiopia. Hydrological Sciences Journal, 67(7):1040-1053. [doi: https://doi.org/10.1080/02626667.2022.2060110]
River basins ; Stream flow ; Deterioration ; Monitoring ; Hydrological data ; Data quality ; Time series analysis ; Transboundary waters ; Gauges ; Land use change / Ethiopia / Omo-Gibe Basin
(Location: IWMI HQ Call no: e-copy only Record No: H051035)
https://www.tandfonline.com/doi/pdf/10.1080/02626667.2022.2060110?needAccess=true
https://vlibrary.iwmi.org/pdf/H051035.pdf
https://vlibrary.iwmi.org/pdf/H051035.pdf
(6.45 MB) (6.45 MB)
Poor availability and accuracy of streamflow data constrains research and operational hydrology. We evaluated the status of forty streamflow stations and data quality in the Omo-Gibe basin, Ethiopia. The method included a 3-week field inspection of the stations. Inspection of stations followed common WMO guidelines for appropriate gauging sites. Feedback of observers was collected, and the streamflow data was analyzed. Most of the stations were installed on rivers at headwater catchments. Only 17% of the stations were fully operational whereas the remaining stations require major maintenance. Common problems of the time series data include short observation period, large number of missing records, and inhomogeneity. Nearly all observers expressed dissatisfaction due to lack of supervision, uncertain salary payments and lack of recognition of their contribution. The findings of this study indicate the need to investigate the institutional barriers that affected the homogeneity, completeness, and timeliness of the stream data.
14 Worako, A. W.; Haile, Alemseged Tamiru; Rientjes, T.; Woldesenbet, T. A. 2022. Error propagation of climate model rainfall to streamflow simulation in the Gidabo Sub-basin, Ethiopian Rift Valley Lakes Basin. Hydrological Sciences Journal, 67(8):1185-1198. [doi: https://doi.org/10.1080/02626667.2022.2072220]
Climate models ; Errors ; Hydrological modelling ; Climate change ; Stream flow ; Rain / Ethiopia / Rift Valley Lakes Basin / Gidabo Sub-Basin
(Location: IWMI HQ Call no: e-copy only Record No: H051243)
(2.55 MB)
This study assesses bias error of rainfall from climate models and related error propagation effects to simulated streamflow in the Gidabo sub-basin, Ethiopia. Rainfall is obtained from a combination of four global and regional climate models (GCM-RCMs), and streamflow is simulated by means of the Hydrologiska Byråns Vattenbalansavdelning (HBV-96) rainfall-runoff model. Five bias correction methods were tested to reduce the rainfall bias. To assess the effects of rainfall bias error propagation, percent bias (PBIAS), difference in coefficient of variation (CV), and 10th and 90th percentile indicators were applied. Findings indicate that the bias of the uncorrected rainfall caused large errors in simulated streamflow. All five bias correction methods improved the HBV-96 model performance in terms of capturing the observed streamflow. Overall, the findings of this study indicate that the magnitude of the error propagation varies subject to the selected performance indicator, bias correction method and climate model.
15 Asfaw, Wegayehu; Rientjes, T.; Haile, Alemseged Tamiru. 2023. Blending high-resolution satellite rainfall estimates over urban catchment using Bayesian Model Averaging approach. Journal of Hydrology: Regional Studies, 45:101287. [doi: https://doi.org/10.1016/j.ejrh.2022.101287]
Rain ; Estimation ; Catchment areas ; Urban areas ; Satellite observation ; Bayesian theory ; Models ; River basins ; Precipitation / Ethiopia / Addis Ababa / Awash River Basin / Akaki Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H051574)
https://www.sciencedirect.com/science/article/pii/S2214581822003007/pdfft?md5=64a629a5b0401baf4f3f2da66556416b&pid=1-s2.0-S2214581822003007-main.pdf
https://vlibrary.iwmi.org/pdf/H051574.pdf
https://vlibrary.iwmi.org/pdf/H051574.pdf
(13.70 MB) (13.7 MB)
Study region: Akaki is a headwater catchment of Awash River Basin that hosts the capital city of Ethiopia, Addis Ababa. The area encompasses several agglomerated towns, water supply, and hydropower reservoirs and is characterized by a chain of mountains and floodplains. Due to basin rainfall, and the expansion of urbanized areas, the catchment is frequently affected by flooding. Study focus: This study evaluates dynamic Bayesian Model Averaging (BMA) approach to improve rainfall estimation over the catchment by blending four high-resolution satellite rainfall estimate (SRE) products. Using daily data (2003–2019) observed at thirteen stations as a reference, seven statistical metrics served to assess the point and spatial scale accuracy of the rainfall estimates.
New hydrological insights: Main findings from this study are: (i) the blended product outperformed the individual SRE products by notably improving correlation with in-situ observed rainfall, and reducing the error of the estimated rainfall, (ii) the blended and individual SRE products performed better in the highlands than the lowlands of the catchment, and (iii) the amount of daily rainfall during the main-rainy season was mostly overestimated by the individual SRE products but was fairly estimated by the blended product. This study showed the nonexistence of surpassing individual SRE products and emphasized the blending of several products for gaining optimal results from each product.
New hydrological insights: Main findings from this study are: (i) the blended product outperformed the individual SRE products by notably improving correlation with in-situ observed rainfall, and reducing the error of the estimated rainfall, (ii) the blended and individual SRE products performed better in the highlands than the lowlands of the catchment, and (iii) the amount of daily rainfall during the main-rainy season was mostly overestimated by the individual SRE products but was fairly estimated by the blended product. This study showed the nonexistence of surpassing individual SRE products and emphasized the blending of several products for gaining optimal results from each product.
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