Your search found 5 records
1 Dembele, M.; Ceperley, N.; Zwart, Sander J.; Salvadore, E.; Mariethoz, G.; Schaefli, B. 2020. Potential of satellite and reanalysis evaporation datasets for hydrological modelling under various model calibration strategies. Advances in Water Resources, 143:103667. [doi: https://doi.org/10.1016/j.advwatres.2020.103667]
Hydrology ; Modelling ; Calibration ; Strategies ; Satellites ; Remote sensing ; Evaporation ; River basins ; Stream flow ; Water storage ; Soil water content ; Climatic zones ; Forecasting ; Datasets ; Performance evaluation ; Spatial distribution / West Africa / Volta River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H049804)
https://www.sciencedirect.com/science/article/pii/S030917082030230X/pdfft?md5=fe6a7ca8d66941a8fd4455b385a1dd8c&pid=1-s2.0-S030917082030230X-main.pdf
https://vlibrary.iwmi.org/pdf/H049804.pdf
https://vlibrary.iwmi.org/pdf/H049804.pdf
(4.54 MB) (4.54 MB)
Twelve actual evaporation datasets are evaluated for their ability to improve the performance of the fully distributed mesoscale Hydrologic Model (mHM). The datasets consist of satellite-based diagnostic models (MOD16A2, SSEBop, ALEXI, CMRSET, SEBS), satellite-based prognostic models (GLEAM v3.2a, GLEAM v3.3a, GLEAM v3.2b, GLEAM v3.3b), and reanalysis (ERA5, MERRA-2, JRA-55). Four distinct multivariate calibration strategies (basin-average, pixel-wise, spatial bias-accounting and spatial bias-insensitive) using actual evaporation and streamflow are implemented, resulting in 48 scenarios whose results are compared with a benchmark model calibrated solely with streamflow data. A process-diagnostic approach is adopted to evaluate the model responses with in-situ data of streamflow and independent remotely sensed data of soil moisture from ESA-CCI and terrestrial water storage from GRACE. The method is implemented in the Volta River basin, which is a data scarce region in West Africa, for the period from 2003 to 2012.
Results show that the evaporation datasets have a good potential for improving model calibration, but this is dependent on the calibration strategy. All the multivariate calibration strategies outperform the streamflow-only calibration. The highest improvement in the overall model performance is obtained with the spatial bias-accounting strategy (+29%), followed by the spatial bias-insensitive strategy (+26%) and the pixel-wise strategy (+24%), while the basin-average strategy (+20%) gives the lowest improvement. On average, using evaporation data in addition to streamflow for model calibration decreases the model performance for streamflow (-7%), which is counterbalance by the increase in the performance of the terrestrial water storage (+11%), temporal dynamics of soil moisture (+6%) and spatial patterns of soil moisture (+89%). In general, the top three best performing evaporation datasets are MERRA-2, GLEAM v3.3a and SSEBop, while the bottom three datasets are MOD16A2, SEBS and ERA5. However, performances of the evaporation products diverge according to model responses and across climatic zones. These findings open up avenues for improving process representation of hydrological models and advancing the spatiotemporal prediction of floods and droughts under climate and land use changes.
Results show that the evaporation datasets have a good potential for improving model calibration, but this is dependent on the calibration strategy. All the multivariate calibration strategies outperform the streamflow-only calibration. The highest improvement in the overall model performance is obtained with the spatial bias-accounting strategy (+29%), followed by the spatial bias-insensitive strategy (+26%) and the pixel-wise strategy (+24%), while the basin-average strategy (+20%) gives the lowest improvement. On average, using evaporation data in addition to streamflow for model calibration decreases the model performance for streamflow (-7%), which is counterbalance by the increase in the performance of the terrestrial water storage (+11%), temporal dynamics of soil moisture (+6%) and spatial patterns of soil moisture (+89%). In general, the top three best performing evaporation datasets are MERRA-2, GLEAM v3.3a and SSEBop, while the bottom three datasets are MOD16A2, SEBS and ERA5. However, performances of the evaporation products diverge according to model responses and across climatic zones. These findings open up avenues for improving process representation of hydrological models and advancing the spatiotemporal prediction of floods and droughts under climate and land use changes.
2 Dembele, M.; Zwart, Sander; Ceperley, N.; Mariethoz, G.; Schaefli, B. 2020. Multivariate and spatially calibrated hydrological model for assessing climate change impacts on hydrological processes in West Africa. [Abstract only]. Paper presented at the European Geosciences Union (EGU) General Assembly 2020, Online, 4-8 May 2020. 2p. [doi: https://doi.org/10.5194/egusphere-egu2020-9143]
Climate change ; Assessment ; Hydrology ; Models ; Calibration ; Multivariate analysis / West Africa
(Location: IWMI HQ Call no: e-copy only Record No: H050011)
https://meetingorganizer.copernicus.org/EGU2020/EGU2020-9143.html?pdf
https://vlibrary.iwmi.org/pdf/H050011.pdf
https://vlibrary.iwmi.org/pdf/H050011.pdf
(0.29 MB) (292 KB)
3 Dembele, Moctar; Vrac, M.; Ceperley, N.; Zwart, Sander J.; Larsen, J.; Dadson, S. J.; Mariethoz, G.; Schaefli, B. 2022. Contrasting changes in hydrological processes of the Volta River Basin under global warming. Hydrology and Earth System Sciences, 26(5):1481-1506. [doi: https://doi.org/10.5194/hess-26-1481-2022]
River basins ; Hydrological cycle ; Global warming ; Hydrological modelling ; Climate change ; Forecasting ; Water availability ; Hydroclimate ; Climatic zones ; Spatial variation ; Datasets / West Africa / Volta River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H051026)
https://hess.copernicus.org/articles/26/1481/2022/hess-26-1481-2022.pdf
https://vlibrary.iwmi.org/pdf/H051026.pdf
https://vlibrary.iwmi.org/pdf/H051026.pdf
(4.33 MB) (4.33 MB)
A comprehensive evaluation of the impacts of climate change on water resources of the West Africa Volta River basin is conducted in this study, as the region is expected to be hardest hit by global warming. A large ensemble of 12 general circulation models (GCMs) from the fifth Coupled Model Intercomparison Project (CMIP5) that are dynamically downscaled by five regional climate models (RCMs) from the Coordinated Regional-climate Downscaling Experiment (CORDEX)-Africa is used. In total, 43 RCM–GCM combinations are considered under three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5). The reliability of each of the climate datasets is first evaluated with satellite and reanalysis reference datasets. Subsequently, the Rank Resampling for Distributions and Dependences (R2D2) multivariate bias correction method is applied to the climate datasets. The bias-corrected climate projections are then used as input to the mesoscale Hydrologic Model (mHM) for hydrological projections over the 21st century (1991–2100).
Results reveal contrasting dynamics in the seasonality of rainfall, depending on the selected greenhouse gas emission scenarios and the future projection periods. Although air temperature and potential evaporation increase under all RCPs, an increase in the magnitude of all hydrological variables (actual evaporation, total runoff, groundwater recharge, soil moisture, and terrestrial water storage) is only projected under RCP8.5. High- and low-flow analysis suggests an increased flood risk under RCP8.5, particularly in the Black Volta, while hydrological droughts would be recurrent under RCP2.6 and RCP4.5, particularly in the White Volta. The evolutions of streamflow indicate a future delay in the date of occurrence of low flows up to 11 d under RCP8.5, while high flows could occur 6 d earlier (RCP2.6) or 5 d later (RCP8.5), as compared to the historical period.
Disparities are observed in the spatial patterns of hydroclimatic variables across climatic zones, with higher warming in the Sahelian zone. Therefore, climate change would have severe implications for future water availability with concerns for rain-fed agriculture, thereby weakening the water– energy–food security nexus and amplifying the vulnerability of the local population. The variability between climate models highlights uncertainties in the projections and indicates a need to better represent complex climate features in regional models. These findings could serve as a guideline for both the scientific community to improve climate change projections and for decision-makers to elaborate adaptation and mitigation strategies to cope with the consequences of climate change and strengthen regional socioeconomic development.
Results reveal contrasting dynamics in the seasonality of rainfall, depending on the selected greenhouse gas emission scenarios and the future projection periods. Although air temperature and potential evaporation increase under all RCPs, an increase in the magnitude of all hydrological variables (actual evaporation, total runoff, groundwater recharge, soil moisture, and terrestrial water storage) is only projected under RCP8.5. High- and low-flow analysis suggests an increased flood risk under RCP8.5, particularly in the Black Volta, while hydrological droughts would be recurrent under RCP2.6 and RCP4.5, particularly in the White Volta. The evolutions of streamflow indicate a future delay in the date of occurrence of low flows up to 11 d under RCP8.5, while high flows could occur 6 d earlier (RCP2.6) or 5 d later (RCP8.5), as compared to the historical period.
Disparities are observed in the spatial patterns of hydroclimatic variables across climatic zones, with higher warming in the Sahelian zone. Therefore, climate change would have severe implications for future water availability with concerns for rain-fed agriculture, thereby weakening the water– energy–food security nexus and amplifying the vulnerability of the local population. The variability between climate models highlights uncertainties in the projections and indicates a need to better represent complex climate features in regional models. These findings could serve as a guideline for both the scientific community to improve climate change projections and for decision-makers to elaborate adaptation and mitigation strategies to cope with the consequences of climate change and strengthen regional socioeconomic development.
4 Dembele, Moctar; Salvadore, E.; Zwart, Sander; Ceperley, N.; Mariethoz, G.; Schaefli, B. 2023. Multiscale water accounting under climate change in a transboundary West African basin [Abstract only]. Paper presented at the European Geosciences Union (EGU) General Assembly 2023, Vienna, Austria and Online, 24-28 April 2023. 1p. [doi: https://doi.org/10.5194/egusphere-egu23-8955]
Water accounting ; Climate change ; Transboundary waters ; River basins ; Models / West Africa / Volta River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H051890)
https://meetingorganizer.copernicus.org/EGU23/EGU23-8955.html?pdf
https://vlibrary.iwmi.org/pdf/H051890.pdf
https://vlibrary.iwmi.org/pdf/H051890.pdf
(0.28 MB) (288 KB)
5 Dembele, Moctar; Salvadore, E.; Zwart, Sander; Ceperley, N.; Mariethoz, G.; Schaefli, B. 2023. Water accounting under climate change in the transboundary Volta River Basin with a spatially calibrated hydrological model. Journal of Hydrology, 626(Part A):130092. [doi: https://doi.org/10.1016/j.jhydrol.2023.130092]
Water accounting ; Climate change ; Transboundary waters ; River basins ; Hydrological modelling ; Water balance ; Water resources ; Water management ; Sustainability ; Water availability ; Water use ; Climate models ; Evaporation ; Land cover ; Land use ; Runoff ; Climatic zones / West Africa / Benin / Burkina Faso / Côte d'Ivoire / Ghana / Mali / Togo / Volta River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H052224)
https://www.sciencedirect.com/science/article/pii/S002216942301034X/pdfft?md5=f4d5176402091d76575e267a91c8113a&pid=1-s2.0-S002216942301034X-main.pdf
https://vlibrary.iwmi.org/pdf/H052224.pdf
https://vlibrary.iwmi.org/pdf/H052224.pdf
(10.80 MB) (10.8 MB)
Sustainable water management requires evidence-based information on the current and future states of water resources. This study presents a comprehensive modelling framework that integrates the fully distributed mesoscale Hydrologic Model (mHM) and climate change scenarios with the Water Accounting Plus (WA+) tool to anticipate future water resource challenges and provide mitigation measures in the transboundary Volta River basin (VRB) in West Africa. The mHM model is forced with a large ensemble of climate change projection data from CORDEX-Africa. Outputs from mHM are used as inputs to the WA+ framework to report on water flows and consumption over the historical baseline period 1991–2020 and the near-term future 2021–2050 at the basin scale, and also across spatial domains including four climatic zones, four sub-basins and six riparian countries. The long-term multi-model ensemble mean of the net inflow to the basin is found to be 419 km3 /year with an inter-annual variability of 11% and is projected to slightly increase in the near-term future (2021–2050). However, evaporation consumes most of the net inflow, with only 8% remaining as runoff. About 4 km3 /year of water is currently used for man-made activities. Only 45% of the available water is beneficially consumed, with the agricultural sector representing 34% of the beneficial water consumption. Water availability is projected to increase in the future due to the increase in rainfall, along with higher inter-model and inter-annual variabilities, thereby highlighting the need for adaptation strategies. These findings and the proposed climate-resilient land and water management strategies can help optimize the water-energy-food-ecosystem nexus and support evidence-based decisions and policy-making for sustainable water management in the VRB.
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