S20

Hydrology, new tools and innovative measurements and citizen science in Africa

African scientists suffered for long from being far from hot spots of science and lacked from technical experts. This situation has changed a lot since some time. An increasing number of high schools and universities have trained numerous young students who stayed for many of them in their home countries. A lot of international cooperation programs have developed capacities of local agencies and research teams to use recent techniques, and the quality of communications and internet capacity have much increased too.
International UNESCO programs like FRIEND or G-WADI, or international programs like AMMA or WATERNET allowed since 20 years to build strong regional communities who are able to share and develop knowledge within Africa. Thus in many regions the most recent technologies and data management tools are frequently used, participative research and environmental surveys are increasing, and citizens are more frequently associated to development and research programs. In the context of climate change impact on water availability, Africa needs to improve its capacity of development of its own research programs based on well trained high level research community. This session aims at proposing African researchers, or colleagues working in/on Africa, to present results of researches using recent, innovative techniques, data, tools, in connection with society and development priorities, and report about research programs involving citizen participation. Among the main topics concerned, but not limitative, are spatial hydrology, innovative measurement and observation techniques, openand big data, participatory science experiment, science literacy and so on. This could provide some meaningful options to deal with challenges and uncertainties in the African context, and it is perfectly linked with specific aspects of the African Union Agenda 2063 where one of the priority areas for the next decade is to have well educated citizens and skills revolution underpinned by Science, technology and innovation. This falls under ‘Inclusive growth and sustainable development’ aspiration of the agenda.

Convener: Gil Mahé | Co-Conveners: Marloes Mul, Hubert H.G. Savenije, Harald Kunstmann, Flavia Tauro, Fernando Nardi, Anil Mishra, Ernest Amoussou, MEDDI Mohamed, Jean-Marie Kileshye-Onema, Dominique Bérod
Orals
| Tue, 31 May, 08:30–15:00|Room Rondelet 1
Posters
| Attendance Tue, 31 May, 15:00–16:30|Poster area

Orals: Tue, 31 May | Room Rondelet 1

Chairpersons: Gil Mahé, Anil Mishra
Socio-economics and citizen science
08:30–08:45
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IAHS2022-97
Conrad Brendel and Alena Bartosova

Reservoir sedimentation is a major problem in South Africa that impacts drinking water supplies, irrigation, recreation, hydropower production, and flood control. Although South Africa has been actively involved in research and monitoring of erosion and sedimentation, an ongoing challenge with assessing reservoir sedimentation is that many basins are ungauged and information required to guide policy and decision making is not available. Thus, there is a need to better understand methods to estimate sediment yields in these areas. Hydrological models can provide detailed spatial and temporal estimates of sediment fluxes. However, when modeling data sparse regions, it can be challenging to find a balance between model complexity and data availability to not only optimize simulation performance, but also to not overparameterize the model.

In this study, we used the open source, semi-distributed Hydrological Predictions for the Environment (HYPE) model to investigate how model routines with different data requirements affected simulations of long-term reservoir sediment yields within the uMngeni River basin in South Africa. Specifically, we assessed the impacts on model performance due to selection of the erosion routine and the stream sedimentation/resuspension method. An ensemble of models for the uMngeni basin was calibrated to sediment yields calculated from reservoir surveys and suspended sediment sampling data for seven reservoirs. In total, the ensemble consisted of 12 model setups representing unique combinations of two erosion routines (Morgan-Morgan-Finney model and HBV-SED index method), three HBV-SED seasonal erosion correction methods (no adjustment, values from earth observation indices, and calibrated values), and three stream sedimentation/resuspension routines (based on bankfull flow, based on bankfull flow with calibrated correction factor, and the Bagnold equation). Upon completion of the ensemble calibration, a matrix of model fit statistics was created to evaluate how sediment simulation performance varied according to model routine complexity and input data requirements. Erosion rates, sources of sediment fluxes, and sediment yields were also compared between the model setups to provide guidance on ranges of potential reservoir impacts. Results from this study can inform the selection of modeling techniques during the development of sediment flux models for regions with limited data.

How to cite: Brendel, C. and Bartosova, A.: Modeling erosion and reservoir impacts in data sparse regions in South Africa, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-97, 2022.

08:45–09:00
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IAHS2022-1
Abdoulaye Faty, Awa Niang, Fernand Kouame, and Alioune Kane

In the Senegal River watershed, land use is undergoing significant dynamics due to intense human activities that place the ecosystem in a precarious balance. The objective of this study is to quantify the landscape dynamics and explore the possible futures of land use using remote sensing, GIS and spatio-temporal modeling tools while coupling with climate change indicators. Socio-economic data and Modis-Terra images (2007, 2014 and 2019) were used. A multi-date classification was used to quantify land use changes. The Land Change Modeler (LCM) model was used to simulate and project land use in the Senegal River watershed up to 2030. The results show that between 2007 and 2019, there will be a significant regression of natural vegetation formations (water bodies, forests and wooded savannahs) and an increase in anthropogenic formations (mosaics of crops and fallow land) for the same period. The three Business-As-Usual (BAU), Rapid Economic Growth (REC) and Coordinated Environmental Sustainability (CES) scenarios, extrapolating current trends, show that by 2030 (the SDG horizon) this landscape will be dominated by crop and fallow land mosaics (+50%). Woody resources occupy 26% of the area in the DEC scenario, 23% in the BAU scenario and 19% in the CER scenario. The DEC scenario gives hope that restoration and preservation of plant resources is still possible if decision makers are aware of it.

How to cite: Faty, A., Niang, A., Kouame, F., and Kane, A.: Which land use scenario for the revitalization of surface runoff in the Senegal River watershed, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-1, 2022.

09:00–09:15
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IAHS2022-746
Eric Kakanda Tshitende, Jean Marie Kileshye Onema, Webster Gumindoga, and Raphael Tshimanga

The Kasai catchment is experiencing poor landuse planning and sediment deposition, thus impacting streamflow. The landuse and landcover change (LULCC) from 2000 to 2020 were estimated using GIS and RS methods.  The results revealed that bare areas, built-up areas, cropland, flooded vegetation, grassland, open water, and shrub cover areas increased by 0.06%, 0.5%, 0.8%, 16.9%, 1.9%, and 78.6%, respectively, whereas tree cover areas decreased by 0.5%. The observed flows and sediments were used to calibrate the SWAT plus. The performance indices for SWAT plus in flow simulation indicated that R2, NSE, and PBIAS were 0.94, 0.87, and 0.55, respectively. Validation results showed R2, NSE, and PBIAS values of 0.83, 0.67, and 2.6, respectively. Performance indices for SWAT plus in sediment simulation revealed that R2, NSE, and PBIAS were correspondingly 0.81, 0.66, and 7.1. Validation results were 0.8 (R2), 0.66 (NSE), and -1.3 (PBIAS). QSWAT plus post-processing was utilised to estimate the monthly environmental flow. The results ranged from 83.04 m3/s to 10079.97 m3/s. The impact LULCC on the streamflow and sediment yield was assessed by running the model with different landcover maps while other variables were maintained constant. The results showed that there was a decrease in total flow by 2.6 % and an increase in suspended sediment yield by 87.3%, an increase in flow by 0.66 % and a decrease in suspended sediment by 36%, a decrease in total flow by 0.09 % and an increase in suspended sediment by 12.09 % which correspondingly to landuse and landcover of 2000 to 2005, 2005-2009, and 2000 to 2020.

Keywords: Environmental flow, GIS, model performance, Remote Sensing, QSWAT plus

How to cite: Tshitende, E. K., Kileshye Onema, J. M., Gumindoga, W., and Tshimanga, R.: Analysis of the changes in landcover, streamflow, and sediment yield in Kasai catchment of the Congo River Basin, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-746, 2022.

09:15–09:30
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IAHS2022-745
Moises Mavaringana, Webster Gumindoga, Jean-Marie Kileshye Onema, and Hodson Makurira

Using the Mann-Kendal test, this study sought to analyse historical trends in hydro-meteorological variables and to establish future trends in selected variables. The study also sought to establish how climate change affects flood inundation extent for the Pungwe River Basin. The historical data was analysed to detect change-point using Pettitt, Standard Normal Homogeneity (SNH), Buishand range and Von Neumann tests. Climate ensembles of 10 Regional Climate Models (RCM’s) from the CORDEX project with RCP 2.6 and RCP 8.5 pathways were selected based on their documented performance on simulating temperature and rainfall in African basins. The historical rainfall and temperature time series and the downscaled climate data were input into the HBV model to generate streamflow for the period of 2022 to 2099. Flood extent for 50-, 100-and 1000-year return periods were predicted using the HEC-RAS hydraulic model. At the annual time-step, a change-point was detected in 2000 and 2012 for Metuchira and Catandica rainfall stations respectively. The results of the Mann Kendall test for 1982 to 2020 indicated a statistically significant and increasing annual trend for 5 of the 9 stations, namely Pungwe Sul, Nhazonia, Catandica, Metuchira, and Pungwe Fronteira. By 2070, annual rainfall at all the 9 studied meteorological stations is predicted to reduce by a maximum of 68 % (22.04 mm/day), with increasing inter-annual variability across all the RCM’s. Temperature is expected to increase by up to 15 % (4.5 oC) over the same period. The HBV model shows good performance for the Gorongosa Ponte station during calibration and validation with Nash Sutcliffe model efficiency 89 and 83 %, respectively. By the 2040s, simulations from HBV revealed that the peak flows for the Pungwe River Basin  will vary from a maximum of about 120 % to a minimum of 57 % from the RCM’s. The analyses also show that by 2070 climate change may cause a minimum of 2784.4 km2  and a maximum of 8235.6 km2 in inundated areas for CanESM2 and CNRM-CM5 RCM’s, respectively. These results are essential for decision making on flood hazard mapping and early warning systems, prompting a pathway for sustainable development.

How to cite: Mavaringana, M., Gumindoga, W., Kileshye Onema, J.-M., and Makurira, H.: Climate change impact on flood events of Pungwe river basin, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-745, 2022.

09:30–09:45
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IAHS2022-76
Mohamed Meddi, Ishak Abdi, and Gil Mahe

The water deficit of recent decades has negatively affected agricultural production as well as surface and underground water resources in Algeria. To assess he impact of the future climate, for (2020-2060) and (2060-2099), on the water resources in several basins, we used analysis of historical average flows and compare them to those that could result from changes in temperature and rainfall. The methodology is based on the GRM2 model with the development of prospective climate change scenarios for both horizons. To study the impact of climate change on water resources, we used the climate projections of the CORDEX Arica model with the two pessimistic (RCP 8.5) and optimistic (RCP 4.5) scenarios. The results of the simulations of the future scenarios showed that the historical seasonality of precipitation fades away for the RCP 4.5 and 8.5 scenarios, and gives way to a more irregular pattern where rainfall is abundant in late autumn and spring.  Furthermore, this interannual evolution of the RCP scenarios indicates an increase in extreme events during these periods, thus increasing the risk of flooding considerably. The results of the simulations of the future scenarios showed a clear decrease of the flows. This decrease varies, for the seven sub-basins composing the plain, between 17 and 50% for the near future and the RC4.5 scenario. For scenario 8.5, the decrease varies between 37 and 55%. For the distant future (2060-2099), the reduction in flows varies between 27 and 45% for the near future and the RC4.5 scenario. For scenario 8.5, the reduction varies between 40 and 62%. We note that the basins which drain part of the Blidean Atlas present lower projected reductions for the future compared to the other basins of the plain. The two stations of the first two are located at the entrance to the plain.

 

How to cite: Meddi, M., Abdi, I., and Mahe, G.: Impact of climate change on the flows of the Mitidja plain basins (Northern Algeria), IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-76, 2022.

09:45–10:00
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IAHS2022-124
Shakirudeen Odunuga, Iyanuoluwa Olufiade, and Olubunmi Adegun

The study examines the water resources potential of Ogun River Basin in Southwestern Nigeria using the rapid water accounting plus (WA+). This was achieved by using data from the Water Productivity (WaPOR) version 2.0 Level 1 with 250m resolution open access database of the Food and Agricultural Organization (FAO). Python and Jupyter notebook programming were used to download data from WaPOR database as well as for the implementation of the Water Pixel model. QGIS and ArcGIS were used to carry out raster calculation and mapping of water indices. Ground based rainfall data from Nigeria Meteorological Agency (NiMET) for three stations (Ikeja, Abeokuta and Ibadan) were used for rainfall validation while Ogun River discharge data at Abeokuta provided the hydrological flow data for the computation of the water balance. The results showed that the WaPOR 2.0 level 1 precipitation data showed close agreement with the in situ observations by the NiMET at the Ikeja, Abeokuta, and Ibadan stations with the coefficient of correlation values varying from 0.618 to 0.687. The basin was a net water generator as precipitation (16471 mm/year) was higher than total evapotranspiration (13888 mm/year), which implies that as a whole, the basin generates surplus water (150.85 mm/year) for the 2018 hydrological year. The exploitable water resources are 12.7 km3/year, while the renewable water resources are higher (14.14 km3/year), which is due to an increase of the basin storage by 1.4 km3/year. The gross inflow is 29.2 km3/year and the total outflow and consumed water is 27.8 km3/year, which resulted in 1.4 km3/year stored as total water storage change (Balance). Also, the average available water was depicted to be 12.1 km3/year, out of which approximately 2.9% was managed. The Managed Water, which is Incremental ET of Managed Water use, was on average 0.1 km3 /year. The study recommends provision of medium sized dams across the basin for proper harvest of the surplus water to increase urban water supply, reduce proliferation of boreholes and control flooding.

How to cite: Odunuga, S., Olufiade, I., and Adegun, O.: Water Accounting of the Ogun River in the Tropical Environment of South-West Nigeria , IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-124, 2022.

Hydrological modelling and innovation
Coffee break
Chairpersons: Hubert H.G. Savenije, Ernest Amoussou, Marloes Mul
10:30–10:45
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IAHS2022-75
Dessalegn Worku Ayalew, Andrea Petroselli, Davide Luciano De Luca, Ciro Apollonio, and Salvatore Grimaldi

Ethiopia is characterized by observed rainfall and runoff data scarcity and consequently, still nowadays the rational formula is commonly applied for estimating the design peak discharge.

In this contribution we would like to verify if more advanced hydrological tools can be applied in such challenging conditions and we provide a comparative assessment of event based and continuous modeling approaches in estimating the design hydrographs for small and ungauged basins.

The event based approach is applied using the freeware software named EBA4SUB. It is a classical approach, specifically tailored for ungauged conditions, that consists in selecting a design rainfall event based on the Depth-Duration-Frequency (DDF) curves’ parameters, estimating the rainfall excess, and transforming it into the direct hydrograph. The continuous approach is applied using the freeware software named STORAGE and COSMO4SUB. STORAGE is designed for generating long and high resolution synthetic rainfall timeseries based on scarce raingauge observations, like daily rainfall amount and DDF parameters, while COSMO4SUB is the continuous rainfall–runoff module.

Results seem promising, in particular we verified that the Ethiopian small and ungauged watersheds can be modeled using advanced approaches that offer more complete design information for the practitioner as respect to the rational formula.

How to cite: Ayalew, D. W., Petroselli, A., De Luca, D. L., Apollonio, C., and Grimaldi, S.: A comparative assessment of event based and continuous rainfall runoff modeling for small and ungauged watersheds in Upper Blue Nile Basin, Ethiopia, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-75, 2022.

10:45–11:00
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IAHS2022-80
Salif Koné, Gil Mahé, Fatogoma Bamba, Jean Emmanuel Paturel, Alain Dezetter, and Eric Servat

In hydrology, enhancing existing models are good ways to establishing efficient and accurate conceptual frameworks for hydrological simulation’s purposes. Methodologically, a framework that has two parameters and three input variables, called SimulHyd, is used in this study to modelling runoff data, on sixteen watersheds of the Niger River and its tributaries, from 1950 to 1999. Purposely, this paper focuses on a model’s inter-comparison method, which summarizes, in tables, then in graphics and in maps, the obtained results. We enhance modelling outputs both in modifying the former french’s GR2M model to obtain a model called SimulHyd model and in developing a semi-distributed modelling from a lumped modelling approach.  SimulHyd stands for Simulation of Hydrological systems.

How to cite: Koné, S., Mahé, G., Bamba, F., Paturel, J. E., Dezetter, A., and Servat, E.: Niger River Basin - Hydrological Modelling: Enhancing Framework Accuracy., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-80, 2022.

11:00–11:15
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IAHS2022-403
Léonard Santos, Jafet Andersson, and Berit Arheimer

Floods pose an increasing challenge for societies in West Africa; causing loss of lives, damaged infrastructure, and food insecurity. Improving flood management is hence an important development priority for the region, which several initiatives aim to contribute to. Hydrological forecasting systems can help, in which a core component is hydrological models. This research focus on the refinement of the hydrological model HYPE across West Africa within FANFAR (www.fanfar.eu).

The FANFAR domain stretches across West Africa (from Cap Verde to Chad), and hence the research focussed spatial hydrology, specifically finding suitable representations of runoff and key hydrological features across the domain. Our starting point was the World-Wide HYPE model (Arheimer et al. 2020). We analysed its performance in the region and found that runoff response was generally too fast, and not sufficiently differentiated between sub-regions (median daily KGE was -0.09 for 151 gauges). We setup an experiment to try four different approaches to regionalize runoff-regulating processes, namely Hydrobelts, Köppen, Soil capacity index, and Hydroclimatic regions. We divided representation of runoff-generating processes in HYPE (infiltration excess, saturation excess, soil storage, subsurface runoff) into regions linked to each regionalization scheme. We found that the Soil capacity index by Wang-Erlandsson et al. (2016) provided the most useful basis for regionalisation, giving the best and most balanced representation of discharge across the domain. However, we also noted that the added value of regionalisation compared to domain-wide calibration was rather limited, possibly due limited data availability. Another key adaptation was to calibrate regulation parameters of dams and floodplain dynamics of the Inland Niger Delta. All in all, this resulted in a much-improved West Africa HYPE model (for 151 daily streamflow gauges the median KGE was 0.36, reaching up to 0.9 at specific locations). This model was put into an operational forecasting chain within FANFAR, where West African hydrological services and disaster managers used it to disseminate alerts and reduce flood impacts.

Here we summarize this hydrological experiment, and how spatial hydrology, big and open data, participatory research, and capacity development can help reaching development priorities.

References

Arheimer et al. 2020, https://doi.org/10.5194/hess-24-535-2020

Wang-Erlandsson, et al. 2016, https://doi.org/10.5194/hess-20-1459-2016

How to cite: Santos, L., Andersson, J., and Arheimer, B.: Improving hydrological modelling across West Africa with the HYPE model, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-403, 2022.

11:15–11:30
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IAHS2022-117
Jean-Emmanuel Paturel, Berenger Kouacou, Franck Lohou, Frédéric Pons, Bernard Dje, Naky Coulibaly, Harouna Karambiri, Valérie Borrell, Andrew Ogilvie, and Eric Servat

In 2007, the WMO Executive Council, at its 66th session, recalled Resolution 16, which gives priority to the rescue and digitization of climate archives and to promote global and regional initiatives to collaborate on DARE (data rescue) and the exchange of scientific knowledge and related technological advances. The Council urged Members to make every effort to prevent the deterioration of climate-relevant data and to make these data available to support climate change analyses and relevant climate services.

Within the framework of operational and scientific research actions around the updating of hydrological standards in West Africa (ActNAO project)  and in response to the call of the WMO, we used the NUNIEAU software (NUmérisation de NIveaux d'EAU en mer ou en rivières - CEREMA's free software) which allows the digitization of all types of paper documents by automatic recognition. This software has been used on rainfall maps in Burkina Faso and Ivory Coast. The use of this tool allows rainfall analysis on an intraday time step, a time step that is very useful for the sizing of structures and networks, the knowledge and management of flash floods in small basins, particularly urban basins, and flood prevention actions...

For example, Intensity-Duration-Frequency curves were reviewed and compared to old ones in order to follow the evolution of rainy events in a context of climate change in Burkina Faso and Côte d’Ivoire. The tendency would be an intensification of short duration rainfall.

This product is intended to be disseminated and dedicated training courses have been organized for researchers and stakeholders in the South and North.

 

How to cite: Paturel, J.-E., Kouacou, B., Lohou, F., Pons, F., Dje, B., Coulibaly, N., Karambiri, H., Borrell, V., Ogilvie, A., and Servat, E.: Data rescue and valorization of old data. Application to rainfall data in Burkina Faso and Ivory Coast using NUNIEAU software, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-117, 2022.

11:30–11:45
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IAHS2022-461
Remko Uijlenhoet, Aart Overeem, Hidde Leijnse, Arjan Droste, and Linda Bogerd

Microwave backhaul links from cellular communication networks provide a valuable “opportunistic” source of high-resolution space–time rainfall information, complementing traditional in situ measurement devices (rain gauges, disdrometers) and remote sensors (weather radars, satellites). Over the past decade, a growing community of researchers has developed, in close collaboration with mobile network operators, retrieval algorithms to convert the raw microwave link signals, stored operationally by their network management systems, to quantitative precipitation estimates.

Operational meteorological and hydrological services as well as private consulting firms are showing an increased interest in using this complementary source of rainfall information to improve the products and services they provide to end users from different sectors, from water management and weather prediction to agriculture and traffic control. The greatest potential of these opportunistic environmental sensors lies in those geographical areas over the land surface of the Earth where the densities of traditional rainfall measurement devices are low: mountainous and to a lesser extent urban areas, but most importantly low- and middle-income countries.

In this presentation we will review the state of the art of opportunistic rainfall monitoring using commercial microwave links, with special reference to its potential and challenges for applications in sub-Saharan Africa.

How to cite: Uijlenhoet, R., Overeem, A., Leijnse, H., Droste, A., and Bogerd, L.: Rainfall monitoring using microwave links from cellular communication networks: potential for sub-Saharan Africa, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-461, 2022.

11:45–12:00
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IAHS2022-468
Pierre Jérôme Zohou, Adéchina Eric Alamou, John Aoga, and Eugène C. Ezin

          Dans cet article, nous présentons deux techniques d'analyse des précipitations dans le sous-bassin de l'Ouémé à Savè au Bénin : l'approche markovienne et les Réseaux de Neurones Artificiels (RNA). Pour ce faire, nous avons utilisé une série de données enregistrées durant la période de 1921 à 2020 par la Météo-Bénin.
Ces dernières ont été utilisées pour caractériser les occurrences des précipitations dans la zone de Savè. En utilisant les approches markovienne et les RNA, nous avons pu montrer dans un premier temps, que les occurrences de précipitations sont bien décrites par une chaîne de Markov d'ordre un à trois, à savoir les tendances des événements entre les états pluvieux ou non pluvieux après plusieurs années et la répartition des précipitations entre les états à long terme. Et en suite les RNA ont permis de mieux apprécier l'influence du passé sur le comportement des précipitations. Ainsi, en modélisant une chaîne de Markov d'ordre trois et les RNA, nous avons obtenu une meilleure description des précipitations.
En effet, les probabilités obtenues avec l'approche markovienne et les probabilités à partir des RNA que nous avons calculés sont quasiment identiques.

Mots Clés : Bénin, approche Markovienne, RNA, précipitations.

How to cite: Zohou, P. J., Alamou, A. E., Aoga, J., and Ezin, E. C.: Caractérisation des occurrences de précipitations dans le sous bassin hydrologique de l’ouémé à Savè : Approche Markovienne et les Réseaux de Neurones Artificiels (RNA), IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-468, 2022.

Land-use and climate change impacts on river regimes
Lunch break / Exhibition for the public
Chairpersons: Harald Kunstmann, Flavia Tauro, Fernando Nardi
13:30–13:45
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IAHS2022-207
Sinetemba Xoxo, Jane Tanner, Denis Hughes, and Sukhmani Mantel

While some progress has been made towards improving the sustainable management of water resources, challenges remain. In the water scarce Doring River, in South Africa, these are associated with achieving equitable sharing of the resource among a range of stakeholders which include commercial farmers and emerging farmers.  A participatory water sharing tool has been developed which aims to contribute to  water governance, and includes some key variables such as  the inclusion of uncertainty, environmental Reserve requirements (environmental flows), and the incorporation of socio-economic factors associated with water use. The Institute for Water Research at Rhodes University developed the water sharing tool in response to the Panta Rhei initiative. The tool promotes water sharing at a community level by different water users/user groups, and it encourages deliberation to identify an optimal water sharing (or reallocation) strategy by communicating frequency distributions of assurance shortfall risk. The tool explicitly considers epistemic and alleatory uncertainty; the water users’ value for environmental water requirements; and considers social heterogeneity using socio-economic factors that may influence the way people make water use decisions. However, the tool has never been applied in practice. To complete the tool’s development, a commercial farming setting (i.e. the Doring River in the Koue Bokkeveld region of South Africa) will be used as a case site. The model allocates the available water resource based on the differing impacts on users (impacts of the same deficit will be different for emerging and commercial farmers for example), and produces information which assists the stakeholders to manage the risks of the shortfalls. Ultimately, the stakeholders select the best water sharing option based on a number of possibilities, produced through various combinations of socio-economic factors. In light of growing water scarcity, and the highly uneven distribution of water often found in developing nations, the tool’s approach can be valuable in negotiating increasing water crisis among very different users/user groups.

How to cite: Xoxo, S., Tanner, J., Hughes, D., and Mantel, S.: Integrating equity into a water allocation model to promote water sharing in environments with vulnerable stakeholders, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-207, 2022.

13:45–14:00
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IAHS2022-235
Théo Vischel, James D. Miller, Youssouph Sané, Fowe Tazen, Gérémy Panthou, Emma Visman, and Christopher M. Taylor and the Additionnal Authors

In West Africa, the increase in the frequency of extreme rainfall in the context of global warming accentuates the risk of damaging floods, particularly in cities that concentrate a rapidly a rapidly growing population. Decision-makers and managers in charge of hydrological risks are increasingly aware of the challenges raised climate change, but their ability to define suitable adaptation strategies remains limited by the lack of tangible and usable scientific information. On the other hand, scientists are developing increasingly sophisticated knowledge on climate change and hydrological impacts in West Africa but are often struggling to translate research results into operational and usable decision support tools.

What is now commonly referred to as the "knowledge-action gap" calls for strengthening the link between scientists and decision-makers and requires the implementation of co-construction strategies that sometimes push actors and scientists to move out of their comfort zone.

Here we will present two attempts of co-construction experiments conducted between 2016 and 2021 within the AMMA2050 program. The first experiment concerns the development of intensity-duration-frequency curves in collaboration with the national meteorological service of Senegal (ANACIM) in order to integrate these curves into the agency's operational climate services. The second experiment  is an attempt to co-construct a climate-hydrology-flood modeling chain between scientists and decision-makers involved in urban planning for the future management of urban floods in the city of Ouagadougou, Burkina Faso.

The objective here is to highlight (i) the technical scientific advances that make it possible to propose useful, usable and, as far as possible, used scientific information; (ii) the functional modes of interaction with decision-makers and (iii) the successes and failures in the approaches taken, (iv) the lessons learned from these two experiences that could help facilitate future co-construction approaches.

How to cite: Vischel, T., Miller, J. D., Sané, Y., Tazen, F., Panthou, G., Visman, E., and Taylor, C. M. and the Additionnal Authors: Bridging the gap between scientific knowledge and action in flood risk management: two attempts of co-construction project between scientists and stakeholders in Senegal and Burkina Faso in the AMMA2050 program., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-235, 2022.

14:00–14:15
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IAHS2022-239
Rhoda A. Odongo, Hans de Moel, Marthe Wens, Dim Coumou, and Anne F. Van Loon

In recent years, East Africa (EA) has been affected by numerous drought events. To better understand the drought hazard and its implications, it is important to analyze the propagation of dry conditions through the hydrological system and identify at what point it leads to negative impacts on society. This way, we define drought events as dry conditions during which actual impacts are felt by communities (i.e. ‘impactful droughts’) rather than using a predefined relative threshold. This study explores the link between standardized and threshold-based drought indices and drought impacts in EA. Drought propagation from meteorological to soil moisture to hydrological drought to finally socio-economic impacts has been investigated in the data-rich regions around the world (i.e. Europe). However, not much has been done in data-poor regions (i.e. Africa), with very different climatic and socio-economic characteristics.

We identify meaningful indicators for region- and sector-specific impact occurrences, focusing on three impact types: crop yield and livestock losses, changes in pasture represented by Normalized Drought Vegetative Index (NDVI), and people affected. In this study, we link these impact types to various drought hazard indices calculated from time series of precipitation, evaporation, soil moisture and discharge for every administrative unit in Kenya, Ethiopia and Somalia. The standardized indices are used with varying accumulation periods (1,3,6,12,24,48 months) to find the best predictors. We use independent but complementary machine learning techniques (correlation, logistic regression and random forest modelling) to identify which indices link best to which drought impacts.

Using the variable threshold based analysis to analyse drought propagation in Isiolo county in Kenya, we find an increase in frequency and duration of hydrological droughts. This has been confirmed in other studies. The correlations and relationships between crop yield anomalies and indices are different in each of the administrative units. The findings in this research will lead to a greater understanding of the effects of drought hazards to communities, and contribute to improved drought monitoring and forecasting. This research can also form the basis for follow up work to explore the effects of adaptation options (i.e. irrigation) on drought hazard and impacts in East Africa.

 

How to cite: A. Odongo, R., de Moel, H., Wens, M., Coumou, D., and F. Van Loon, A.: Exploring the link between drought indices and socio-economic impacts in East Africa, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-239, 2022.

14:15–14:30
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IAHS2022-500
Laurent Bruckmann, Amaury Tilmant, Khady Yama Sarr, Ibrahima Barry, Fama Gueye, Massaer Mbaye, and Clément Sambou

Managing the WEFE nexus is a prerequisite towards the sustainable management of water and connected resources at the river basin scale. The challenge is even more important in transboundary river basins such as the Senegal River where the four riparian countries (Guinea, Mali, Mauritania, Senegal) share a common vision: to transform the river into a food-energy-transportation hub in West Africa. This vision requires the construction of hydroelectric power plants, modern irrigation systems and river transport infrastructure, and often requires constant river flows. Several dams already exist and several more are planned in the coming decades. These developments directly threaten the livelihoods of riverine communities that depend on the river banks, mainly for flood-recession agriculture and fishing.

Evaluating the WEFE nexus and its objectives usually involves indicators describing how well the sectoral objectives are met in terms of food production, energy production or percentage of the population with access to safe drinking water and sanitation services. These indicators are often aggregated at the river basin level, which masks local realities: the water needs, water management practices water management practices and inequalities in access to water at communities or households’ level.

The objective of this communication is to present a portfolio of regional and community-level indicators to analyze the WEFE nexus across different spatial and temporal scales. The construction of this portfolio is a two-stage process. Firstly, the definition of relevant indicators is carried out on the basis of consultation with a variety of participants involved in water management in the Senegal River (researchers and experts, institutional stakeholders, civil society actors, local communities). Secondly, local data describing the state of the local indicators of the nexus at the local level are collected from field surveys. We will also show how these indicators can enrich the analysis of basin-wide hydroeconomic models by assessing multi-scale trade-offs, as well as the distributional impacts of nexus interventions. This work is part of the H2020 GoNexus project, which aims at improving the governance of the WEFE nexus in transboundry river basins.

How to cite: Bruckmann, L., Tilmant, A., Sarr, K. Y., Barry, I., Gueye, F., Mbaye, M., and Sambou, C.: The challenge of integrating local communities to evaluate the WEFE Nexus: the example of the Senegal River, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-500, 2022.

14:30–14:45
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IAHS2022-562
Antonio Annis and Fernando Nardi

The increasing availability of remotely sensed and social media crowdsourcing is bringing new distributed georeferenced data and opportunities for better monitoring and managing natural disasters. On the other hand, hydrogeomorphic models demonstrated their ability to parsimoniously delineate floodplain domains and assess river basin hydrologic forcing. In this contribution we present and test a Data Assimilation (DA) framework for real time flood forecasting supported by hydrogeomorphic floodplain terrain processing. The presented novel DA framework seeks to optimize the computational domain of a 2D hydraulic model, improving rapid flood detection using satellite images, and filtering geotagged crowdsourced data for flood monitoring. Different cases studies are presented where both traditional and innovative measurements are adopted, jointly and separately, for analyzing in comparative terms the performance of flood forecasting models with specific focus on the computational efficiency the ability to cope with data scarcity in ungauged river basins.

How to cite: Annis, A. and Nardi, F.: Crowdsourcing, Remote sensing and hydrogeomorphic modelling for supporting Data Assimilation for near real time flood forecasting in data scarce regions, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-562, 2022.

14:45–15:00
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IAHS2022-673
Julien Malard-Adam, Ki. Sheejakumar, Joel Harms, and Wietske Medema

Citizen science has a strong potential to contribute to the democratisation of science worldwide. In addition, such approaches can lead to the creation of “living” datasets that evolve over time, even in regions where few hydrological instruments have been installed.

Citizen science approaches, however, do face a number of hurdles. One major challenge is the need for a central server to receive, manage and host the data contributed by volunteers; such servers require expert knowledge to configure and are also quite costly to maintain or rent over extended periods of time. These difficulties pose a challenge to the long-term financial sustainability of citizen science initiatives in the long term, especially after project funding has ceased. In addition, the centralisation of data on a server creates a very strong dependency for the participating communities; if their access to the internet is limited or costly, or if the server is not maintained after the end of the project, communities will be unable to contribute new data or even view and use previously contributed data.

In this context, distributed databases, such as Constellation, offer a different approach. In these systems, every device (phone or computer) that contributes data to or reads data from the network is a client and sever in its own right and can store and transmit community data to other participants in the network, all without the need for a central server. The low barrier to entry and absence of server costs allows such networks to be rapidly developed and deployed with minimal budgets, all while becoming stronger and more resilient as they grow in popularity and users. In the African context, such an approach may contribute to wider adoption of citizen science tools and projects, as well as to better data sovereignty and sustainability.

How to cite: Malard-Adam, J., Sheejakumar, Ki., Harms, J., and Medema, W.: Distributed database technologies for citizen science and data sovereignty, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-673, 2022.

Posters: Tue, 31 May, 15:00–16:30 | Poster area

P1
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IAHS2022-49
Harmel Obami-Ondon, Médard Ngouala Mabonzo, and Martin Tchoumou

 RÉSUMÉ

Cette étude a pour but de déterminer la qualité physico-chimique des points d’eau de consommation et des travaux ménagers des quartiers Manianga et Kintélé Stade au Nord de Brazzaville. Les échantillons d’eau ont été prélevés entre les mois août et octobre 2021, dont quatre (04) sources et un (01) puits durant cette étude. La caractérisation de ces eaux s’est basée sur des paramètres mesurés in-situ et au laboratoire. En plus, cette étude a fait appel à des méthodes hydrochimies qui utilisent les diagrammes de Piper, de Stabler, de Schoeller Berkaloff, de Stiff, de Wilcox et des méthodes statistiques classiques avec le logiciel XLSTAT. Les résultats obtenus sont comparés aux normes l’OMS pour eau de boisson et montrent que les eaux ont une température qui varie de 26,3 à 26,8 °C. Elles sont acides, avec un pH qui varie de 6,09 à 6,82. Les eaux sont faiblement minéralisées, avec une conductivité électrique moyenne de 63,2 μS/cm. Elles contiennent de faibles teneurs en fer qui varient de 0,01 à 0,04 mg.L-1 qui sont inférieures à la valeur guide OMS (0,3 mg.L-1). Dans ces eaux le Pb et le Cr présentent des valeurs inferieures à celle de l’OMS. L’analyse nous a permis également, de mettre en évidence la prédominance de faciès chimiques global chlorurée et sulfatée calcique et magnésienne dans ces eaux de la banlieue de Brazzaville. Les eaux de la zone d’étude sont de bonne qualité et aptes pour une consommation humaine sous réserve des résultats d’analyse microbiologique au préalable.

Mots-clés : ressources en eaux, physico-chimique, hydrogéochimique, Manianga et Kintélé stade.

How to cite: Obami-Ondon, H., Ngouala Mabonzo, M., and Tchoumou, M.: Etude des caractéristiques hydrogéochimiques des points d’eau de consommation dans la banlieue de Brazzaville : cas du quartier Manianga et Kintélé stade (République du Congo)., IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-49, 2022.

P2
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IAHS2022-213
Camille Ollivier, Simon Carriere, Tom Heath, Albert Olioso, Ludovic Oudin, and Frédéric Satgé

In November 2021, the United Nations has declared that Madagascar current humanitarian crisis was the world first famine due to drought induced by climate change. Understand the factors triggering these crises is fundamental to anticipate and reduce the effects of future crises. In the ongoing climate change context, rainfall deficit is a key variable in setting up these crises. However, the Malagasy weather station network is far too sparse to describe the spatial variability of rainfall. Thus, this study compares 21 gridded precipitation products (see Fig. 1) to 19 gauges data to assess their reliability to monitor Madagascar precipitation pattern. Based on four statistical indices (Kling-Gupta Efficiency, Root Mean Square Error, Correlation coefficient and Biais), WFDEI-GPCC, CMORPH-BLD and, MSWEP appeared the most reliable product at national scale (Fig. 1). However, the products performances varied throughout Madagascar because the island counts four contrasted bioclimatic zones due to topographic and meteorological influence. To circumvent this variability issue, we developed a new product based on ensemble approach (“EM” in the Fig. 1). EM is calculated from a weighted average of the products according to their KGE score. The weights are specifically defined by bioclimatic zone. EM shows better performances at both regional and national scale. Finally, we evaluated the quality of our results by comparing them with five independent gauge dataset and on a different period. These satisfactory results allow us to continue studying the impact of rainfall related droughts on humanitarian crisis.

 

Figure 1: Scores for 21 gridded products + the new product created based on ensemble approach (« EM »). The monthly precipitation estimated by these products is compared to the monthly precipitation measured by 19 gauges data between 2011 and 2016. Four statistical indices (Kling-Gupta Efficiency, Root Mean Square Error, Correlation coefficient and Biais) are shown. Their optimum is indicated by the dashed green line. The red point is the median value obtained when considering only dry season, and the blue dot is the median value when considering only wet season. The products are sorted by the KGE median value.

 

How to cite: Ollivier, C., Carriere, S., Heath, T., Olioso, A., Oudin, L., and Satgé, F.: Assessment of 21 gridded precipitation datasets quality in estimating rainfall in Madagascar, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-213, 2022.

P3
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IAHS2022-409
kingsley Nnaemeka Ogbu, Oldrich Rakovec, Luis Samaniego, Gloria Chinwendu Okafor, Bernhard Tischbein, and Hadush Meresa

Predictive hydrologic modelling to understand and support agricultural water resources management and food security policies in Nigeria is a demanding task due to the paucity of hydro-meteorological measurements. This study assessed the skill of using different remotely-sensed products in a multi-calibration framework for evaluating the performance of the mesoscale Hydrologic Model (mHM) across four (4) different data-scarce basins within the Guinea-Sudano region of Nigeria.  Satellite rainfall estimates (SFEs) obtained from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), Climate Prediction Center (CPC), European Center for Medium-Range Weather Forecast (ECMWF) Reanalysis 5th Generation (ERA5), Global Precipitation Climatological Center (GPCC) and Multi-Source Weighted Ensemble Precipitation (MSWEP) models were used to drive the mHM for different basins across different climatic regions in Nigeria. The multiscale parameter regionalization (MPR) approach was implemented to overcome the problems of over-parameterization and equifinality of model parameters during model calibration. Model calibration was first performed using discharge (Q), and next calibrated by using a combination of discharge (Q) and actual evapotranspiration (AET) for each setup driven by a rainfall product. A multi-variable approach using both Q and AET was also used during model evaluation. The mHM model driven with CHIRPS dataset showed reasonable results (0.5 < KGE ≤ 0.85) during calibration with both Q and AET variables while KGE varied between 0.34 – 0.63 during model validation using the same variables across all basins under consideration. This study underscores the utility of the CHIRPS model for hydrologic modelling in sub-Saharan Africa as well as the spatial predictive skill of the mHM. Generally, this study draws special attention to the MPR approach as a good alternative to consider for distributed hydrologic modelling in poorly-gauged basins.

How to cite: Ogbu, K. N., Rakovec, O., Samaniego, L., Okafor, G. C., Tischbein, B., and Meresa, H.: Evaluating the skill of the mesoscale Hydrologic Model (mHM) for simulating River Discharge in Sparsely-Gauged Basins in Nigeria, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-409, 2022.