HS2.1.10 | Advances in African hydrology and climate: monitoring, modelling, water management, food and water security
EDI PICO
Advances in African hydrology and climate: monitoring, modelling, water management, food and water security
Convener: Meron Teferi Taye | Co-conveners: Moctar Dembélé, Fiachra O'Loughlin
PICO
| Thu, 18 Apr, 16:15–18:00 (CEST)
 
PICO spot 3
Thu, 16:15
The African continent is experiencing various impacts of climate induced sequential droughts, floods, heatwaves, and alteration between two extremes. These changes are causing water and food insecurity in the region. The advances seen in hydrological models in better reproductions of observed variables such as streamflow and water availability are improving predictions of socio-economic risks of floods, droughts, and water stress. However, in data-sparse regions the use of hydroclimatic models for disaster risk reductions still requires improvement.

This session aims to bring together communities working on different strands of African hydrology, climate risks, water and food security, and environmental risks. We welcome both fundamental and applied research in the areas of hydrological process understanding, monitoring, drought/flood forecasting and mapping, seasonal forecasting, water resources management, climate impact assessment and societal implications. Interdisciplinary studies that combine the physical drivers of water-related risks and their socio-economic impacts in Africa are encouraged. Case studies showcasing practical innovative solutions relevant for decision making under large uncertainty are welcomed.

PICO: Thu, 18 Apr | PICO spot 3

Chairpersons: Meron Teferi Taye, Moctar Dembélé, Fiachra O'Loughlin
16:15–16:20
Catchment modelling
16:20–16:22
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PICO3.1
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EGU24-8158
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ECS
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Highlight
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On-site presentation
Marlies H Barendrecht, Ruben Weesie, Alessia Matanó, Maurizio Mazzoleni, and Anne F. Van Loon

During the past decades, the county of Kitui in Kenya, has experienced severe droughts. Both rain seasons have failed for several years in a row. While the region is known for its aridity and the droughts it experiences, the region also experiences regular flooding. Both drought and flood events have had devastating impacts, leading to widespread water and food insecurity. In this study, we developed a system-dynamics model to investigate the interplay between drought and flood risk and how this is influenced by human-water interactions. We model the system’s hydrology, as well as drought and flood impacts and human actions and adaptation. We aim to estimate model parameters using hydrological and impact data and fit the model to the case study areas. The fitted model is used to investigate changes in drought and flood risk over the years and how these vary across three different case study areas. We investigate how both climatic drivers and human actions and responses to the changing environment influence drought and flood risk. This analysis provides insights into the main drivers of drought and flood risk and the model allows for an exploration of the policies and measures that could be implemented to reduce risk in the future.

How to cite: Barendrecht, M. H., Weesie, R., Matanó, A., Mazzoleni, M., and Van Loon, A. F.: Investigating the human-water dynamics leading to increased drought and flood risk in Kitui, Kenya., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8158, https://doi.org/10.5194/egusphere-egu24-8158, 2024.

16:22–16:24
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PICO3.2
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EGU24-19265
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ECS
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On-site presentation
Sven Berendsen, Justin Sheffield, Chiara Corbari, Nicola Paciolla, Diego Cezar Dos Santos Araujo, Ahmad Al Bitar, Kamal Labbassi, and Zoltan Szantoi

Water management is a problem of matching supply and demand whilst sustaining environmental conditions for a range of sectors and ecosystems, potentially under changing conditions of climate or demand. In dryland regions, this is particularly difficult given low available water supply and high climate variability, often with lack of data for operations, planning and design. Addressing these challenges at national scale requires whole-system approaches to incorporate the range of relevant sectors and their interactions, and multi-scale approaches to capture the large-scale drivers of water availability and the fine-scale variability of supply and demand within catchments, irrigation districts or urban areas.

In the context of the AFRI-SMART project “EO-Africa multi-scale smart agricultural water management” funded under the ESA EO Africa - National Incubators EXPRO+ programme, we have developed a multi-scale, multi-model approach to help address water management challenges in Morocco. On-going drought conditions in the country for the past 5 years have left reservoirs without water for irrigation, which must be prioritized for public water supply, impacting on food production, agricultural exports and farmer incomes. More accurate information on water resources distribution in space and time across scales and sectors is needed to address sustainable agriculture, to help guarantee food and water security, and increase resilience to hydro-meteorological extremes.

At national scale multiple sources of information from ground observations, satellite remote sensing, and climate and hydrological models are integrated to provide the best estimate of hydroclimate and drought indices to characterize the large-scale variability in water supply. This feeds into basin scale hydrological modeling, focused on the Oum Er-rbia basin using the HydroBlocks modelling framework, which combines a 1-D land surface model with a cluster-based landscape representation, allowing large-domain simulations at 10s metres resolution. HydroBlocks is coupled to the RAPID stream flow routing scheme to provide high resolution stream flow estimates. Predicted stream flow is routed to the main reservoirs in the basin which are simulated using a simple mass balance approach. Withdrawals from the reservoirs are supplied to one of the basin’s irrigation districts of Doukkala. Actual and optimized irrigation water needs for specific crops, at fine resolution (daily, 10 m) are predicted using the energy-crop-water balance model FEST-EWB-SAFY driven by Landsat LST and Sentinel2 vegetation indices.

The system is used to provide historic reconstructions of water availability and analyzed to identify times of supply risks. The system is also implemented in monitoring and seasonal forecast mode as a tool to understand upcoming risks to water supply and potential interventions to reduce risks, such as provision of early warning of risks, options for adjusted reservoir management, or altered/optimized irrigation scheduling. An open online decision support tool has been developed to provide intuitive near real-time visualization of information from the satellites/models and explore forecasts and future scenarios. We also discuss the collaboration with end user groups in helping to define the management problem and identification of critical decisions in water management across scales.

How to cite: Berendsen, S., Sheffield, J., Corbari, C., Paciolla, N., Dos Santos Araujo, D. C., Al Bitar, A., Labbassi, K., and Szantoi, Z.: Multi-scale and multi-model approaches to water management – application to drought and irrigation in Morocco, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19265, https://doi.org/10.5194/egusphere-egu24-19265, 2024.

16:24–16:26
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EGU24-2318
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ECS
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Virtual presentation
Oumar Jaffar, Abdessamad Hadri, El Mahdi El Khalki, Khaoula Ait Naceur, Mohamed El Mehdi Saidi, Yves Tramblay, and Abdelghani Chehbouni

Hydrology research can benefit significantly from large-sample hydrology studies by offering the possibility for better hydrological models’ assessment and by providing a suitable ground for identifying catchment characteristics that influence model performance. In our study, we conducted a performance assessment of eight monthly lumped rainfall-runoff models (GR2M, XM, WM, VUB, abcd, DWBM, GR5M, and Wapaba) in 30 Moroccan catchments, forced by rainfall data from 34 rain gauges. During the study period 1983-2019, we investigated the relationship between model performance (quantified with KGE) and both model complexity and structural attributes. Furthermore, we conducted correlation analysis to explore possible connections between this performance and catchment features (more than 180 features were considered), and we additionally examined how the models respond to three precipitation input data, namely ERA5, CHIRPS, and PERSIANN-CDR. Our findings revealed that no hydrological model was the best (or the worst) across the entire set of catchments. The model performance was found to be more influenced by model structure than by its degree of complexity, and more by hydro-climatic characteristics, particularly those related to calibration and calibration relative to validation, than by non-hydro-climatic factors. Among the investigated features, the Pearson correlation between observed rainfall and runoff was the strongest characteristic influencing model performance. Furthermore, this study (i) emphasized the essential role of rainfall and runoff data richness, in terms of wet and dry years, in enhancing model performance even if the calibration data is only relatively richer than the validation data and (ii) showed that dry periods are more beneficial to model performance than wet ones. Finally, our study revealed a consistent pattern in the models’ responses to the different rainfall forcings; with ERA5 consistently yielding the best model performance and PERSIANN-CDR consistently resulting in underperformance. This consistent behavior of the models was best explained by the linearity between the employed rainfall products and the catchments' observed runoff.

How to cite: Jaffar, O., Hadri, A., El Khalki, E. M., Ait Naceur, K., Saidi, M. E. M., Tramblay, Y., and Chehbouni, A.: Hydrological Model Performance Assessment across several Moroccan Catchments: Investigating the Effect of Model Attributes, Catchment Features, and Precipitation Inputs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2318, https://doi.org/10.5194/egusphere-egu24-2318, 2024.

16:26–16:28
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PICO3.4
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EGU24-2694
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On-site presentation
Seifu Tilahun, Afia Sarpong Anane Gyebi, Junias Adusei-Gyamfi, Andoh Kwaku Amponsah, Gerald Atampugre, and Olufunke Cofie

The transformation of the food system is intricately linked to the effective management of land and water resources, particularly in regions where diverse land uses compete for limited space. The upper Offin sub-basin serves as a prime example of this complexity, where agricultural, mining, and agroforestry practices fight for arable land, influencing the local food system and changes in hydrological processes. This study aims to comprehend the flow paths, the status of water resources, and land use changes in the agroforestry-dominated landscape of the upper Offin basin in Ghana. To assess historical land use patterns, Landsat images were utilized, alongside trend analyses of past hydro-climatic variables and a Thornthwaite-based water balance incorporating inputs from remote sensing and secondary data spanning from 1981 to 2022. Furthermore, the study instrumented an upland Mankran watershed in the upper Offin, where citizen scientists measured basic hydrological variables in three landscape positions—such as daily rainfall, streamflow rates, and groundwater levels—and water quality parameters (nitrate, phosphate, and mercury) from June to October 2023. The analysis revealed that annual and monthly rainfall exhibited minimal changes over the study period (1981–2022). Forest areas experienced a general decrease, while croplands and built-up areas increased between 2008 and 2021, impacting water balance components. Actual evapotranspiration (AET) based on the water balance model and WaPOR data demonstrated a decreasing trend, while streamflow at the basin outlet increased from 1986 to 2012. The runoff coefficient and the hydrological simulation based Thornthwaite-based water balance demonstrated that subsurface flow dominated the runoff processes, constituting approximately 20% of the average annual rainfall. This is also supported by the nitrate concentrations only peaked in rivers in June, while agricultural wells exhibited consistently high concentrations throughout the rainy period, suggesting leaching through subsurface flow. Phosphate concentrations increased in streams as the rainy period progressed, mirroring well concentrations, and mercury concentrations were low in surface water but four times higher in groundwater, indicating further the subsurface flow dominance. This study provides crucial insights for informed decision-making regarding the hydrological processes amid changing landscapes for sustainable agriculture and biodiversity preservation in the region. The emphasis on subsurface flow dominance underscores its significance in potential transport mechanisms for water quality within the landscape. Landscape management interventions must consider the role of subsurface flow to safeguard environmental resources, enhance water quality, and protect human health.

How to cite: Tilahun, S., Anane Gyebi, A. S., Adusei-Gyamfi, J., Amponsah, A. K., Atampugre, G., and Cofie, O.: The Interplay between Land Use Changes and Hydrological Processes in the Upper Offin Basin of Ghana, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2694, https://doi.org/10.5194/egusphere-egu24-2694, 2024.

16:28–16:30
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PICO3.5
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EGU24-13773
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ECS
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On-site presentation
Irenee Felix Munyejuru and James Stagge

The transboundary Nile River Basin (NRB) occupies a tenth of the African continent and supports the daily livelihood of approximately 300 million people in 11 riparian countries. The NRB is hydrologically complex: two major watersheds, the Blue and White Nile, contribute about 85% of the total annual discharge; more than 50 % of the White Nile’s water is lost over the Sudd wetland; and the Blue and White Nile watersheds produce dramatically different seasonal hydrologic responses due to differences in hydroclimate and lake/wetland storage. The Inter-Tropical Convergence Zone (ITCZ) drives anomalies in temperature and precipitation; however, this atmospheric driver likely produces distinct hydrologic responses that depend on the spatial center over the Blue or the White Nile headwaters. Quantifying this effect requires a well-calibrated hydrologic model of the entire watershed under near-natural conditions, including hydrologic routing through major lakes and the Sudd wetland. This study aims to calibrate such a hydrologic model and recreate the hydrologic response of the major watersheds in the NRB using recovered records that extend to 1901, thereby greatly increasing the period used for model calibration and approximating near-natural responses prior to construction of several modern reservoirs. We employed GR4J, a parsimonious rainfall-runoff hydrologic model, because of its flexibility and minimal data requirements to match the NRB’s limited data availability, particularly during the early 1900s. Climate drivers, including precipitation and daily minimum/maximum temperatures were based on the Global Soil Wetness Project Phase 3 (GSWP3). Discharge data for model calibration were acquired from the Global Runoff Data Centre (GRDC) and through digitization of long discharge records from Hurst (1958). The NRB was discretized into 36 hydrological response units (HRUs), and calibrated using stepwise, multi-objective approach at 16 gauge locations between 1901 and 1964. In addition to avoiding the effects of several modern reservoirs, this early calibration period also avoided the most severe effects of climate change, as supported by the lack of discernible trends using the Mann-Kendall test. Our results show a successful calibration of the GR4J hydrological model to reasonably reproduce discharge at multiple locations across the NRB, with Nash-Sutcliffe Efficiencies of 0.83 and 0.64 at the outlets of the Blue and the White Nile, respectively. Additionally, the calibrated model accurately captured an abrupt change of Lake Victoria levels during the 1960s, affirming its reliability in simulating regional climate disruptions and lake dynamics. The model can therefore be used to study the sensitivity of major watersheds in the NRB and serves as a benchmark for understanding anthropogenic-induced departures from the natural hydrological behavior of the Nile River.

Keywords: Nile River Basin, GR4J, Calibration, Hydrology

How to cite: Munyejuru, I. F. and Stagge, J.: Multi-Objective Calibration of Nile River Basin Using Recovered Records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13773, https://doi.org/10.5194/egusphere-egu24-13773, 2024.

16:30–16:32
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PICO3.6
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EGU24-3573
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ECS
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On-site presentation
Patrick Sogno, Igor Klein, Soner Uereyen, Felix Bachofer, and Claudia Kuenzer

Water, a fundamental resource for both ecosystems and human populations, faces escalating challenges in Africa due to water stress and changes in climate, demography, and socioeconomics. Because these changes are happening at a rapid pace, it is essential to understand the dynamics of water bodies and the factors that impact them to ensure sustainable usage strategies. Our research aims to analyze the long-term trends of surface water availability in Africa, identify the causal impacts on major water bodies, and explore the similarities between different lakes.

We use daily time series based on Earth observation, including the MODIS-based Global WaterPack for a daily uninterrupted time series of the continent's surface water area. Furthermore, we incorporate daily time series of hydrologically relevant variables such as precipitation, total evapotranspiration, groundwater, soil moisture, and Gross Primary Productivity (GPP) to analyze their impact on surface water dynamics of major African lakes. For this, we employ the Peter and Clark Momentary Conditional Independence causal identification algorithm. Our findings reveal subbasin-wide surface water and GPP to be the dominant drivers of surface water dynamics in most cases. We further find that dynamically similar lakes often share common drivers, allowing the generation of regional lake clusters. Understanding the drivers of African lakes may significantly help in the formulation of sustainable development strategies.

In conclusion, our continent-wide analysis provides valuable insights, particularly beneficial for stakeholders engaged in international development and ecosystem protection and restoration. As we deal with the challenges of water resource management in Africa, our research aims to contribute substantively to the formulation of strategies that foster sustainability and resilience in the face of evolving environmental and socio-economic conditions.

How to cite: Sogno, P., Klein, I., Uereyen, S., Bachofer, F., and Kuenzer, C.: Exploring Trends, Patterns, and Drivers of African Surface Water Dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3573, https://doi.org/10.5194/egusphere-egu24-3573, 2024.

Hydromet data & climate models
16:32–16:34
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PICO3.7
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EGU24-4687
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ECS
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On-site presentation
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Kevin Schwarzwald and Richard Seager

The recent 5-season drought in the Horn of Africa, which contributed to food security issues that nearly resulted in a declaration of famine by the UN, has renewed interest in the “East African Paradox” (cf. Rowell et al., 2015): despite observed drying trends in the March-April-May “long” rains, global coupled climate models—whose output is increasingly used to drive hydrological models and inform projections of the socioeconomic risks of climate change in East Africa—project increases in seasonal rainfall totals over both the historical period and throughout future projections in the region. This ‘Paradox’ could arise from low-frequency internal variability causing drying even if long-term trends are wetting or from structural biases in climate models (e.g. simulation of the equatorial Pacific Ocean) that cause spurious trends in model simulations. Large Ensembles, including for SST-forced runs, make differentiating between internal variability and biases in model mean behavior more feasible, and another decade of observational data since the emergence of the ‘Paradox’ helps improve our understanding of historic internal variability.

We use a large multi-model ensemble of opportunity of coupled and SST-forced runs from the latest model generation (CMIP6), spanning the observational record, to revisit the magnitude and causes of the ‘Paradox’. We find that drying trends in the long rains are timescale-dependent and weaker than they were during the peak ‘Paradox’ period. This is mostly well modeled by the SST-forced ensemble, though coupled models continue to have erroneously strong wetting trends. The ‘Paradox’ therefore is reduced to what are the causes of low frequency SST trends and why coupled models cannot reproduce them.  We will discuss if these changes are the result of natural variability temporally masking the forced trend and what the sign of that trend might be.  These results have implications for projections of future climate impacts with a potentially quantifiable range of internal variability providing more actionable information than the deep uncertainty on forced trends introduced by structural model errors.

How to cite: Schwarzwald, K. and Seager, R.: Revisiting the ‘East African Paradox’: CMIP6 models also fail to simulate observed drying trends in the Horn of Africa Long Rains, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4687, https://doi.org/10.5194/egusphere-egu24-4687, 2024.

16:34–16:36
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PICO3.8
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EGU24-8886
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On-site presentation
Vincent Hoogelander, Nick van de Giesen, Rolf Hut, Jianzhi Dong, Camille Le Coz, and George Sserwada

Sub-Saharan Africa heavily relies on remotely-sensed rainfall measurements due to a lack of in-situ rainfall data. While a high number of satellite-based rainfall products do exist, they are typically developed and tested in regions with a high density of ground data. The Trans-African Hydro-Meteorological Observatory (TAHMO) aims to tackle the ground data gap by installing and operating a dense network of weather stations in Sub-Saharan Africa. As part of the TEMBO Africa project, TAHMO data were used to make a new regional rainfall product in East Africa based on the SM2Rain algorithm.  Subsequently, this regional product was merged with a reanalysis product (ERA5) and two MW/IR-based rainfall products (IMERG-L and CHIRPS) based on the Statistical Uncertainty analysis-based Precipitation mERging framework (SUPER). Within this framework, merging weights are based on error variances of the rainfall products determined from quadruple collocation on a pixel-to-pixel basis. The merged product and the individual products are evaluated using data of the individual TAHMO stations. Our findings indicate that the merged product outperforms the individual products in most selected evaluation metrics.  ERA5 has the highest contribution in the merged product, followed by SM2Rain. Both IMERG and CHIRPS have limited contribution in the merged product due to a high error variance. The ultimate goal of this study was to develop a workflow to enhance the accuracy of rainfall measurements in Sub-Saharan Africa by leveraging information from TAHMO data and different existing products, contributing to the improvement of remotely-sensed rainfall measurements in Sub-Saharan Africa.

We welcome suggestions on possible improvements and operational implementation, as well as ideas on how to use this merged product to understand the sources of error in satellite-based rainfall measurements in Sub-Saharan Africa.

 

TEMBO Africa: The work leading to these results has received funding from the European Horizon Europe Programme (2021-2027) under grant agreement n° 101086209. The opinions expressed in the document are of the authors only and no way reflect the European Commission’s opinions. The European Union is not liable for any use that may be made of the information

How to cite: Hoogelander, V., van de Giesen, N., Hut, R., Dong, J., Le Coz, C., and Sserwada, G.: Enhancing Rainfall Estimates in East Africa by Merging TAHMO Precipitation Gauge Data with Remote Sensing Rainfall Products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8886, https://doi.org/10.5194/egusphere-egu24-8886, 2024.

16:36–16:38
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PICO3.9
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EGU24-6712
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On-site presentation
Jan Bliefernicht, Samuel Guug, Rainer Steinbrecher, Frank Neidl, Ines Spangenberg, Leonard K. Amekudzi, Emmanuel Quansah, Patrick Davies, Heye Bogena, Roland Baatz, Ursula Gessner, Thomas Jagdhuber, Francis Oussou, Seyni Salack, Belko Diallo, Kehinde O. Ogunjobi, Souleymane Sy, Windmanagda Sawadogo, Verena Huber Garcia, and Harald Kunstmann

West Africa is a data-poor region, and long-term hydrometeorological field experiments are very limited but are essential for a better understanding of climate change and land use change impacts in this vulnerable region. This study provides a detailed overview of WASCAL hydrometeorological observatory, which was established in 2013 in the Sudan savanna of Burkina Faso and Ghana. This region is characterized by strong land use changes due to a rapid increase of agricultural land. The observatory is therefore designed to study the effects of land use changes on land-atmosphere exchange processes and other terrestrial land surface processes and characteristics. It consists of a network of state-of-the-art hydro-meteorological measurement equipment (e.g., automatic weather stations, agrometeorological stations) complemented by innovative devices such as cosmic ray neutron sensors for improved soil moisture monitoring. A unique component of the observatory is a micrometeorological experiment using eddy covariance towers implemented at five contrasting land use sites to study the impacts of land use change on water, energy, and greenhouse gas fluxes. The datasets of the WASCAL observatory are needed as key information for the development and evaluation of land surface models, hydrological models, and improved regional climate models and other environmental modelling approaches and products. In this presentation, we provide a detailed overview of the current development of the WASCAL observatory. In addition, selected results from the inter-twined field, remote sensing, and RCM modeling studies are presented.

How to cite: Bliefernicht, J., Guug, S., Steinbrecher, R., Neidl, F., Spangenberg, I., Amekudzi, L. K., Quansah, E., Davies, P., Bogena, H., Baatz, R., Gessner, U., Jagdhuber, T., Oussou, F., Salack, S., Diallo, B., Ogunjobi, K. O., Sy, S., Sawadogo, W., Huber Garcia, V., and Kunstmann, H.: Developments and Challenges in Operating a Hydrometeorological Research Observatory in the Western Sudanian Savanna - Ten Years of WASCAL Observatory Experience, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6712, https://doi.org/10.5194/egusphere-egu24-6712, 2024.

16:38–16:40
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PICO3.10
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EGU24-9889
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ECS
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On-site presentation
Derrick Muheki, Bas Vercruysse, Christophe Verbruggen, Dominique Kankonde Ntumba, Ed Hawkins, Félicien Meunier, Fils Makanzu Imwangana, Hans Verbeeck, Julie M. Birkholz, José Mbifo, Kim Jacobsen, Koen Hufkens, Krishna K. T. Chandrasekar, Olivier Dewitte, Olivier Kapalay Moulasa, Pascal Boeckx, Peter Thorne, Seppe Lampe, Théophile Besango Likwela, and Wim Thiery

Local and distant archives of observed weather data present unique opportunities for scientists to obtain long time series of the historical hydrology and climate for many regions of the world. Unfortunately, most of these observational records are still to-date available only on paper, and thus require digitization and transcribing to machine-readable formats to facilitate analysis of hydroclimatic trends. Here we discuss the data rescue efforts for hydroclimatic data recorded at 36 climate stations in the Democratic Republic of Congo from the early 1950’s to-date. We describe the procedures we follow to digitize over 10,000 paper records of daily precipitation and temperature within archives both in the Democratic Republic of Congo and Belgium, and subsequently the steps to transcribe this data set using different methods including machine learning. Furthermore, we undertake quality control and quality assessment of the transcribed data. The resultant time series, comprised of millions of observations from the archived data, will resolve the challenges of limited available hydroclimatic data within the Congo basin and expedite research on the hydroclimate in the basin.

How to cite: Muheki, D., Vercruysse, B., Verbruggen, C., Ntumba, D. K., Hawkins, E., Meunier, F., Imwangana, F. M., Verbeeck, H., Birkholz, J. M., Mbifo, J., Jacobsen, K., Hufkens, K., Chandrasekar, K. K. T., Dewitte, O., Moulasa, O. K., Boeckx, P., Thorne, P., Lampe, S., Likwela, T. B., and Thiery, W.: Data rescue of millions of daily precipitation and temperature records collected within the Congo Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9889, https://doi.org/10.5194/egusphere-egu24-9889, 2024.

Miscellaneous
16:40–16:42
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PICO3.11
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EGU24-335
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ECS
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On-site presentation
Bertil Nlend, Fréderic Huneau, and Suzanne Ngo Boum-Nkot

The utility of isotope techniques in hydrological investigations stems from their ability to label water sources and cycling processes including surface/groundwater interaction, water residence times, flow pathways, evaporation fluxes, and solute processes, to name a few. In Africa, they have been applied since four decades following the severe drought of the 1970s, and can now be summarized in important case studies. This review focusing on Cameroon (often called the little Africa) aims to put together all the stable and radioactive isotopic data (>500 samples from rainfall, surface and groundwater) published in the country to: (i) identify the drivers responsible for precipitation isotopes spatial variation and climatological implications, (ii) elucidate the groundwater recharge mechanisms over the countries and relationships with rivers, and (iii) highlight the existence of paleo-groundwater in the country. It is found that rainfall stable isotopes variation is linked to the migration of the Intertropical Convergence Zone (ITCZ). The groundwater recharge can be diffuse and focused. This latter mechanism is mainly observed in the semi-arid region. It is in this relatively dry region that most of the paleo-groundwater resources are identified thanks to 14C dating. This information will be useful to develop water management strategies regarding all the challenges (e.g., climatic and demographic) faced by the country. Finally, this paper discusses the gaps groundwater isotope hydrology can still fill for contributing to a sustainable development of the country. Reflections provided here can be extend in each country of the sub-Saharan Africa region.

How to cite: Nlend, B., Huneau, F., and Ngo Boum-Nkot, S.: Isotope Hydrology progress in sub-Saharan Africa. What information for water management? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-335, https://doi.org/10.5194/egusphere-egu24-335, 2024.

16:42–16:44
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PICO3.12
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EGU24-20554
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On-site presentation
Deforestation and water availability in data-scarce Mulanje area, Malawi
(withdrawn)
Tom van Steijn
16:44–16:46
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PICO3.13
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EGU24-5288
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On-site presentation
Victor Gómez-Escalonilla, Oumou Diancoumba, Dasso Yolande Traoré, Esperanza Montero, Miguel Martín-Loeches, and Pedro Martínez-Santos

Groundwater plays a vital role in drinking water supply, food security and ecosystem services. Approximately 2.5 billion people worldwide rely exclusively on groundwater to meet their daily needs, while hundreds of millions of farmers depend on groundwater resources to sustain their livelihoods. Groundwater potential mapping based on machine learning (ML-GPM) can be used to support groundwater exploration, planning and management practices. Most ML-GPM studies aim to predict a positive or negative outcome, that is, to identify areas of high or low groundwater potential. This work takes this conventional bivariate outcome approach one step further by predicting borehole yields and applying a multiclass approach. The method is illustrated through an application over a study area of 21,000 km2, including the administrative region of Bamako and the municipalities of Kati and Kangaba in the Koulikoro region of southern Mali. Logistic Regression, Gradient Boosting and Extra Trees classifiers were trained on an imbalanced multiclass database of 483 boreholes and 20 explanatory variables. The explanatory variables include information on lithology, geomorphology, soil, land use/land cover, topography, drainage and slope-related variables and rainfall, among others. All models returned prediction scores between 0.80 and 0.87. The most important variables include elevation, vegetation cover, basement depth and geology. The alluvial sediments of the Niger river banks, especially in the southern and northern sectors, are clearly associated with the most productive class. In contrast, the Mandingue plateau has the lowest groundwater potential. The piedmont areas present an intermediate groundwater perspective. These maps could be used to inform water supply policy at a regional scale.

How to cite: Gómez-Escalonilla, V., Diancoumba, O., Traoré, D. Y., Montero, E., Martín-Loeches, M., and Martínez-Santos, P.: Spatial prediction of borehole yield in southern Mali using machine learning classifiers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5288, https://doi.org/10.5194/egusphere-egu24-5288, 2024.

16:46–16:48
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PICO3.14
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EGU24-668
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ECS
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On-site presentation
Tégawindé Vanessa Rosette Kaboré

Arid and semi-arid areas are characterized by low annual rainfall that is unevenly distributed in time and space. These low and variable rainfall conditions are exacerbated by the effects of climate change, resulting in increasing agricultural losses for rain-fed crops. To overcome this, several water conservation techniques have been developed to safeguard agricultural yields. For example, supplemental irrigation using catchment basins is a climate change adaptation solution that has been promoted for many years in drought-prone areas. Unfortunately, this technique has had limited success in the Sahel due to the large amount of water lost through infiltration into the basins. These losses are closely related to the type of lining chosen to seal the runoff collection basins. Using a factorial analysis model, this paper highlights farmers' preferences for four of the most popular liners in Burkina Faso. Based on Waso-2 method, the survey was conducted in 2022 among 41 pond-owning farmers in the Central, Central Plateau and Central South regions. The results clearly show that the choice of liner has little to do with its availability and cost: producers focus all their attention on the liner's ability to improve the watertightness of their ponds and on the complexity of its maintenance. Concrete is therefore the first choice of producers as it is the most watertight, weatherproof, and durable, but also the most expensive. It is followed by plastic sheeting, a highly waterproof material available on the market, but not very durable. Clay comes third, despite its availability and low cost. Well-known in traditional architecture for ensuring the comfort of buildings, clay has proved ineffective for waterproofing submerged structures where the ground is unstable or cracked. Bitumen came last, as it is little known for pond protection and is not available in rural Burkina Faso.

Keywords: Rainwater harvesting basin, sealing solutions, supplemental irrigation, Waso-2.

How to cite: Kaboré, T. V. R.: Analysis of farmers' perception about sealing techniques for runoff harvesting ponds: the case of Burkina Faso., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-668, https://doi.org/10.5194/egusphere-egu24-668, 2024.

16:48–16:50
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EGU24-13236
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ECS
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Virtual presentation
Aida Bargués Tobella, Leigh A. Winowiecki, Douglas Sheil, and Tor G. Vågen

Soil infiltration is a critical hydrological process governing water security and related ecosystem services. The infiltration capacity of soils is largely controlled by their hydraulic conductivity. Hence, understanding soil hydraulic conductivity is critical for effective soil and water management. Despite recent efforts in assembling measurements of soil hydraulic conductivity, global databases and derived pedotransfer functions lack coverage in the tropics. Africa, in particular, remains sparsely represented in these global databases, and representative observations of soil hydraulic properties are few and of mixed form and quality.

In this presentation, we introduce a new dataset of soil infiltration measurements and accompanying indicators of soil and land health collected systematically using the Land Degradation Surveillance Framework (LDSF) in 3573 plots from 83 100 km2 sites across 19 countries in sub-Saharan Africa and present the results from a recent study* where we used these data to (a) determine field-saturated hydraulic conductivity (Kfs) and (b) explore which variables best predict variation in Kfs.

Our results show that sand content, soil organic carbon (SOC), and woody cover had a positive relationship with Kfs, whereas grazing intensity and soil pH had a negative relationship. Our findings highlight that, despite soil texture being important, structure also plays a critical role. These results suggest significant opportunities to improve soil hydrological functioning through management and restoration practices that protect and enhance soil structure. Enhancing SOC content, limiting livestock stocking rates, promoting vegetation cover, particularly woody vegetation, and preventing and halting soil erosion can increase Kfs. This evidence can guide sustainable land management practices and restoration interventions across the region for improved soil health and water security.

Our dataset expands existing regional and global databases of soil hydraulic properties, improving coverage for Africa and providing field data for underrepresented land uses and soils. As such, we envision that this dataset can contribute to improved understanding and prediction of soil hydraulic properties and to improved Earth system and land surface models for applications in Africa.

 

* Bargués-Tobella, A., Winowiecki, L.A., Sheil, D., and Vågen, T.G. Determinants of soil field-saturated hydraulic conductivity across sub-Saharan Africa: texture and beyond. Water Resources Research. DOI 10.1029/2023WR035510. In-press.

How to cite: Bargués Tobella, A., Winowiecki, L. A., Sheil, D., and Vågen, T. G.: Determinants of soil field-saturated hydraulic conductivity across sub-Saharan Africa: texture and beyond, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13236, https://doi.org/10.5194/egusphere-egu24-13236, 2024.

16:50–18:00