Hagen Koch’s research while affiliated with Potsdam Institute for Climate Impact Research and other places

In many river basins worldwide, decision-making depends on limited data and information. Yet, decisions, like the planning of a new multi-purpose dam, must be taken relying on available data. The incorporation of socio-economic developments, climate or land use changes into this process remains a separate concern. Undoubtedly, authorities worldwide possess undisclosed data, which complicates scientific efforts. This study aims to address the challenges of developing a hydrological and water management model for the data-scarce and extensively managed Volta River Basin in West Africa. To overcome the limitations posed by sparse easily accessible observational data, a time- and resource-demanding data integration approach was applied using a diverse array of data sources covering various time periods, including manually digitized analog records from hydrological yearbooks, graphics, and other multilingual sources. This approach has been shown to enhance the spatio-temporal availability of data, thereby allowing for the optimization of model parameters to simulate the increasing impact of human intervention on river discharge. The incorporation of comprehensive data has enhanced the robustness of the model, where complex hydrological processes and water management dynamics are captured with greater accuracy. This would not have been possible if only the easily accessible data had been used.

Understanding people's perceptions of climate change and associated environmental risks is paramount in assessing how individuals respond to climate change. Awareness of the consequences of climate change determines the present and future behaviours and expectations, as well as the actions taken to mitigate the likely impacts. We surveyed the perceived and expected climate change consequences of experts and community members in the Lake Victoria basin in East Africa, compared them with hydro-meteorological observations and projections, and established that some perceived trends, such as increasing temperature or rainfall intensity, correspond with meteorological observations. However, the perceived increase in drought occurrence (believed to be a recent consequence), was not substantiated by the meteorological data. It was only in the northwestern region that drought frequency increased since the year 2000, while the rest of the basin did not experience such a trend. Community members were concerned about the already noticeable consequences of climate change on their livelihoods through agriculture or fishing, while experts were mainly focused on the amplification of hazards such as floods and droughts. This divergence may imply that experts underestimate the consequences that society is already facing. Nevertheless, both groups expect that climate change will undoubtedly lead to the deterioration of human well-being by affecting food security, increasing poverty, and increasing the incidence of disease. This is a serious concern that requires immediate attention. Such insights into people's climate change perceptions can help policy-makers, researchers, and community members to better tailor adaptation solutions acceptable to the local context. Effective governance is essential to enable people to adapt to climate change and other challenges, including those resulting from the impacts of globalisation, demographic trends, and the degradation and scarcity of resources.

Das Einzugsgebiet der Spree ist hydrologisch und wasserwirtschaftlich stark von der Entwicklung von Braunkohleförderung und-ver-stromung, verbunden mit Grundwasserabsenkungen, Versickerungsverlusten, Sümpfungswassereinleitungen, Kühlwassernutzung in thermischen Kraftwerken sowie Flutung ehemaliger Tagebaue, einem komplexen wasserwirtschaftlichen System und einem kontinen-talen Klima geprägt. Im Projekt GLOWA Elbe wurden für das Gebiet Szenarien des globalen Wandels für den Zeitraum 2003 bis 2052 analysiert. Im Jahre 2004 war es das Ergebnis, dass das gegenwärtige System der Wasserbewirtschaftung die Folgen des angenomme-nen Klimawandels nicht ausgleichen kann. Nach Ablauf der ersten 20 Jahre des Simulationszeitraumes 2003 bis 2022 werden in diesem Artikel die in GLOWA Elbe und weiteren Projekten erzeugten Ergebnisse sowie die genutzten Eingangsdaten, Szenarien und Modelle hinsichtlich ihrer Übereinstimmung mit beobachteten Abflüssen bzw. Witterungsverlauf analysiert. Es zeigt sich, dass die in den Projekten genutzten Bergbauszenarien der Entwicklung bis zum jetzigen Zeitpunkt entsprechen, während die Szenarien zur klimatischen Entwicklung zum Teil deutlich von den Beobachtungen abweichen. Letzteres hat erhebliche Konsequen-zen für die simulierten Abflüsse. Weiterhin kann gezeigt werden, dass auch in stark anthropogen überprägten Flusseinzugsgebieten die Auswirkungen des Klimawan-dels unter Nutzung hydrologischer und wasserwirtschaftlicher Modelle zuverlässig abgeschätzt werden können, wobei insbesondere die genutzten Klimaszenarien/-modelle eine erhebliche Unsicherheit hervorrufen. Deswegen ist es unabdingbar, in entsprechenden Klimafolgenstudien Eingangsdaten diverser Klimaszenarien/-modelle zu nutzen und die gesamte Bandbreite der hydrologischen/was-serwirtschaftlichen Ergebnisse darzustellen. Schlagwörter: Spree, Szenarien, Klimawandel, Bergbau, Wasserbewirtschaftung In terms of hydrology and water management, the Spree river catchment in eastern Germany is strongly influenced by the development of lignite mining and power generation (groundwater lowering, seepage losses, mine water discharges, cooling water use in thermal power plants, flooding of former opencast mines), a complex water management system and a continental climate. The GLOWA Elbe project analysed scenarios of global change for the Spree for the period 2003 to 2052. In 2004, one result was that the current system of water management cannot compensate for the consequences of the assumed climate change. After the first 20 years of the simulation period (2003 to 2022), this article analyses the results generated in GLOWA Elbe and other projects as well as the input data, scenarios and models used with regard to their agreement with observed discharges and weather patterns. The mining scenarios used in the projects correspond to the development up to the present time, while the scenarios for climatic development partly deviate significantly from the observations. The latter has considerable consequences for the simulated discharges. Furthermore, it can be shown that the impacts of climate change can be reliably estimated in river basins heavily anthropogenically influenced using hydrological and water management models, although the climate scenarios/models used introduce considerable uncertainty. Therefore, it is indispensable to use input data from various climate scenarios/models in corresponding climate impact studies and to present the entire range of hydrological/water management results.

This study presents the assessment of water scarcity associated with livestock production in a watershed in Southern Brazil where 115 farms (poultry, pig, and milk) are located. The methods, AWARE—available water remaining, and BWSI—blue water scarcity index, were applied monthly for the year 2018, and the characterization factors (CF) were regionalized into five scenarios evaluated by varying water availability and environmental water requirements. Livestock water consumption accounted for 94.1% of the total water consumed. Low water scarcity was observed in all scenarios (BWSI < 0). The highest CFAWARE was observed in scenario 3, ranging from 2.15 to 9.70 m³ world eq.m³, with higher water scarcity in summer. In the same scenario, pig production presented the highest annual average water scarcity footprint (WSF) of 90.3 m³ world eq./t carcass weight. Among milk production systems, pasture-based systems presented the highest annual average WSF of 52.7 m³ world eq./t fat protein corrected milk, surpassing semi-confined and confined systems by 12.4% and 3.5%, respectively. In scenario 3, poultry production presented an annual average WSF of 49.3 m³ world eq./t carcass weight. This study contributes knowledge to the livestock sector to perform the assessment of water scarcity.

Land use and Land cover change (LULCC) is a major global problem, and projecting change is critical for policy decision-making. Understanding LULCCs at the watershed level is essential for transboundary river basin management. The present study aims to analyse the past and future LULCCs in two significant watersheds of the Senegal River basin (SRB) in West Africa: Bafing and Faleme. This study used Landsat images from 1986, 2006 and 2020 and the Random Forest classification method to analyze past LULCCs in these two watersheds. The results revealed: In Bafing, vegetation, settlement, agricultural areas and water increased, while the bareground decreased significantly between 1986-2020. In Faleme, two periods have different trends. Between 1986-2006, vegetation, settlement, agricultural areas and water increased, while bareground decreased. Between 2006-2020, settlement increased, while vegetation, agricul�tural areas, water and bareground decreased. To predict LULCCs in 2050 under business-as�usual assumptions, the Multilayer Perceptron and Marcov Chain model (MLP-MC) was used. The MLP-MC shows better results on Bafing than on Faleme but without questioning its application on the two watersheds. Bafing has seen a trend towards ”more people, more trees”, while Faleme has seen a trend towards ”more people, more deforestation”. These results contribute to develop appropriate land management policies and strategies to achieve or to maintain sustainable development in the SRB.

Hydropower is the world’s largest and most widely used renewable energy source. It is expected that climate and land use changes, as well as hydraulic engineering measures, will have profound impacts on future hydropower potential. In this study, the hydropower potential of the Bafing watershed was estimated for the near future (P1: 2035–2065) and the far future (P2: 2065–2095). For this purpose, the moderate scenario ssp 126 and the medium–high scenario ssp 370 were used to explore possible climate impacts. In three management scenarios, we tested the interaction of the existing Manantali Dam with two planned dams (Koukoutamba and Boureya) using an ecohydrological water management model. The results show that, under ssp 126, a 6% increase in annual river flow would result in a 3% increase in hydropower potential in the near future compared with the historical period of 1984–2014. In the far future, the annual river flow would decrease by 6%, resulting in an 8% decrease in hydropower potential. Under ssp 370, the hydropower potential would decrease by 0.7% and 14% in the near and far future, respectively. The investment in the planned dams has benefits, such as an increase in hydropower potential and improved flood protection. However, the dams will be negatively affected by climate change in the future (except in the near future (P1) under ssp 126), and their operation will result in hydropower potential losses of about 11% at the Manantali Dam. Therefore, to mitigate the effects of climate change and adjust the operation of the three dams, it is essential to develop new adaptation measures through an optimization program or an energy mix combining hydro, solar, and wind power.

Understanding land use and cover (LULC) dynamic is of great importance to sustainable development in Africa where deforestation is a common problem. This study aimed to assess the historical and future dynamics of LULC in the Nakambé River Basin. Landsat images were used to determine LULC dynamics for the years 1990, 2005 and 2020 using Random Forest classification system in Google Earth Engine while the predicted LULC of 2050 was simulated using the Markov Chain and Multi-Layer-Perceptron neural network in Land Change Modeler. The findings showed significant changes in LULC patterns. From 1990 to 2020, woodland and shrubland decreased by − 45% and − 68%, respectively, while water body, cropland and bare land/built-up increased by 233%, 51%, and 75%, correspondingly. From 2020 to 2050, the results revealed that under the Business-as-usual scenario, bare land/built-up and water bodies could continue to increase by 99% and 1%, respectively. However, cropland, shrubland, and woodland could decrease by − 32.61%, − 33.91%, and − 46.86%, respectively. Under the afforestation scenario, the contrary of Business-as-usual could occur. While woodland, shrubland, and cropland would increase by 22.24%, 51.57%, and 18.13%, correspondingly, between 2020 and 2050, the area covered by water bodies and bare land/built-up will decrease by − 6.16% and − 39.04%, respectively. The results of this research give an insight into past and future LULC dynamics in the Nakambé River Basin and suggest the need to strengthen the policies and actions for better land management in the region.

Global hydro-climatic trends are ambiguous, challenging the management of water resources. This challenge is addressed in the current study by investigating the impacts of hydro-climatic trends and upstream water management on hydropower generation at the Bagré dam. Modified Mann–Kendall trend test, Standard Normal Homogeneity Test and Pettit test were applied to some selected hydro-climatic variables for the trend and the change year detection, whereas the relationship between upstream dam management, hydro-climatic variables and hydropower were assessed through the Spearman correlation. The results revealed an annual positive trend for all hydro-climatic variables except for water level, lake evaporation and outflow. The break years observed in hydropower generation (2002) and inflow (2006) were mainly due to the construction of the Ziga dam in 2000 and its management change in 2005, respectively. The study also showed that hydropower generation declines each May (30.36 MWh) and June (16.82 MWh) due to the significant increase in irrigation withdrawals (1.94 hm³ in May and 0.67 hm³ in June). The results of this study highlighted the non-linearity in the relationship between hydropower generation and hydro-climatic variables as none of the correlation coefficients (apart from turbine) are very strong (>0.8). As many human activities occurred in the basin, further research should be focused on the use of semi-distributed models to assess the impacts of water-use and land-use change on hydropower generation.

The São Francisco River Basin in Brazil’s Northeast region suffered from a serious multi-year drought, which started in 2012. This drought was characterized by long periods of water stress, variability and unpredictability of levels and flows of rivers and reservoirs, decreases in hydropower generation, and rising of conflicts between agricultural and electrical sectors. Besides, the electricity sector faced a crisis due to its dependency on hydroelectricity generation. Applying a Multi-Criteria Decision Analysis (MCDA) can contribute to resolve such conflicts. Particular challenges are establishing transparent rules for water level management at the dams and securing electricity supply. Ultimately, identifying options to invest in sustainable power sources may positively impact the regional electricity matrix. We used Soft Systems Methodology to structure the decision-making context and set the main objectives to be considered in the MCDA. Different scenarios of reservoir management were simulated using the Soil and Water Integrated Model and Incomplete Pairwise Comparison, while bibliographic research and expert interviews led to the selection of indicators for structuring the MCDA. We present projections for hydropower generation and meeting of water demands of further users, based on two climate change projections. The driest scenario shows a reduction in hydropower generation, indicating the necessity to reconfigure the composition of electricity sources, considering economic, technical and social-environmental constraints. These elements of the structuring phase are prerequisites for the evaluation phase of the MCDA.

Ethiopia, Sudan and Egypt are currently embroiled in a politically charged conflict that surrounds the soon-to-be-completed Grand Ethiopian Renaissance Dam (GERD), with Ethiopia’s energy objectives purportedly conflicting with the water needs in Sudan and Egypt. Here we show that the multiple political and environmental challenges that surround GERD could be mitigated by explicitly coupling its operation to variable solar and wind power, which would create an incentive for Ethiopia to retain a seasonality in the Blue Nile flow. We found that this could deliver fivefold benefits across the three countries: decarbonizing power generation in the Eastern Africa Power Pool; allowing compliance with Sudan’s environmental flow needs; optimizing GERD’s infrastructure use; harmonizing the yearly refilling schedules of GERD and Egypt’s High Aswan Dam; and supporting a strong diversification of Ethiopian power generation for domestic use and for Eastern Africa Power Pool exports. These results argue for an explicit integration of complementary hydro, solar and wind power strategies in GERD operation and Eastern Africa Power Pool expansion planning. [Read article here: https://rdcu.be/cikbq]