An integrated, landscape-based approach to model the formation and hydrological functioning of wetlands in semiarid headwater catchments of the Umzimvubu River, South Africa

Wetlands are very important elements of the landscape in almost every environment. Addressing the continued loss of wetland area worldwide, wetlands are recognized as highly vulnerable with regard to natural and anthropogenic system changes. Consequently, the research of their natural and socio-economical functions, importance for the water and nutrient cycles and their role as wildlife habitats received increasing scientific and public awareness in the past decades. The landscape of the semi-arid Eastern Cape Province, South Africa, is characterized by the occurrence of different types of palustrine wetlands. Intensive afforestation in the headwaters of the Umzimvubu catchment since 1989 has changed downstream wetland characteristics, but little attention was given to evaluate and quantify these impacts. Addressing this research deficit, the main objectives of this dissertation are the development of an integrated, landscape-based research approach to improve the understanding of the formation, functioning and dynamics of wetlands and the prognostic modeling and assessment of afforestation impacts on these wetland systems. The conceptual and methodological approach of this dissertation is based on three individual aspects: i) observation and data mining; ii) integrated system analysis; and iii) system modeling and assessment integrating empirical field studies, laboratory analysis, GIS and remote sensing techniques, system analysis and process-oriented, plant growth and hydrological modeling, This integrated research approach provides information regarding a generalized understanding of dominant environmental processes at wetland and catchment scale and the impact of afforestation on wetland and basin hydrology. By means of this effort three main wetland types, being different in terms of landscape position, extent and size of the tributary catchment, soils, vegetation composition and hydrological dynamics, could be identified. The hydrodynamics of plateau and slope wetlands are mainly controlled by recharge mechanisms, while larger valley bottom wetlands are driven by interlinked ground-/surface water dynamics, discharge/recharge processes and direct rainfall input. Coupling plant growth and hydrological modeling, it was found that wetland dynamics and their landscape functions will be influenced by afforestation in terms of altered recharge/discharge mechanisms; reduced base flows addressed to increased interception losses and reduced water retention capability as a result of net loss of wetland area. In addition, such changes will affect environmental functions and biodiversity due to habitat loss and alterations. Integrating the results and information of the present study, an integrated landscape model was developed aiming to characterize wetland formation and emphasizing impacts of human activities on past and recent wetland and landscape dynamics

How Climate Extremes Influence Conceptual Rainfall-Runoff Model Performance and Uncertainty

Rainfall-runoff models are frequently used for assessing climate risks by predicting changes in streamflow and other hydrological processes due to anticipated anthropogenic climate change, climate variability, and land management. Historical observations are commonly used to calibrate empirically the performance of conceptual hydrological mechanisms. As a result, calibration procedures are limited when extrapolated to novel climate conditions under future scenarios. In this paper, rainfall-runoff model performance and the simulated catchment hydrological processes were explored using the JAMS/J2000 model for the Berg River catchment in South Africa to evaluate the model in the tails of the current distribution of climatic conditions. An evolutionary multi-objective search algorithm was used to develop sets of parameters which best simulate “wet” and “dry” periods, providing the upper and lower bounds for a temporal uncertainty analysis approach to identify variables which are affected by these climate extremes. Variables most affected included soil-water storage and timing of interflow and groundwater flow, emerging as the overall dampening of the simulated hydrograph. Previous modeling showed that the JAMS/J2000 model provided a “good” simulation for periods where the yearly long-term mean precipitation shortfall was 0.7) during “wet” periods using parameters from a long-term calibration, “wet” parameters were not recommended for the Berg River catchment, but could play a large role in tropical climates. The results of this study are likely transferrable to other conceptual rainfall/runoff models, but may differ for various climates. As greater climate variability drives hydrological changes around the world, future empirically-based hydrological projections need to evaluate assumptions regarding storage and the simulated hydrological processes, to enhanced climate risk management

Enhancing the Uptake of Earth Observation Products and Services in Africa Through a Multi-level Transdisciplinary Approach

Africa stands to gain from Earth Observation (EO) science, products and applications. However, its use and application remain below potential on the continent. This article examines how EO can better serve the needs of African users. First, we argue that a successful uptake of EO services is conditional on understanding the African context and matching EO development and deployment to it. Using reference cases, we find that actors outside Africa drive most EO initiatives, whereas country-level expenditures on EO remain low. Recent developments, such as the African space policy and strategy, and initiatives in partnerships with Africa-based organisations to develop a community of practice on EO hold the potential to fill the identified gaps. The analysis indicates that most EO users are either government organisations or researchers, with very few cases involving other types of users. It is generally assumed that users at the local levels are educated and digitally literate, or that the transmission of EO-based knowledge is achieved by government officers and researchers. Although still very few, potentials are emerging for the private sector to deploy EO products and services such as crop or index-based insurance directly to farmers. These private initiatives have prospects for further developing indigenous EO capacity as envisioned in the African space policy and strategy. We then formulate recommendations for a transdisciplinary approach that integrates user contexts, attributes and needs to enhance the uptake of EO products and services in Africa. We conclude by proposing actions to close some of the identified gaps and seize emerging opportunities

Enhancing the Uptake of Earth Observation Products and Services in Africa Through a Multi-level Transdisciplinary Approach.

Africa stands to gain from Earth Observation (EO) science, products and applications. However, its use and application remain below potential on the continent. This article examines how EO can better serve the needs of African users. First, we argue that a successful uptake of EO services is conditional on understanding the African context and matching EO development and deployment to it. Using reference cases, we find that actors outside Africa drive most EO initiatives, whereas country-level expenditures on EO remain low. Recent developments, such as the African space policy and strategy, and initiatives in partnerships with Africa-based organisations to develop a community of practice on EO hold the potential to fill the identified gaps. The analysis indicates that most EO users are either government organisations or researchers, with very few cases involving other types of users. It is generally assumed that users at the local levels are educated and digitally literate, or that the transmission of EO-based knowledge is achieved by government officers and researchers. Although still very few, potentials are emerging for the private sector to deploy EO products and services such as crop or index-based insurance directly to farmers. These private initiatives have prospects for further developing indigenous EO capacity as envisioned in the African space policy and strategy. We then formulate recommendations for a transdisciplinary approach that integrates user contexts, attributes and needs to enhance the uptake of EO products and services in Africa. We conclude by proposing actions to close some of the identified gaps and seize emerging opportunities. Supplementary Information The online version contains supplementary material available at 10.1007/s10712-022-09724-1

Harmonised observations of climate forcing across Africa: an assessment of existing approaches and their applicability

A crucial aspect of coordinated climate action is the ability to measure, attribute, report and verify the drivers of climate change not only globally, but down to national level. This requires the enhancement of current observation infrastructures around the world, particularly in less-studied regions such as the African continent. Methodological protocols play an essential role in assuring interoperability among existing and new monitoring stations and networks. However, although the availability and accessibility of the body of existing methodological knowledge is crucial to fill existing observational gaps in a harmonised and resource-efficient way, there are very few efforts documented to systematically compile and assess it. This work aims to identify environmental observation methodologies which, on one hand, are applicable in Africa and, on the other hand, compatible with ongoing international and European monitoring initiatives. It draws from a systematic inventory of 140 environmental methodological protocols related to the measurement and estimation of the main climate forcing components within the atmospheric, oceanic, and terrestrial domains. In order to identify existing methodologies readily applicable for various observational purposes in under-studied regions, the feasibility of these protocols was determined based on a basic assessment of the financial and human resources needed for their implementation. Finally, a harmonised approach is proposed to enhance observational capacity in Africa with the differentiation of at least two types of sites. ‘Basic’ sites, where highly feasible environmental measurements can be performed to improve spatial coverage of main biomes, anthromes, and land use types, and advanced ‘key sites’, where a large set of variables measured at a high temporal resolution would enable a better understanding of driving processes in representative systems and managements across the continent, albeit requiring the application of less readily feasible methodologies

Determining Hydrological Variability Using a Multi-Catchment Model Approach for the Western Cape, South Africa

Understanding the impacts of climate change requires the development of hydrological modelling tools. However, data scarcity hinders model application, performance, process simulation and uncertainty, especially for Sub-Saharan Africa. In this study, a multi-catchment approach was used to assess hydrological process variability in the Western Cape (WC) of South Africa using the JAMS/J2000 rainfall–runoff model and a Monte Carlo analysis (MCA). Due to much steeper slopes and lower evapotranspiration, the models suggest that WC is dominated by surface runoff from mountainous regions and regional groundwater flow. The results highlight the impact of the catchment size, availability and position of hydroclimatic and anthropogenic factors and the frequency of the signal-to-noise ratio (water balance). For large catchments (>5000 km2), the calibration was able to achieve a Nash–Sutcliffe efficiency (NSE) of 0.61 to 0.88. For small catchments (2), NSE was between 0.23 to 0.39. The large catchments had an overall surface runoff, interflow and baseflow contribution of 44, 19 and 37%, respectively, and lower overall uncertainty. The simulated flow components for the small catchments were variable and these results are less certain. The use of a multi-catchment approach allows for identifying the specific factors impacting parameter sensitivities and in turn provides a means to improve hydrological process simulation

Determining Hydrological Variability Using a Multi-Catchment Model Approach for the Western Cape, South Africa

Understanding the impacts of climate change requires the development of hydrological modelling tools. However, data scarcity hinders model application, performance, process simulation and uncertainty, especially for Sub-Saharan Africa. In this study, a multi-catchment approach was used to assess hydrological process variability in the Western Cape (WC) of South Africa using the JAMS/J2000 rainfall–runoff model and a Monte Carlo analysis (MCA). Due to much steeper slopes and lower evapotranspiration, the models suggest that WC is dominated by surface runoff from mountainous regions and regional groundwater flow. The results highlight the impact of the catchment size, availability and position of hydroclimatic and anthropogenic factors and the frequency of the signal-to-noise ratio (water balance). For large catchments (>5000 km2), the calibration was able to achieve a Nash–Sutcliffe efficiency (NSE) of 0.61 to 0.88. For small catchments (<2000 km2), NSE was between 0.23 to 0.39. The large catchments had an overall surface runoff, interflow and baseflow contribution of 44, 19 and 37%, respectively, and lower overall uncertainty. The simulated flow components for the small catchments were variable and these results are less certain. The use of a multi-catchment approach allows for identifying the specific factors impacting parameter sensitivities and in turn provides a means to improve hydrological process simulation

AN INFORMATION SYSTEM FOR INTEGRATED LAND AND WATER RESOURCES MANAGEMENT IN THE KARA RIVER BASIN (TOGO AND BENIN)

ABSTRACT A prerequisite for integrated land and water resources management (ILWRM) is KEYWORDS Integrated land and water resources management (ILWRM); holistic hydrological river basin analysis; web-based information system; River basin information system (RBIS); the Kara river basi

Object oriented extraction of wetlands based on synergistic use of multispectral and microwave remote sensing data

The Tibetan Plateau (TP) is identified as a global climate change hotspot due to its relevance for the Asian monsoon circulation system. Glacial melt and receding permafrost indicate significant changes within this climate system. Spatio-temporal information is required to gain a better understanding of the interactions of system components and ongoing processes. By numerous studies, Earth Observation data analysis has been shown as being a suitable tool which enables to monitor mid- and long-term environmental changes. A new object oriented classification approach which is based on synergies between the optical remote sensing products and SAR data was developed for automatic and seasonal-adaptive extraction of parameters for wetland area derivation and characterization. It was shown that the derived parameters are important indicators for environmental change analyses. The developed method is appropriate to monitor wetland responses with high temporal and spatial resolution according to climate change and human impacts within large regions like the TP