Tag: Climate Change Downscaling Techniques

Abstract

This research paper focuses on implementing two Nature-Based Solutions (NBS) in the Sarantapotamos river basin upstream of Magoula settlement, evaluating their effectiveness through flood hydrograph calculations before and after NBS, and under future climate scenarios, encompassing lower, mean, and upper conditions representing ± 95%. The study area covers an area of 226 km² in Attica, Greece, susceptible to extreme flood events. The research contributes to NBS knowledge, emphasizing flood resilience and protecting settlements downstream. Land cover change and retention ponds, applied individually and combined, serve as NBS approaches. Flood hydrographs are calculated using the time–area (TA) diagram method in a geographic information system (GIS) with the Hydrological Engineering Center’s Hydrological Modeling System (HEC-HMS). Results demonstrate NBS effectiveness in current climate conditions, reducing peak discharge by 9.3% and 28% for land cover change and retention ponds, respectively. The combined NBS achieves a 40.5% peak discharge reduction and a significant 15.7% total flood volume decrease. Under climate change scenarios, impacts on design precipitation and flood hydrographs vary. The upper climate change scenario exhibits a 3348% increase in peak discharge and a 600% rise in total flood volume, while the lower scenario sees a 44.6% reduction in total flood volume. In the mean climate change scenario, land cover change and retention ponds reduce peak discharge by 9.73% and 23.11% and total flood volume by 9.25% and 2.17%, respectively. In conclusion, retention ponds show substantial peak discharge reduction, while land cover changes extend the time to peak, emphasizing their potential in flood risk management.

Abstract

In the framework of the coordinated regional modeling initiative Med-CORDEX (Coordinated Regional Climate Downscaling Experiment), we present an updated version of the regional Earth System Model ENEA-REG designed to downscale, over the Mediterranean basin, the models used in the Coupled Model Intercomparison Project phase 6 (CMIP6). The regional ESM includes coupled atmosphere (WRF), ocean (MITgcm), land (Noah-MP, embedded within WRF), and river (HD) components with spatial resolution of 12 km for the atmosphere, 1/12° for the ocean and 0.5° for the river rooting model. For the present climate, we performed a hindcast (i.e. reanalysis-driven) and a historical simulation (GCM-driven) over the 1980–2014 temporal period. The evaluation shows that the regional ESM reliably reproduces the mean state, spatial and temporal variability of the relevant atmospheric and ocean variables. In addition, we analyze the future evolution (2015–2100) of the Euro-Mediterranean climate under three different scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5), focusing on several relevant essential climate variables and climate indicators for impacts. Among others, results highlight how, for the scenarios SSP2-4.5 and SSP5-8.5, the intensity, frequency and duration of marine heat waves continue to increase until the end of the century and anomalies of up to 2 °C, which are considered extreme at the beginning of this century, will be so frequent to become the norm in less than a hundred years under the SSP5-8.5 scenario. Overall, our results demonstrate the improvement due to the high-resolution air–sea coupling for the representation of high impact events, such as marine heat waves, and sea-level height.

Abstract

Rainfall is changing in intensity and abundance for much of the world as a result of global climate change. Rwanda has been negatively affected by a changing climate, exacerbated by human impact on land and water resources. In most parts of the country, the rainfall pattern has changed over the last decades resulting in both enhanced flooding and water shortage/scarcity in much of the country, especially in the Capital City of Kigali and peripheries which is the main economic hub of the country with strong links to the East African region. Changes in precipitation have affected agricultural production, hydropower production, and water supplies, and has been a result of increased flash floods in the city. This study developed a new predictive model of rainfall patterns in the City of Kigali (CoK) in the Republic of Rwanda using evolutionary methodologies that apply machine learning techniques of Fuzzy Inference Systems (FIS) trained via Genetic Algorithms, Neuro Network Systems and a comparative Support Vector Machine tool, and assessment downscaled climate change combinations with predicted rainfall patterns. The models were calibrated and validated using measured rainfall data in the City of Kigali from 1991 through 2023. The model results show the developed Geno Fuzzy Inference System (GENOFIS) model performed better than the Adaptive Neuro-Fuzzy Inference System (ANFIS) and Support Vector Machine (SVM) models. The Coefficient of Efficiency (CE), and Root Mean Square Error (RMSE) were used as diagnostic measures for model performance evaluation. Models generated with GENOFIS are therefore recommended for rainfall and related prediction patterns in the City of Kigali for climate change adaptation and resilience policy and planning.

Abstract

This study explored how the water balance components of the Middle Tapi Basin (MTB) might alter between 2010 and 2100 as an outcome of climate change. We used an approach were Statistically downscaled future predicted data for temperature and rainfall for five different Global circulation models were employed under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5). The baseline and future scenarios’ monthly analyses of multiple water balance indicators also showed that RCP 4.5 and RCP 8.5 will see an increase in maximum temperature of 5.2% and 9.5%, respectively, by the end of the century. The baseline period contribution from monsoonal rainfall and streamflow was also 89.3% and 90.6%, but in future scenarios, the figures are likely to reduce to 75.2% and 57.8% for RCP 4.5 and 70.8% and 54.7% for RCP 8.5. While the average inflow estimates at the Ukai dam tend to rise by 19.2% and 46.8% till the distant future scenario for RCP 4.5 and RCP 8.5, respectively. In future scenarios, the percentage of groundwater flow and surface runoff contributions will be lesser due to the higher evapotranspiration rate and revaporisation of water to the root zone. Even though the monsoonal rainfall tends to reduce, the flow duration curves for the future scenarios exhibited a consistent increase in water availability compared to their respective historical counterparts, possibly due to more frequent and severe rainfall events.

Abstract

As the impacts of climate change increase, Small Island Developing States (SIDS) in particular shall face increasingly significant adaptation challenges. Past climate adaptation efforts within SIDS have had limited success. As such, the purpose of this systematic literature review has been to identify areas of importance for facilitating climate adaptation, particularly within Small Island Developing States (SIDS), and more specifically, to assess the extent to which participatory justice within decision-making processes is recognised as an important component of climate adaptation through the lens of water management. This review process utilised the SPIDER tool to guide the literature search across SCOPUS, Web of Science and EBSCO host databases, generating 495 publications that were reduced to a total of 70 sources guided by PRISMA, informing the review’s results and discussion. Thematic analysis of the selected studies was applied, utilising the Values-Rules-Knowledge framework. Through this analysis, five principles were created and comprise the major conclusions of this review: (1) ensuring community engagement, (2) expanding available options through local experimentation, (3) ensuring that monitoring and evaluation of adaptation initiatives are taken seriously, (4) adopting decision-making mechanisms that are systems-oriented and inclusive, and (5) investing only if there is a long-term commitment to protecting SIDS. It is hoped that these principles can serve as a comprehensive guide for funding agencies, applied projects and research aiding climate adaptation within SIDS.

Abstract

Hydroclimate combines hydrology and climate variables, including the influence of water resources and their processes on Earth’s climate pattern and the change in the hydrological cycle. This review aimed to investigate the historical, current, and future projections of hydroclimatic variables within the Awash River basin. The spatiotemporal climate fluctuations caused by meteorological anomalies, catchment topographical processes, and human activities impact hydroclimatic variables. This systematic review was conducted to define and conceptualize hydroclimatic variables’ trends and variation. Scopus, Web of Science, and Google Scholar were used to assess relevant works of literature. Most of the rainfall stations in the basin exhibited an increasing and decreasing trend; however, this was not statistically significant. The mean, maximum, and minimum temperature variables continuously increased in the basin while streamflow declined. Besides, hydroclimatic variables and trends in response to climate change differ by local topography, length of data and statistical methods. Additionally, the basin encounters various trends and patterns in hydroclimate variables over time. This review emphasizes the importance of historical, current, and future climate change scenarios in the development of water resources and practices for sustainable environmental management. As a result, reviewing the findings provides a scientific basis for evidence-based practice for environmental and water resource managers, researchers, and policymakers.