On the relative importance of the climate change factors along the river Scheldt considering climate scenarios for upstream inland and downstream coastal (mean sea level and surge) boundary conditions

To improve on the efficacy of flood risk mitigation measures, it is essential to investigate the relative importance of the future impact pressures. This is more so in areas which are found to be hot spots for flooding. One such area was identified in the Scheldt region located in Belgium. The Dendermonde area is a place where both the downstream coastal and the upstream river flow boundary conditions interact and jointly control the floodrisk. Downstream of this area, the coastal level changes include both the sea level rise and storm surge changes due to climate change impacts on the wind climate over the North Atlantic and North Sea region. Upstream of the Dendermonde area lies the Dender river which introduces an extra pressure on the Dendermonde area. Against this back drop, impact analysis was performed using a hydrodynamic model that accounts for such changes. The climate data for future scenarios were extracted from the climate databases PRUDENCE (http://prudence.dmi.dk),ENSEMBLES (http://www.ensembles-eu.org/), IPCC AR4 (www-pcmdi.llnl.gov/ipcc/about_ipcc.php) and CERA (CLM from MPI-M/MaD)

Assessment of climate change impact on hydrological extremes in two source regions of the Nile River Basin

The potential impact of climate change was investigated on the hydrological extremes of Nyando River and Lake Tana catchments, which are located in two source regions of the Nile River basin. Climate change scenarios were developed for rainfall and potential evapotranspiration (ETo), considering 17 General Circulation Model (GCM) simulations to better understand the range of possible future change. They were constructed by transferring the extracted climate change signals to the observed series using a frequency perturbation downscaling approach, which accounts for the changes in rainfall extremes. Projected changes under two future SRES emission scenarios A1B and B1 for the 2050s were considered. Two conceptual hydrological models were calibrated and used for the impact assessment. Their difference in simulating the flows under future climate scenarios was also investigated. <br><br> The results reveal increasing mean runoff and extreme peak flows for Nyando catchment for the 2050s while unclear trend is observed for Lake Tana catchment for mean volumes and high/low flows. The hydrological models for Lake Tana catchment, however, performed better in simulating the hydrological regimes than for Nyando, which obviously also induces a difference in the reliability of the extreme future projections for both catchments. The unclear impact result for Lake Tana catchment implies that the GCM uncertainty is more important for explaining the unclear trend than the hydrological models uncertainty. Nevertheless, to have a better understanding of future impact, hydrological models need to be verified for their credibility of simulating extreme flows

Spatio-temporal impact of climate change on the groundwater system

Given the importance of groundwater for food production and drinking water supply, but also for the survival of groundwater dependent terrestrial ecosystems (GWDTEs) it is essential to assess the impact of climate change on this freshwater resource. In this paper we study with high temporal and spatial resolution the impact of 28 climate change scenarios on the groundwater system of a lowland catchment in Belgium. Our results show for the scenario period 2070–2101 compared with the reference period 1960– 1991, a change in annual groundwater recharge between −20% and +7%. On average annual groundwater recharge decreases 7%. In most scenarios the recharge increases during winter but decreases during summer. The altered recharge patterns cause the groundwater level to decrease significantly from September to January. On average the groundwater level decreases about 7 cm with a standard deviation between the scenarios of 5 cm. Groundwater levels in interfluves and upstream areas are more sensitive to climate change than groundwater levels in the river valley. Groundwater discharge to GWDTEs is expected to decrease during late summer and autumn as much as 10%, though the discharge remains at reference-period level during winter and early spring. As GWDTEs are strongly influenced by temporal dynamics of the groundwater system, close monitoring of groundwater and implementation of adaptive management measures are required to prevent ecological loss

A holistic model for coastal flooding using system diagrams and the Source–Pathway–Receptor (SPR) concept

Coastal flooding is a problem of increasing relevance in low-lying coastal regions worldwide. In addition to the anticipated increase in likelihood and magnitude of coastal floods due to climate change, there is rapid growth in coastal assets and infrastructure. Sustainable and integrated coastal flood management over large areas and varying coastline types cannot be simply treated as local combinations of flood defences and floodplains. Rather, a system level analysis of floodplains is required to structure the problem as a first step before applying quantitative models. In this paper such a model is developed using system diagrams and the Source–Pathway–Receptor (SPR) concept, to structure our understanding of large and complex coastal flood systems. A graphical systems model is proposed for the assessment of coastal flood systems with regard to individual elements and their topological relationships. Two examples are discussed – a unidirectional model for a large-scale flood system, and a multi-directional model for a smaller-scale system, both based on the Western Scheldt estuary. The models help to develop a comprehensive understanding of system elements and their relationships and provide a holistic overview of the coastal flood system. The approach shows that a system level analysis of floodplains is more effective than simple topographic maps when conveying complex information. The models are shown to be useful as an a-priori approach to making assumptions about flood mechanisms explicit and informing inputs to numerical models

Rainfall variability related to sea surface temperature anomalies in a Pacific–Andean basin into Ecuador and Peru

The spatiotemporal modes of seasonal rainfall variability and their relation with sea surface temperature anomalies (SSTA 1.2 indices) are examined in the transition from the coastal plain towards the western Andes cordillera in southern Ecuador/northwestern Peru using instrumental records (1970–2000) collected from the Catamayo–Chira basin. A multi-criteria data analysis is conducted within different elevation ranges. The criteria involve rotated principal components, cross correlations and temporal changes of anomalies in rainfall quantiles. <br><br> The results confirm that SSTA 1.2 indices influence rainfall variability over the coastal plain (< 510 m a.s.l.) where forcing is dominant within December–May. The El Niño Southern Oscillation also plays a role inland of the coastal plain where a region of ENSO-like rainfall variability is found on the southeastern part of the basin (4°30'–5° S/79°15'–80° W) within March–May (MAM). This suggests that inland distance and elevation are only partial controls of ocean–atmospheric forcing up to ~ 1300 m a.s.l. Our analysis also provides evidence of the SSTA 1.2 indices influence in a large altitudinal range ~ 1400–2700 m a.s.l. confined to the southeastern basin. This region is found consistently perturbed by ENSO within MAM. We conclude that geo-morphological features of the southwestern Ecuadorian Andean ridges play a twofold role in the control of ocean–atmospheric forcing. They can modulate the atmospheric circulation, leading to a dissipation of the signal, or they might favor meteorological processes, leading to enhancement of orographic precipitation. This would explain the observed ENSO signals in instrumental records at locations as high as 2700 m a.s.l

Quantifying the impact of climate change from inland, coastal and surface conditions

The impact of climate change for the short, mid and long term horizons is investigated for an area along the Scheldt river, at the confluence with the Dender river. The downstream coastal boundary comprises of the sea level rise and storm surges from the North Sea while the upstream inland boundary comprises of rainfall and related runoff discharges. The third surface boundary comprises of wind speed and direction along the Scheldt. The climate change scenarios are based on statistical analysis of an ensemble of (at least 20) simulation results with Regional Climate Models (RCMs). The RCM results are provided by the CERA database, the EU-FP5 PRUDENCE and the EU-FP6 ENSEMBLES database. Outputs of precipitation, temperature, potential evapotranspiration, wind speed, wind direction and Sea Level Pressure (SLP) have been validated for historical periods and correlations are accounted for when quantifying future changes till 2100