Optimal Water Allocation for an Alpine Hydropower System Under Changing Scenarios

The operating rules of water allocation in the alpine OFIMA hydropower network of the Maggia River basin (Canton Tessin, Switzerland) are investigated in response to changes in the production policy and environmental and climatic factors. The study was carried out by means of a nonlinear programming approach where the objective function is approximated to a quadratic form with linear constraints, and implemented on a monthly time scale. Two systemís configurations with different details were accordingly investigated and compared to assess the response of the hydropower network to changes in the production policy, in the magnitude of the inflows and to different environmental requests. The optimal solution of water allocation corresponding to the new hypothetical production policy shows marked differences but similar benefits when compared to the one of the present operating rules, thus suggesting the good flexibility of the real network under such change. In its whole, this paper therefore highlights the importance of supporting strategic decisions by means of informatics tools and, in addiction, it provides a useful case study to test the performances of the software AQUARIUS implementing such a nonlinear programming techniqu

Time-Dependent Z-R Relationships for Estimating Rainfall Fields from Radar Measurements

Abstract. The operational use of weather radars has become a widespread and useful tool for estimating rainfall fields. The radar-gauge adjustment is a commonly adopted technique which allows one to reduce bias and dispersion between radar rainfall estimates and the corresponding ground measurements provided by rain gauges. This paper investigates a new methodology for estimating radar-based rainfall fields by recalibrating at each time step the reflectivity-rainfall rate (Z-R) relationship on the basis of ground measurements provided by a rain gauge network. The power-law equation for converting reflectivity measurements into rainfall rates is readjusted at each time step, by calibrating its parameters using hourly Z-R pairs collected in the proximity of the considered time step. Calibration windows with duration between 1 and 24 h are used for estimating the parameters of the Z-R relationship. A case study pertaining to 19 rainfall events occurred in the north-western Italy is considered, in an area located within 25 km from the radar site, with available measurements of rainfall rate at the ground and radar reflectivity aloft. Results obtained with the proposed method are compared to those of three other literature methods. Applications are described for a posteriori evaluation of rainfall fields and for real-time estimation. Results suggest that the use of a calibration window of 2–5 h yields the best performances, with improvements that reach the 28% of the standard error obtained by using the most accurate fixed (climatological) Z-R relationship

Increasing flood risk under climate change: a pan-European assessment of the benefits of four adaptation strategies

Future flood risk in Europe is likely to increase due to a combination of climatic and socio-economic drivers. Effective adaptation strategies need to be implemented to limit the impact of river flooding on population and assets. This research builds upon a recently developed flood risk assessment framework at European scale to explore the benefits of adaptation against extreme floods. Four different adaptation measures are simulated in a physically based modeling framework, including the rise of flood protections, reduction of the peak flows through water retention, reduction of vulnerability and relocation to safer areas. Their sensitivity is assessed in several configurations under a high-end global warming scenario over the time range 1976-2100. Results suggest that the future increase in expected damage and population affected by river floods can be compensated by a combination of different adaptation measures. The adaptation efforts should favor measures targeted at reducing the impacts of floods, rather than trying to avoid them. Conversely, adaptation plans only based on rising flood protections have the effect of reducing the frequency of small floods and exposing the society to less-frequent but catastrophic floods and potentially long recovery processes.JRC.H.7-Climate Risk Managemen

Ensemble flood risk assessment in Europe under high end climate scenarios

AbstractAt the current rate of global warming, the target of limiting it within 2 degrees by the end of the century seems more and more unrealistic. Policymakers, businesses and organizations leading international negotiations urge the scientific community to provide realistic and accurate assessments of the possible consequences of so called “high end” climate scenarios.This study illustrates a novel procedure to assess the future flood risk in Europe under high levels of warming. It combines ensemble projections of extreme streamflow for the current century based on EURO-CORDEX RCP 8.5 climate scenarios with recent advances in European flood hazard mapping. Further novelties include a threshold-based evaluation of extreme event magnitude and frequency, an alternative method to removing bias in climate projections, the latest pan-European exposure maps, and an improved flood vulnerability estimation.Estimates of population affected and direct flood damages indicate that by the end of the century the socio-economic impact of river floods in Europe is projected to increase by an average 220% due to climate change only. When coherent socio-economic development pathways are included in the assessment, central estimates of population annually affected by floods range between 500,000 and 640,000 in 2050, and between 540,000 and 950,000 in 2080, as compared to 216,000 in the current climate. A larger range is foreseen in the annual flood damage, currently of 5.3 B€, which is projected to rise at 20–40 B€ in 2050 and 30–100 B€ in 2080, depending on the future economic growth

Global warming increases the frequency of river floods in Europe

EURO-CORDEX, a new generation of downscaled climate projections, has become available for climate change impact studies in Europe. New opportunities arise in the investigation of potential effects of a warmer world on meteorological and hydrological extremes at regional scales. In this work, an ensemble of EURO-CORDEX RCP 8.5 scenarios is used to drive a distributed hydrological model and assess the projected changes in flood hazard in Europe through the current century. Changes in magnitude and frequency of extreme streamflow events are investigated by statistical distribution fitting and peak over threshold analysis. A consistent method is proposed to evaluate the agreement of ensemble projections. Results indicate that the change in frequency of discharge extremes is likely to have a larger impact on the overall flood hazard as compared to the change in their magnitude. On average in Europe, flood peaks with return period above 100 years are projected to double in frequency within a time range of three decades.JRC.H.7-Climate Risk Managemen

Climate Change and Critical Infrastructure - Floods

This study investigates the change in the level of risk to critical infrastructure due to the impact of climate change on the frequency and severity of floods. We implement a case study focused on the power grid to demonstrate the methodology. The consideration of the power outage substantially changes the estimated losses from the flood scenario. The economic losses due to the interruption of the daily economic activity are 3 to 5 times greater if the power outage outside the inundated area is taken into consideration. The cost of transmission asset repairs far outweighs the daily economic losses, and amounts to 95-98% of the total cost.JRC.E.2-Technology Innovation in Securit

PESETA III - Task 7: River Floods

In Europe around 216,000 people are exposed each year to river flooding and annual flood damage amounts to €5.3 billion. In most regions of Europe we see an increase of flood risk due to global warming. Under a 2°C global warming scenario and considering current socio-economic conditions, flood impacts could more than double, with around 525,000 people annually exposed to floods and €12.5 billion of expected annual losses. Under the RCP8.5 pathway 2°C will occur in the early 2040s, hence impacts on present society under near term (2021-2050) climate conditions are very close to those under a 2°C warming scenario. Longer term climate conditions (2071-2100) under a RCP8.5 scenario imposed on present society, on the other hand, could result in around 717,000 people annually exposed to floods while direct flood damages could see a more than three-fold increase with respect to current conditions, reaching €17.5 billion of average annual losses.JRC.E.1-Disaster Risk Managemen

Development and evaluation of a framework for global flood hazard mapping

AbstractNowadays, the development of high-resolution flood hazard models have become feasible at continental and global scale, and their application in developing countries and data-scarce regions can be extremely helpful to increase preparedness of population and reduce catastrophic impacts.The present work describes the development of a novel procedure for global flood hazard mapping, based on the most recent advances in large scale flood modelling. We derive a long-term dataset of daily river discharges from the hydrological simulations of the Global Flood Awareness System (GloFAS). Streamflow data is downscaled on a high resolution river network and processed to provide the input for local flood inundation simulations, performed with a two-dimensional hydrodynamic model. All flood-prone areas identified along the river network are then merged to create continental flood hazard maps for different return periods at 30′′ resolution. We evaluate the performance of our methodology in several river basins across the globe by comparing simulated flood maps with both official hazard maps and a mosaic of flooded areas detected from satellite images. The evaluation procedure also includes comparisons with the results of other large scale flood models. We further investigate the sensitivity of the flood modelling framework to several parameters and modelling approaches and identify strengths, limitations and possible improvements of the methodology

A global streamflow reanalysis for 1980–2018

Global and continental scale hydrological reanalysis datasets receive growing attention due to their increasing number of applications, ranging from water resources management, climate change studies, water related hazards and policy support. Until recently, their use was mostly limited to qualitative assessments, due to their coarse spatial and temporal resolution, large uncertainty and bias in the model output, and limited extent of the dataset in space and time. This research reports on the setup of a gridded hydrological model with quasi-global coverage, able to reproduce a seamless 39-year streamflow simulation in all world’s medium to large river basins. The model was calibrated at 1226 river sections with a total drainage area of 51 million km2 within 66 countries, using ECMWF’s latest atmospheric reanalysis ERA5. A performance assessment revealed large improvements in reproducing past discharge observations, in comparison to the calibration used in the current operational setup of the hydrological model as part of the Copernicus – Global Flood Awareness System (GloFAS, www.globalfloods.eu), with median scores of Kling-Gupta Efficiency KGE = 0.67 and correlation r = 0.8. The simulation bias was also dramatically reduced and narrowed around zero, with more than 60% of stations showing percent bias within ±20%. Pronounced regional differences in the simulation results remain, pointing out the need for detailed investigation of the hydrological processes in specific regions, including parts of Africa and South Asia. In addition, observed discharges with high data quality is key to achieving skillful model output. The new calibrated model will become part of the operational runs of GloFAS in the next system release foreseen for Spring 2020, together with a near real time extension of the streamflow reanalysis