Search

In deze STOWA publicatie ‘Zoek het zelf uit’: Kleinschalige oplossingen voor een robuustere regionale zoetwatervoorziening wordt een overzicht gegeven van de maatregelen die waterbeheerders en watergebruikers in de regio kunnen treffen om de zelfvoorzienendheid op het gebied van zoetwater te vergroten. Dit sluit aan bij de ambities die in het Deltaprogramma zijn geformuleerd om de watertekorten die in de toekomst worden verwacht naast de maatregelen in het hoofdwatersysteem met lokale maatregelen in de regio te ondervangen. Er is een groot aantal van dit soort maatregelen beschikbaar om de neerslag die in een gebied valt beter te benutten, waarmee de zelfvoorzienendheid kan worden vergroot. Een flink aantal pilot studies loopt nog of zijn in het recente verleden afgerond.

Binnen Kennis voor Klimaat worden kleinschalige oplossingen ontwikkeld om de zoetwatervoorziening te verbeteren. In deze studie zijn de mogelijkheden voor opschaling onderzocht. Het gaat om de oplossingen (1) drains2buffer (D2B), (2) regelbare en klimaatadaptieve drainage (RD/KAD), (3) kreekruginfiltratie (KRI), (4) freshmaker (FM), (5) verticale ASR (VASR), (6) waterconservering door stuwen (WCST) en (7) waterconservering door slootbodemverhoging (WCSB).

Binnen Kennis voor Klimaat worden kleinschalige maatregelen ontwikkeld om de zoetwatervoorziening te verbeteren. In deze studie zijn methoden ontwikkeld waarmee de potentie van dergelijke maatregelen op het schaalniveau van een groter gebied, voor hoog en laag Nederland, kan worden verkend. In deze studie zijn de opschalingsmogelijkheden bekeken voor de volgende lokale zoetwateroplossingen: (1) drains2buffer, (2) regelbare en klimaatadaptieve drainage, (3) kreekruginfiltratie, (4) Freshmaker, (5) verticale ASR, (6) waterconservering door stuwen en (7) waterconservering door slootbodemverhoging.

The latest climate impact assessments show that climate change will cause an increasing mismatch between demand and supply of fresh water in many densely populated deltas around the world. Recent studies for the Netherlands show that the current water supply strategy is not climate proof in the long-run. Therefore, a future ‘climate proof’ fresh water supply is national priority on the Dutch water policy agenda

[1] CO2 fluxes for the Netherlands and surroundings are estimated for the year 2008, from concentration measurements at four towers, using an inverse model. The results are compared to direct CO2 flux measurements by aircraft, for 6 flight tracks over the Netherlands, flown multiple times in each season. We applied the Regional Atmospheric Mesoscale Modeling system (RAMS) coupled to a simple carbon flux scheme (including fossil fuel), which was run at 10 km resolution, and inverted with an Ensemble Kalman Filter. The domain had 6 eco-regions, and inversions were performed for the four seasons separately. Inversion methods with pixel-dependent and -independent parameters for each eco-region were compared. The two inversion methods, in general, yield comparable flux averages for each eco-region and season, whereas the difference from the prior flux may be large. Posterior fluxes co-sampled along the aircraft flight tracks are usually much closer to the observations than the priors, with a comparable performance for both inversion methods, and with best performance for summer and autumn. The inversions showed more negative CO2 fluxes than the priors, though the latter are obtained from a biosphere model optimized using the Fluxnet database, containing observations from more than 200 locations worldwide. The two different crop ecotypes showed very different CO2 uptakes, which was unknown from the priors. The annual-average uptake is practically zero for the grassland class and for one of the cropland classes, whereas the other cropland class had a large net uptake, possibly because of the abundance of maize there. © 2012. American Geophysical Union. All Rights Reserved.

Kennis voor Klimaat, Rijkswaterstaat en STOWA/Deltaproof hielden op 31 mei en 1 juni 2012 het tweedaags symposium ‘Verzilting & waterbeheer: uitdagingen voor beleid, kennis en beheer’ over de toenemende verzilting van ons grond- en oppervlaktewater, die extra wordt aangejaagd door klimaatverandering. In deze Zoet-Zoutkrant o.a. de volgende bijdragen: - Toenemende verzilting vereist mentale omslag bij waterbeheerders en gebruikers; - Omgaan met zout: niet-technische maatregelen : voors en tegen van het beprijzen van zoetwater; - Wat kunnen we doen in het hoofdwatersysteem om zoetwatertekorten en verzilting tegen te gaan? : zoutindringing voorkomen, maar tegen welke prijs?; - Zoutgevoelige natuur en landbouw : flexibeler omgaan met chloridenormen; - Verzilting en waterbeheer, maatregelen in het regionale systeem: het ene waterschap is het andere niet...

The Weather Research and Forecasting Model (WRF) and the The Weather Research and Forecasting Model (WRF) and the Regional Atmospheric Mesoscale Model System (RAMS) are frequently used for (regional) weather, climate and air quality studies. This paper covers an evaluation of these models for a windy and calm episode against Cabauw tower observations (The Netherlands), with a special focus on the representation of the physical processes in the atmospheric boundary layer (ABL). In ad-dition, area averaged sensible heat flux observations by scintillometry are utilized which enables evaluation of grid scale model fluxes and flux observations at the same horizontal scale. Also, novel ABL height observations by ceilometry and of the near surface longwave radiation divergence are utilized. It appears that WRF in its basic set-up shows satisfactory model results for nearly all atmospheric near surface variables compared to field observations, while RAMS needed refining of its ABL scheme. An important inconsistency was found regarding the ABL daytime heat budget: Both model versions are only able to correctly forecast the ABL thermodynamic structure when the modeled surface sensible heat flux is much larger than both the eddy-covariance and scintillometer observations indicate. In order to clarify this discrepancy, model results for each term of the heat budget equation is evaluated against field observations. Sensitivity studies and evaluation of radiative tendencies and entrainment reveal that possible errors in these variables cannot explain the overestimation of the sensible heat flux within the current model infrastructure.

Inverse modelling of carbon sources and sinks requires an accurate quality estimate of the modelling framework to obtain a realistic estimate of the inferred fluxes and their uncertainties. So-called "representation errors" result from our inability to correctly represent point observations with simulated average values of model grid cells. They may add substantial uncertainty to the interpretation of atmospheric CO2 mixing ratio data. We simulated detailed variations in the CO2 mixing ratios with a high resolution (2 km) mesoscale model (RAMS) to estimate the representation errors introduced at larger model grid sizes of 10 100 km. We found that meteorology is the main driver of representation errors in our study causing spatial and temporal variations in the error estimate. Within the nocturnal boundary layer, the representation errors are relatively large and mainly caused by unresolved topography at lower model resolutions. During the day, convective structures, mesoscale circulations, and surface CO2 flux variability were found to be the main sources of representation errors. Interpreting observations near a mesoscale circulation as representative for air with the correct footprint relative to the front can reduce the representation error substantially. The remaining representation error is 0.5 1.5 ppm at 20 100 km resolution.

International audience; Inverse modelling of carbon sources and sinks requires an accurate estimate of the quality of the observations to obtain a realistic estimate of the inferred fluxes and their uncertainties. Representation errors, defined here as the mismatch between point observations and grid cell averages, may add substantial uncertainty to the interpretation of atmospheric CO2 concentration data. We used a high resolution (2 km) mesoscale model (RAMS) to simulate the variations in the CO2 concentration to estimate the representation errors for grid sizes of 10?100 km. Meteorology is the main driver of representation errors in our study causing spatial and temporal variations in the error estimate. Within the nocturnal boundary layer the representation errors are relatively large and mainly determined by unresolved topography at lower model resolutions. During the day, surface CO2 flux variability and mesoscale circulations were found to be the main sources of representation errors. Careful up-scaling of point observations can reduce the importance of the representation error substantially. The remaining representation error is in the order of 0.5?1.5 ppm at 20?100 km resolution.

The concentrations of CO2 and CH4 in the atmosphere are at the highest level they have been in the past 650,000 years. "The Continental-Scale Greenhouse Gas Balance of Europe", edited by A. Johannes Dolman, Annette Freibauer and Riccardo Valentini, highlights current results of research into the European greenhouse gases budget, including human-induced and biospheric sources and sinks. Much of this work is executed through the CarboEurope project, one of the world’s foremost research programs on continental-scale carbon cycle research.

International audience; Atmospheric CO2 modeling in interaction with the surface fluxes, at the regional scale is developed within the frame of the European project CarboEurope-IP and its Regional Experiment component. In this context, five meso-scale meteorological models at 2 km resolution participate in an intercomparison exercise. Using a common experimental protocol that imposes a large number of rules, two days of the CarboEurope Regional Experiment Strategy (CERES) campaign are simulated. A systematic evaluation of the models is done in confrontation with the observations, using statistical tools and direct comparisons. Thus, temperature and relative humidity at 2 m, wind direction, surface energy and CO2 fluxes, vertical profiles of potential temperature as well as in-situ CO2 concentrations comparisons between observations and simulations are examined. These comparisons reveal a cold bias in the simulated temperature at 2 m, the latent heat flux is often underestimated. Nevertheless, the CO2 concentrations heterogeneities are well captured by most of the models. This intercomparison exercise shows also the models ability to represent the meteorology and carbon cycling at the synoptic and regional scale in the boundary layer, but also points out some of the major shortcomings of the models.

Quantification of sources and sinks at global and regional scales requires not only a good description of the land sources and sinks of carbon, but also of the synoptic and mesoscale meteorology. An experiment was performed in les Landes, South West France, to determine the variability in concentration gradients and fluxes of CO2 . Several aircraft sampled the CO2 concentration and fluxes over the area, while fixed stations observed the fluxes and concentrations at high precision. Several (mesoscale) meteorological modeling tools were used to plan the experiment and flight patterns. Results show that at regional scale the relation between profiles and fluxes is not obvious, and strongly influenced by airmass history and mesoscale flow patterns. This calls for an experimental and modeling strategy that takes into account the large spatial gradients in concentrations and the variability in sources and sinks that arise from different land use types. We briefly describe such an analysis.

International audience