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Stoll S.,ETH Zurich | Hendricks Franssen H.J.,ETH Zurich | Hendricks Franssen H.J.,Jülich Research Center | Butts M.,DHI Water - Environment - Health | Kinzelbach W.,ETH Zurich
Hydrology and Earth System Sciences | Year: 2011

Climate change related modifications in the spatio-temporal distribution of precipitation and evapotranspiration will have an impact on groundwater resources. This study presents a modelling approach exploiting the advantages of integrated hydrological modelling and a broad climate model basis. We applied the integrated MIKE SHE model on a perialpine, small catchment in northern Switzerland near Zurich. To examine the impact of climate change we forced the hydrological model with data from eight GCM-RCM combinations showing systematic biases which are corrected by three different statistical downscaling methods, not only for precipitation but also for the variables that govern potential evapotranspiration. The downscaling methods are evaluated in a split sample test and the sensitivity of the downscaling procedure on the hydrological fluxes is analyzed. The RCMs resulted in very different projections of potential evapotranspiration and, especially, precipitation. All three downscaling methods reduced the differences between the predictions of the RCMs and all corrected predictions showed no future groundwater stress which can be related to an expected increase in precipitation during winter. It turned out that especially the timing of the precipitation and thus recharge is very important for the future development of the groundwater levels. However, the simulation experiments revealed the weaknesses of the downscaling methods which directly influence the predicted hydrological fluxes, and thus also the predicted groundwater levels. The downscaling process is identified as an important source of uncertainty in hydrological impact studies, which has to be accounted for. Therefore it is strongly recommended to test different downscaling methods by using verification data before applying them to climate model data. © Author(s) 2011.

Berglund S.,HydroResearch AB Stora Marknadsvagen | Bosson E.,Swedish Nuclear Fuel and Waste Management Company | Sassner M.,DHI Water - Environment - Health
Ambio | Year: 2013

This paper presents an analysis of present and future hydrological conditions at the Forsmark site in Sweden, which has been proposed as the site for a geological repository for spent nuclear fuel. Forsmark is a coastal site that changes in response to shoreline displacement. In the considered time frame (until year 10 000 ad), the hydrological system will be affected by landscape succession associated with shoreline displacement and changes in vegetation, regolith stratigraphy, and climate. Based on extensive site investigations and modeling of present hydrological conditions, the effects of different processes on future site hydrology are quantified. As expected, shoreline displacement has a strong effect on local hydrology (e.g., groundwater flow) in areas that change from sea to land. The comparison between present and future land areas emphasizes the importance of climate variables relative to other factors for main hydrological features such as water balances. © 2013 The Author(s).

Berglund S.,HydroResearch AB | Bosson E.,Swedish Nuclear Fuel and Waste Management Company | Selroos J.-O.,Swedish Nuclear Fuel and Waste Management Company | Sassner M.,DHI Water - Environment - Health
Ambio | Year: 2013

This paper describes solute transport modeling carried out as a part of an assessment of the long-term radiological safety of a planned deep rock repository for spent nuclear fuel in Forsmark, Sweden. Specifically, it presents transport modeling performed to locate and describe discharge areas for groundwater potentially carrying radionuclides from the repository to the surface where man and the environment could be affected by the contamination. The modeling results show that topography to large extent determines the discharge locations. Present and future lake and wetland objects are central for the radionuclide transport and dose calculations in the safety assessment. Results of detailed transport modeling focusing on the regolith and the upper part of the rock indicate that the identification of discharge areas and objects considered in the safety assessment is robust in the sense that it does not change when a more detailed model representation is used. © 2013 The Author(s).

Bosson E.,University of Stockholm | Bosson E.,Swedish Nuclear Fuel and Waste Management Company | Sabel U.,DHI Water - Environment - Health | Gustafsson L.-G.,DHI Water - Environment - Health | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012

This study has simulated the terrestrial hydrology associated with different climate, landscape, and permafrost regime scenarios for the field case example of the relatively well characterized coastal catchment of Forsmark, Sweden. The regime scenarios were selected from long-term simulation results of climate, topographical, shoreline, and associated Quaternary deposit and vegetation development in this catchment with a time perspective of 100,000 years or more and were used as drivers for hydrological simulations with the three-dimensional model MIKE SHE. The hydrological simulations quantify the responses of different water flow and water storage components of terrestrial hydrology to shifts from the present cool temperate climate landscape regime in Forsmark to a possible future Arctic periglacial landscape regime with or without permafrost. The results show complexity and nonlinearity in the runoff responses to precipitation changes due to parallel changes in evapotranspiration, along with changes in surface and subsurface water storage dynamics and flow pathways through the landscape. The results further illuminate different possible perspectives of what constitutes wetter/drier landscape conditions, in contrast to the clearer concept of what constitutes a warmer/colder climate. Copyright 2012 by the American Geophysical Union.

Glas M.S.,Max Planck Institute for Marine Microbiology | Sato Y.,Australian Institute of Marine Science | Sato Y.,James Cook University | Ulstrup K.E.,DHI Water - Environment - Health | Bourne D.G.,Australian Institute of Marine Science
ISME Journal | Year: 2012

The microenvironmental dynamics of the microbial mat of black band disease (BBD) and its less virulent precursor, cyanobacterial patch (CP), were extensively profiled using microsensors under different light intensities with respect to O 2, pH and H 2 S. BBD mats exhibited vertical stratification into an upper phototrophic and lower anoxic and sulphidic zone. At the progression front of BBD lesions, high sulphide levels up to 4977 M were measured in darkness along with lower than ambient levels of pH (7.430.20). At the base of the coral-BBD microbial mat, conditions were hypoxic or anoxic depending on light intensity exposure. In contrast, CP mats did not exhibit strong microchemical stratification with mostly supersaturated oxygen conditions throughout the mats at all light intensities and with levels of pH generally higher than in BBD. Two of three replicate CP mats were devoid of sulphide, while the third replicate showed only low levels of sulphide (up to 42 M) present in darkness and at intermediate light levels. The level of oxygenation and sulphide correlated well with lesion migration rates, that is virulence of the mats, which were greater in BBD than in CP. The results suggest that biogeochemical microgradients of BBD shaped by the complex microbial community, rather than a defined pathogen, are the major trigger for high virulence and the associated derived coral mortality of this disease. © 2012 International Society for Microbial Ecology All rights reserved.

Schmoker C.,University of Las Palmas de Gran Canaria | Schmoker C.,DHI Water - Environment - Health | Hernandez-Leon S.,University of Las Palmas de Gran Canaria | Calbet A.,CSIC - Institute of Marine Sciences
Journal of Plankton Research | Year: 2013

Here we review all published data on phytoplankton growth and microzooplankton grazing using the dilution technique to better understand the role of this group of grazers in different regions of the oceans, and to identify the knowledge gaps that require future efforts. A total of 1525 data points assimilated from 110 studies were included and grouped using the biogeographic subsets defined by Longhurst et al. [(1995) An estimate of global primary production in the ocean from satellite radiometer data. J. Plankton Res., 17, 1245-1271]. Total median phytoplankton growth rates in each of the subsets varied between 0.15 (Polar Southern) and 0.83 day-1 (Trades Atlantic), with the corresponding microzooplankton grazing rates ranging between 0.07 (Polar Southern) and 0.48 day-1 (Trades Indian). The median percentage of primary production (PP) grazed by microzooplankton was relatively constant among the regions and ranged from 49 to 77%, with the lowest percentage found in the Westerlies Southern and the highest in the Coastal Indian. Despite strong evidence that microzooplankton grazing impacts were highly variable, no global drivers for this variability (temperature, chlorophyll concentration) were identified in the analysis. As a global carbon budget, the overall consumption of phytoplankton for all regions was 31.3 Gt C year-1, which accounted for 62.4% of the total PP grazed daily. The amount of carbon ingested by micro-and mesozooplankton varied proportionally to the PP and the consumption was five times higher for micro-than for mesozooplankton. As concluding remarks of the study, we present some suggestions that may improve the quality of the data obtained with the dilution technique. © 2013 The Author.

Gill A.B.,Cranfield University | Bartlett M.,Cranfield University | Thomsen F.,DHI Water - Environment - Health
Journal of Fish Biology | Year: 2012

The considerable extent of construction and operation of marine renewable energy developments (MRED) within U.K. and adjacent waters will lead, among other things, to the emission of electromagnetic fields (EMF) and subsea sounds into the marine environment. Migratory fishes that respond to natural environmental cues, such as the Earth's geomagnetic field or underwater sounds, move through the same waters that the MRED occupy, thereby raising the question of whether there are any effects of MRED on migratory fishes. Diadromous species, such as the Salmonidae and Anguillidae, which undertake large-scale migrations through coastal and offshore waters, are already significantly affected by other human activities leading to national and international conservation efforts to manage any existing threats and to minimize future concerns, including the potential effect of MRED. Here, the current state of knowledge with regard to the potential for diadromous fishes of U.K. conservation importance to be affected by MRED is reviewed. The information on which to base the review was found to be limited with respect to all aspects of these fishes' migratory behaviour and activity, especially with regards to MRED deployment, making it difficult to establish cause and effect relationships. The main findings, however, were that diadromous species can use the Earth's magnetic field for orientation and direction finding during migrations. Juveniles of anadromous brown trout (sea trout) Salmo trutta and close relatives of S. trutta respond to both the Earth's magnetic field and artificial magnetic fields. Current knowledge suggests that EMFs from subsea cables may interact with migrating Anguilla sp. (and possibly other diadromous fishes) if their movement routes take them over the cables, particularly in shallow water (<20 m). The only known effect is a temporary change in swimming direction. Whether this will represent a biologically significant effect, for example delayed migration, cannot yet be determined. Diadromous fishes are likely to encounter EMFs from subsea cables either during the adult movement phases of life or their early life stages during migration within shallow, coastal waters adjacent to natal rivers. The underwater sound from MRED devices has not been fully characterized to determine its acoustic properties and propagation through the coastal waters. MRED that require pile driving during construction appear to be the most relevant to consider. In the absence of a clear understanding of their response to underwater sound, the specific effects on migratory species of conservation concern remain very difficult to determine in relation to MRED. Based on the studies reviewed, it is suggested that fishes that receive high intensity sound in close proximity to construction may be physiologically affected to some degree, whereas those at farther distances, potentially up to several km, may exhibit behaviour responses; the effect of which is unknown and will be dependent on the properties of the received sound and receptor characteristics and condition. Whether there are behavioural effects on the fishes during operation is unknown but any change to the environment and subsequent response by the fishes would need to be considered over the lifetime of the MRED. It is not yet possible to determine if effects relating to sound exposure are biologically significant. The current assumptions of limited effects are built on an incomplete understanding of how the species move around their environment and interact with natural and anthropogenic EMFs and subsea sound. A number of important knowledge gaps exist, principally whether migratory fish species on the whole respond to the EMF and the sound associated with MRED. Future research should address the principal gaps before assuming that any effect on diadromous species results in a biological effect. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

Ranasinghe R.,Technical University of Delft | Larson M.,Lund University | Savioli J.,DHI Water - Environment - Health
Coastal Engineering | Year: 2010

Submerged breakwaters (SBWs) are becoming a popular option for coastal protection, mainly due to their low aesthetic impact on the natural environment. However, SBWs have rarely been employed for coastal protection in the past and therefore, their efficacy remains largely unknown. The main objective of the present study was to investigate the structural and environmental conditions that govern the mode of shoreline response (i.e shoreline erosion vs shoreline accretion) to SBWs. The relative importance of the key structural and environmental parameters governing the response mode to a single shore parallel SBW is investigated through a combination of theoretical analysis and numerical modelling. Using physical considerations, a theoretical response-function model is derived under several simplifying assumptions including parallel depth contours, linear wave theory, shore normal waves, and no wave-current interaction. Numerical modelling is undertaken with the Mike21 model suite to simulate the depth averaged velocity fields (without morphological updating) due to waves acting on a single shore-parallel SBW located on a schematised beach with parallel depth contours. In total 92 coupled wave-current simulations were undertaken. The results indicate that the mode of shoreline response to the SBW can be expressed in terms of the two non-dimensional parameters hB/H0 and (sB/hB)3/2(LB/hB)2(A3/hB)1/2 (variables defined in the text). © 2010 Elsevier B.V.

Eriksson C.,DHI Water - Environment - Health | Engqvist A.,Aythya AB
Ambio | Year: 2013

The water turnover of two coastal areas, Forsmark and Laxemar-Simpevarp, has been modeled for 13 selected years between 6500 bc and 9000 ad by utilizing information about past, present, and future bathymetry. The Forsmark area can be described as an open-ended funnel, and is analyzed with a 3D-model (MIKE 3-FM); the Laxemar area is partitioned into clusters of sub-basins treated with a discrete coupled basin model (CouBa). In all simulations, the main variation factor is the land uplift. The 3D-model domain is successively modified. For the CouBa approach the successive basin configurations are objectively deduced based on the 3D domain modifications. The average age (AvA) of the resident water relative to the open coast is generally lower for the Forsmark area. A typical progression is that the AvA values increase until a sub-basin ceases to be connected to the coastal zone. This disconnection is often preceded by a lowered AvA. © 2013 The Author(s).

Sunyer M.A.,DHI Water - Environment - Health | Madsen H.,DHI Water - Environment - Health | Ang P.H.,DHI Water - Environment - Health
Atmospheric Research | Year: 2012

In most cases climate change projections from General Circulation Models (GCM) and Regional Climate Models (RCM) cannot be directly applied to climate change impact studies, and downscaling is therefore needed. A large number of statistical downscaling methods exist but no clear recommendations exist of which methods are more appropriate, depending on the application. This paper compares five statistical downscaling methods based on a common change factor methodology using results from four different RCMs driven by different GCMs. Precipitation time series for a future scenario are generated for a location north of Copenhagen for the period 2071-2100 under climate change projections by the scenario A1B. Special focus is given to the changes of extreme events since downscaling methods mainly differ in the way extreme events are generated. There is a significant uncertainty in the downscaled projected changes of the mean, standard deviation, skewness and probability of dry days. Large uncertainties are also observed in the downscaled changes in extreme event statistics. However, three of the four RCMs analysed show an increase in the extreme precipitation events in the future. The uncertainties are partly due to the variability of the RCM projections and partly due to the variability of the statistical downscaling methods. The paper highlights the importance of acknowledging the limitations and advantages of different statistical downscaling methods as well as the uncertainties in downscaling climate change projections for use in hydrological models. © 2011 Elsevier B.V.

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