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WaterGAP (Water - Global Assessment and Prognosis) is a tool for modeling global water use and water availability. It participates among other models in the ISIMIP initiative (The Inter-Sectoral Impact Model Intercomparison Project). As part of this initiative, the water temperature should be calculated by participating hydrological models because it plays a vital role in many chemical, physical and biological processes. Therefore, the subject of this master thesis is to implement the physically based surface water temperature computation after VAN BEEK ET AL. (2012) and WANDERS ET AL. (2019) into WaterGAP and compare the results to the statistical regression approach by PUNZET ET AL. (2012). The computation is validated with observed water temperature data obtained from the GEMStat water quality database. The results are good for arctic and temperate latitudes. Surface water temperatures for tropical rivers are overestimated, most likely due to the overestimation of precipitation temperatures, incoming radiation and groundwater temperatures. The comparison with the regression model by PUNZET ET AL. (2012) shows matching results. The regression model even matches with WaterGAP results for most of the simulations of the future under climate change conditions, where the regression model should stop working due to changing environmental parameters. Several assumptions had to be made in order to implement the water temperature calculation in Water-GAP. These include, e.g., discharge temperatures for power plant cooling water, precipitation and surface runoff temperatures. For model improvements, perhaps three different values for the different regions of the world should be used to cool down the precipitation and surface runoff. The model could also be improved by refining the ice formation calculation, especially for the conditions when the ice melts, breaks up and is transported downstream. Furthermore, the feedback to the river channel roughness could be implemented if ice has formed. The WaterGAP model upgraded with the water temperature calculation will help the ISIMIP initiative in the future.
Floodplains play an important role in the terrestrial water cycle and are very important for biodiversity. Therefore, an improved representation of the dynamics of floodplain water flows and storage in global hydrological and land surface models is required. To support model validation, we combined monthly time series of satellite-derived inundation areas (Papa et al., 2010) with data on irrigated rice areas (Portmann et al., 2010). In this way, we obtained global-scale time series of naturally inundated areas (NIA), with monthly values of inundation extent during 1993–2004 and a spatial resolution of 0.5°. For most grid cells (0.5°×0.5°), the mean annual maximum of NIA agrees well with the static open water extent of the Global Lakes and Wetlands database (GLWD) (Lehner and Döll, 2004), but in 16% of the cells NIA is larger than GLWD. In some regions, like Northwestern Europe, NIA clearly overestimates inundated areas, probably because of confounding very wet soils with inundated areas. In other areas, such as South Asia, it is likely that NIA can help to enhance GLWD. NIA data will be very useful for developing and validating a floodplain modeling algorithm for the global hydrological model WGHM. For example, we found that monthly NIAs correlate with observed river discharges.
In Belize, which is well known for the Belize Barrier Reef and its offshore atolls, coastal lagoons are frequent morphological features along the coast. They represent transitional environments between siliciclastic and carbonate settings. In order to shed light into the Holocene evolution of coastal lagoon environments, five localities along the central coast of Belize were selected as coring sites. These include four coastal lagoons and one marsh area, namely Mantatee Lagoon, Mullins River Beach, Colson Point Lagoon, Commerce Bight Lagoon and Sapodilla Lagoon. A total of 26 sediment cores with core lengths ranging from 109 cm to 500 cm, were drilled using a Lanesky-vibracorer. Overall, 73 m of Holocene sediments and Pleistocene soil were recovered. Together with 58 radiocarbon dates the sediments reveal details on the sediment architecture and depositional features of the localities.
Marine inundation of the mainland and coastal lagoon formation started around 6 kyrs cal BP.
As a response to sea-level rise during the Holocene transgression, facies retrograded towards the coast, as seen in marginal marine overlying brackish mollusk faunas. Evidence for late Holocene progradation of facies due to sea-level stagnation is largely lacking. The occurrence of landward thinning sand beds, hiatuses and marine fauna in lagoonal successions are indications of event (overwash) sedimentation. Sediments recovered are largely of Holocene age (<7980 cal BP), overlying Pleistocene sections. Analyses of sediment composition and texture, radiocarbon dating and mollusk shell identification were used to describe and correlate sedimentary facies.
XRD analyses have identified quartz as the dominant mineral, with the Maya Mountains as main source of coastal lagoon sediments. The most common sedimentary facies include peat and peaty sediment, mud, sand, and poorly sorted sediments. Pleistocene soil forms the basement of Holocene sediments. Holocene mud represents lagoon background permanent sedimentation.
Peats and peat-rich sequences were deposited in mangrove swamp environments, whereas sandy facies mainly occur in the shoreface, beach, barriers, bars, barrier spits and overwash deposits. Facies successions could be identified for each locality, but it has proven difficult to correlate the stratigraphic sequences, especially among localities. These differences among the five locations studied suggest that apart from regional influence such as sea-level rise, local environmental factors such as small-scale variation in geomorphology and resulting facies heterogeneity, connectivity of the lagoon with the sea, antecedent topography and river discharge, were responsible for coastal sedimentation and lagoon development in the Holocene of Belize.
Faunal composition and distribution patterns of mollusk assemblages from 20 shell concentrations in cores collected in coastal lagoons, a mangrove-fringed tidal inlet and the marginal marine area (shallow subtidal) show considerable variation due to environmental heterogeneity and the interplay of several environmental factors in the course of the mid-late Holocene (ca. 6000 cal BP to modern). The investigated fauna ≥2 mm comprises 2246 bivalve, gastropod and 11 scaphopod specimens. Fifty-three mollusk species, belonging to 42 families, were identified. The bivalve Anomalocardia cuneimeris and cerithid gastropods are the dominant species and account for 78% of the total fauna. Diversity indices are low in concentrations from lagoons and relatively high in the marginal marine and tidal inlet areas.
Based on cluster analysis and nonmetric multidimensional scaling (NMDS), seven lagoonal assemblages and three marginal marine/tidal inlet assemblages were defined. A separation between lagoonal and marginal marine/tidal inlet assemblages seen in ordination indicates a lagoon-onshore gradient. The statistical separation among lagoonal assemblages demonstrates environmental changes during the Holocene evolution of the coastal lagoons, which is probably related to the formation of barriers and spits. The controlling factors of species distribution patterns are difficult to figure out, probably due to the heterogeneity of the barrier-lagoon systems and the interaction of paleoecological and paleoenvironmental factors. In addition to the taxonomic analysis, a taphonomic analysis of 1827 valves of A. cuneimeris from coastal lagoons was carried out. There is no relationship between depth and age of shells and their taphonomic condition. Size-frequency distributions and right-left valve ratios of A. cuneimeris suggest that valves were not transported over long distances but were deposited parautochthonously in their original habitat. Shells from tidal inlet and marginal marine environments were also predominantly deposited in their original habitats.
Since the Belize coast was repeatedly affected by hurricanes and the paleohurricane record for this region is poor, the sediment cores have been examined in order to identify storm deposits.
The paleohurricane record presented in this study spans the past 8000 years and exhibits three periods with increased evidences of hurricane strikes occurring at 6000-4900 cal yr BP, 4200-3600 cal yr BP and 2200-1500 cal yr BP. Two earlier events around 7100 and 7900 cal yr BP and more recent events around 180 cal yr BP and during modern times have been detected. Sand layers, redeposited corals and lagoon shell concentrations have been used as proxies for storm deposition. Additionally, hiatuses and reversed ages may indicate storm influence. While sand layers and corals represent overwash deposits, the lagoon shell concentrations, which mainly comprise the bivalve Anomalocardia cuneimeris and cerithid gastropods, have been deposited due to changes in lagoon salinity during and after storm landfalls. Comparison with other studies reveals similarities with one record from Belize, but hardly any matches with other published records. The potential for paleotempestology reconstructions of the barrier-lagoon complexes along the central Belize coast differs depending on geomorphology, and deposition of washovers in the lagoon basins is limited, probably due to the interplay of biological, geological and geomorphological processes.
Geoelektrische Methoden sind weit verbreitet und werden häufig zur Erkundung des oberflächennahen Untergrundes eingesetzt. Angewendet werden standardmäßig meist nur linienhafte Anordnungen der Sender- und Empfängerelektroden, die nur wenige Zehner Meter lang sind. Hierdurch haben diese Methoden nur geringe Eindringtiefen. Um größere Eindringtiefen und 3-dimensionale Informationen über den Untergrund zu erhalten, sind in der vorgestellten Studie die Empfänger- und Senderdipole in mehr oder weniger regelmäßigen Abständen über das Untersuchungsgebiet verteilt worden. Mit jeder Empfängerstation sind kontinuierlich die elektrischen Spannungen in bis zu drei Richtungen aufgezeichnet worden. Für die Einspeisungen wurde ein Rechtecksignal verwendet, das sich gut von den Störfrequenzen und den natürlichen Spannungen abhebt. Die Richtungen der Einspeisedipole sind entsprechend den örtlichen Gegebenheiten, jedoch möglichst parallel zu den Messrichtungen, gewählt worden. Zur Auswertung der erhobenen Messdaten wurde ein Programmpaket entwickelt, das eine weitestgehend automatisierte Auswertung der Daten erlaubt. Die Bestimmung der scheinbaren spezifischen Widerstände und ihrer Messfehler wurde an den fouriertransformierten Datenzeitreihen durchgeführt. Hierdurch konnten Störeinflüsse minimiert werden und es wurde möglich selbst stark verrauschte Datensätze auszuwerten. Um die erhobenen Daten interpretieren zu können sind die berechneten scheinbaren spezifischen Widerstände als Grundlage für Inversionen und Modellstudien verwendet worden. Die oben beschriebene Methode wurde im Rahmen der vorliegenden Arbeit in zwei unterschiedlichen Messgebieten angewandt.
Messgebiet im Hohen Vogelsberg
Im Juli 2007 wurde damit begonnen, die Forschungsbohrung Sichenhausen-Eschwald im Hohen Vogelsberg abzuteufen. Ziel war es, Informationen über den strukturellen Aufbau des größten geschlossenen Vulkankomplexes Mitteleuropas zu gewinnen. Die Gesteinsansprache der Tiefbohrung lieferte bereits relativ früh Hinweise darauf, dass ein großer magmatischer Körper aufgeschlossen wurde.Aufgrund der begrenzten räumlichen Aussagekraft der Bohrung und fehlender Geländebefunde war es nicht möglich, den Mechanismus der Platznahme und die Größe des Körpers näher zu beschreiben. Die Kampagne hatte das Ziel diese Lücke zu schließen und ein 3-dimensionales Modell des Untergrundes zu erstellen.In dem annähernd quadratischen Untersuchungsgebiet, das eine Fläche von ca. 25 $km²$ aufweist, wurden 20 Datenlogger zur Aufzeichnung der elektrischen Spannungen aufgebaut. Die Empfängerdipole waren zwischen 20 m und 30 m lang. Insgesamt wurden 36 Stromeinspeisungen mit Stromstärken zwischen 28 A und 40 A an 16 unterschiedlichen Positionen für jeweils 2 bis 3 verschiedene Dipolrichtungen vorgenommen. Die Einspeisedipole waren zwischen 100 m und 300 m lang. Insgesamt konnten 1.439 scheinbare spezifische Widerstände berechnet werden.Die Ergebnisse der Modellierungen und der Inversion der Daten zeigen, dass mit der Forschungsbohrung ein domartiger Körper angebohrt wurde. Anhand der Ergebnisse kann die räumliche Ausdehnung des Körpers eingegrenzt und ein vorher noch nicht kartierter Gang nachgewiesen werden.
Messgebiet im Bereich der Kinzigtalsperre
Das etwa Ost-West verlaufende Kinzigtal bildet die naturräumliche und geologische Grenze zwischen dem vulkanischen Vogelsberg im Norden und dem, in diesem Bereich aus Sedimentgesteinen aufgebauten, Spessart im Süden.Die zwischen Steinau a. d. Str. und Bad Soden-Salmünster befindliche Kinzigtalsperre dient dem Hochwasserschutz und der Regulierung des Pegels der Kinzig bei Dürreperioden. Der aufgestaute See ist relativ flach und weist im Normalstau maximale Tiefen von ca. 6~m auf. Der Stausee ist jedoch über weite Teile etwa 4~m tief. In dieser Kampagne betrug der Abstand zwischen den einzelnen Empfängerstationen etwa 100 m bis 300 m. Es wurde aufgrund der beengten Platzverhältnisse eine Dipollänge von ca. 48 m für die Einspeise- und die Empfängerdipole im Messgebiet gewählt. Insgesamt wurden 14 Empfängerstationen im Messgebiet aufgebaut, von denen sich Neun auf dem Seegrund befanden. Das Messraster orientierte sich am vermuteten Verlauf der Kinzigtalstörung. An 8 Positionen sind in 21 Richtungen elektrische Ströme mit Stärken zwischen 2,2 A und 40 A in den Untergrund eingespeist worden. Es konnten 536 scheinbare spezifische Widerstände berechnet werden. Ziel war es, den Verlauf der Störung näher zu bestimmen und die Tiefe der im Untergrund vorhandenen salinären Grundwässer zu bestimmen. Die Bestimmung des Verlaufs der Kinzigtalstörung sowie die Tiefenbestimmung der salinären Grundwässer war mit den erhobenen Daten jedoch nicht möglich.
Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. The spatial density of available data sites is often changing with time. This paper investigates the application of statistical distance, like one minus common variance of time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation observed in Austria. Choosing statistical distance instead of geographical distance in interpolation of an actually available coarse observation network yields more robust interpolation results at sites of a denser network with actually lacking observations. The performance enhancement is in or close to mountainous terrain. This has the potential to parsimoniously densify the currently available observation network. Additionally, the success further motivates search for conceptual rain-orography interaction models as components of spatial rain interpolation algorithms in mountainous terrain.
Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. This paper investigates the application of statistical distance, like one minus common variance of observation time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation observed in Austria. Choosing statistical distance instead of geographical distance in interpolation of available coarse network observations to sites of a denser network, which is not reporting for the interpolation date, yields more robust interpolation results. The most distinct performance enhancement is in or close to mountainous terrain. Therefore, application of statistical distance in the inverse distance weighting interpolation or in similar methods can parsimoniously densify the currently available observation network. Additionally, the success further motivates search for conceptual rain-orography interaction models as components of spatial rain interpolation algorithms in mountainous terrain.
Spatial interpolation of precipitation data is uncertain. How important is this uncertainty and how can it be considered in evaluation of high-resolution probabilistic precipitation forecasts? These questions are discussed by experimental evaluation of the COSMO consortium's limited-area ensemble prediction system COSMO-LEPS. The applied performance measure is the often used Brier skill score (BSS). The observational references in the evaluation are (a) analyzed rain gauge data by ordinary Kriging and (b) ensembles of interpolated rain gauge data by stochastic simulation. This permits the consideration of either a deterministic reference (the event is observed or not with 100% certainty) or a probabilistic reference that makes allowance for uncertainties in spatial averaging. The evaluation experiments show that the evaluation uncertainties are substantial even for the large area (41 300 km2) of Switzerland with a mean rain gauge distance as good as 7 km: the one- to three-day precipitation forecasts have skill decreasing with forecast lead time but the one- and two-day forecast performances differ not significantly.