Using paleolimnological techniques, I have studied surface-water acidification and the effects of liming in Swedish lakes on a decadal to millennial time-scale. The overall objective was to contribute to the discussion on the fulfilment of goals within the Swedish liming program. One of the main goals of this program is to restore lakes to natural or nearly natural conditions, i.e. to a reference condition as termed in the EU Water Framework Directive. In this context, a key issue is to define reference conditions. This is a central theme of my thesis, as lake sediments offer a unique way to study past lake conditions. Past lake-water acidity of 12 reference lakes in the Swedish liming program (ISELAW) was determined using diatom analysis of sediment cores. Pollen, lead, and flyash from coal/oil combustion were used as indicators of impact from land use and atmospheric pollution. A general trend in these lakes is an initial decline in pH after lake formation due to natural soil processes, which was then followed by rather low pH values (pH 5.3-6.5). In six of the lakes pH increased as a result of expansion of agriculture (burning, forest grazing) 2000 to 1000 years ago. Local mining and long-range airborne pollution have also impacted the lakes since medieval time. These results show that the conditions of the study lakes were not natural prior to industrialization and recent (20th century) acidification. The ISELAW lakes were selected on the basis of representing typical limed lakes, and they have been limed and monitored since at least the 1980s. A comparison of chemical/biological monitoring data and the paleolimnological data gives somewhat diverging results. Most of the monitoring data suggest that the lakes were subjected to acidification during the 20th century, but the paleolimnological data can only identify clear evidence of acidification in five of the 12 lakes, hence, all lakes were probably not recently acidified. According to conclusions from monitoring the lakes have recovered following liming. The paleolimnological data give a more complex picture and three different responses have been identified: 1) a return to a diatom composition found in the lake one hundred to several thousand years ago; 2) very small shifts in the diatom composition; or 3) a diatom composition previously not found in the lake. The latter response raised the question whether liming can cause an unnatural diatom community. A comparison of diatoms in surface sediment samples of 31 limed lakes with pre-industrial reference samples from 291 lakes showed that liming does not create an unnatural diatom composition. These results illustrate that the goals for liming were not reached in all of the limed lakes, and that paleolimnology can play an important role for assessments of acidification and liming. The comparative study also highlights the importance of designing monitoring programs that can produce reliable and long data series. Given the results of the paleolimnological investigations, it is obvious that we cannot assume that the 19th century represented a natural or near natural state, and thus is a realistic reference conditions. Natural long-term lake development and previous land-use impacts need to be considered in defining reference conditions. Neither can we disregard the fact that humans always will impact nature. Although paleolimnological studies are time consuming, I believe that they could be simplified to the extent that paleolimnology could become a routine method for environmental management.

This Ph.D. thesis focuses on the characteristic of littoral vegetation in reservoirs with a storage function and on the factors that may affect it. The current state of the littoral vegetation in different types of biotopes was detected by a detailed survey of the littoral in Lipno reservoir. Complexes of environmental factors characteristic for different types of biotopes were described. The dynamics of littoral vegetation in response to changes in water level fluctuations was monitored in a protected bay during three years. Based on the results, the vegetation zonation was described in the eulittoral zone of an aquatic ecosystem with irregular fluctuations in water levels. The thesis also deals with the use of a breakwater structure to protect littoral vegetation in erosion exposed biotopes. The results of all three studies are used as a basis for proposals for supporting the development of littoral vegetation in the eulittoral zone in reservoirs as defined in the Water Framework Directive.

Im 6. Informationsblatt zur »Umsetzung der Wasserrahmenrichtlinie in Sachsen« liegt der Schwerpunkt auf der Umsetzung von Maßnahmen zur Verbesserung des Gewässerzustands. Zum einen wird eine Zwischenbilanz zum Stand der Arbeiten gezogen. Zum anderen wird beleuchtet, ob die bisherigen Anstrengungen ausreichend sind, um die hoch gesteckten Ziele in Sachsen erreichen zu können. Außerdem werden Projekte des LfULG und seiner Partner vorgestellt, die beispielhaft für Sachsen sein können.

The vegetation in the riparian zone of a watercourse in fluences the water state with multiple factors, first via direct substance discharge and secondly via shadow casting on the water surface. Shadowing directly regulates the solar radiant energy arriving at the water surface. Solar radiation input to aquatic environments is the most important abiotic factor for aquatic flora and fauna habitat development. Thus, to adequately asses the ecological state of water courses it is necessary to quantify the solar surface irradiance E (W=m2) arriving on the water surface. When estimating the solar surface irradiance the complex coherence between incoming solar radiation, atmospheric in uences, and spatial-temporal geometries need to be investigated. This work established a work flow to compute the solar surface irradiance for water bodies using different remote sensing data. The work flow was tested on regional level for a section of the river Freiberger Mulde, Saxony, for the year 2016. Product of the calculations is a map visualising the annual sum of the solar surface irradiance (kWh=m2) arriving on the Freiberger Mulde water surface and the surrounding terrain. Based on these information bio-hydrological issues can be further examinated.

The European Water Framework Directive commits the member states to achieve the good ecological status for all waterbodies. For this purpose on the level of the national states monitoring programs are established with the aim to verify the actual status by means of regular surveys. Already in the past remote sensing data in conjunction with methods of geospatial data analysis revealed the added value in terms of monitoring strategies regarding the European Water Framework Directive. Depending on the type of data they can be used for example for the determination of several parameters of rivers and streams. The present analyses show how it is possible to determine the parameter of width variation of small and medium rivers based on digital orthophotos. Because this parameter strongly depends on the geometric quality of the riverbank line, its determination is given particular attention. It turns out that mainly riparian vegetation has a large impact on the visibility of the riverbank line. In a multi-stage process different methods for the identification of affected areas are developed with the aim to reconstruct the true riverbank line in a second step. Finally these data form the basis for the determination of river width variations.

Rivers are the lifelines of our environment. For this reason they are always in the focus of environmental studies. For the assessment of the ecological status of rivers the member states of the European Union have developed different monitoring programs and approaches. The shadowing of a river affects the temperature of the water and also the energy balance of the water body. Therefore changes in temperature also in uence the biological and chemical status of rivers and lakes. The main objective of this study is the simulation of the shadowing of a section of the river Freiberger Mulde for a full year. This ensures that effects of different sun positions over the year (azimuth, elevation) and also local topography conditions in the close environment of the river section are taken into account. For all analyses a digital surface model and a digital elevation model with a geometric resolution of 2 m is available. The result of this simulation is a raster layer which represents the theoretical annual hours of shadowing of the river section. The results indicate a decrease of illumination of partly more than 80 %. In future this information can be expanded by means of further affecting factors such as the consideration of the phenological status of deciduous trees in the riparian zone.

Im 6. Informationsblatt zur »Umsetzung der Wasserrahmenrichtlinie in Sachsen« liegt der Schwerpunkt auf der Umsetzung von Maßnahmen zur Verbesserung des Gewässerzustands. Zum einen wird eine Zwischenbilanz zum Stand der Arbeiten gezogen. Zum anderen wird beleuchtet, ob die bisherigen Anstrengungen ausreichend sind, um die hoch gesteckten Ziele in Sachsen erreichen zu können. Außerdem werden Projekte des LfULG und seiner Partner vorgestellt, die beispielhaft für Sachsen sein können.

The European Water Framework Directive (WFD; 2000/60/EC) was incorporated into the Swedish legislation in 2004 through the ordinance Förordningen om förvaltningenav kvaliteten på vattenmiljön (SFS 2004:660). The objective is that all water bodies shall reach a good status by the year 2015. In Sweden the comprehensive plans of the municipalities can play a large role in reaching these goals. A comprehensive plan deals with the long term water and land use of the municipality, which can facilitate an early consideration of water management in the planning process of the municipality. In Sweden five river basin districts have been established in accordance with the Water Framework Directive. The focus of this study is on the Northern Baltic Sea river basin district. Action strategies have been created for each river basin district, dictating what measures the authorities, among them the municipalities, need to take. The purpose with this study is to find out to what extent the municipalities have taken the action strategies regarding the Northern Baltic Sea river basin and the water quality standards set in Förordningen om förvaltningen av kvaliteten på vattenmiljön (SFS 2004:660) into account when working with their comprehensive plans. The study also sheds light on the municipalities’ view on the demands made on them and what actions can facilitate the working process. The study was made in three parts; a survey, literature studies and interviews. An overall study of all the municipalities in the county of Stockholm was made and three were selected for an in-depth study. The results of the study show that the demands on the municipalities have not been met due to lack of knowledge. The municipalities are aware of the existence of the Water Framework Directive but find it hard to interpret the environmental quality standards and the action strategies. The municipalities wish for a clearer legal definition of the environmental quality standards and a better definition of how the implementation of the action strategies can be made. The municipalities are asking for a clarification of the demands they can make on other organizations and of the demands made on them by the county boards and the River Basin District Authorities.

La qualité des services écosystémiques qu'offrent les lacs est liée à la structure et au fonctionnement de leur écosystème. Protéger leur masse d'eau est devenu un objectif global qui requiert une meilleure compréhension de leur fonctionnement, un suivi et une évaluation de leur qualité. Expliquer les hétérogénéités spatio-temporelles des variables physico-chimiques et du phytoplancton est un problème récurrent rencontré en écologie et en hydrobiologie. Comprendre la dynamique de ces hétérogénéités est aussi un prérequis essentiel pour évaluer, protéger et restaurer objectivement les écosystèmes lacustres. En ce qui concerne la surveillance, les hétérogénéités spatio-temporelles introduisent des incertitudes sur la représentativité des mesures par rapport à l'entièreté de la masse d'eau qui est donc discutable et doit être vérifiée. En Europe, la directive cadre sur l'eau (DCE) initiée en 2000 définit un cadre pour la gestion et la protection des eaux. La classification des masses d'eau en fonction de leur état écologique est un point important dans l'implémentation de cette directive. Pour les lacs et les retenues, l'évaluation de cet état écologique est basée sur des paramètres biologiques, physico-chimiques et hydromorphologiques. Les indicateurs liés au phytoplancton et aux paramètres physico-chimiques sont calculés à partir de quatre prélèvements réalisés pendant la période d'activité biologique pour une année sur un plan de gestion de six ans. Dans ce contexte, la modélisation tridimensionnelle (3D) et la prise en compte des forçages qui conduisent aux hétérogénéités spatio-temporelles est une condition préalable nécessaire tant en limnologie appliquée que théorique. Cette thèse aborde la complexité du fonctionnement des lacs et la capacité des modèles 3D à reproduire leur fonctionnement. L'apport de la modélisation 3D est présenté i) pour la compréhension du fonctionnement de lacs de différentes tailles, ii) couplée aux observations satellitaires, pour l'étude de l'influence des forçages par le vent et de l'hydrodynamique sur l'abondance et la distribution spatiale de phytoplancton, iii) dans le cadre de la DCE, pour l'évaluation des incertitudes d'une évaluation de l'état écologique d'un plan d'eau. Pour cela, deux modèles 3D ont été créés et analysés, un pour le lac de Créteil (42~ha) et un autre pour le Léman (580~km$^2$). Celui du lac de Créteil a été validé à partir de données à hautes fréquences acquises en trois points du lac. Il reproduit correctement son hydrodynamique complexe, sa structure thermique, l'alternance entre les périodes de stratification et les épisodes de mélange, ainsi que les ondes internes. Le modèle du Léman a été validé en utilisant des données mensuelles et bimensuelles en deux stations de prélèvement du lac. Il reproduit aussi correctement son hydrodynamique et la variabilité saisonnière de paramètres physico-chimiques et biologiques. Les résultats des simulations mettent en avant les mécanismes physiques et hydrodynamiques responsables de l'apparition de sites où la biomasse de phytoplancton observée est plus élevée. Dans le cadre de la DCE, ces résultats montrent aussi une variabilité spatiale importante des sous-états écologiques basés sur les différents paramètres qui dépendent du choix des dates des campagnes de mesure et du point d'échantillonnage. Ces résultats ont aussi été utilisés pour estimer la représentativité d'une station de prélèvement. Les résultats de cette thèse i) confirment que le fonctionnement des plans d'eau de toute taille est complexe et que les processus physiques génèrent des hétérogénéités spatio-temporelles, ii) suggèrent que le vent et l'hydrodynamique influencent significativement l'abondance et la distribution spatiale du phytoplancton et que iii) ces hétérogénéités peuvent biaiser notre estimation du statut écologique des plans d'eau dans le cadre de la DCE / The quality of ecosystem services provided by lakes is related to the ecosystem structure and functioning. Protecting water bodies is therefore a global goal that requires a better understanding of their function, a monitoring and a water quality assessment. Explaining spatio-temporal heterogeneities of physico-chemical parameters and phytoplankton has been a recurrent ecological and hydrobiological issue. Understanding the dynamics of these heterogeneities is an essential prerequisite for objectively assessing, protecting and restoring freshwater ecosystems. Moreover, three-dimensional (3D) and taking into account and drivers of these heterogeneities are essential prerequisites for theoretical and applied limnology. Concerning the monitoring, spatio-temporal heterogeneities are responsible of uncertainties on the representativeness of the data versus the whole lake which might be questionable and needs to be verified. In Europe, the Water Framework Directive (WFD) initiated in 2000 defines a framework for managing and protecting water bodies in Europe. The classification of water bodies into ecological status is a key issue for the implementation of that framework. For lakes and reservoirs, the assessment of this status is based on biological, physico-chemical and hydro-morphological indicators. Physico-chemical and phytoplankton indicators are calculated based on four observations at an unique sampling station over the growing season, this evaluation being assessed one year for a six-year management plan. In this context, this thesis focuses on the complexity of lakes functioning and the capability of three-dimensional (3D) models to reproduce their functioning. The contribution of 3D models is presented i) for understanding the functioning of lakes of different sizes, ii) coupled to satellite observations, for studying of the influence of wind forcing and hydrodynamics on phytoplankton abundance and spatial heterogeneities, iii) in the context of the WFD, for assessing uncertainties in the lake ecological status assessment. To do that, two 3D models have been created and analyzed, one for Lake Créteil (42 ha) and another for Lake Geneva (580 km2). Lake Créteil 3D model was validated by using high frequency data recorded at three stations. It reproduces well the complex hydrodynamic functioning of the lake, its thermal structure, the alternation between thermal stratification episodes and mixing events, and internal waves. Lake Geneva 3D model was validated by using monthly and bimonthly data at two stations. It reproduces also properly the hydrodynamic functioning of the lake and the seasonal variability of biological and physico-chemical parameters. Simulation results highlight physical and hydrodynamic mechanisms responsible for the occurrence of seasonal hot-spots in phytoplankton abundance. In the context of the WFD, simulation results show also a strong spatial variability of lake ecological status depending on the timing of the four sampling dates as well as the location of the sampling station. These results were also used to assess to representativeness of sampling stations. The results of this thesis suggest that i) the functioning of lakes of different sizes is complex and physical processes generates spatio-temporal heterogeneities, ii) wind and hydrodynamics influence the abundance and the spatial distribution of phytoplankton et iii) spatio-temporal heterogeneities can bias our evaluation of lake ecological status in the WFD

No description available.