Peter Chifflard

Scales and drivers of temporal pCO2 dynamics in an Alpine stream

The role of inland waters for the global carbon cycle is now recognized and evidence increasingly suggests that stream ecosystems disproportionately contribute to the carbon cycle. Understanding the dynamics and drivers of stream water partial pressure of CO2 (pCO2) and CO2 evasion fluxes from streams to the atmosphere is imperative for assessing the role of climate change on the carbon cycle in stream ecosystems. Monitoring pCO2 over 3 years, we here report on the seasonal, diurnal, and event-driven dynamics of pCO2 in the hyporheic zone and stream water of an Alpine stream and assess possible drivers of these dynamics. Our findings suggest that both catchment-derived CO2 delivered by shallow groundwater into the stream and in-stream respiration continuously build up pCO2 in the hyporheic zone. Depending on stream water temperature and assumedly on primary production (inferred from photosynthetically active radiation), hyporheic CO2 contributes to stream water pCO2 and ultimately to CO2 outgassing to the atmosphere. Diurnal patterns of stream water pCO2 increasingly built up during extended base flow and streambed-scouring storms caused the collapse of these diurnal patterns. Post storm recovery of the diurnal pCO2 patterns was generally rapid. Our findings suggest that decreasing gas exchange velocity related to receding discharge drives recovery dynamics. We found that average CO2 outgassing fluxes during night exceeded those during day by up to 1.8 times. Our study highlights temperature and hydrology—key components of climate change—as major drivers of pCO2 dynamics in Alpine streams. They also underscore the necessity to consider day-night differences in CO2 outgassing fluxes to properly establish carbon budgets and regional estimates of CO2 outgassing to the atmosphere.

Influence of Cover Beds on Slope Hydrology

Abstract Numerous case studies carried out in the subdued mountains of Germany during the last decades have revealed that periglacial cover beds play a decisive role in hillslope hydrology. Considering the omnipresence of cover beds in sloped terrain of the mid-latitudes, knowledge of slope-water paths is crucial not only for flood forecast but also for understanding how contaminants pass through ecosystems. Since periglacial cover beds are usually composed of different sedimentary layers, they show a high spatial variability of physical soil parameters, which are, in turn, responsible for small-scale variations of the hydraulic properties. Regardless of bedrock type, the observations reported in this chapter from different regions lead to the conclusion that there is a clear relationship between subsurface layering and runoff-generation processes. The hydraulic anisotropic structure of the deepest (basal) layer is the major factor controlling subsurface water-flow paths. On one hand, this layer acts as an aquitard for seeping water because of its high bulk density. On the other hand, once water has percolated into this layer, it is able to flow in lateral directions because of the coarse clasts oriented parallel to the slope. Therefore, such a cover bed may be treated neither as an aquifer nor as an aquiclude. Besides, as a function of pre-moisture, a nonlinear runoff response to precipitation or snow-melt of the investigated catchments was identified.

Hydromorphology and Biodiversity in Headwaters — An Eco- Faunistic Substrate Preference Assessment in Forest Springs of the German Subdued Mountains

Springs are autochthonous inland freshwater ecosystems, which occur where groundwater reaches the surface [1-2]. From a limnological point of view springs are divided into two subtypes: the springhead (eucrenal) and the springbrook (hypocrenal), because of a differen‐ tiation in their species composition caused by differences of structural and environmental parameters [3]. That is only part of the reality for the hypocrenal when springs connected with flowing surface waters and be integrated into the upper part of a stream system (headwater). Regarding the common limnological spring types based on hydromorphological properties (rheocrene spring: fast flowing or falling water occurrence; helocrene spring: diffuse or laminar flowing water occurrence; limnocrene spring: water occurrence in a still water pool), springs can also occur in still surface waters without run-off [4-5]. This is of importance for the understanding and interpretation of species presence and biodiversity of springs, because depending on the spring type it is a lotic or a lentic aquatic ecosystem with an appropriate flow velocity as a hydromorphological factor (lotic: 0.1 to 1 m/s; lentic: 0.001 to 0.01 m/s) [6]. Furthermore, it should be emphasized that springs are ecotones with boundary or transition areas between different habitats [7]. The species composition is influenced by interacting with other different species communities and can be characterized as taxa rich regarding the whole habitat (crenon) [8]. Beside typically aquatic spring species (crenocenosis) other aquatic fauna elements occur from groundwater (stygobionts) and related surface waters (brook/river biota or still-water biota). Also semi-aquatic and terrestrial fauna are an integrated part in spring ecotones with specific transition zones as fauna elements (semi-aquatic: Fauna hygropetrica, Fauna liminaria; terrestrial: hydrophilic terrestrial fauna) [9-10]. Springs in the German subdued mountains are commonly cold stenothermic habitats, which means the mean annual

The significance of soil moisture in forecasting characteristics of flood events. A statistical analysis in two nested catchments

Abstract We examine the feasibility and added value of upscaling point data of soil moisture from a small- to a mesoscale catchment for the purpose of single-event flood prediction. We test the hypothesis that in a given catchment, the present soil moisture status is a key factor governing peak discharge, flow volume and flood duration. Multiple regression analyses of rainfall, pre-event discharge, single point soil moisture profiles from representative locations and peak discharge, discharge duration, discharge volume are discussed. The soil moisture profiles are selected along a convergent slope connected to the groundwater in flood plain within the small-scale catchment Husten (2.6 km²), which is a headwater catchment of the larger Hüppcherhammer catchment (47.2 km², Germany). Results show that the number of explanatory variables in the regression models is higher in summer (up to 8 variables) than in winter (up to 3 variables) and higher in the meso-scale catchment than in the small-scale catchment (up to 2 variables). Soil moisture data from selected key locations in the small catchment improves the quality of regression models established for the meso-scale catchment. For the different target variables peak discharge, discharge duration and discharge volume the adding of the soil moisture from the flood plain and the lower slope as explanatory variable improves the quality of the regression model by 15%, 20% and 10%, respectively, especially during the summer season. In the winter season the improvement is smaller (up to 6%) and the regression models mainly include rainfall characteristics as explanatory variables. The appearance of the soil moisture variables in the stepwise regression indicates their varying importance, depending on which characteristics of the discharge are focused on. Thus, we conclude that point data for soil moisture in functional landscape elements describe the catchments’ initial conditions very well and may yield valuable information for flood prediction and warning systems.

Water research in Germany: from the reconstruction of the Roman Rhine to a risk assessment for aquatic neophytes

Germany does not only have a long tradition in water research, but a very active community of scientists and practitioners working on a vast range of “water topics.” This thematic issue, which was initiated by four water-related research associations (German Hydrological Society; German Limnological Society; Hydrological Sciences Commission within German Water Association; Working Group Hydrology within German Geographical Society), is a testimony of both the quality and diversity of the water research currently undertaken by Germany’s scientific community. Key topics include hydrology and hydromorphology; water quality; aquatic and riparian ecosystems; water in agriculture and forestry; and water management and supply. The manuscripts contained in this thematic issue do not only cover a period of more than two millennia, but also address all types of water resources and a multitude of both established and newly developed methods that help us to better understand the processes governing the hydrological cycle, aquatic ecosystems and the management and operation of various water infrastructures.

Cooperation as Significant Factor in Successful Scientific Research with the Example of the Research Institute WasserCluster Lunz

Th e Biological Station Lunz was founded in 1905 by Dr. Carl Kupelwieser. At that time limnology was just evolving as an independent line of research, and the fi rst research teams devoting themselves to the large alpine lakes and plankton emerged in Europe. Th e founding of the station at Lunz was meant to provide new development opportunities for this young fi eld of research here in the eastern and pre-alpine region (Ruttner 1955). Back then, the wide fi eld of general hydrobiology and the domain of morphogenesis and hereditary physiology were combined as scientifi c objectives (Woltereck 1906). A team of four scientists from diff erent natural science disciplines were invited to develop this research focus here. Next to the two research priorities, a second important objective of the station was to provide favorable conditions as a host station for domestic and foreign scientists in diff erent lines of research. In 1912, as the need for education in the fi eld of limnology was recognized, a boat house by the lake DER DONAURAUM

Kooperation als wesentlicher Faktor für den Erfolg der wissenschaftlichen Forschung am Beispiel des Forschungsinstitutes WasserCluster Lunz

Die biologische Station Lunz wurde 1905 von Dr. Carl Kupelwieser gegründet. Zu dieser Zeit war die Limnologie eine sich gerade eigenständig entwickelnde Forschungsrichtung, und es entstanden die ersten Forschungsgruppen in Europa, die sich mit den großen Alpenseen und Plankton beschäftigen. Die Gründung der Station in Lunz sollte dieser jungen Forschungsrichtung hier im ostund voralpinen Bereich neue Entwicklungsmöglichkeiten bieten (Ruttner 1955). Als wissenschaftliche Zielsetzungen wurden damals das weite Feld der allgemeinen Hydrobiologie und der Bereich der Formbildungsund Vererbungsphysiologie zusammengefasst (Woltereck 1906). Ein Team aus vier Wissenschaftlern unterschiedlicher naturwissenschaftlicher Fachrichtungen wurde eingeladen, um hier diesen Forschungsschwerpunkt zu entwickeln. Neben den beiden Forschungsschwerpunkten war es eine zweite wichtige Zielsetzung der Station, als Gaststation für inund ausländische Wissenschaftler verschiedener Forschungsgebiete günstige Voraussetzungen zu bieten. Im Jahre 1912 wurde ein BootsDER DONAURAUM