TY - JOUR A1 - Lischeid, Gunnar A1 - Kalettka, Thomas A1 - Holländer, Matthias A1 - Steidl, Jörg A1 - Merz, Christoph A1 - Dannowski, Ralf A1 - Hohenbrink, Tobias Ludwig A1 - Lehr, Christian A1 - Onandia, Gabriela A1 - Reverey, Florian A1 - Pätzig, Marlene T1 - Natural ponds in an agricultural landscape BT - external drivers, internal processes, and the role of the terrestrial-aquatic interface JF - Limnologica : ecology and management of inland waters N2 - The pleistocenic landscape in North Europe, North Asia and North America is spotted with thousands of natural ponds called kettle holes. They are biological and biogeochemical hotspots. Due to small size, small perimeter and shallow depth biological and biogeochemical processes in kettle holes are closely linked to the dynamics and the emissions of the terrestrial environment. On the other hand, their intriguing high spatial and temporal variability makes a sound understanding of the terrestrial-aquatic link very difficult. It is presumed that intensive agricultural land use during the last decades has resulted in a ubiquitous high nutrient load. However, the water quality encountered at single sites highly depends on internal biogeochemical processes and thus can differ substantially even between adjacent sites. This study aimed at elucidating the interplay between external drivers and internal processes based on a thorough analysis of a comprehensive kettle hole water quality data set. To study the role of external drivers, effects of land use in the adjacent terrestrial environment, effects of vegetation at the interface between terrestrial and aquatic systems, and that of kettle hole morphology on water quality was investigated. None of these drivers was prone to strong with-in year variability. Thus temporal variability of spatial patterns could point to the role of internal biogeochemical processes. To that end, the temporal stability of the respective spatial patterns was studied as well for various solutes. All of these analyses were performed for a set of different variables. Different results for different solutes were then used as a source of information about the respective driving processes. In the Quillow catchment in the Uckermark region, about 100 km north of Berlin, Germany, 62 kettle holes have been regularly sampled since 2013. Kettle hole catchments were determined based on a groundwater level map of the uppermost aquifer. The catchments were not clearly related to topography. Spatial patterns of kettle hole water concentration of (earth) alkaline metals and chloride were fairly stable, presumably reflecting solute concentration of the uppermost aquifer. In contrast, spatial patterns of nutrients and redox-sensitive solutes within the kettle holes were hardly correlated between different sampling campaigns. Correspondingly, effects of season, hydrogeomorphic kettle hole type, shore vegetation or land use in the respective catchments were significant but explained only a minor portion of the total variance. It is concluded that internal processes mask effects of the terrestrial environment. There is some evidence that denitrification and phosphorus release from the sediment during frequent periods of hypoxia might play a major role. The latter seems to boost primary production occasionally. These processes do not follow a clear seasonal pattern and are still not well understood. KW - Ponds KW - Kettle holes KW - Water quality KW - Land use KW - Hydrogeomorphic type KW - Shore vegetationa Y1 - 2018 U6 - https://doi.org/10.1016/j.limno.2017.01.003 SN - 0075-9511 SN - 1873-5851 VL - 68 SP - 5 EP - 16 PB - Elsevier GMBH CY - München ER - TY - JOUR A1 - Musolff, Andreas A1 - Schmidt, Christian A1 - Rode, Michael A1 - Lischeid, Gunnar A1 - Weise, Stephan M. A1 - Fleckenstein, Jan H. T1 - Groundwater head controls nitrate export from an agricultural lowland catchment JF - Advances in water resources N2 - Solute concentration variability is of fundamental importance for the chemical and ecological state of streams. It is often closely related to discharge variability and can be characterized in terms of a solute export regime. Previous studies, especially in lowland catchments, report that nitrate is often exported with an accretion pattern of increasing concentrations with increasing discharge. Several modeling approaches exist to predict the export regime of solutes from the spatial relationship of discharge generating zones with solute availability in the catchment. For a small agriculturally managed lowland catchment in central Germany, we show that this relationship is controlled by the depth to groundwater table and its temporal dynamics. Principal component analysis of groundwater level time series from wells distributed throughout the catchment allowed derivation of a representative groundwater level time series that explained most of the discharge variability. Groundwater sampling revealed consistently decreasing nitrate concentrations with an increasing thickness of the unsaturated zone. The relationships of depth to groundwater table to discharge and to nitrate concentration were parameterized and integrated to successfully model catchment discharge and nitrate export on the basis of groundwater level variations alone. This study shows that intensive and uniform agricultural land use likely results in a clear and consistent concentration-depth relationship of nitrate, which can be utilized in simple approaches to predict stream nitrate export dynamics at the catchment scale. (C) 2016 Elsevier Ltd. All rights reserved. KW - Water quality KW - Nitrate KW - Lowland catchment KW - Export regime KW - Concentration-discharge relationship Y1 - 2016 U6 - https://doi.org/10.1016/j.advwatres.2016.07.003 SN - 0309-1708 SN - 1872-9657 VL - 96 SP - 95 EP - 107 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Janssen, Annette B. G. A1 - Arhonditsis, George B. A1 - Beusen, Arthur A1 - Bolding, Karsten A1 - Bruce, Louise A1 - Bruggeman, Jorn A1 - Couture, Raoul-Marie A1 - Downing, Andrea S. A1 - Elliott, J. Alex A1 - Frassl, Marieke A. A1 - Gal, Gideon A1 - Gerla, Daan J. A1 - Hipsey, Matthew R. A1 - Hu, Fenjuan A1 - Ives, Stephen C. A1 - Janse, Jan H. A1 - Jeppesen, Erik A1 - Joehnk, Klaus D. A1 - Kneis, David A1 - Kong, Xiangzhen A1 - Kuiper, Jan J. A1 - Lehmann, Moritz K. A1 - Lemmen, Carsten A1 - Oezkundakci, Deniz A1 - Petzoldt, Thomas A1 - Rinke, Karsten A1 - Robson, Barbara J. A1 - Sachse, Rene A1 - Schep, Sebastiaan A. A1 - Schmid, Martin A1 - Scholten, Huub A1 - Teurlincx, Sven A1 - Trolle, Dennis A1 - Troost, Tineke A. A1 - Van Dam, Anne A. A1 - Van Gerven, Luuk P. A. A1 - Weijerman, Mariska A1 - Wells, Scott A. A1 - Mooij, Wolf M. T1 - Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective JF - Aquatic ecology : the international forum covering research in freshwater and marine environments N2 - Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary. KW - Water quality KW - Ecology KW - Geochemistry KW - Hydrology KW - Hydraulics KW - Hydrodynamics KW - Physical environment KW - Socio-economics KW - Model availability KW - Standardization KW - Linking Y1 - 2015 U6 - https://doi.org/10.1007/s10452-015-9544-1 SN - 1386-2588 SN - 1573-5125 VL - 49 IS - 4 SP - 513 EP - 548 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Musolff, Andreas A1 - Schmidt, Christian A1 - Selle, Benny A1 - Fleckenstein, Jan H. T1 - Catchment controls on solute export JF - Advances in water resources N2 - Dynamics of solute export from catchments can be classified in terms of chemostatic and chemodynamic export regimes by an analysis of concentration-discharge relationships. Previous studies hypothesized that distinct export regimes emerge from the presence of solute mass stores within the catchment and their connectivity to the stream. However, so far a direct link of solute export to identifiable catchment characteristics is missing. Here we investigate long-term time series of stream water quality and quantity of nine neighboring catchments in Central Germany ranging from relatively pristine mountain catchments to agriculturally dominated lowland catchments, spanning large gradients in land use, geology, and climatic conditions. Given the strong collinearity of catchment characteristics we used partial least square regression analysis to quantify the predictive power of these characteristics for median concentrations and the metrics of export regime. We can show that median concentrations and metrics of the export regimes of major ions and nutrients can indeed be inferred from catchment characteristics. Strongest predictors for median concentrations were the share of arable land, discharge per area, runoff coefficient and available water capacity in the root zone of the catchments. The available water capacity in the root zone, the share of arable land being artificially drained and the topographic gradient were found to be the most relevant predictors for the metrics of export regime. These catchment characteristics can represent the size of solute mass store such as the fraction of arable land being a measure for the store of nitrate. On the other hand, catchment characteristics can be a measure for the connectivity of these solute stores to the stream such as the fraction of tile drained land in the catchments. This study demonstrates the potential of data-driven, top down analyses using simple metrics to classify and better understand dominant controls of solute export from catchments. (C) 2015 Elsevier Ltd. All rights reserved. KW - Water quality KW - Catchment KW - Nutrient export KW - Tile drain KW - Export regime KW - Concentration-discharge relationships Y1 - 2015 U6 - https://doi.org/10.1016/j.advwatres.2015.09.026 SN - 0309-1708 SN - 1872-9657 VL - 86 SP - 133 EP - 146 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Sachse, Rene A1 - Petzoldt, Thomas A1 - Blumstock, Maria A1 - Moreira, Santiago A1 - Paetzig, Marlene A1 - Ruecker, Jacqueline A1 - Janse, Jan H. A1 - Mooij, Wolf M. A1 - Hilt, Sabine T1 - Extending one-dimensional models for deep lakes to simulate the impact of submerged macrophytes on water quality JF - Environmental modelling & software with environment data news N2 - Submerged macrophytes can stabilise clear water conditions in shallow lakes. However, many existing models for deep lakes neglect their impact. Here, we tested the hypothesis that submerged macrophytes can affect the water clarity in deep lakes. A one-dimensional, vertically resolved macrophyte model was developed based on PCLake and coupled to SALMO-1D and GOTM hydrophysics and validated against field data. Validation showed good coherence in dynamic growth patterns and colonisation depths. In our simulations the presence of submerged macrophytes resulted in up to 50% less phytoplankton biomass in the shallowest simulated lake (11 m) and still 15% less phytoplankton was predicted in 100 m deep oligotrophic lakes. Nutrient loading, lake depth, and lake shape had a strong influence on macrophyte effects. Nutrient competition was found to be the strongest biological interaction. Despite a number of limitations, the derived dynamic lake model suggests significant effects of submerged macrophytes on deep lake water quality. (C) 2014 Elsevier Ltd. All rights reserved. KW - Lake model KW - Macrophytes KW - Water quality Y1 - 2014 U6 - https://doi.org/10.1016/j.envsoft.2014.05.023 SN - 1364-8152 SN - 1873-6726 VL - 61 SP - 410 EP - 423 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Lischeid, Gunnar A1 - Kalettka, Thomas T1 - Grasping the heterogeneity of kettle hole water quality in Northeast Germany JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - In the young moraine landscape in Northeast Germany, small glacially created ponds, the so-called kettle holes, are very abundant. They exhibit large spatial heterogeneity, seemingly rendering each kettle hole unique. However, this would not be consistent with any scientific approach. Thus, a classification scheme has been developed for kettle holes in Northeast Germany based on morphology, hydrodynamics and connection to stream networks of the kettle holes as well as size, topography and land use of the respective catchment. These indices are assumed to be related both to water quality as well as to biological issues of the kettle holes. Starting in the mid-1990s, an extensive monitoring program has been established in the federal state of Brandenburg, Germany. In this study, a subset comprising 1,316 samples from 79 kettle holes was analysed, where 21 parameters had been determined. Sampling intervals varied widely, and were between bi-weekly and three-monthly at most sites. A nonlinear principal component analysis was performed. The first four components explained 90% of the variance. These components seem to provide quantitative measures of phosphorus release from the sediments during hypoxic periods, agricultural solute input, algae primary production, and geogenic compounds. This allowed differentiating between the natural and anthropogenic impact factors on water quality. In addition, scores of single components were related to properties of the kettle holes and their environments. The results contribute to a better understanding of biological and biogeochemical processes and can be used to verify the effects of conservation and management strategies for kettle holes. KW - Kettle holes KW - Water quality KW - Monitoring KW - Land use KW - Isomap Y1 - 2012 U6 - https://doi.org/10.1007/s10750-011-0764-7 SN - 0018-8158 SN - 1573-5117 VL - 689 IS - 1 SP - 63 EP - 77 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Al-Mashaikhi, K. A1 - Oswald, Sascha Eric A1 - Attinger, Sabine A1 - Büchel, G. A1 - Knöller, K. A1 - Strauch, G. T1 - Evaluation of groundwater dynamics and quality in the Najd aquifers located in the Sultanate of Oman JF - Environmental earth sciences N2 - The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, delta H-2 and delta O-18 variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region. KW - Environmental isotopes KW - Groundwater KW - Najd aquifer KW - Oman KW - Recharge KW - Water quality Y1 - 2012 U6 - https://doi.org/10.1007/s12665-011-1331-2 SN - 1866-6280 VL - 66 IS - 4 SP - 1195 EP - 1211 PB - Springer CY - New York ER -