Parameterization and regionalization of redox based denitrification for GIS-embedded nitrate transport modeling in Pleistocene aquifer systems

Merz, Christoph; Steidl, Jörg; Dannowski, Ralf

doi:10.1007/s00254-008-1665-6

Cited by 33 publications

(16 citation statements)

References 27 publications

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“…These largely confined aquifers are characterised by low flow velocities, long groundwater residence times and strongly anaerobic conditions due to thick covering till layers and are therefore well protected against contamination (Wendland et al 2008, Merz et al 2009. Merz et al (2009) also describe aerobic areas in groundwater recharge regions with high NO 3 concentrations, which only in places are identified by the predictions of the RF NO3 model. However, predictions are accompanied by rather high uncertainties, so that higher concentrations are at least within the confidence limits of the model.…”

Section: Discussionmentioning

confidence: 99%

Nation-wide estimation of groundwater redox conditions and nitrate concentrations through machine learning

Knoll

Bach

2020

Environ. Res. Lett.

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The protection of water resources and development of mitigation strategies require large-scale information on water pollution such as nitrate. Machine learning techniques like random forest (RF) have proven their worth for estimating groundwater quality based on spatial environmental predictors. We investigate the potential of RF and quantile random forest (QRF) to estimate redox conditions and nitrate concentration in groundwater (1 km × 1 km resolution) using the European Water Framework Directive groundwater monitoring network as well as spatial environmental information available throughout Germany. The RF model for nitrate achieves a good predictive performance with an R 2 of 0.52. Dominant predictors are the redox conditions in the groundwater body, hydrogeological units and the percentage of arable land. An uncertainty assessment using QRF shows rather large uncertainties with a mean prediction interval (MPI) of 53.0 mg l −1 . This study represents the first nation-wide data-driven assessment of the spatial distribution of groundwater nitrate concentrations for Germany.

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Section: Discussionmentioning

confidence: 99%

Nation-wide estimation of groundwater redox conditions and nitrate concentrations through machine learning

Knoll

Bach

2020

Environ. Res. Lett.

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“…Sediment types deposited over the study area consist of a range of clastic sediments of glacial fluvial origin and till. Typically, permeable and porous sands form aquifer bodies, and more impermeable and lower conductivity till beds consisting of clay, silt, and calcium‐containing sands forming predominantly aquitards (Ehlers, Grube, Stephan, & Wansa, ; Merz & Pekdeger, ; Merz, Steidl, & Dannowski, ).…”

Section: Methodsmentioning

confidence: 99%

Characterizing hydrological processes within kettle holes using stable water isotopes in the Uckermark of northern Brandenburg, Germany

Vyse

Semiromi

Lischeid

et al. 2020

Hydrological Processes

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Understanding the hydrologic connectivity between kettle holes and shallow groundwater, particularly in reaction to the highly variable local meteorological conditions, is of paramount importance for tracing water in a hydro(geo)logically complex landscape and thus for integrated water resource management. This article is aimed at identifying the dominant hydrological processes affecting the kettle holes' water balance and their interactions with the shallow groundwater domain in the Uckermark region, located in the north-east of Germany. For this reason, based on the stable isotopes of oxygen (δ 18 O) and hydrogen (δ 2 H), an isotopic mass balance model was employed to compute the evaporative loss of water from the kettle holes from February to August 2017.Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region.Based on the calculated evaporation/inflow (E/I) ratios, most of the kettle holes (86.7%) were ascertained to have a partially open, flow-through-dominated system. Moreover, we identified an inverse correlation between E/I ratios and the altitudes of the kettle holes. The same holds for electrical conductivity (EC) and the altitudes of the kettle holes. In accordance with the findings obtained from this study, a conceptual model explaining the interaction between the shallow groundwater and the kettle holes of Uckermark was developed. The model exhibited that across the highest altitudes, the recharge kettle holes are dominant, where a lower ratio of E/I and a lower EC was detected. By contrast, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and EC could be identified. The kettle holes existing in between were categorized as flow-through kettle holes through which the recharge takes place from one side and discharge from the other side. K E Y W O R D S evaporation, groundwater inflow, kettle hole, stable water isotope, surface-groundwater interactions

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“…3). Much of that heterogeneity can be ascribed to the enormous heterogeneity of unconsolidated sediments (Merz et al 2009) and soils in this Pleistocenic landscape, ranging from coarse sandy soils to clayey loam soils. In addition, erosion processes resulted in substantial spatial heterogeneity at the range of a few 10 m as well (Sommer et al 2008).…”

Section: Groundwater Head and Surface Water Levelmentioning

confidence: 99%

Forensic hydrology: what function tells about structure in complex settings

et al. 2016

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Facing the challenges of the European Water Framework Directive and competing demands requires a sound knowledge of the hydrological system. This is a major challenge in regions like Northeast Germany. The landscape has been massively reshaped during repeated advances and retreats of glaciation during the Pleistocene. This resulted in a complex setting of unconsolidated sediments with high textural heterogeneity and with layered aquifer systems, partly confined, but usually of unknown number and extent of single aquifers. The Institute of Landscape Hydrology aims both at a better understanding of hydrological processes and at providing a basis for sustainable water resources management in this region. That would require sound information about the respective regions of interest that are rarely available at sufficient degree of detail. Thus, there is urgent need for alternative approaches. For example, time series of groundwater head, lake water level and stream runoff do not only depend on (unknown) geological structures, but in turn can reveal information about major geological features. To that end, different approaches have been developed and successfully applied at different scales, based both on advanced time series analysis and dimension reduction approaches and on well-known and rather simple methods. This approach has been coined ''forensic hydrology'': Like in a crime story, numerous pieces of evidence are combined in a systematic way to end up with a consistent conceptual model about the prevailing cause-effect relationships. An example is given for the Quillow catchment in Northeast Germany in a rather complex geological setting.

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Parameterization and regionalization of redox based denitrification for GIS-embedded nitrate transport modeling in Pleistocene aquifer systems

Cited by 33 publications

References 27 publications

Nation-wide estimation of groundwater redox conditions and nitrate concentrations through machine learning

Nation-wide estimation of groundwater redox conditions and nitrate concentrations through machine learning

Characterizing hydrological processes within kettle holes using stable water isotopes in the Uckermark of northern Brandenburg, Germany

Forensic hydrology: what function tells about structure in complex settings

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