Ralf Kunkel

The GROWA98 model for water balance analysis in large river basins—the river Elbe case study

Abstract An area differentiated water balance analysis in the river Elbe basin (German part) for the hydrological period 1961–1990 was carried out using the GROWA98 model. The mean long-term total runoff was modelled as a function of the regional interaction of the site conditions climate, soil, geology, topography and land use. The total runoff was separated into the direct runoff (interflow and surface runoff) and groundwater runoff (base flow) using base-flow indices, depending on area characteristics (e.g. geology, depth for groundwater). In this way, the regional dominant runoff components, i.e. pathways for the displacement of nutrients from soil to surface water were identified. The model results were validated by comparing the calculated runoff levels with measured data from 120 sub-basins of the river Elbe-catchment area. In general, the differences between modelled and measured runoff values were less than 15%, indicating the reliability of the chosen procedure. This allows further model applications, e.g. for the quantification of the diffuse nutrient input into groundwater and surface waters differentiated to the runoff components.

New phenomena in homoepitaxial growth of metals

The growth of Pt(111) by Pt vapour deposition is studied by He diffraction as a function of substrate temperature and deposition rate. At a deposition rate of about 2.5×10−2 monolayers/second several growth modes are observed: layer-by-layer (2D-) growth at 450 K≲Ts≲800 K, multilayer (3D-) growth at 340 K≲Ts≲450 K and reentrant layer-by-layer (2D-) growth at Ts≲340 K. The observed growth modes and in particular the reentrant 2D-growth are shown to be characteristic of growing Pt(111) under clean conditions, i.e. not influenced by contaminants. The influence of the intra- and interlayer mass transport on the growth mode is discussed in the light of experimental and simulation results. The 3D-growth mode is attributed to the existence of an activation barrier which suppresses the descent of adatoms from the top of the growing adatom islands onto the lower terraces. The barrier can be overcome by thermal adatoms at Ts≳450 K enabling interlayer mass transport which leads to 2D-growth. The reentrant 2D-growth occurs due to a break down of this barrier for small, irregularly shaped islands.

Model based impact analysis of policy options aiming at reducing diffuse pollution by agriculture—a case study for the river Ems and a sub-catchment of the Rhine

Abstract In this paper an integration of the agricultural economic model RAUMIS with the hydrological models GROWA98 and WEKU is presented. The focus lies on an area wide, regionally differentiated, consistent link-up between the indicator “nitrogen balance surplus” and nitrogen charges into surface waters. The model network is used to analyze the status quo situation in the year 1999 for two river catchments in Germany that feature very distinct natural and socio-economic conditions. Regarding agriculture, the study areas include regions with specializations in cash crops, in intensive livestock featuring high nitrogen surplus, and extensive livestock production on permanent grassland. Due to regionally varying hydrological conditions quite different shares of agricultural nitrogen surpluses ranging from 25 to 92% enter surface waters. Furthermore, impacts of alternative nitrogen reduction measures namely a limitation of livestock density and a tax on mineral nitrogen are quantified. Measures of the nitrogen reduction potential and costs in terms of agricultural income forgone are taken into account in the assessment. Results regarding the effects of restricting the livestock density or tax mineral nitrogen highlight that the mitigation of diffuse water pollution problems requires regionally tailored measures.

On the shape of the in-phase TEAS oscillations during epitaxial growth of Pt(111)

The growth of Pt(111) from its vapour phase is investigated by means of TEAS (thermal energy atom scattering) in a wide range of substrate temperatures: 100-800 K. The evolution of the in-phase He specular peak height during Pt deposition is studied in particular. At higher substrate temperatures (T s >500 K), the in-phase peak height exhibits longlived temporal oscillations with a clearly asymmetric shape. This asymmetry, which increases with temperature, reveals substantial coarsening of the adatom islands during monolayer deposition, most likely due to Ostwald ripening processes.

TEODOOR: a distributed geodata infrastructure for terrestrial observation data

Within the TERENO initiative, four terrestrial observatories, collecting huge amounts of environmental data, are being set up since 2008. To manage, describe, exchange and publish these data, the distributed Spatial Data Infrastructure TEODOOR (http://www.tereno.net) was created. Each institution responsible for an individual observatory sets up its own local data infrastructure, which may communicate with each other to exchange data and metadata internally or to the public by OGC compliant Web services. The TEODOOR data portal serves as a database node to provide scientists and decision makers with reliable and well-accessible data and data products. Various tools like hierarchical search or Web-GIS functions allow a deeper insight into the different observatories, test sites and sensor networks. Sensor data can be queried and selected for measured parameters, stations and/or time periods, and can be visualized and downloaded according to a shared TERENO data policy. Currently, TEODOOR provides free access to data from more than 500 monitoring stations.

Integrated Agricultural and Hydrological Modeling within an Intensive Livestock Region

An interdisciplinary model network consisting of the regional agricultural economic model RAUMIS and the hydro(geo)logical models GROWA/WEKU is used to analyze the effect of different scenarios of maximum agricultural nitrogen balance surplus on water quality. The study area is the federal state of Lower Saxony, Germany, which features heterogeneous natural site conditions as well as agricultural production structures. A focus of the study is the modeling of supra-regional manure transports that, according to the models results, considerably increase due to a lowering of maximum nitrogen balance surpluses. The assessment of the examined nitrogen reduction measures reveals that adequate indicators have to be applied. In this regard, the model results show that even though the analyzed measure leads to a substantial overall reduction of agricultural nitrogen surpluses, nitrogen discharges into surface and groundwater can regionally increase.

Forecasting the effects of EU policy measures on the nitrate pollution of groundwater and surface waters

We used the interdisciplinary model network AGRUM [corrected] to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area differentiated (100 m x 100 m) approach. AGRUM [corrected] combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. For areas showing predicted nitrate concentrations in percolation water above the European Union (EU) groundwater quality standard of 50 mg NO3-N/L, effective agri-environmental reduction measures need to be derived and implemented to improve groundwater and surface water quality by 2015. The effects of already implemented agricultural policy are quantified by a baseline scenario projecting the N-surpluses from agricultural sector to 2015. The AGRUM [corrected] model is used to estimate the effects of this scenario concerning groundwater and surface water pollution by nitrate. From the results of the model analysis the needs for additional measures can be derived in terms of required additional N-surplus reduction and in terms of regional prioritization of measures. Research work will therefore directly support the implementation of the Water Framework Directive of the European Union in the Weser basin.

Q-SOS—A Sensor Observation Service for Accessing Quality Descriptions of Environmental Data

The worldwide Sensor Web comprises observation data from diverse sources. Each data provider may process and assess datasets differently before making them available online. This information is often invisible to end users. Therefore, publishing observation data with quality descriptions is vital as it helps users to assess the suitability of data for their applications. It is also important to capture contextual information concerning data quality such as provenance to trace back incorrect data to its origins. In the Open Geospatial Consortium (OGC)’s Sensor Web Enablement (SWE) framework, there is no sufficiently and practically applicable approach how these aspects can be systematically represented and made accessible. This paper presents Q-SOS—an extension of the OGC’s Sensor Observation Service (SOS) that supports retrieval of observation data together with quality descriptions. These descriptions are represented in an observation data model covering various aspects of data quality assessment. The service and the data model have been developed based on open standards and open source tools, and are productively being used to share observation data from the TERENO observatory infrastructure. We discuss the advantages of deploying the presented solutions from data provider and consumer viewpoints. Enhancements applied to the related open-source developments are also introduced.

Projected impact of climate change on irrigation needs and groundwater resources in the metropolitan area of Hamburg (Germany)

Irrigated agriculture is an important economic factor in the rural parts of the metropolitan area of Hamburg. It is commonly expected that climate change will reduce the groundwater quantities available for field irrigation. Against this background, the ratio of irrigation need and groundwater recharge (IGR-ratio) is suggested as an indicator to assess climate change impacts on the vulnerability of groundwater resources towards overexploitation by agricultural irrigation. The IGR-ratio has been assessed based on the distributed water balance model mGROWA, i.e. under consideration of the simulated groundwater recharge levels and the field crop-specific irrigation need of the commonly cultivated field crops. The spatial IGR-ratio distribution determined for the observed reference period 1971–2000 has shown that the delineated vulnerable areas coincide with the regions for which high irrigation quantities have been documented at present. Additionally, the IGR-ratio depicts the areas in which irrigation is currently still negligible, but in which the introduction of irrigation into agricultural practice would lead to an immediate overexploitation of the sustainably available groundwater budget. The possible impact of future climate on IGR-ratios was determined by using a model chain of mGROWA and the regional climate models REMO and WETTREG2010. The related ensemble simulations did not provide a uniform tendency of possible future IGR-ratio changes. Whereas the mGROWA–WETTREG2010 realisations projected a very high increase in the IGR-ratios, the mGROWA–REMO realisations did not show a pronounced trend of increasing IGR-ratios. Therefore, considerable uncertainties remain regarding the future bandwidth of IGR-ratio changes.

Conception and Implementation of an OGC-Compliant Sensor Observation Service for a Standardized Access to Raster Data

The target of the Open Geospatial Consortium (OGC) is interoperability of geographic information, which means creating opportunities to access geodata in a consistent, standardized way. In the domain of sensor data, the target will be picked up within the OGC Sensor Web Enablement Initiative and especially reached through the Sensor Observation Service (SOS) standard. This one defines a service for a standardized access to time series data and is usually used for in situ sensors (like discharge gauges and climate stations). Although the standard considers raster data, no implementation of the standard for raster data exists presently. In this paper an OGC-compliant Sensor Observation Service for a standardized access to raster data is described. A data model was developed that enables effective storage of the raster data with the corresponding metadata in a database, reading this data in an efficient way, and encoding it with result formats that the SOS-standard provides.