H. Bormann

Regionalisation concept for hydrological modelling on different scales using a physically based model: Results and evaluation

Abstract A regionalisation concept for hydrological modelling on different scales using a physically based simulation model is presented. It enables us to calculate regional water balances by simulating a limited number of representative ecotopes (=hydro-pedotopes) instead of all units using a physically based model system (soilvegetation-atmosphere-transfer-scheme). Using a cluster analysis the hydrological quantities (e.g. monthly values of actual evapotranspiration, groundwater recharge, surface runoff and interflow of all ecotopes were analysed and groups of similar behaviour defined. For each of these clusters one representative ecotope is chosen. Results of an application of this concept are presented: The water fluxes of a 1000 km2 catchment in Germany were calculated and simulated runoff compared with measured. Simulating selected representative instead of all ecotopes reduces the number of necessary simulation runs by up to 95%. The results suggest that the quality of the simulation is not effected by using representative instead of all ecotopes. Because the data were not aggregated the spatial pattern of properties and fluxes is preserved. In order to evaluate the model results, the uncertainties concerning the data base (e.g. soil map, weather data) and the assumptions included in the regionalisation concept are investigated. Because in this concept no model calibration is performed, the applicability is only limited by the data availability (spatial and temporal resolution). The model shows a reliable hydrological behaviour and is a suitable tool for landscape management.

Effects of data availability on estimation of evapotranspiration

Abstract For computing evapotranspiration, climate data are required in a sufficiently detailed temporal and spatial resolution. Depending on the model approach the necessary temporal resolution varies between one hour and one day. Due to non-linearities in the Penman-Monteith equation it is not possible to compute potential evapotranspiration from mean daily climate data because the results will not equal those based on hourly measured data. Because hourly data are only available on a limited number of climate stations it is important to investigate whether it is possible to disaggregate daily into hourly values. If the disaggregation fails one has to choose another model approach depending on the data available. In this study the actual and the potential evapotranspiration are calculated by a soil vegetation atmosphere transfer model (SVAT) using physically based and empirical approaches and different temporal resolutions of climate data. The quality of the different approaches is evaluated by calculating the differences in evapotranspiration using high resolved locally measured and disaggregated climate data. In addition to the temporal resolution it is studied whether climate data can be transferred from nearby weather stations. The results suggest that the information losses due to disaggregation of daily values are small compared to the spatial variability of the climate data.

Impacts of landscape management on the hydrological behaviour of small agricultural catchments

Abstract Changes of agricultural land use often induce changes of the hydrological behaviour of Catchments. Because only the effects on a few processes are measurable, modelling and simulating the hydrological processes can help to estimate the impact of land use changes on distinct hydrological quantities (e.g. evapotranspiration, groundwater recharge, runoff production, channel runoff). While selecting management measures hydrological models can serve as tools for decision making. Possible aims are the reduction of flood events, guaranteeing the supply of drinking water (amount and quality) and optimising use of irrigation water in agriculture. In order to forecast the effects of management on hydrology a physically based, deterministic model system is applied which consists of two model parts, an one dimensional soilvegetation-atmosphere-transfer model (SVAT) and a distributed catchment model. The sensitivity of the model and its parameters is shown by scenarios whose quantitative model results are transferred to qualitative statements concerning effects of landscape management on hydrology. Especially the effect of land use changes due to EC policy (applying different fallow practices) on the catchment water balance and on the channel runoff (flood events) is investigated, additionally the reestablishment of channels and the impact of plant growth in channels.

The impact of hydrodynamics and texture on the infiltration of rain and marine waters into sand bank island sediments — Aspects of infiltration and groundwater dynamics

Interactions of different hydrological and geophysical processes on an emerging sand bank island are investigated focusing on the example of the Kachelotplate located west of Juist Island, southern North Sea. Measurements of groundwater levels, groundwater salinity, hydraulic conductivity of the sediment and the retention curve as well as the analysis of tide gauge and precipitation data from adjacent islands allow us to develop a conceptual model of the dominant hydrological processes. The main hydrological features are (i) dilution of the brackish groundwater caused by the positive water balance, (ii) infiltration of saline water due to sporadic inundation events during storm tides and (iii) limited lateral flow processes between seawater and groundwater driven by tidal conditions. Hence, from the hydrological point of view the future development of the Kachelotplate sand bank will strongly depend upon the inundation frequency of the sand bank island which will affect the development of a freshwater lens and hence of an environmental milieu suitable for plant development and therefore dune stabilisation.

Regionalization scheme for the simulation of regional water balances using a physically based model system

Abstract The regional simulation of hydrological behaviour is often performed by applying simplified model approaches adapted from the local scale. This is done because averaging the input parameters is not feasible due to the non-linear model behaviour. A region is assumed to be an ensemble of a number of ecotopes (hydrologically homogenous areas). The simulation of all computational units of a region is not possible due to excessive computer cost. A regionalization scheme is presented which enables us to calculate regional water balances by simulating a limited number of representative ecotopes instead of all units using a physically based (not simplified) model system. This concept is based on a cluster analysis of simulation results of theoretical ecotopes (all reasonable combinations of model parameters). The link between these theoretical ecotopes and the real ecotopes, derived by overlaying digital maps, is accomplished by ‘characteristic values’ which are integral measures of the soil hydrological properties (e.g. water available for plants, travel time, height of capillary flux). Simulating selected representative instead of all ecotopes reduces the number of desired simulation runs up to 95% without affecting the quality of the simulation results and without losing the spatial distribution of hydrological properties.

On the Transferability of the Concept of Drinking Water Protection Zones from EU to Latin American Countries

The present study compares different legal texts on the quality of drinking water, the protection of surface waters and the establishment of drinking water protection areas in the European Union and selected countries in Latin America: Argentina, Brazil and Chile. In the context of a case study, carried out for the Argentine drinking water reservoir Paso de las Piedras, current management practice, its deficits in terms of catchment management practice and possible improvements are discussed based on the concept of water protection zones. The comparison of drinking water standards reveals that the regulations in the investigated Latin American countries comply with the standards of the Wold Health Organisation, while some differences are detected compared to the standards defined by the European Union (e.g., use of bulk parameters; individual standards). While within the European Union the definition and establishment of drinking water protection zones is a standard procedure, it is not explicitly suggested by national Latin American Laws. However, establishment of protection zones for drinking water reservoirs is feasible in accordance with water and environmental laws. The case study reveals that enforcement of the respective laws mostly fails. Protection zones are not implemented. Based on the findings, and according to European and German regulations on water protection zones, measures are suggested how to improve the raw water quality in the reservoir. Recommendations are provided for Latin American countries in general.

Towards an Indicator Based Framework Analysing the Suitability of Existing Dams for Energy Storage

The increasing contribution of renewable energy to the total energy supply requires addition storage capacity due to the variable availability of renewable energy sources. Pumped energy storage systems can contribute to this necessary storage by converting electric energy into potential energy of the stored water. Since the investment costs and the ecological as well as social consequences are enormous, the question arises whether existing dams and reservoirs can be used for this purpose. This study analyses relevant characteristics and identifies suitable indicators to be used for the assessment of the suitability of existing dams and reservoirs for installing an additional pumped energy storage system. The indicators encompass physical and environmental characteristics. An impact analysis and a conflict analysis with respect to already existing water uses of single- or multi-purpose dams amend the analysis. Based on the identified indicators and potential conflicts, an indicator based framework is developed describing a strategy to analyse the suitability of existing dams for energy storage, quantifying the physical potentials of a site, considering the environmental restrictions and setting priorities in terms of conflict resolution among competing water uses.

Recommendations for Capacity Development in Water Resources Engineering and Environmental Management in Latin America

Socioeconomic development often causes environmental and water related problems. Any solution requires knowledge, willingness and sufficient financial and technical means. Such capacity is limited in many developing and threshold countries. To identify opportunities for strengthening capacity in water and environmental management, we analysed University curricula, identified synergies between Universities and practice, explored the potential of vocational training and awareness raising, and developed regional concepts for risk communication. The results present ways how Universities can make capacity development in the water sector in Latin America more efficient. We recommend to modernize curricula, to strengthen vocational training, to intensify public involvement and cooperation with practice, and provide methodological advice for implementation.

Modellbasierte Szenarioanalyse zur Anpassung des Entwässerungsmanagements im nordwestdeutschen Küstenraum

Für das Verbandsgebiet des I. Entwässerungsverbandes Emden wurde untersucht, welche Auswirkungen durch den Klimawandel und die Veränderung der Flächennutzung auf das Entwässerungssystem zu erwarten sind. Zukünftig potenziell zu entwässernde Wassermengen wurden quantifiziert und den aufgrund des Meeresspiegelanstiegs abnehmenden Sielkapazitäten gegenübergestellt. Zukünftige Entwässerungsbedarfe konnten abgeschätzt und die Zukunftstauglichkeit der vorhandenen Entwässerungsinfrastruktur bewertet werden.

Hydrology of (shallow) Coastal Regions

The water cycle of coastal regions is characterized by the interplay between the different hydrological processes. It can be described by the general water balance equation of a system, quantifying the change of water in a defined area.