Mass fluxes of xenobiotics below cities: challenges in urban hydrogeology

Urban areas are the focus of major ecological, social and economical activity. They are thus also prime locations of increasing conflict with regard to water use and water protection. As a direct and/or indirect consequence of urban land use and human activity, urban water systems are frequently polluted with organic contaminants including waste water-born xenobiotics such as pharmaceuticals, personal care products (collectively known as PPCPs) and endocrine-active substances. This study reviews new integrated methodologies including flux calculations as well as chemical investigations for determining the impact of human activities on urban water systems and on processes within the urban watershed. The use of indicator substances, representing different contaminant sources and pathways, integral pumping tests and mass balance approaches are suitable alternatives within these environments. The issues are explored using contaminant mass balance examples from Halle/Saale and Leipzig, German

Improving water management education across the Latin America and Caribbean region

Education can help secure inclusive and resilient development around water resources. However, it is difficult to provide the latest science to those managing water resources (both now and in the future). Collectively, we hypothesize that dissemination and promotion of scientific knowledge using students as central agents to transfer theoretical knowledge into practice is an efficient way to address this difficulty. In this study, we test this hypothesis in the Latin America and Caribbean (LAC) region as a representative case study region. First, we use a literature review to map a potential gap in research on education around water resources across the LAC region. We then review potential best practices to address this gap and to better translate water resources education techniques into the LAC region. Integral to these efforts is adopting students as agents for information transfer to help bridge the gap between the global state-of-the science and local water resources management. Our results highlight the need to establish a new standard of higher educational promoting exchange between countries as local populations are vulnerable to future shifts in climate at global scales and changes in land usage at regional scales. The new standard should include peer-to-peer mentoring achieved by jointly exchanging and training students and practitioners in water management techniques, increasing access to water data and pedagogic information across the region, and lowering administration roadblocks that prevent student exchange

A new scenario free procedure to determine flood peak changes in the Harz Mountains in response to climate change projections

Study area: Six catchments of different hydrological characteristics in the Harz Mountains, Germany. Study focus: A new scenario free method for determining changes of flood peaks considering climate change is developed. Compared to existing methods, it accounts for heavy rainfall changes by a newly developed factor with two seasons and establishes a numerical relationship to a greater number of relevant climate predictors. For easier application, it is based on frequently available daily measurements. A functional test of the factor for heavy rainfall changes and its adjustment algorithm for the precipitation time series is performed. Using a regional AR5 ensemble, for the first time the error and the uncertainty of a new scenario free method are estimated and compared with an existing method. The new method is applied in the Harz Mountains, where the sensitivity of the region to different climate predictors is investigated. New hydrological insights for the region: The adjusting algorithm for precipitation is able to adjust the time series while maintaining mass balance. The new method has a lower error than the reference method, with better matches of changes in the median of the climate ensemble as well as the most ensemble members. In general, the uncertainty of the seasonal results is below the climate uncertainty of the AR5 ensemble. Regarding future flood peaks, the regional catchments are most sensitive to mean precipitation changes, followed by heavy rainfall changes especially in the winter season. Mean temperature changes are of minor significance, but the catchments characteristics are important. The new method can be recommended for assessments of climate change impacts on floods in low to average mountain regions in Germany and Europe

Daily vs. hourly simulation for estimating future flood peaks in mesoscale catchments

Daily hydrological models are commonly used to study changes in flood peaks due to climate change. Although they often lead to an underestimation of absolute floods, it is assumed that future flood peaks in smaller mesoscale catchments are less underestimated when examining the relative change signal of floods. In this study, the applicability of this hypothesis is investigated by comparing the results of a daily hydrological model set, calibrated on runoff hydrographs, with an hourly model set calibrated on flood peak distributions. For analysis, a daily RCP8.5 climate model ensemble is disaggregated to hourly values and the runoff is simulated on a daily and hourly basis for six mesoscale catchments in Central Germany. Absolute floods and relative flood changes are compared between both model sets. The results show significant differences between the absolute floods of both model sets, in most cases caused by underestimations due to the daily modeling process. In contrast, the differences between the two model sets are not significant for the relative change signal of the floods, especially for higher return periods. To improve results in climate studies with coarse modeling time step, the use of relative change signal of floods instead of absolute values is recommended

Small hydrological research basins in Germany

Small research basins are hotspots of hydrological research. They are extensively equipped to measure different hydrological parameters with high temporal and spatial resolution. The resulting data are the basis for the identification of regional basin characteristics and hydrological processes, statistical analyses, model development and parameter identification. Altogether these comprehensive research activities address a wide range of objectives and goals, such as analyses of initial landscape genesis, water and nutrient balance, or current climate projections on runoff patterns. The German IHP/HWRP working group "FRIEND/ERB" supports such research activities in small hydrological basins in Germany and contributes to UNESCO’s International Hydrological Program (IHP) as well as the Hydrology and Water Resources Program (HWRP) of WMO. Its focus is on catchments smaller than 50km²with continuous data acquisition of time series longer than 5 years. They are operated by universities, environmental authorities and other research institutions. This presentation illuminates the German research in selected small hydrological research basins ranging in size from 0.06 km² to 50 km². It summarizes the objectives, measured variables and chosen methodical aspects. Continuous measurements at the respective gauges will in future be more and more supplemented by spatially and temporally higher resolution measurement campaigns. The advancement of sensor and IT technologies promotes a continuous increase in data volumes, allowing for more precise and specific analyses and predictions as well as the possibility of a better understanding of the prevailing hydrological processes including their spatio-temporal variability. But often this requires the development of new evaluation methods. The use of models supports these goals. Scenarios allow the evaluation of different land use and management strategies and of possible impacts caused by climate change.The evaluation of the German IHP/HWRP working group "FRIEND/ERB" emphasises an increasing need for high resolution measurements and long time series as well as regular updates of all research activities in small hydrological basins. Only their continuation will also in future provide valuable contributions to research, teaching and the management of environmental problems. Their integration into a research network increases the efficiency of the activities and provides opportunities for joint evaluations

Application of integral pumping tests to investigate the influence of a losing stream on groundwater quality

Losing streams that are influenced by wastewater treatment plant effluents and combined sewer overflows (CSOs) can be a source of groundwater contamination. Released micropollutants such as pharmaceuticals, endocrine disrupters and other ecotoxicologically relevant substances as well as inorganic wastewater constituents can reach the groundwater, where they may deteriorate groundwater quality. This paper presents a method to quantify exfiltration mass flow rates per stream length unit Mex of wastewater constituents from losing streams by the operation of integral pumping tests (IPTs) up- and downstream of a target section. Due to the large sampled water volume during IPTs the results are more reliable than those from conventional point sampling. We applied the method at a test site in Leipzig (Germany). Wastewater constituents K+ and NO3− showed Mex values of 1241 to 4315 and 749 to 924 mg mstream−1 d−1, respectively, while Cl− (16.8 to 47.3 g mstream−1 d−1) and SO42− (20.3 to 32.2 g mstream−1 d−1) revealed the highest observed Mex values at the test site. The micropollutants caffeine and technical-nonylphenol were dominated by elimination processes in the groundwater between upstream and downstream wells. Additional concentration measurements in the stream and a connected sewer at the test site were performed to identify relevant processes that influence the concentrations at the IPT wells.ISSN:1027-5606ISSN:1607-793