The Soil and Water Assessment Tool (SWAT) has been applied to the Ic watershed, Brittany, France, to evaluate scenarios for reduction of nitrate in stream water. For the simulated period the model showed fair results with a mean index of agreement of 0.64 at the watershed outlet for discharge and nitrate loads. The management goal for the watershed is the meeting of drinking water threshold at the watershed outlet. An analysis of observed data revealed that nitrate loads would have to be reduced by at least 17% on average to reach that goal. Scenarios investigated cover fertilizer reduction and the introduction of wetland buffer zones. Decreased nitrogen inputs were realized on a) selected subbasins and b) all agricultural fields; wetlands were placed at three model subbasins. Most effective measures were a 50% fertilizer decrease on selected subbasins resulting in a range of 13 22 % reduction of nitrate loads with a high uncertainty. Consequently, none of the tested measures is likely to achieve a sufficient reduction. Combined measures such as enhanced fertilizer management and concurrent introduction of wetlands seem to be the most promising way to approach the drinking water threshold.

The MIA-CSO project is currently led by the department “Point and non.point source pollution control of surface water” in the KWB. Its overall objective is to develop a model-based planning instrument for impact based CSO control. To that aim, an integrated monitoring in the river Spree and in the Berlin sewer system will be carried out in order to calibrate two numerical models before they are used for CSO impact assessment. A module shall be developed to allow the statistical analysis of the model results. This module will be based on Uncertainty and Sensitivity Analysis (UA and SA). The principle of such analysis is to investigate the effects of model input uncertainties on model outputs: UA establishes a mapping of model assumption into model inferences and SA is the study of how uncertainty in a model output can be apportioned to different sources of uncertainty in the model inputs. This study focuses on Sensitivity Analysis. First of all, four of the main SA techniques are described and explained mathematically. The first technique is a screening method called the Morris algorithm. This qualitative method allows one to classify the inputs in order of importance. The most important ones can then be selected for further study. Furthermore, this technique gives an idea of the linearity or nonlinearity of the effects for every input. The second technique, based on Regression Analysis, works under the assumption that the model is linear or monotonous. It gives a qualitative indication of the relative effects of each input. The third and fourth techniques, called Fourier Amplitude Sensitivity Test and the Sobol’ method, aim at calculating indicators of the relative effects of each input, called the sensitivity effects. They work without any assumption on the model and they can traduce the effects of interactions between the model inputs. Using the free software SimLab, three methods are tested in this study: Morris, FAST and Sobol’. They are applied on catchment Berlin XII in Friedrichshain, under the framework of ATV-A 128, a linear, empirical model used for designing storage tanks in combined sewer systems. After a calibration step, rules are expounded in order to define how to use these techniques and how to have reliable results. Then, the Sensitivity Analysis itself is performed for Berlin XII. Among the nine inputs of interest, the Morris screening allows to choose the four most important ones (the CODconcentration in the wastewater, the COD-concentration in the rainwater, the specific water need and the total impervious area). While the five other inputs are considered constant, FAST and Sobol’ are performed and give the exact relative effects of the four inputs. It appears that two inputs are more important than the two others. For these inputs (COD-concentration in the rainwater and specific water need), further uncertainty study should be done and the lack of data should be corrected.

During the ISM study in the year 2007 first water quality simulations of the Berlin river Spree (stretch Charlottenburg) under consideration of combined sewer overflows (CSO) from the drainage system had been carried out. The period of September 2005 was simulated. A good correlation of simulation results with water quality measurements could only be observed for those days where the model boundary conditions were clearly defined (spot samples at the inflowing streams). However, these spot samples are carried out only once a month. Given the simulation period of one month and the temporal resolution of 15 minutes this data availability for the inflowing streams is not sufficient. Even more, some parameters had to be assessed entirely since no measurements were available. The data situation was especially critical for the inflow of the Landwehrkanal into the river Spree. No continuous measurement data was available for the following parameters: water temperature, oxygen content, pH and conductivity. For these parameters hydrographs had been assumed according to those at gauge Mühlendammschleuse with an offset calculated by the difference between the spot sampling at Landwehrkanal and the continuous values at Mühlendammschleuse. Furthermore, during the simulations within the ISM study a second storm event with overflows could not be considered since the simulation of the drainage system (software INFOWORKS CS) carried out by Berliner Wasserbetriebe was not yet available. The objective of the water quality simulations carried out within SAM-CSO was to take into account the full boundary conditions for the Landwehrkanal (continuous data now available). By comparison with the former simulation results the relevance of the inflow Landwehrkanal on the processes in the river Spree is shown. A second simulation was carried out with meteorological data of high temporal resolution. Former simulations were conducted with daily averages for e.g. air temperature, wind speed, etc. The influence of the temporal resolution of the input data on the diurnal hydrographs of different water quality parameters was analysed (focus on water temperature and dissolved oxygen). Finally, for the last simulation the data for the additional CSO event on 16-17 September 2005 was used (simulated by Berliner Wasserbetriebe with INFOWORKS CS). The results show that considering meteorological data of high temporal resolution and continuous data for the boundary condition Landwehrkanal have a significant influence on the quality of the water quality simulation results for river Spree, especially for the parameters oxygen content, pH and conductivity. Now, for September 2005 simulation results are available that are based on the best set of data that is currently available for the studied river stretch.

Eine optimierte Abwasserbehandlung führte seit den 1990er Jahren zu stark abnehmenden, kontinuierlich aus Punktquellen in die Vorfluter eingeleiteten Nährstofffrachten (HEINZMANN, 1998, SENSTADT, 2001), wodurch sich die Wasserqualität der aufnehmenden Gewässer Berlins merklich verbesserte. Episodische Belastungen durch Mischwasserentlastungen stellen jedoch weiterhin eine bedeutende Ursache einer herabgesetzten Wasser- und Sedimentqualität und eine der wichtigsten Managementaufgaben für die Berliner Stadtspree und der Kanäle dar (vgl. LESZINSKI ET AL., 2006, RIECHEL 2009). Hinsichtlich des von der EU-WRRL geforderten guten ökologischen und chemischen Zustandes der Binnengewässer bzw. des guten ökologischen Potenzials für stark veränderte und künstliche Gewässer, stellt die Lebensraumfunktion für die aquatischen Lebensgemeinschaften der Berliner Gewässer das wesentliche gewässerinterne Schutzziel dar. Neben dem erheblichem ökologischen Gefährdungspotenzial, das insbesondere von extremen Ereignissen der Mischwasserentlastung ausgeht, reduzieren vorrangig hydromorphologische Defizite (Stauhaltung, Uferbefestigung, Sohleintiefung, etc.) die Lebensraumqualität für die aquatischen Lebensgemeinschaften. Aufgrund der Schifffahrtsnutzung der Berliner Spree und der Kanäle stellen Wellenschlag und Sunk- und Schwalleffekte während Schiffspassagen eine zusätzliche, bedeutende Belastung dar (vgl. LESZINSKI ET AL., 2006). Wie in der Studie „Immissionsorientierte Bewertung von Mischwasserentlastungen in Tieflandflüssen“ (LESZINSKI ET AL., 2007) dargelegt, liegen die in Laboruntersuchungen ermittelten Ansprüche bzw. Toleranzen hinsichtlich der Wasserqualität für die Fischarten und Arten wirbelloser Bodenorganismen der Berliner Spree und der Kanäle in einem vergleichbaren Bereich (JACOB ET AL., 1984, LAMMERSEN, 1997). Die Herleitung von Gütestandards hinsichtlich der Wasserqualität für die Fischfauna schließt somit den Schutz der Lebensgemeinschaft der wirbellosen Bodenorganismen mit ein. Ebenso besteht bei beiden Organismengruppen ein grundsätzlicher, vergleichbarer funktioneller Zusammenhang zwischen der Ausprägung der Lebensgemeinschaft und der hydromorphologischen und strukturellen Lebensraumausstattung des Gewässers (z.B. SHELDON, 1968, KARR & SCHLOSSER, 1978, MINSHALL, 1984; MINSHALL & ROBINSON, 1998, TANIGUCHI & TOKESHI, 2004). So korrelieren Artenzahl und Diversität beider Organismengruppen höchst signifikant negativ mit dem Ausbaugrad der Ufer. Als Resultat der verschiedenen Belastungen findet sich in der Berliner Stadtspree eine extreme Dominanz von wenigen sehr anspruchslosen, toleranten Arten. Folglich sind Verbesserungen des ökologischen Zustandes und des Besiedlungspotenzials für wirbellose Bodenorganismen und Fische neben der Reduzierung der negativen Auswirkungen der Mischwasserentlastung, vorrangig durch Aufwertung der Uferstrukturen zu erreichen. Strukturelle Aufwertungen der Ufer müssen zusätzlich die hydrodynamische Belastung durch den schiffsinduzierten Wellenschlag berücksichtigen, um einerseits das Besiedlungspotenzial zu erhöhen, andererseits die Ufer vor Erosion zu schützen. Die vorliegende Studie gibt Hinweise auf die Möglichkeiten und Grenzen einer Revitalisierung der Berliner Stadtspree und der Kanäle am Beispiel der Fischfauna, indem sie die wesentlichen Belastungen und deren Auswirkungen skizziert. Potenzielle Maßnahmen zur Aufwertung der Uferstruktur sollten aufgrund der oben angesprochenen sehr ähnlichen Wirkmechanismen zwischenUmweltausprägungen und Zusammensetzung der Lebensgemeinschaften beiden, wirbellosen Bodenorganismen und Fischen, zu Gute kommen. Zur Beurteilung möglicher struktureller Maßnahmen wird zunächst davon ausgegangen, dass die negativen Auswirkungen der Mischwasserentlastung derart minimiert werden können, dass sie keine akute Beeinträchtigung der Wasserqualität und der aquatischen Lebensgemeinschaften mehr verursacht. Des Weiteren soll beurteilt werden, ob durch solche Maßnahmen ein Lebensraum für Fischarten geschaffen werden kann, die höhere Ansprüche an die Sauerstoffbedingungen im Gewässer haben als die aktuelle Lebensgemeinschaft.

An international review of the market, current practices and R&D projects on the topic of rainwater harvesting management was performed. The review highlighted leading countries in different regions of the world, but also the variety of practices and acceptance. Current R&D issues and further research needs are identified and discussed. The application of RWHM techniques at household level seems to be mature, but sanitary risks exist when rainwater is used inside homes and also reserve on economical an environmental aspects can be drawn when drinking water supply is available. Promising concepts are being developed and demonstrated at larger scale such as industrial or commercial buildings or even urban catchments where the use of rainwater and the operation of the systems are under full control. For schemes of this scale, the integration and optimization of several beneficial aspects such as –traditionally- additional water supply and stormwater management, but also urban planning with water and green spaces, energy compensation in buildings and in the cities or ecological enhancement seems to be promising. Specific expertise will be required to best plan these schemes according to the local conditions and targets and to operate, maintain and upgrade them over their entire life time.

Well biofouling is a complex and not yet sufficiently understood process. Water wells represent a unique habitat, since they create a link between the anaerobic ground water containing Fe(II) and the aerobic surface. This groundwater is rich in soluble Fe(II) and the presence of trace amounts of free oxygen in the well screens presents ideal conditions for the growth of iron bacteria. The ochreous deposits produced block not only the filter area, but also the adjacent gravel pack or even parts of the aquifer, and result in a steady decrease of well performance. In this project, the bacterial communities of several Berlin wells have been compared using standard microscopic techniques and molecular techniques like DGGE. The aim of this study is to identify the responsible bacteria and associated processes that lead to well clogging. The sampling system allows easy and effective collection of undisturbed biofilm samples with minimal impact on normal well operation. Fingerprinting analysis indicates the presence of bacterial populations that are ubiquitous in the wells and certain indicator bacteria which can be found in only few wells. Free water and biofilm populations show distinct similarities. Some well populations can be grouped in clusters, depending on the location of the well. Further comparison with chemical data of the wells is planned to asses the impact of chemical conditions of the respective groundwater on the bacteria responsible for clogging. A sampling device was designed and built for exposure of carrier materials into different Berlin drinking water abstraction wells. In addition, samples from well components (pumps and pipes) and water samples were collected. The DNA was extracted using the FastDNA SPIN Kit for Soil (MP). 16S rDNA polymerase chain reaction (PCR) of the V3 region and denaturing gradient gel electrophoresis (DGGE) analyses were performed on the DNA samples (Muyzer et al., 1993).

The overall objective of MIA-CSO is to develop a model-based planning instrument for impact based CSO control. The objective of this study was to examine the potential and the drawbacks of different model coupling techniques that may be taken into account within the MIA-CSO project.