Freie Universität Berlin Department of Earth Sciences Institute of Geographical Sciences Master thesis Impact Assessment of Floating Houses on Water Temperature and Dissolved Oxygen in Himpenser Wielen, Leeuwarden (Netherlands) Janko Lenz Matriculation number: 4958994 Berlin, 29.01.2018 2 Impact Assessment of Floating Houses on Water Temperature and Dissolved Oxygen in Himpenser Wielen, Leeuwarden (Netherlands) by Janko Lenz in fulfillment of the requirements for the degree of Master of Science Geographical Sciences, area of concentration “Environmental Hydrology” at the Freie Universität Berlin First Supervisor: Prof. Dr. Achim Schulte, Freie Universität Berlin Second Supervisor: Prof. Dr. Ir. Floris Boogaard, Hanze University of Applied Science Groningen 3 4 Abstract Large floating structures have the potential to overcome the challenge of land scarcity in urban areas. They offer opportunities for energy and food production or even habitation. On the other hand they influence the physical and chemical characteristics and hence living conditions in the water body they are floating in. A monitoring of these impacts is needed to enable the development of building legislation on future construction projects. For the present thesis floating houses at Himpenser Wielen in Leeuwarden (Netherlands) were selected, were a measurement campaign was carried out in autumn 2017. Two multi- parameter probes were utilized for monitoring of water temperature and dissolved oxygen content. Pioneering work was a 10-day measurement under a floating house. Vertical temperature profiles were recorded to detect differences in heat transport. Additionally an underwater drone was used for investigation of mussels and macrophytes underneath the floating house. Water temperature was lower in open water compared to the area under the house, by 0.15K on average. Checked against the shaded area it was lower by 0.14K at the water bottom and 0.1K near the water surface respectively. Dissolved oxygen content was higher in open water than in shaded area, by 0.8mg/l in shallower and 2.8mg/l in greater depths. Long-term measurement has a high potential for monitoring the environmental impact of floating houses. In the presented thesis it could show diurnal cycles of water temperature and dissolved oxygen, also in greater depths. Moreover a high dependency of these parameters on weather condition was determined. Further research, taking at least one year, would show effects of floating structures on the seasonal variations of water temperature and dissolved oxygen content. Other parameters, like nutrients, should also be investigated over longer periods. In addition the development of a more suitable method for measurement under floating houses remains as a challenge. 5 Acknowledgements The author wrote his bachelor thesis about the impact of floating solar panels on the evaporation of lakes. After answering this question a new one came up: What is the impact of floating structures on water quality? During studies of Environmental Hydrology at the Freie Universität Berlin the concept for a master thesis project on this topic was developed. As solar companies only produce modules, but are not responsible for monitoring their environmental impact, the challenge arose to find a partner, who was interested in the concept and possessed the equipment for implementation. Fortunately INDYMO united both properties and accepted me for an internship. Special thanks are due to Mr. de Lima, who not only mentored me throughout this time, but was always available for exchanging knowledge and ideas. Conducting a measurement campaign at floating houses is inconceivable without the help of local residents. Of particular note are the families Luiks, de Roos and Renkema, who allowed me to fix devices on their property. 6 Content Abstract ................................................................................................................................... 5 Acknowledgements ................................................................................................................ 6 List of figures .......................................................................................................................... 9 List of acronyms ................................................................................................................... 12 1 Introduction ....................................................................................................................... 14 1.1 Problem setting ......................................................................................................................... 14 1.2 Very Large Floating Structures .............................................................................................. 15 1.3 Outline of the thesis ................................................................................................................. 17 2 Current state of research .................................................................................................. 19 2.1 Theoretical background ........................................................................................................... 19 2.2 Potential impact of floating houses........................................................................................ 22 2.3 Empirical Background ............................................................................................................. 23 2.3.1 Mega-Float ......................................................................................................................... 23 2.3.2 Studies from the Netherlands ......................................................................................... 25 3 Research approach ........................................................................................................... 30 4 Own preliminary works ..................................................................................................... 31 5 Study area .......................................................................................................................... 33 6 Material and Methods ........................................................................................................ 38 6.1 Materials .................................................................................................................................... 38 6.1.1 Devices ............................................................................................................................... 38 6.1.2 Software ............................................................................................................................. 42 6.2 Methods ..................................................................................................................................... 43 6.2.1 Period A .............................................................................................................................. 43 6.2.2 Period B .............................................................................................................................. 45 6.2.3 Period C ............................................................................................................................. 46 6.2.4 Period D ............................................................................................................................. 46 7 6.2.5 Weather conditions ........................................................................................................... 48 6.2.6 Underwater images .......................................................................................................... 49 6.2.7 Calibration .......................................................................................................................... 49 6.2.8 Questionnaires .................................................................................................................. 50 7 Results ............................................................................................................................... 51 7.1 Results of period A ................................................................................................................... 51 7.2 Results of period B ................................................................................................................... 58 7.3 Results of period C .................................................................................................................. 64 7.4 Results of period D .................................................................................................................. 71 7.5 Further results........................................................................................................................... 76 7.6 Verification of hypotheses ....................................................................................................... 78 8 Discussion ......................................................................................................................... 80 8.1 Discussion of results ................................................................................................................ 80 8.2 Discussion of methods ............................................................................................................ 81 8.3 Recommendations ................................................................................................................... 82 9 Conclusion 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