Διαστασιολόγηση οικιακών ομβροδεξαμενών σε περιοχές με διαφορετικό βροχομετρικό καθεστώς

Abstract

The lack of sufficient available water resources to meet the demands of urban water usage in areas, such as the Greek Islands, is a common problem towards local water resources management and there are many techniques regarding water collection and storage that are investigated to potentially contribute to reduce the problem. Among them, RainWater Harvesting (RWH) systems is a common practice usually operating at a household scale, ensuring the provision of water that is suitable for a number of uses, such as laundry, toilet, garden, etc. RWH tanks cannot be formulated, because the size is strongly affected by various local variables, such as local rainfall, the collection surface area, the demand and the number of served residents. Methods for RWH tank sizing vary from country to country depending on standards and regulations adopted by each country, and the size can be determined either by using the daily or monthly water balance method or using the dry period demand method. In Greece, the main reasons that cause problems in the use and rational management of water resources are both the unequal distribution of water resources and demand in space and time. It is worth noting that there is not a proposed methodology to calculate the size of rainwater harvesting tank in Greece. The aim of this undergraduate thesis is the investigation of such a system’s operation under various combinations regarding the number of residents, the collection area and the tank size, for two Greek Islands that are characterized by different rainfall regime. On the one hand, Corfu island (Ionian Sea, NW Greece) appears one of the highest annual precipitation depth in Greece, and, on the other site, Naxos Island (Aegean Sea, Eastern Greece) is an area of low precipitation depth. The entire analysis is performed after developing and implementing a daily water balance model, which allows to calculate the efficiency coefficient (Reliability, Re (%)) of the system for various combinations. Finally, the corresponding results given in graphs are capable for sizing the rainwater harvesting tanks in RWH systems Greece for domestic use and for a standard Re (%). The analysis is performed using the historic daily precipitation timeseries for these two islands and, also, after applying three climate change scenarios. Results show that the local precipitation regime affects the system’s performance, that is satisfactory only for Corfu. In Naxos Island, especially in case of households with more than two members and for small collection areas, the system cannot meet the demand, even after using the maximum tank size that is investigated.