PROBLEM AND ITS SETTING
Water, although one of the most fundamental human needs, is often not readily available for the world’s poor. To address this need, many water-supply and distribution technologies have been successfully implemented to provide clean, reliable water in close proximity to its end users. Rainwater harvesting is one of these options available for consumers. It has the potential to provide water for a variety of purposes. Rainwater harvesting is one of the most basic forms of water collection and has been used for millennia around the world as a means of collecting and storing water for future use (UN-HABITAT). Rainwater harvesting is just one of many options for water supply in areas where water is scarce. It is a valuable resource, which should be exploited in the most efficient way to protect the people's health and livelihood. It has several distinct benefits over other water supply options, yet there are also major drawbacks. Unlike municipal water, rainwater is typically readily available and free to use. Construction logistics and materials are less than those needed for a groundwater well or public distribution network, although the capacity of the system is limited by regional rainfall. Installation costs can be high, often limiting the system size, but they are typically cheaper than installing piped networks. Furthermore, a systematic collection and recharging of ground water is a recent development and is gaining importance as one of the most feasible and easy to implement remedy to restore the hydrological imbalance and prevent a crisis. Meanwhile, a rainwater tank is a water tank used to collect and store rain water runoff, typically from rooftops via rain gutters (Wikipedia). It is designed in order to sustain the water supply for a maximum consumption as well as for future demands at low-cost. The water level in a storage tank should be sized so the tank will routinely fill and drain during the demand cycle. This is because stagnant water in a tank becomes “stale” as it ages (Mihelcic and Zimmerman). Rainwater harvesting is the means of collecting and storing rain water in large, durable containers, usually, collecting from rooftop gutters (Wikipedia). The basic premise is simple: connect a holding tank to a set of gutters which collect rain from the roof. This study will not consider ground runoff as a water source, but will only consider rooftop rainwater runoff as a source for water consumption. Rooftop rainwater harvesting (RWH) is a simple method of collecting rainwater for domestic supply. A typical system includes a collection surface (a rooftop), a conveyance system (gutters), a treatment method (first flush diversion), and a storage tank. Design of an efficient and reliable system considers the end use of the water, availability and appropriateness of materials, accessibility and quality of other water sources, the size of the roof, the quality of the roof runoff, and a variety of other parameters. Diversion of the first flush is a simple and effective way to improve the quality of water entering the rainwater tank. The goal of a first flush diversion system is to prevent the initial portion of runoff flowing off of the roof from entering the storage tank. The assumption is that the initial portion of water contains the most contaminants because the rain washes debris from the roof surface. The most intriguing question in the design of a first flush diversion system is what depth of runoff should be diverted to adequately improve the quality of stored water. Rooftop rainwater harvesting systems are rarely 100% reliable, meaning that they are unlikely to meet demand all of the time. RWH systems can be limited by available rainfall, roof size, tank size, cost, or they can be over-taxed with high demand. Each of these will reduce the reliability of the system. In this case, the study will only concentrate on the certain premises of the university which...
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