Sizing the first flush and its effect on the storage-reliability-yield behavior of rainwater harvesting in Rwanda

Rainwater harvesting is a technology used to supply water for domestic purposes in developing countries. Rooftop rainwater harvesting involves collection of rainwater from a rooftop via a guttering system and storage in a cistern. During dry weather, dust and other pollutants accumulate on the roof surface and are washed off at the beginning of the next rain. The initial contaminated volume of water flowing from a roof after a rainstorm is known as the first flush and research has shown that diverting it from the main supply can improve the quality of stored water. This thesis considers a variety of design options for rainwater harvesting, set in the context of rural Bisate Village in northwestern Rwanda. Fieldwork evaluated the potential for rainwater harvesting at three community-scale locations; a health clinic, a primary school, and a house for gorilla trackers and by analysis of the water quality, sought to characterize the first flush phenomenon using an apparatus to collect discrete time-sequenced volumes of runoff. The reliability of a rainwater harvesting system is a measure of its ability to produce the water needed by the system users and depends partially upon the rainfall distribution of the area, the size of the collection roof, the capacity of the storage tank, and the daily demand for the water. The storage-reliability-yield (SRY) behavior of a rainwater harvesting system indicates trends in reliability as storage (cistern size) and yield (demand) are varied. A SRY simulation model was run to mimic daily use of the system and calculate the reliability. The recommended first flush diversion was simulated and evaluated against several management options. The simulations showed that the reliability is not drastically affected by diversion of the first flush.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Doyle, Kelly C. (Kelly Carroll)

Advisor dc:contributor.advisor

• Peter Shanahan.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/44289

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44289