QUALITATIVE AND QUANTITATIVE ASSESSMENT OF RAINWATER HARVESTING FROM ROOFTOP CATCHMENTS: CASE STUDY OF OKE-LANTORO COMMUNITY IN ABEOKUTA, SOUTHWEST NIGERIA

Abstract

Quantitative and qualitative assessment of Rainwater harvesting system from rooftop runoff from acatchment at Oke-Lantoro Community in Abeokuta, Southwest Nigeria was determined using eightroof designs in respect to slope and six selected roofing sheet materials respectively. The resultshowed that the steeper the roof slope the more the rainwater harvested irrespective of rainfall amountand duration. The roof pattern with a large and steep slope designed with gutter tends to harvest morewater and at a higher rate. Physico-chemical analysis of the harvested water samples gave resultswhich varied from various drinking water quality regulatory standards. Sample from galvanized roofingsheet was influenced by zinc and lead in quantity beyond human consumption level, while the asbestosroofing sheet water sample gave higher calcium and magnesium contents which reflected in thetotal hardness value. Sample from the aluminum roofing sheet gave the best result but it was alsoaffected by the influence of atmospheric dust particles and faecal materials of birds, lizards and othersmall organisms. Considering the results of the physico-chemical tests, the harvested water samplescould be put to other domestic uses, as they cannot be consumed directly.