Evaluating the Potential for Rainwater Harvesting for Non-Potable Use at the National University of Lesotho

Maeti Antoinette George; Tsebo Mohale; Lemohang Mpokathe

Abstract

An alarming rate of population growth and industrial and agricultural activities has put water resources at risk of over-abstraction. Despite adequate water in Lesotho, dry months and regular water cuts by the water utility affect institutions of higher learning like the National University of Lesotho, jeopardising the community’s health through poor basic hygiene. Research on the potential of supplementary water supply, like rainwater harvesting, is scarce, and this study addressed this gap. This research aimed to examine the possibility of reducing Water and Sewerage Company (WASCO) water usage at the National University of Lesotho (NUL) campus through rainwater harvesting for toilet flushing, as the most compromised practice, using specific buildings. A quantitative data-collection method was used, including determining NUL water demand, collecting annual rainfall data in Roma, and annual harvesting capacity from rooftops across fourteen buildings on campus. The study was restricted to specific rooftop catchments and tank sizing, and the estimated theoretical annual harvesting potential did not account for storage limitations, temporal rainfall – demand mismatch, first-flush diversion, and RWH system reliability. Findings showed that with a total roof area of 26,234 m² and a runoff coefficient of 0.9, the estimated harvestable volume is 17,306.57 m³. At least 17,306,569 L of water supply can be replaced through rainwater harvesting. NUL should practice rainwater harvesting to reduce reliance on WASCO water supply. Apart from economic benefits, environmental benefits include flood reduction on campus and nearby areas in Roma, low energy requirements for water treatment, and ecological benefits that are inclined towards availability and long-term management of water. It is worth noting that, in the midst of climatic variations, historical rainfall data and projected rainfall conditions have to be taken into consideration to estimate the performance of RWHs. To address this, a behavioral model has to be utilized in order to perform mass balance and reliability of precipitation and track changes in Roma inputs, outputs, and storage volume. This study focuses on a major higher-education institution in Lesotho where seasonal rainfall variability and recurrent interruptions of centralized water supply create a specific need for supplementary non-potable water sources. The goal is to assess a localized rooftop rainwater harvesting to provide a dependable backup supply for non-potable water needs. The university will also achieve SDGs 3 and 6.

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