Assessment of rainwater harvesting in Northern Ghana

Abstract

This study assesses the current state of rainwater harvesting in the Northern Region of Ghana and makes recommendations regarding if and how rainwater harvesting could be used to address Pure Home Water's goal of reaching 1 million people in the next five years with safe drinking water. Three principal aspects of the water supply are considered: quality, quantity, and cost. Bacteriological water quality is tested to determine the level of risk. Rainwater supplies ranged from low (1 to 10 E.coli CFU/100ml) to intermediate risk (10 to 99 E. coli CFU/100ml.) Time-based reliability is simulated using a simulation model in Microsoft Excel. Reliability ranges from five percent to ninety-nine percent. Unit cost per cubic meter is calculated for surveyed rainwater harvesting systems in Northern Ghana. The unit cost of water from these designs ranged between approximately $1/m3 and $10/m3. Storage-reliability-yield relationship is developed and graphed for the Northern Region. This curve is useful for properly sizing rainwater harvesting systems. The use of a filter to post-treat rainwater before consumption is recommended, both for use with the rainwater, but also for provision of safe water when the users rely on a supplementary unimproved source, usually a dugout or dug well, for water supply. The feasibility of low-cost underground storage should be investigated. The geology and soil conditions in the Tamale region might provide a suitable match for a cheaper storage mechanism using plastic tarps and constructed pits.

(cont.) If the cost of storage could be lowered, rainwater harvesting could contribute in a larger way to Pure Home Water's mission and reach more people. Do-it-yourself rainwater harvesting in the Northern Region of Ghana is a fairly widespread. Finding ways to improve the quantity and quality of informal harvesting is a potential means for improving water supply for many low income households in the Northern Region. Currently, rainwater harvesting presents an opportunity to extend water supply to rural dwellers where few other alternatives are available.