Rainwater harvesting for multiple uses: a farm-scale case study

Abstract

Rainwater harvesting (RWH) alternatives from runoff and roof collection were evaluated for implementation in a farm in subtropical Mexico. Groundwater extraction and bulk water purchase in tanker trucks were evaluated and compared to RWH. The main water uses included irrigation (trees and seasonal crops), domestic (showers and toilets), and semi-industrial (food processing and cleaning). For all uses, except tree irrigation, a disinfection system was included as part of the process. Financial and non-financial factors were considered in the evaluation. Heavy seasonal rainfall during hurricane/monsoon season (June–September) contrasted with extremely dry months (November–May). Large water storage requirements and extended detention time result from this seasonal rainfall phenomenon. The space available for construction of water storage facilities was constrained at the site of study. These factors must be accounted for in RWH systems that show marked discrepancies between the time of rainwater collection and its use. The financial assessment showed that a new groundwater well would cost less (US dollars per m3) compared to RWH alternatives. However, in situations where water rights are not available, or if groundwater extraction is charged to the user, implementation of RWH may be more feasible. Therefore, RWH systems must be evaluated case by case, particularly for those users that experience marked seasonal rainfall conditions.