Over the 2010 – 2011 period and beyond, FAO, in partnership with the Government of Jamaica embarked on an initiative entitled Promoting rainwater harvesting and small-scale irrigation in South Saint Elizabeth, Jamaica, with the aim of increasing the availability of water on small-scale farmers’ holdings  through improved rainwater harvesting and efficient water use technologies. 

The work also sought to empower farmers to improve their on-farm water management so that they would be less reliant on trucked water during dry periods. One of the main outputs of this initiative was the identification of critical areas for rainwater harvesting (RWH), zoning areas with low, medium and high degrees of harvesting potential using Geographic Information Systems (GIS) tools. This was achieved through a review of rainfall and other relevant climatic data in the area, the development and validation of water deficit models and, on the basis of these activities, the preparation of GIS maps of water deficits for each month.

A methodology to establish RWH potential using data on rainfall reliability and long-term means, as well as agricultural land use data, was developed. Rainfall thresholds are based on statistical values, expressed as percentiles (P). Reliable rainfall at 75 percent (P75) was used as the basis for determining RWH potential.

The final map outputs generated included: - 16 thematic maps to assist in determining rainwater harvesting potential directly or indirectly; - 4 rainfall maps with relevant information on rainfall for agricultural lands; - 1 monthly evaporation map; - 1 soil internal drainage map; - Agricultural land use and water demand maps; and - 1 rainwater harvesting potential map.