Abstract
This study aims to estimate the cost of rainwater harvesting and use efficiency in sorghum production in Jazan by calculating the average cost per unit of water (m(3)) of dam construction, restoration, and annual maintenance and analyzing data from a randomly distributed questionnaire in Jazan in 2016. This study has five key results. (1) The cost of rainwater harvesting through earthworks increased from 0.682 riyals/m(3) at a 5% discount rate to 1.828 riyals/m(3) at a 15% discount rate. (2) The cost of rainwater harvesting through concrete dams increased from 1.340 riyals/m(3) at a 5% discount rate to 3.694 riyals/m(3) at a 15% discount rate. (3) A 10% change in the amount of water, agricultural labor, or chemical fertilizers leads to a corresponding change in sorghum production of 3.9%, 2.5%, or 1.9%, respectively. (4) The marginal return on water in sorghum production was similar to 326.12 SR/thousand m(3) in Jazan in 2015. (5) Rainwater is not economically efficient for sorghum production because the harvesting cost outweighs its marginal productivity. Thus, harvested rainwater should not be used agriculturally but rather domestically to reduce desalination costs in Jazan and throughout Saudi Arabia.