Rainwater Harvesting in a Greenhouse for Crop Water Requirements

This paper reports the investigation of having rainwater harvesting system on an agriculture greenhouse. Conventional greenhouses are either installed with roof gutter and downpipe or none of those appliances. In both cases, rainwater is discarded. As such, should the rainwater be harvested and fed to crops instead, the rainwater presents as an alternative water source for farmers. To explore further, computer model was developed using Storm Water Management Model version 5. The greenhouse roof was simulated as catchment, and the amount of rainwater intercepted by the catchment was directed to a water storage tank, then the stored water was delivered via driplines to irrigate crops. Based on the collected rainfall data for a month, it was found that 89% of the month was without rain. After the modelling efforts, it was found that the stored water allowed longer period of crop watering and cutting down the period of no water to 3–40% of the simulated month. Since the model was not made to model detailed crop watering, it was resorted to simulate the final discharge of the model system to deliver water demand scenarios of 2, 4, 6 and 8 mm/day. The stored water allowed consistent supply of 2 mm/day which could support early crop growth. The modelling results also indicated that the stored water could only partially supply 4, 6 and 8 mm/day.