Modeling of Mixed Crop Field Water Demand and a Smart Irrigation System

Taiwan average annual rainfall is approximately 2500 mm. In particular, 80% of the rainfall occurs in summer, and most of the heavy rainfall is caused by typhoons. The situation is worsening as climate change results in uneven rainfall, both in spatial and temporal terms. Moreover, climate change has resulted the variations in the seasonal rainfall pattern of Taiwan, thereby aggravating the problem of drought and flooding. The irrigation water distribution system is mostly manually operated, which produces difficulty with regard to the accurate calculation of conveyance losses of channels and fields. Therefore, making agricultural water usage more efficient in the fields and increasing operational accuracy by using modern irrigation systems can ensure appropriate irrigation and sufficient yield during droughts. If agricultural water, which accounts for 70% of the nation's total water usage, can be allocated more precisely and efficiently, it can improve the efficacy of water resource allocation. In this study, a system dynamic model was used to establish an irrigation water management model for a companion and intercropping field in Central Taiwan. Rainfall and irrigation water were considered for the water supply, and the model simulated two scenarios by reducing 30% and 50% of the planned irrigation water in year 2015. Results indicated that the field storage in the end block of the study area was lower than the wilting point under the 50% reduced irrigation water scenario. The original irrigation plan can be reduced to be more efficient in water usage, and a 50% reduction of irrigation can be applied as a solution of water shortage when drought occurs. However, every block should be irrigated in rotation, by adjusting all water gates more frequently to ensure that the downstream blocks can receive the allocated water to get through the drought event.