Center for Embedded Network Sensing

Over-irrigation with reclaimed water may cause crop yield reduction and groundwater quality degradation. Continuous and automatic monitoring strategies are desirable as a means of guiding management schemes to avoid these problems. In this work, an optimal irrigation management scheme known as Receding Horizon Control (RHC) is proposed to balance water reuse and soil/groundwater quality. In this scheme, a wireless networked sensor array is deployed to provide on-line feedback to the simulators on which the management algorithm depends. A simulation model including a one- (vertical) dimensional form of the Richards equation coupled to energy and solute transport equations is automatically updated with real-time soil moisture, temperature, nitrate, and salinity sensor data on a regular basis. A genetic algorithm-based control scheme determines the optimal irrigation rate using current observations which continuously maximizes the reclaimed water usage while maintaining salinity and nitrate in soils at a certain level. Results from simulated soil moisture/nitrate control where maximum soil moisture/nitrate level throughout the soil depth is maintained are presented. On-site soil moisture control in Palmdale, CA, where reclaimed water is irrigated with center-pivot irrigation system at an agricultural site, is also demonstrated. An on-going field experiment in Merced, CA where automatic irrigation system is set up to control salinity level in soils is presented as well. The results demonstrate that coupling in situ observations with RHC process control algorithm is a viable strategy for achieving water reuse and agricultural objectives while minimizing negative impacts on environmental quality.