Optimum Soil Water Content Sensors Placement in Drip Irrigation Scheduling Systems: Concept of Time Stable Representative Positions

Soil water content sensors placement is an important factor affecting the efficiency of drip irrigation scheduling systems. The main goal of this study is to introduce the concept of time stable representative positions (TSRPs) in soil water content-based drip irrigation scheduling systems and to investigate if such positions, which can provide representative water content readings during the whole duration of the irrigation cycle, can be identified for a wide set of conditions. To this end, several numerical experiments were conducted using a custom-made mathematical model, implementing a system-dependent boundary condition in order to be able to simulate the operation of drip irrigation scheduling systems based on soil water content sensors. The results obtained indicated that sensors' representativeness considerably varies according to the sensor position, the existing conditions (e.g.,meteorological conditions or soil hydraulic properties), and the irrigation systems characteristics, however, at least one (or more) TSRP can be identified in all the examined cases. Based on the obtained results, recommendations for the optimum sensor placement are provided. Finally, numerical simulation models proved to be efficient tools for the further investigation of optimum sensors placement under various conditions in order to improve irrigation management. (C) 2016 American Society of Civil Engineers.