Soil moisture measurement error by TDR in Zanjan's flood spreading station

The TDR device is implicating to monitor soil and hydrology of flood spreadingstations all over the country. Along this concept, the surveying of errors that caused bylong-term installation of sensors, have been realized in Zanjan flood spreading station.For this purpose, six profiles in flood spreading and two others in non flood spreadingarea have been dug with 1.5 m depth and totally 36 bury able sensors installed indifferent layers. The soil moisture was determined along two years with time interval ofone week. The results show some interruptions in the data time series that caused by thedevice’s message of “time measurement failed”. The temporal and spatial analyses ofdata series, state increasing of missed data from primary to second year because ofleaching and from west to east zone for the reason of high volumetric concentration ofwater in that area. With dividing the data collection period to three nearly 70 daysperiods at every layer indicated that, the percent of missed data increased twin alongwith time and declination of moisture. The main source of error is leaching the particlesaround the electromagnetic guide rods of sensors and adding to the pores and interfacialdistance of rods and soil particles.