Evaluation of Water Levels and Flow Rates Measured in Irrigation Canal Using Limnigraph, Pressure and Ultrasonic Sensors

Abstract

Anything that cannot be measured cannot be managed. Based on the thought, the aims of this study are to evaluate water levels and flow rates measured by Limnigraph (OEL), pressure sensor (PS) and ultrasonic sensors (US) in the open irrigation canal. Limnigraph and pressure sensor sensed water levels and flow rates under un-fluctuating conditions in the Stilling Well and ultrasonic sensors directly measured them from water surface under fluctuating conditions at the Kartalkaya Dam in Kahramanmaraş. Assuming Limnigraph water level and flow rates readings correct and water levels and flow rates of Limnigraph were compared with that of pressure and ultrasonic sensor. Mean Absolute Percentage Error (MAPE) and ANOVA tests were done on 2454 observations. Average of water level and flow rates of limnigraph, pressure and ultrasonic sensor were 928±4.9 mm and 4.61±0.038 m3s-1, 927±4.9mm and 4.62±0.037 m3s-1, and 922±4.9 mm and 4.58±0.037 m3s-1, respectively. Differences between the average water levels and flow rates were 1 mm (928-927) and 0.01 m3s-1 (4.61-4.62) under un-fluctuating and 6 mm (928-922) and 0.03 m3s-1 (4.61-4.58) under fluctuating conditions. The fluctuation increased the differences between the average water levels and flow rates. MAPE of water levels and flow rates for pressure and ultrasonic sensor were calculated as 0.741% and 1.466% under un-fluctuation, and 1.453% and 2.490% under fluctuation conditions, respectively and since they were below 10%, the levels of agreement between the two data sets are considered as “very good”. However, fluctuation conditions increased MAPEs from 0.741% to 1.453%, from 1.466% to 2.490%. The water levels and flow rates of both sensors were not statistically different from those of optic encoder Limnigraph. Accordingly, both sensors can be used to measure water levels and flow rates in open irrigation canal but un-fluctuating conditions should be preferred. In addition, ultrasonic sensors can be used in environments that block, corrode the pressure sensors and make it difficult to use by floating objects.