Comparison of Different Methods for Detecting Irrigation Canals Leakage

Abstract

This research investigates some field methods to evaluate water leakage from irrigation canals, in order to find a reliable method of identifying and quantifying losses. This study was conducted in two canal lines in Piedmont, north-western Italy, which have different hydraulic, morphological, geological and hydrogeological contexts. A hydrogeological characterization of the study area was carried out for every investigated canal, in order to evaluate the relationships between groundwater and canal water. The water losses from irrigation canals were subsequently estimated using various methods. The methodologies are: empirical formulas, inflow-outflow test and two tracers method. Inflow-outflow test is easy to apply and efficient; however it sometimes is inadequate because of the high instrumental error, especially in canals with low velocity and discharge. The two tracers method is considered a more rigorous methodology, with a low error. This method is not reliable, however, in cases of low discharge and laminar flow, resulting in inadequate tracer diffusion. The comparison of the results shows that the empirical formulas heavily underestimated the real amount of the losses. The results of inflow-outflow method and two tracers method are similar, both in sandy-gravelly and impermeable bed canals.