A System for Measuring Water Levels in Open-Air Irrigation Canals Fausto Freire Carrera, Harry Saltos Sanchez, Yelitza Garcia-Orellana and Olga Chadrina EPJ Web Conf., 248 (2021) 02011 Published online: 26 April 2021 DOI: 10.1051/epjconf/202124802011