WATER QUALITY INDEX (WQI) CALCULATION FOR THE EVALUATION OF PHYSICO-CHEMICAL QUALITY OF RAINWATER COLLECTED IN RESERVOIRS FULL OF SAND (RFS) - HAINGOTSEHENO, RANDRIAMAHEFA; Chrysostome, Randriamboavonjy Jean; ROBERT, REJO; Tojonirina, Andriambinintsoa Ranaivoson (International Journal of Advance Research and Innovative Ideas In Education, 2020)