GANGTOK, Dec 3: The glaciers in Mount Khangchendzonga in Sikkim side have shown an estimated annual retreat of 4.15 m during two decades from 1986 to 2005 which could possibly led to some reduction of water availability in future. This was stated by Union environment minister Jairam Ramesh in his reply to a question raised by Sikkim MP OT Lepcha in the Rajya Sabha recently.