32-Impact of urbanization on the trophic status of Kumaun Lakes, Uttaranchal

Abstract

Lake Nainital is one among a group of lakes occurring in the southern fringe of the Kumaun Lesser Himalaya. Bhimtal, Naukuchiatal and Sattal, popularly known as the Lake Region of Bhimtal are located in close proximity of Nainital Lake. Physiographically, these lakes are in the southern fringe of the Lesser Himalayas in Kumaun region of Uttaranchal. These lakes are being used as drinking water source, irrigation and recreation etc. In the past few decades, unplanned developments and urbanisation in the lakes catchment have caused serious problem related to pollution, eutrophication and accelerated sedimentation.

The total phosphorus recorded, more than 127.25 14/1, indicates that the lake has entered in the hypereutrophic condition. The Carlson TPTSI used for determining trophic state index of the four lakes revealed that lake Nainital is the most eutrophic lake in the Kumaun region (74) followed by Bhimtal lake (51), Khurpatal (44), Sattal (32) and Naukchiatal (20). Increasing trend of nutrients (i.e., Nitrate nitrogen and total phosphorus) since 1954 clearly indicates that the anthropogenic activities have greatly accelerated the natural process of eutrophication. Further, the study reveals that diversion of drain water away from the lake catchment reduces PO4-P loading by a significant proportion (60%). It clearly indicates that the increasing population in Nainital lake catchment has accelerated the nutrient loading in th lake and it has reached in hypereutrophic stage in past few decades.