TN-109 : Isotope techniques for lake water balance and sedimentation

Abstract

Water balance and sedimentation are the two very important aspects of lake studies. Lakes are not the eternal features on earth and most lakes have a limited life in terms of quantity of water. Identification of recharge zones of lakes and precise estimation of different components of water balance equation such as precipitation, evaporation, surface and subsurface inflow and outflow are therefore the first step in hydrological studies of lakes. The conventional methods of estimating these parameters are indispensable but are not properly equipped to measure some of the parameters such as subsurface inflow and outflow. The isotopic methods have contributed significantly to measure these parameters with fair accuracy.

Sedimentation of coarse and fine particles in lakes reduces the water capacity of lakes and is the most serious problem threatening the life of almost each and every lake. The understanding of the causes of sedimentation, estimatation of sedimentation rates and study of sediment distribution patterns are the essential tasks of hydrologists working on lakes. In situations where long-term record of sediment data on lakes do not exist, isotopic techniques are the only way of estimating sedimentation Yates. These techniques are also helpful in finding out the sediment distribution patterns and in predicting the lake bed configuration. The continuous monitoring of suspended sediment concentration is also possible using nucleonic sediment gauge. The isotopic techniques are much less time-consuming and are very precise with the advent of very sophisticated isotopic instruments.

The isotopic techniques for the study of water balance and sedimentation of lakes including case studies have been discussed in detail. The instrumentation, status of lake studies in India and brief details of the conventional techniques have also been described in this report.