Geographica Augustana - Institut für Geographie und ...

similar, but however we find an enrichment of heavier stable isotopes in the northern tributaries.The enrichment bases on the atmospheric circulation that brings the precipitation first to thenorthern catchments and causes their higher 2 H and 18 O values. A second approach to explain thisphenomenon lies in the northward extend of the Indian Monsoon that could have an influence onthe isotopic composition of the different water sources.Fig. 2: Development of mean 2 H values of water samples along the main river profile.b) Hydrograph SeparationTo quantify the contribution of the tributaries to the total runoff of the main stream we used as afirst approach a simple mixing equation (Eq. 1) based on the mass balances for tracer fluxes (Pinderand Jones, 1969):Q bas =Q tot *(c tot -c dir )/(c bas -c dir ) Eq. 1First estimations (Fig. 3) show that the contribution of the tributaries to the total stream flow ofthe Gunt River varies between circa 40 % during summer and zero in winter. The fraction oflakewater discharge ranges over the year from 40 to 70 %. To confirm these estimations we have toinclude more data of the monitoring network especially the hydrochemical parameters.25