Application of isotope method to evaluation of evaporation from the surface of drainless water reservoirs

A method to assess evaporation rate from the surface of drainless water reservoirs for a long-term period (season, year) using natural tritium was suggested. The method was realized using as an example Sarykamysh lake in Central Asia. The investigations involved 3 isotope surveys of the reservoir in summer and autumn of 1986 and in spring of 1987. Tritium concentration in the studied samples of water and atmospheric moisture condensate was determined using the RACKBETA-1219 (Pharmacia, Sweden) liquid scintillation counter with preliminary concentrating by electrolysis. It is shown that tritium distribution in the lake is determined by morphometric characteristics (depth, transparency), wind and convective displacements of water masses, as well as the role of mechanisms forming their isotope composition. Evaporation value of 0.92±0.55 m was established