Simplified mod& based on differential material balances have been proposed for determining the leakage rate from a solar pond operated batchwise. It has been found that discriminating the exact mechanism of leakage is possible only when the rate of evaporation is known or when the rate of crystallization of a salt is meastlred. Repeated measurements with different initial brine depths seem necessary to find the best approximation suitable for a particular pond. SYMBOLS ;: -constant in the linearized form of t(H) -constant in the linearized form of L(H) c concentration, g/cm3 h -brine level from a fixed reference, cm H effective average brine depth, cm k -proportionality constant for diffusion, cm!hr K coefficient of IY in Eq. 5 A" -coefficient of Win Eq. 8 L hydraulic seepage rate, cmJ/hr.cm2 pond surface nr constant defined in Eq. 19 ni constant defined in Eq_ 21 t -extent of solids crystallized, g/g H,O evaporated t time, hour IV& W, -constants in the approximate form of W(f) I#' -instantaneous evaporation rate. cm'jhr.cm* pond surface m -. average value of IV for 24 hours, cm,Ihr rv, -uptake of water from ground, cm3/br.cm2 pond surface Greek fetters -exponent in Eq. 31 -exponent in Eq. 32 Dcsalinarion, 11 (1972) 303-313 s. PANCliARA-rNAM P -density corrected to some reference temperature. g&m" Pse -density of salt bed, g NaCl as solid/cm3 bed volume 0 -time interval in the approximate form of Ii'(r), hr Subscriprs A -B -0 -5 SB -$1' non-crystallizing component crystallizing component initial quantity salt (crystallized form of A) salt bed water