PREDICTION OF EFFECTIVE SATURATION CONCENTRATION AT SPILLWAY PLUNGE POOLS

Bubbles entrained in spillway plunge pools are subject to the hydrosta tic force of the water column, increasing the pressure within the entr ained bubbles. This phenomenon is important for the exchange of atmosp heric gases such as nitrogen and oxygen, often causing dissolved gas s upersaturation downstream of the plunge pool. A weighted average or ef fective bubble depth is introduced to predict more accurately gas tran sfer at spillways. A theory is developed for estimating the effective bubble depth given the spillway angle of inclination, velocity, and de pth of dow at jet impact and tailwater depth. The relationship is fitt ed to dissolved oxygen and methane data previously reported by the aut hors and is successfully applied to four Bureau of Reclamation spillwa ys for which both oxygen and nitrogen measurements were available.