The aeration performance with respect to oxygen transfer of a smooth w
eir, a cobble-faced weir, and a cobble-faced chute was investigated in
a large laboratory flume. The maximum difference between upstream and
downstream water surfaces was 0.7 m. A review of existing relationshi
ps to predict aeration at weirs indicated that prototype-scale model s
tudies and actual prototype data were limited in this range of drop he
ights. In addition, most laboratory testing has been conducted at grea
ter drop heights and lower unit discharges. To reduce experimental unc
ertainty, a procedure was developed which uses an enhanced-oxygen atmo
sphere over the flume water surface. The uncertainty in values of the
deficit ratio (r) developed from the testing procedure is +/-0.040. Ae
ration was greatest with the cobble-faced weir and lowest with the chu
te. The superior performance of the cobble-faced weir relative to the
smooth weir is attributed to weir surface roughness achieved by overla
ying the weir crest with cobbles. A new relationship to predict the de
ficit ratio for a cobble-faced weir was developed that is similar to t
he relationship of Avery and Novak (1978) and includes a dimensionless
term to account for tailwater depth.