The current work describes the development of a non-intrusive optical metho
d for the quantitative determination of water heights along a hydraulic jum
p in shooting water flows on a water table. The technique involves opticall
y superimposing a series of alternating dark and clear fringes on the water
flow. It is proposed that the fringe deviations seen under a hydraulic jum
p can be simulated using a series of optical prisms oriented along the dire
ction of the hydraulic jump. The height of each prism gives the local maxim
um water height at the fringe location. Three types of theoretical prism co
nfigurations (isosceles flat-topped prism, scalene flat-topped prism and ro
unded-topped prism models) have been studied for two flow systems: shooting
flow around a wedge and around a cylinder. Equations relating the physical
characteristics of the deviated fringes to the height of the theoretical p
rism and hence the local water height are presented. The variation in water
height along a hydraulic jump for flow around a wedge obtained using the o
ptical technique has been compared with heights obtained using a depth gaug
e. The results were in good agreement for the range of Froude numbers studi
ed (Fr = 1.9-3.6). The rounded-topped prism model led to the best agreement
with the physical measurements, within 11% throughout the range of conditi
ons studied. The uncertainty associated with the water height determination
using the optical technique is +/-10%.