Hawaiian Commercial & Sugar – Seepage Metric

This study compared three seepage estimates of the Hawaiian Commercial & Sugar concrete-lined irrigation canal system in Maui, Hawaii, to evaluate logging flow meter technology applied to the inflow-outflow method.

Numerous tests were conducted under short reach and highly variable flow conditions to determine if seepage in excess of 15% of inflow could be detected using paired acoustic Doppler flow meters.  Results were contradictory; comparing instrumental uncertainty to seepage indicated flow measurement uncertainty overwhelmed seepage signal in the majority of cases.  Additionally, computed seepage rates, in excess of 15% of inflow, were consistently higher than generally accepted maximum rates for concrete-lined canals by several times.  Measured values ranged from -1.926 to 0.786 m.day-1, which resembled un-lined sand or gravel bed materials.  A theoretical global seepage calculation ranged from -0.183 to -0.281 m.day-1, an average system loss of -0.219 m.day-1 while a single direct measurement, using the ponding method, indicated -0.116 m.day-1 of loss, within a limited test reach area.

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