Water Discharge Measurement in Agricultural Catchments Using Critical Depth Flumes Affected by Sediment Deposition

Abstract

AbstractFlumes and weirs are hydraulic structures used to measure soil erosion and runoff at the outlet of agricultural catchments. Long-throated flumes use critical flow theory to determine discharge from a single water depth measurement upstream of the flume structure. In erodible catchments, sediments often deposit at the entrance of the flume, just where water level is measured, preventing proper discharge determination. This work proposes the combination of critical depth theory with two models of water flow at free overfalls that may be applied when the exit of the flume presents a drop. The method allows the recording of discharge measurements when the upstream water level sensor fails because of the accumulation of sediments. This paper proposes three discharge predictors: (1) one based on critical flow theory, (2) another based on the momentum balance between the critical section and the free overfall section, and (3) the third based on energy balance between the upstream water section and the fr...