Grassland Water District

Site Description

A broad crested weir (Repogle Flume) was designed and constructed for the Hollow Tree Drain site. Hollow Tree Drain conveys a large amount of operational spill as well as local wetland drainage from duck clubs that obtain water supply from the Santa Fe Canal. In the past this was a very difficult site at which to obtain reliable flow data. The channel banks were unstable, the site was subject to backwater and the stage variation made it difficult to select a suitable stage sensor. With the concrete flume, flows have been establised and the broad crested weir allows complete flushing of debris and sediment without impacting the throat of the flume. The site is now capable of measurements of +/- 2% for flow. Instrumentation at the site comprises a Keller pressure transducer to measure the stage upstream of the weir and an electrical conductivity sensor. This site has been the easiest to maintain. Hollow Tree Drain shares a gauge house with S-Lake Drain.