Uniformly Discharging Lateral Weirs

In certain applications, such as automated irrigation systems, multiple lateral weirs are housed in open channels in which spatially decreasing flow occurs. When the channel bed slope and the friction slope are very small, spatially decreasing subcritical channel flow results in a rising profile in the reach containing the multiple lateral weirs. This causes nonuniform distribution of weir outflows. For purposes of analysis, a single equivalent weir is considered and it is shown that uniform water surface profile ensuring uniform outflow can be obtained by modifying the weir system geometry. The proposed methods are simple and easy to construct, even in existing channels. A number of tests were conducted to verify the proposed methods. The present study is limited to rectangular open channels.