Modeling Lateral from Heading to First Check Structure
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I am assessing the feasibility of installing a ramp flume on a surface irrigation lateral between the lateral heading (where the lateral shoots off the main canal) and the first check structure. Modeling under steady state conditions, I originally placed the most-downstream (DS) cross-section 0.01 ft DS of the check and assumed a normal slope downstream boundary condition. However, this led to two issues: 1) the head is the same US and DS of the check (even though gates are closed and check is not being overtopped) - as if the check wasn't even there and 2) water does not back up behind the check as expected, rather, the head is much lower than expected. Turnouts were not used as lateral structures as they greatly reduced the head behind the check when added - unlike the real-world condition.
Given the segment of interest being between the heading and first check, do you have any advice for where to place the most-downstream cross-section? Is a normal slope boundary condition feasible for this application? Any advice on this application is appreciated.