ASCE recently featured an article on improving flow from irrigation splitter boxes

Irrigation splitter boxes are used in piped gravity-flow systems to divert water from the main supply line to local users, but when flow is high and turbulent, the split isn't uniform. In the paper, the authors show how to implement a solution they designed and tested successfully; this paper is available in ASCE's Journal of Irrigation and Drainage Engineering for free for a limited time, courtesy of ASCE Library.
Benefit from our findings.