An easy to use calculation method for weir operations in controlled drainage systems

If operated appropriately, drainage systems may serve as vast reservoirs to retain or release water and solutes. This paper describes the hydraulic principles ruling the unsteady reaction of groundwater levels as related to drainage control operations. A set of governing equations suited to be implemented in computer codes was deduced focusing on non steady-state drainage, weir hydraulics, and effects of ditch maintenance. Based upon a simplified layout, two easy to handle computer codes were developed (MATLAB/Octave and Excel versions) enabling local engineers to assess system performance. Controlled drainage systems may be used to reduce leaching of agrochemicals from agricultural land and are valuable tools for preventive flood control. Controlled drainage may further support effective field operations necessary for crop production.

► Analysis of interconnected unsteady drainage, groundwater and ditch storage.
► Providing an Excel- and Matlab/Octave computer code.
► Benefits of weir-controlled drainage.
► Effect of drain spacing and ditch maintenance on preventive flood control.