Assessment of Subsurface Drainage Performance in Large‐Scale Agricultural Fields: A Case Study

The assessment of subsurface drainage systems aims to ensure efficient system performance and to provide meaningful feedback to farmers and drainage system managers. Such evaluations support decision‐making by indicating whether system performance is satisfactory and identifying necessary corrective measures. This study assessed the performance of a horizontal subsurface drainage system covering 4990 ha in the Pančevački Rit area during the 2021 growing season. A comprehensive field investigation was conducted, including inspections of 103 drains, excavation of 400 soil pits, analysis of 800 soil samples and measurement of hydraulic conductivity at 25 representative locations. In addition, the system capacity was reassessed through recalculation of the drainage discharge rates, drain spacing and drain diameters. Collected data were analysed and classified, with particular emphasis on the degree of drain obstruction, as reduced flow profiles directly impair overall system functionality. Outlet inspections showed that 85% of the analysed drains were non‐functional, mainly due to physical blockages restricting water flow. In upstream sections, 42% of drains exhibited tolerable clogging (up to 40%), whereas approximately 58% showed moderate to severe obstruction, resulting in partial or complete loss of functionality. The results were extrapolated to a wider area to estimate the investment required for drainage rehabilitation measures.