A preliminary study of an alternative controlled drainage strategy in surface drainage ditches: Low-grade weirs

This study examined hydrological characteristics of low-grade weirs, an alternative controlled drainage strategy in surface drainage ditches. Chemographs of vegetated and clear scraped (control) replicates of weir vs. non-weir treatments were compared to determine differences in time to peak (Tp) and time to base (Tb). Drainage ditches Tp and Tb were affected by both vegetation and weir presence. The order of treatment efficiency for Tp was observed to be: non-vegetated non-weir < vegetated non-weir < non-vegetated weir < vegetated weir. Furthermore, Tb for each ditch was the reverse relationship from Tp where vegetated weir > non-vegetated weir > vegetated non-weir > non-vegetated non-weir. Low-grade weirs increase chemical retention time (vegetated and clear scraped), the average time a molecule of contaminant remains in the system. Future research in water quality improvement and weir management will yield useful information for non-point source pollutant reduction.