Performance of an agricultural wetland-reservoir-irrigation management system
Haverstock, M.J., Madani, A., Baldé, H., VanderZaag, A.C., Gordon, R.J. (2017). Performance of an agricultural wetland-reservoir-irrigation management system. Water, [online] 9(7), http://dx.doi.org/10.3390/w9070472
Plain language summary
The right amount of water is critical for producing crops. Agricultural tile drainage systems are beneficial to farmers by reducing soil moisture in the springtime to facilitate a timely planting. On the other hand, during the summer time the amount of rainfall may not meet the crop water demand making irrigation necessary. This study involved the design, construction and evaluation of a wetland-reservoir-irrigation system, which is a system that attempts to collect drainage water, clean it, and store it for irrigation in the summer. To clean the water, constructed wetlands have gained recognition as a management option for the treatment of various agricultural wastewaters. The study system was established in Nova Scotia, Canada, with the goal to capture, treat, and re-use agricultural sub-surface drainage water. The farm field was 1.8 ha in size, equipped with a tile drain system. The excess water was directed to a two part constructed wetland to be treated, then into a reservoir irrigation pond. The system was monitored for 14 months and measurements were conducted of water flow and concentrations of Escherichia coli (E. coli) and nitrate-nitrogen (NO3-—N). The constructed wetlands showed mass reductions of both E. coli and NO3—N by 63.3% and 67.6% respectively. However, during the warmer months, E. coli concentrations increased to 178 Colony Forming Units (CFU) per 100 mL. Thus, the reservoir water would be best used for crops that are not consumed raw. The volume of water obtained and captured through the system to the irrigation reservoir exceeded typical irrigation requirements of drained land. Thus, this system could prove to benefit additional land through irrigation beyond the drainage area.
Constructed wetlands (CW) have gained recognition as a management option for the treatment of various agricultural wastewaters. This study involved the design, construction, and initial evaluation of a wetland-reservoir-irrigation (WRI) system. The system was established in Truro, Nova Scotia, Canada, with the goal to capture, treat, and re-use agricultural sub-surface drainage water. It consisted of a 1.8-ha area of a cropped field that was systematically tile drained. Drainage water was directed through a 2-cell CW and then into a reservoir-irrigation pond. Flow rate hydraulics, residence time distributions, and treatment efficiencies for nitrate-nitrogen (NO3--N) and Escherichia coli (E. coli) were monitored for 14 months. Mass reductions of NO3--N and E. coli from the CW were 67.6% and 63.3%, respectively. However, average E. coli concentrations increased to 178 CFU 100 mL-1 in the reservoir during the warm season. It may therefore be best to use reservoir water for irrigation of crops that are not consumed raw. To aid in the future design of similar systems, mean first-order rate constants (ks) for NO3--N and E. coli were calculated to be 8.0 and 6.4 m y-1, respectively. The volume of water collected in the reservoir exceeded typical irrigation requirements of the drained land and could therefore provide irrigation to additional land beyond the drainage area.