Water quality improvements from implementation of tailwater recovery systems

Abstract

Impacts of nutrient loading from agricultural landscapes have gained widespread attention and led to the implementation of conservation practices aimed at mitigating nutrient loss to downstream systems. A relatively new conservation practice, tailwater recovery (TWR) systems, has been considered as a potential mitigation strategy. The objective of this study was to compare concentrations and loads between effluent of TWR systems (TE) and effluent of similar catchments without TWR systems (CE), under the same agronomic management. Tailwater recovery systems, CE, and paired differences between TE and CE were compared over seasons. Nutrient concentrations and hydrologic discharge were monitored at five TWR system outflow and control catchment outflow locations on a flow event basis. Results revealed that of all experimental analytes, including total suspended solids, total phosphorus, total Kjeldahl nitrogen, nitrate–nitrite, and ammonium, only total phosphorus concentrations were greater (F1,97 = 8.58, p < 0.005) at CE locations than TE locations. The difference between loads of TE and CE showed reduced loads per hectare leaving TWR systems. This included loads of total phosphorus, total nitrogen, organic nitrogen, total inorganic nitrogen, and nitrate–nitrite. Analyses revealed no differences across seasons for TE and paired differences between TE and CE. However, CE concentrations and loads were seasonally different, where ammonium was greater in the summer than in the winter and spring, but not different than fall. Additionally, only loads of total nitrogen were different across seasons, where winter was greater than spring, but not different than summer and fall. This study provides evidence that TWR systems are a positive contribution to reducing nutrient loads compared to control locations.