Hydraulic control in willow phytoremediation systems at Fort Drum, New York

A hydraulic control study was initiated in phytoremediation systems at Fort Drum, New York in fall 2007. Continuous data loggers were installed in a creek, untreated seeps and treated seeps (1-year-old and 6-year-old willow phytoremediation systems) to determine water table dynamics and measure hydraulic control. An unbalanced, completely randomized design was applied to measure water table change inside and outside of willow systems (small-scale) and raised willow planting beds (micro-scale). The study objective was to determine phytoremediation effectiveness in establishing hydraulic control using a sine wave function to describe diurnal, plant-mediated max-min water table amplitudes from September to November 2007. Amplitude was compared among treatments with ANOVA (small-scale) and paired-difference t-tests (micro-scale). Amplitude differed among treatments and reflected substantial hydraulic control in the 6-year-old treated seep system. Average amplitude (excluding rain events) in the 6-year-old system was 9.2 mm d-1 (1.5-16.9 mm d -1) and was consistently different from zero. Amplitudes in other treatments (systems) ranged from 1.8 to 2.8 mm d-1 and were not different from zero. Amplitude inside raised planting beds was greater than that observed outside raised planting beds. Diurnal water table fluctuations were strongly affected by rain events. Monitoring and analysis of diurnal water table fluctuations revealed the first empirical evidence of a tailored phytoremediation-based hydraulic control effect.;Keywords: Diurnal water table fluctuation, Salix.