The watersheds were monitored using H-flumes equipped with automated water monitoring stations (see picture below). Sampling was conducted year-round with flow apportioned discrete samples collected during snowmelt and storm events to characterize nutrient and sediment loads, and bacteria concentrations in addition to the hydrologic characteristics of each event. In addition:
The two watersheds composed entirely of perennial vegetation will use a paired watershed study design to evaluate water quality and quantity differences between perennial vegetation on undisturbed soils and corn-soybean row crop agriculture on the study hillslope. The basic premise of a paired watershed design is that there is a quantifiable, statistically significant relationship between paired water quality data for the two watersheds. The water quality values do not need to be equal between the two watersheds, but rather the relationship must be consistent over time except for the influence of changes imposed on the treatment watershed. The approach used two watersheds (control and treatment) and two periods of study referred to as calibration and treatment. During the control period (February 2011 through May 2013), each of the watersheds was composed entirely of perennial vegetation on undisturbed soils and treated identically. In late May 2013, the treatment watershed (NVe) was converted to row crop production while the control watershed (NVw) remained as perennial vegetation on undisturbed soils.
The third watershed quantified the effect of perennial vegetation on undisturbed soils located on the hillslope to treat water leaving the portion of the watershed with a long history of row crop production situated at the top of the hillslope (NVm-field). This watershed was evaluated using an above-and-below design consisting of two nested watersheds. Water quality and quantity differences were assessed for individual events between the monitoring stations capturing the row cropped portion of the watershed and the monitoring station located at the base of the hillslope below the perennial vegetation treatment area (NVm). The site will be used to quantify the water quality benefits from the targeted placement of perennial vegetation in landscape positions that may serve as treatment areas for water leaving row crop agriculture.
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