Nutrient and sediment concentrations, loads, yields, and rainfall characteristics at USGS surface and subsurface-tile edge-of-field agricultural monitoring sites in Great Lakes States (ver. 2.1, September 2023)

This data release focuses on nutrient and sediment concentrations, loads, and yields at USGS surface and subsurface-tile edge-of-field (EOF) agricultural monitoring sites in Great Lakes States. Water quality and rainfall metrics are summarized by individual flow events to evaluate the contribution of EOF losses to headwater stream networks in agricultural landscapes. USGS EOF sites are components of multiple local, state, and federal studies with goals of characterizing agricultural influences on water quality and/or documenting water-quality changes as a result of conservation adoption. As part of this data release, data from within 306 site years are provided that were developed from 5 local, state, and federal programs. These cooperative programs include: Great Lakes Restoration Initiative – Priority Watersheds (GLRI; https://wim.usgs.gov/geonarrative/glri-eof/) University of Wisconsin Discovery Farms (http://www.uwdiscoveryfarms.org/) University of Wisconsin-Platteville Pioneer Farm (https://www.uwplatt.edu/department/pioneer-farm) Sand County Foundation (https://sandcountyfoundation.org/) Mississippi River Basin Initiative (MRBI; https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/home/?cid…) Data from these programs span 5 Great Lake States (Wisconsin, Michigan, Ohio, Indiana, and New York) and include data from private farms under a variety of farming systems, landscapes settings, soil types, and climate. The methods used to collect this data were consistent with USGS EOF monitoring methods (https://pubs.usgs.gov/of/2008/1015/). Data represent all flow and rainfall characteristics at surface and subsurface-tile stations from contributing areas that range in size from 0.7 to 641 acres. Flow data, including total flow volume, flow-weighted mean concentrations, total loads, and total yields, were computed for each flow event. A flow event was defined as any period of flow at a station that was classified as a storm and represents flow that was related to rainfall or snowmelt. In the combined flow and rain table, multiple flow events were combined if they occurred within 2 hours of each other, to account for similar rainfall/runoff characteristics. Linked to each flow event, rainfall metrics were computed (rain total, duration, intensity, erosivity, and antecedent rainfall). Rain metrics were also computed for the entire rainfall record, which are in the rain event table. Similar to the combined flow-related rain metrics, rainfall was combined into a single event if it occurred within 2 hours of the previous rainfall. There were occurrences of continuous flow between rain events, which were not associated with a period of rainfall or snowmelt, likely due to excessive soil saturation or shallow groundwater discharge. These periods of intermittent tile discharge were not classified as a storm. Monitoring was conducted year-round to evaluate flow characteristics among seasons and variation in weather, field conditions, and agricultural activities.