Nutrient and sediment concentrations, loads, yields, and rainfall characteristics collected at a USGS subsurface-tile edge-of-field agricultural monitoring site in South Central Michigan within the Maumee River Basin, 2019-2023

This data release contains nutrient and sediment concentrations, loads, and yields from a USGS subsurface-tile edge-of-field (EOF) agricultural monitoring site. Sampling and flow monitoring were performed at the outlet of a subsurface-tile that drains 14.7 acres of cultivated cropland. The site is located in South Central Michigan and discharges into a headwater stream of the Maumee watershed. Through a cooperative agreement between the USGS and the USDA Natural Resources Conservation Service (NRCS) in Michigan, data was collected from May 22, 2019, through March 19, 2023. Water quality and rainfall metrics are summarized by individual flow events to evaluate the contribution of EOF losses to a headwater stream. The methods used to collect this data followed USGS EOF monitoring methods (https://pubs.usgs.gov/of/20081015/) and the contents of this data release are consistent with a related EOF data release (Komiskey et. al 2023). 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.