Selected hydrograph events from Raccoon River Watershed

We analyzed daily nitrate concentration (c) and discharge (Q) data for a four-year period (2016-2019) from five nested, agricultural watersheds in the Midwestern United States. We partitioned the hydrograph into stormflow and baseflow periods and examined the nitrate export patterns of those periods separately through the analysis of their concentration-discharge (c-Q) relationships. Baseflow showed consistently positive c-Q chemodynamic slope, while stormflow c-Q relationships showed a much weaker chemostatic pattern. This suggests that water source contributions during baseflow are nonstationary. Anomalous flow periods greatly influenced overall c-Q patterns, suggesting that understanding event-scale characteristics is critical when interpreting seasonal or annual patterns. The watersheds span two distinct landforms shaped by differences in geologic history resulting in natural landscape properties that necessitated different drainage infrastructure across the study area. The density of built drainage infrastructure was a strong predictor of c-Q relationship and nitrate load, with more drainage infrastructure associated with higher loads and more chemostatic export patterns across all watersheds. This suggests that how humans ‘replumb’ the subsurface in response to geologic conditions has implications for hydrologic connectivity, homogenization of source areas, and subsequently nutrient export. This resource is the time series of discharge and nitrate partitioned into stormflow ("siteeventsdataframe.RDS") and baseflow ("sitenonevents.RDS").