Controls on Storm Event Transport of Nitrate and DOC Derived Using Sensor based Monitoring Approach.

Abstract:

Storm events play an important role in the timing, quantity and quality of nutrients and carbon delivered from watersheds to downstream waters. Recent studies have used data from automated sensor-based monitoring in human-impacted catchments to infer storm event controls on nutrient mobilization and export. Such understanding is needed in light of changes in climate variability including temperature, precipitation regime and storm frequency (duration and intensity), and the increased dominance of non-point nutrient sources in human impacted watersheds. Heterogeneity of land-use within catchments can also interact with climate conditions to affect nutrient retention and the timing and magnitude of storm event nutrient mobilization and export. Examining storm responses across a variety of land use distributions can provide a more mechanistic understanding of nutrient mobilization and provide a window on catchment behavior during extreme climate events (ECE).

We conducted an intensive water quality monitoring effort to track storm event patterns in multiple sub-watershed spanning a range of land use (highly impervious, highly agricultural, and highly lawn dominated) and the larger watershed within which they were nested (Oyster River watershed, NH). Continuous and high frequency in situ measurements in combination with intensive flow monitoring and periodic grab sampling were used to track water quality during several dozen storm events over a three year period. This study examines the role of catchment geometry, land-use distribution and time of year of occurrence. Initial results indicate these factors provide a secondary control, with total runoff being a primary control, with varying strength over the monitoring period.