Using High Frequency Sensor Data to Assess Watershed Water Quality Vulnerability to Changes in Precipitation Magnitude and Frequency
Abstract
Excess agriculturally derived nitrate has caused systemic harm to water quality throughout the Mississippi River Basin and the northern Gulf of Mexico. Predicted changes in precipitation for the region, i.e. increasing precipitation event magnitude and frequency, may worsen water quality further by limiting time for fertilizer assimilation by crops and mobilizing legacy nitrogen stored within soils and groundwater. Further understanding of key transport and transformation processes is needed to assess watershed vulnerability to temporal changes in precipitation. In this study we analyzed high frequency sensor data for nitrate, discharge and water temperature spanning five years from eight watersheds within the Midwest in order to better understand underlying controls on nitrogen transport and transformation and thus water quality response to changes in precipitation as anticipated for the region. Using frequency analysis techniques coupled with geospatial analysis we show that nitrate was strongly cross correlated with discharge for all agricultural watersheds and that cross-correlation increased with watershed size, indicating the dominant role of hydrology in controlling transport and regulating biogeochemistry for these basins. Peak nitrate concentrations were positively correlated with percent cropland for all exceedance probabilities, which underscores the pervasive role of land use in controlling nitrogen dynamics within intensively managed agricultural basins within the region. Temporal offsets between peaks in nitrate concentration and discharge, potentially due to slow or spatially distributed biogeochemical transformations, resulted in maximum nitrate loading occurred at intermediate discharge. Together, these results can guide further work towards understanding how underlying sources and stores may change the trajectory of water quality improvement as agriculture takes steps towards a more sustainable future.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H41F..06H
- Keywords:
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- 1848 Monitoring networks;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY