Twenty years of seasonal predictions reveal when, where, and why nutrient concentration standards may be exceeded across the Illinois River Basin
Abstract
Anticipation of, and management to ameliorate, extreme water quality events in freshwater systems demands models capable of dynamic water quality prediction and source tracking across large river basins. Tracking the delivery of nutrients to sensitive downstream waters benefits from the integration of every contributing small watershed, their accumulated in-stream processes, together with larger scale hydroclimatic drivers, but the cost of producing reach-specific estimates across entire basins has traditionally limited predictions to long-term averages of static conditions. Here we present a new dynamic version of the USGS's SPARROW model and predict the past twenty years of seasonal total nitrogen and total phosphorus concentrations for every river reach of the Illinois River Basin (IRB). For river reaches that were predicted to exceed water quality standards (at least 60% by length), exceedance usually occurred during both summer lowflow and high runoff periods in agriculture-dominated areas. Across the IRB, nearly 30% of excess nutrient delivery to streams comes from legacy nutrients that have accumulated in storage repositories such as soils, groundwaters, and riparian vegetations and lagged in their delivery to rivers by seasons, years, or even decades. With appropriate datasets, this dynamic modeling approach could be updated to forecast next-season nutrient conditions with a better accounting of lagged delivery.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H13D..04S