Utilizing National Water Model Output to Improve Runoff Risk Tools Used for Nutrient Application

Lakes and streams in the Great Lakes and upper Midwest suffer water quality issues attributed to runoff of nutrients every year. Runoff also affects crop production and revenue due to the loss of nutrients. It is important to stakeholders and agricultural decision makers to know when to avoid applying nutrients to farm fields. The operational Runoff Risk tools, developed through a collaborative effort with the National Weather Service and Great Lakes states, offer real-time forecasting guidance about when to avoid applying nutrients due to the likelihood of a runoff event. The tools use output from the Sacramento Soil Moisture Accounting Model with Heat Transfer and Enhanced Evapotranspiration (SAC-HTET) model to predict the categorical risk of runoff events at the edge of field scale. These Runoff Risk tools are being operationally used in Michigan, Minnesota, Ohio, and Wisconsin, with additional on-going coordination with New York, Indiana, and Illinois. The anticipated operationalization of the National Water Model (NWM) by the National Weather Service has resulted in the opportunity to integrate NWM-simulated output into the Runoff Risk tools. Migration to the NWM (as of version 2.1) will ensure that the tools gain continuous improvements that come at a much finer spatial resolution than earlier versions. This study aims to utilize the relevant meteorological and hydrological variables from gridded NWM output and develop methods for relating them with runoff events that could transport nutrients, ultimately improving model skill of the Runoff Risk tools.