Calibration of the Agricultural Policy/Environmental eXtender (APEX) model for use in western Washington

While the invention of artificial fertilizers has drastically increased food production capability across the globe, misuse of these fertilizers can have unintended side effects on the health of humans and the environment, including groundwater contamination, eutrophication of freshwater ecosystems, and accumulation of nitrous oxide in the atmosphere. To better control nutrient runoff from agricultural land, evaluation and implementation of best management practices (BMP's) are needed. Such practices can include restoration of riparian buffers on streams and altering the timing and rate of fertilizer application. Models that track the flow of nutrients on a small watershed scale can remotely evaluate the effectiveness of BMP's. The Hooper Lab in the Biology Department is working with the Agricultural Policy/ Environmental eXtender (APEX) model to fit this need in Whatcom County. This model will be able to track nutrient flow through watersheds, taking into account a variety of environmental factors such as hydrology, topography, and soil type. The APEX model has been partially constructed and calibrated, but it requires testing across a greater range of conditions before it can be used. Our project focuses on building a database of stream discharge levels and nutrient concentrations from several watersheds around Whatcom County to calibrate and validate APEX output against real-world data. We collected stream discharge data in the field and analyzed water samples in the lab for concentrations of ammonium, nitrate, phosphate, total nitrogen, and total phosphorous. We have also worked on constructing watersheds for APEX using GIS software. The long-term goal is to use APEX to evaluate and prioritize BMP projects in western Washington.