Given limited restoration funding and slim economic margins on local farms, we need to understand sources of reactive nitrogen, of which nitrate is a part, and what management practices will be most effective in reducing loading. To help with this understanding, the Hooper lab at WWU has been working with the Agricultural Policy/Environmental eXtender (APEX) Model. APEX was developed by the U.S. Dept. of Agriculture – Agricultural Research Service (USDA-ARS) to understand effects of field- or watershed-scale farm management practices on transport of nitrogen, phosphorus and sediment to adjacent waterways. While APEX holds a lot of promise for modeling best management practices (BMPs) at scales relevant to local watersheds, it was developed in Texas and the Midwest, and therefore needs calibration and validation for the different crops (e.g., perennial berries, such as blueberry and

raspberry) and riparian buffers (e.g., shrubs and trees instead of herbaceous) common in the Pacific Northwest.

Two sequential WWU masters students have made good progress in calibrating and validating APEX for hydrology and crop growth in a Whatcom County test watershed, Kamm Creek (Monks 2016, Cohan 2018). However, results for nutrients are not satisfactory. We are continuing to work on this problem. Following successful calibration and validation of APEX at Kamm Creek, we aim to test APEX in different sub-watersheds, across a variety of dominant land uses in the Nooksack Watershed. Our long-term goal is to test different BMP scenarios in APEX to help spatially prioritize locations and identify most cost-effective strategies for nutrient reduction.