Nitrogen immobilization in streams partially determines the balance between N loading and export from headwater catchments.  We sought to quantify in-stream nitrate immobilization rates across the watershed to assess the role of the stream network in modifying observed watershed N loading patterns and controlling spatial distributions of stream network nitrate.  We focused on the 212 km² watershed of the West Fork of the Gallatin River, Big Sky for analysis of landuse change impacts on water quality because of its accelerated land development and interspersed wilderness.  We conducted 40 stream tracer tests (21 steady-state and 19 slug additions) in eight stream reaches across a range of discharges, development intensities, ambient nitrate concentrations, and seasons.  Six of the eight streams were paired for comparison based on similar watershed area and total discharge; each pair included a stream of high and low ambient nitrate, reflecting varying degrees of exurban development and upland wastewater disposal.  This work represents a first step toward integrating watershed and stream network biogeochemistry in a rapidly developing mountain watershed.