Biodynamic modeling was used to identify primary routes of metal exposure (food or water) in Hydropsyche larvae, a commonly used biomonitor. Enriched stable isotopes (⁶⁵Cu and ¹⁰⁶Cd) were used to trace the physiological parameters controlling bioaccumulation from the dissolved phase. A unidirectional influx rate constant from solution (k_u) indicated that Hydropsyche has a high uptake rate for both Cu (3.25 ± 0.04 L g^-1 d^-1) and Cd (3.17 ± 0.13 L g^-1 d^-1). Loss rate constants (k_e) were also fast (Cu: 0.229 ± 0.03 d^-1, Cd: 0.296 ± 0.03 d^-1) and help explain why this organism persists in contaminated systems. These rate constants were used in a biodynamic model to delineate the sources of bioaccumulated metal contributed by dissolved and dietary sources in nature. Using a long-term dataset from a mine-impacted river, modeled bioaccumulation values were compared to measured field concentrations in Hydropsyche. The model predicts that less than 10% of total Cu body burden in Hydropsyche is due to dissolved Cu sources. Dissolved Cd exposure accounts for approximately 40-50% of total Cd body burden. Results indicate that while Cu bioaccumulation is primarily driven by dietary exposure, Cd bioaccumulation is influenced by both dissolved and dietary sources.