Most of the world’s rivers have been substantially modified by human activities. A notable example is the Upper Clark Fork River (UCFR) in western Montana, USA, where historic mining and floods have resulted in the largest U.S. Environmental Protection Agency superfund site. Ecological restoration in the UCFR and floodplains included the removal of metal-laden floodplain soils, reconnecting the floodplains to the main stem, and re-vegetation of over 70 km of river. Restoration activities were expected to recover “healthy” ecosystem signatures and shift biogeochemical processes. Our team’s objective was to analyze the water chemistry of the river and identify signatures of changing ecosystem “health” using dissolved organic matter (DOM) composition and character as we expected allochthonous composition from the floodplain and landscape to increase over time. We measured DOM quality by absorbance spectroscopy and 3D excitation-emission matrix fluorescence spectroscopy and DOM quantity by an organic carbon analyzer. Fluorescence DOM characterization revealed dominant humic-like, terrestrial signals across all sites seasonally and annually, therefore another mechanism to decipher the timing of “healthy” terrestrial signals became our next goal. We analyzed the DOM data annually across five years for increases in absorbance values at 254nm and humification index (HIX) values and decreases in fluorescence index (FI) values with changing concentrations, all of which reflect increases in terrestrial contributions to the river. These data were paired with UCFR hydrologic flow patterns (snow melt onset, spring runoff, and base flow) to understand how ecological regimes change each year. Aromatic DOM composition was greater in the headwaters where more intense floodplain restoration efforts occurred. We attributed this result as an increase in allochthonous terrestrial DOM delivered to the river reflecting successful floodplain-to-river connectivity from restoration efforts.