Variation of dissolved organic carbon during snowmelt in soil and stream waters of two headwater catchments, Summit County, Colorado

Hydrological controls on the spatial and temporal variation of dissolved organic carbon (DOC) were investigated in the Deer Creek and Snake River catchments, located in the Rocky Mountains near Montezuma, Colorado. Measurements at these sites during spring snowmelt showed that stream DOC concentrations increased with the rising limb of the hydrograph, peaked before maximum discharges, then declined rapidly as melting continued. Hydrological catchment responses, including flow paths through and residence times of water in the catchment, are among the main factors controlling DOC variation in such headwater streams. Our objectives were to document aspects of the spatial variation of landscape DOC source areas and to determine quantitative characteristics of the flushing response. At a variety of locations within the basins, DOC concentrations were measured in the vadose zone, in the saturated zone, and in the streams. Water sampled from lysimeters in the upper soil showed an accumulation of DOC during periods of low flow and a pronounced decline in DOC concentration during snowmelt. Results indicated that spatial and temporal variations of snowmelt and soil properties, in addition to topography, are important determinants of the catchment hydrochemical response.