Dissolved organic carbon load variability in the rainfall season dominated its interannual variability in the snowmelt driven basin: Evidence from 41 years data of headwater streams

Abstract

Numerous reports have observed variations of dissolved organic carbon (DOC) under the changing environment. From the DOC load variability perspective, however, how much of the variability in DOC load occurred among different seasons, and which season was most synchronized with the interannual variability remains unknown. The weekly DOC concentration and daily discharge records from four headwater streams with long-term records in the snowmelt driven basin of Harp Lake, south-central Ontario, Canada, were used to answer these issues. We also examined the contributions of variabilities in discharge and DOC concentration to the variability in DOC load. We found that the variability of DOC load in the rainfall season (autumn) instead of snowmelt season (spring) was most closely synchronized with its interannual variability, suggesting that if the DOC variability in the rainfall season stabilized, the interannual variability would be more stable. The interannual variabilities for discharge, DOC concentration and DOC load showed an insignificant decreasing trend in the monitored 41 years, and the respective contributions of the variability trend of discharge and DOC concentration to DOC load in rainfall season increased from 28.82% to 144.58% and decreased from 71.18% to À44.58% because the change trend of discharge variability was greater than that in DOC concentration.This study provides a case information in determining which factors contribute most to the variability of DOC load in the watershed, and which season may dominate its variability throughout the year.

Role of Lakes, Flood, and Low Flow Events in Modifying Catchment‐Scale DOC:TN:TP Stoichiometry and Export

“…Our DOC, TN, and TP was exported during high flow events, similar to that of other headwater streams (e.g., Ockenden et al., 2016). So far no clear changes in long‐term DOC exports in our catchments have been detected (Wu et al., 2023). The highest fluxes of DOC, TN and TP from our study catchments occurred in spring, during snowmelt, which is similar to other studies reporting the highest share of annual export of TN and DOC during snowmelt, in response to infiltrating meltwater (Boyer et al., 2000; Sebestyen et al., 2009).…”

Enhanced Role of Streamflow Processes in the Evolutionary Trends of Dissolved Organic Carbon

“…In this cold climate, approximately one-third of precipitation falls as snow, resulting in snow cover persisting from December to April. During the spring snowmelt period (March–May), streamflow contributes to around 50% of the total annual runoff …”

“…During the spring snowmelt period (March−May), streamflow contributes to around 50% of the total annual runoff. 33 This study utilized a data set from 1978 to 2018, including daily streamflow and temperature measurements, as well as daily or weekly measurements of DOC and SO 4 from January 1979 to December 2018. The data set has undergone thorough quality testing and has been previously employed to investigate changes in water quantity and quality.…”