Valley-wide export of solutes from the Hubbard Brook watershed

Previously, most studies of solute export at the Hubbard Brook Experimental Forest have focused on small, headwater streams, with some work also examining export from the entire Hubbard Brook valley. Export of solutes from watersheds of intermediate size (e.g. 100-1000 ha) has, however, received less attention. Thus, we have expanded the list of permanent, routine sampling locations for streamwater chemistry to include some intermediate-sized watersheds. We began a valley-wide survey of streamwater chemistry and morphology at the Hubbard Brook Experimental Forest in April, 2000. This survey is a contribution to the ongoing Valley-Wide Streamwater Initiative at HBEF that we began in 1996.

Between 4 May and 8 June 2000 we surveyed 8 tributaries to the main Hubbard Brook, draining south-facing watersheds. The 8 tributaries account for approximately 985 ha (33%) of the 3000-ha Hubbard Brook Valley. For each tributary, we surveyed physical and chemical parameters from the main Hubbard Brook to the first running water. Those streams, with large (>20 ha watershed area) perennial branches, were treated as separate watersheds and each branch was surveyed. At junctions of smaller streams, we surveyed only the section with the higher flow.

For each 100-m interval along the tributaries, we quantified channel form, substrate, presence of moss and organic debris dams, and identified nearby vegetation. We also made field measurements of pH, conductance, and water temperature at 100-m intervals using a laboratory-calibrated field meter. Water samples were collected at discrete points where the field meter indicated significant changes in any of the 3 parameters above. These discrete samples were later measured in the lab for pH, conductance, and acid neutralizing capacity (ANC) to confirm the field readings.

Chemical parameters, especially pH, varied considerably within and among watersheds. The pH and conductivity generally changed gradually from first running water downstream, but we did find large differences in chemical composition for some streams draining adjacent watersheds (e.g., the east and west branches of Beaver Brook).

Likens, G. E. and D. C. Buso. 2006. Variation in streamwater chemistry throughout the Hubbard Brook Valley. Biogeochemistry 78:1-30.

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