Dissolved organic carbon concentrations, pH and conductivity of water flowing from eroding and restored peatland catchments

Water was collected  from gullies within an eroding blanket bog. The bog is on a large high-altitude plateau blanket bog in the eastern part of the Cairngorms National Park, Scotland, UK (56.93° N, − 3.16° E, 642 m asl). 

At Balmoral DOC concentrations were measured from water flowing through six v-notch weirs. Three weirs measured drainage from mini catchments that had undergone restoration and three measured drainage from  degraded mini-catchments with multiple upstream erosion gullies and bare peat. Restoration at this site included reprofiling and vegetating (turving) of peat haggs, bunding using coir logs to ‘slow the  flow’ and encourage Sphagnum growth, and mulching of areas of bare peat with locally sourced vegetation.

The six V-notch weirs conforming to British Standard 3680:Part 4A:1981 (British Standards Institute, 1981) were constructed from 18 mm marine plywood. Initially 90°, 65 l s^-1, V-notch plates cut from 1 mm aluminium plate were fitted. Weirs were installed at sites identified in the experimental design phase. Each weir was embedded into the peat by 20cm vertically and 20-40cm horizontally and supported by two posts embedded 60-80cm into the peat. Where required the weirs were extended to ensure that there were no leaks between the bank and the weir. A stilling well equipped with a capacitive water logger was installed at each weir. The stilling wells were manufactured from 800 mm long, 43 mm diameter, ABS waste pipe tubing. After a period of evaluation (November 2020 – May 2021) the 90°, 65 l/s, V-notch plates were replaced with 28.4°, 15 l s^-1 plates in order to improve low-flow (<6cm head) accuracy. The water loggers were set to record water levels every 10 minutes. Raw data was downloaded every 6 months and processed in a Python script using the BS 3680 formula.

Water samples were taken from each weir (if water was present behind the weir on the sampling day)  over a two year period from September 2021 to September 2023  After samples are delivered to the laboratory the protocol for wet chemistry analysis follows the protocol of the National Water Inventory of Scotland (NWIS) project. pH, conductivity and turbidity were then measured on all samples before a 100ml subsample was filtered through a 0.45 µm membrane. The remaining unfiltered sample is stored in a cold room and the filter membrane was retained, air dried and stored in plastic bags, for potential further analysis. The filtered water was analysed for DOC on a Skalar TOC analyser (Norcross, USA).