Initial changes in hydrology and water quality following restoration of a shallow degraded peatland in the South west

Transcription

1 Initial changes in hydrology and water quality following restoration of a shallow degraded peatland in the South west David Luscombe 2 David Smith 1,, Emilie Grand-Clement 2, and Richard E. Brazier 2 1 Exmoor Mires-on-the-Moors Project Manager, South West Water 2 Geography, College of life and Environmental Science, University of Exeter

2 Mires project research questions What is the effect of restoration on: Water quantity Water quality Gas fluxes Peat accumulation Biodiversity Agricultural productivity

3 Where are we working? One Dartmoor Catchment Two Exmoor Catchments Both Exmoor and Dartmoor locations are geo-climatically marginal upland blanket peatlands.

4 Methods Water Quantity In-situ depth to water table measurements at >200 locations across 8 experimental pools and within 3 headwater catchments. Discharge quantified for 7 drainage features and at 3 catchment outlets. Full suite of meteorological variables are recorded at each catchment. All data retrieved via a GPRS/VHF remote telemetry system and logged every 15 minutes.

5 Methods Water Quality Storm-flow sampling using ISCO pump sampler DOC measurements (UV spectrophotometer) Colour: UV - vis Spectrometer Abs 400nm Fulvic/Humic ratio (E4/E6) ph

6 Exmoor Study Catchments Headwater catchments Dominated by Molinia caerulea Shallow peat deposits (~0.4 to ~1m) Dense, vegetated anthropogenic drainage features

7 Exmoor, Catchment Drainage Dense drainage in shallow peat Ca. 20m

8 Experimental Pool setup Artificial Drain Dip well Peat Soil Mineral Soil/ Bedrock Water Table Pressure Transducer

9 Results: Water quantity (1) Hydrological Function Pre-Restoration Timeseries extract unrestored Aclands catchment (June 13 Feb 14) Dry Summer followed by very wet winter season. Base flow is consistently low, and almost disappears during July 2013.

10 Results: Water quantity (2) Hydrological Function Post-Restoration (Spooners) EP Number Instantaneous Change (cm) 1 n/a Right: Average DWT for each EP during the restoration period. Above: Instantaneous change in DWT following restoration. Restoration of drainage ditch

11 Results: Water quantity (3) Hydrological Function Post-Restoration Despite notable spatial variability within catchments, when examining the change in water table depth over longer (base flow) periods, there is an average (cross EP) decrease in depth to groundwater (during non rainfall-runoff event periods) of between cm. Initial results indicate that storm flow production is reduced to approximately 32% of its pre-restoration level, following catchment restoration. In the studied time periods base flow volumes vary between approximately 201% and 48% of pre restoration levels. Results are highly uncertain and require processing of more rainfall runoff events to improve our understanding and constrain uncertainty.

12 Results water quality (1) Pre and post restoration # samples: Pre - Post

13 Results water quality (2) Seasonal variations

14 Results water quality (2) Seasonal variations No significant effect of restoration on DOC and colour concentrations so far. Variations in DOC concentrations are likely to be due to overlapping climatic factors rather than restoration only Overall, the observed decrease in storm flow at the scale of the catchment would still result in lower DOC fluxes.

15 But Results are spatially heterogeneous and uncertain. Longer post-restoration timeseries and restoration of remaining monitoring catchments will improve our understanding. Conclusions Catchments exhibit flashy flows and low base flow maintenance verging on ephemeral. Early indications are that restoration is raising water tables and reducing storm flow. Decrease in storm flow post restoration will have positive effects for DOC export at the scale of the catchment.

16 Thanks to all the project partners/funders