Plynlimon experimental catchments, Wales UK

Location of the Plynlimon catchments, Wales, UK

Catchment size

• Wye: 10.6 km²
• Severn: 8.7 km²

Climate

Humid climate, with annual average precipitation of about 2650 mm.

Geology

The generalised pattern is of parent materials, which are similar throughout the catchments (Palaeozoic grits, mudstones and shales, or drifts composed of them) and therefore soil differentiation is mainly dependent on drainage. Thus the impeded drainage of the plateaux and wider interfluves have led to the accumulation of organic deposits - blanket peat - whilst the more freely draining slope soils are podzolized. In the valey bottoms, drainage is also impeded and there occurs a complex of peat and gleyed mnineral soils, the balance of which at any site is the result of local topography. Whilst the two catchmnents are almost identical in soil types, the lower parts of steeper slopes in the Wye are mantled by a free-draining brown earth; steeper slopes in the Severn have skeletal soils or patchy podzols.

Topography

The landscape of Plynlimon is dominated by rolling hills dissected by steep valleys. The altitudinal range is from 319 m ODN in the Severn and 341 m in the Wye up to 738 m. In terms of slopes, the Severn is locally steeper than the Wye catchment. Both catchments have limited development of valley flat areas associated with hort alluvial reaches. Most reaches are confined within valley side slopes. Most streams are flowing over bed rock, sometimes with a shallow covering of river sediments. The irregularities in the profiles are typical of British upland channels. The steps often coincide with resistant bands of rock Such rock controls are apparent in both catchments. Although there are slope angles greater than 25° which are local to the lower parts of the Wye catchment the vast majority of slopes in both catchments are in the range 0° to 15°. The major differences between the two catchments concern the degree to which the extensive Tertiary plateaux of Plynlimon are crossed by their tributary streams.

Vegetation/Land use

The Wye catchment is 98.8% grassland, while in the Severn forestry is dominant, covering 67.5% of the catchment.

Context of investigation

• Ecological Processes & Resilience
• Environmental Monitoring & Observation
• Soil
• Sustainable Land Management
• Water Resources

Measurements/Equipment

• Climate station
• Suspended sediments
• Solute transport
• Soil moisture
• Ecological Processes & Resilience
• Sustainable Land Management
• Water Resources

Links to project webpages

• Plynlimon: a critical zone observatory, CEH

other Links

• Plynlimon in wikipedi
• Plynlimon at theHistory of Hydrology Wiki

References

• Beven, K.J., Kirkby, M.J., Schofield, N., Tagg, A.F., 1984. Testing a physically-based flood forecasting model (TOPMODEL) for three U.K: catchments. Journal of Hydrology, 69, 119-143.
• Beven, K.J., 1979. On the Generalized Kinematic Routing Method. Water Resources Research, 15(5), 1238-1242.
• Beven, K.J., 2012. Rainfall-Runoff Modelling The Primer, Second Edition. John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, UK, ISBN 978-0-470-71459-1.
• Benettin, P., Kirchner, J.W., Rinaldo, A., Botter G., 2015. travel time distributions at Plynlimon, Wales. WATER RESOURCES RESEARCH, 51(5), 3259-3276, DOI: 10.1002/2014WR016600.
• Crisp, D.T., Beaumont, W.R.C., 1996. The trout (Salmo trutta L.) populations of the headwaters of the Rivers Severn and Wye, mid-Wales, UK. The Science of the Total Environment, 177, 113-123, DOI: 10.1016/0048-9697(95)04889-8.
• Francis, I.S., Taylor, J.A. 1989. The effect of forestry drainage operations on upland sediment yields: a study of two peat-covered catchments. Earth Surface Processes and Landforms, 14(1), 73-83, DOI: 10.1002/esp.3290140107.
• Francis, I.S. 1987. Blanket peat erosion in mid- Wales: two catchment studies. Unpublished Ph.D. thesis, University of Wales.
• Francis, I.S., 1990. Blanket peat erosion in a mid-wales catchment during two drought years. Earth Surface Processes and Landforms, 15(5), 445–456, DOI: 10.1002/esp.3290150507.
• Herndon, E.M., Dere, A.L., Sullivan, P.L., Norris, D., Reynolds, B., Brantley, S.L. 2015. Landscape heterogeneity drives contrasting concentration–discharge relationships in shale headwater catchments. Hydrol. Earth Syst. Sci., 19, 3333-3347, DOI: 10.5194/hess-19-3333-2015
• Hudson, J.A., Gilman, K., 1993. Long-term variability in the water balances of the PLYNLIMON CATCHMENTS. JOURNAL OF HYDROLOGY, 143(3-4), 355-380, DOI: 10.1016/0022-1694(93)90199-J.
• Hudson, J.A., Gilman, K., Calder, I.R., 1997. Land use and water issues in the uplands with reference to the Plynlimon study. HYDROLOGY AND EARTH SYSTEM SCIENCES, 1(3) 389-397.
• Hudson, J.A., Crane, S.B.; Blackie, J. R., 1997. The Plynlimon water balance 1969-1995: the impact of forest and moorland vegetation on evaporation and streamflow in upland catchments. HYDROLOGY AND EARTH SYSTEM SCIENCES, 1(3), 409-427.
• Kirchner, J.W., 2016. Aggregation in environmental systems - Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity. Hydrol. Earth Syst. Sci., 20, 299–328, DOI: 10.5194/hess-20-299-2016.
• Kirkby, C., Newson, M.D., Gilman, K., 1991. Plynlimon research: The first two decades. IH Report No. 109 published by the Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire, UK, ISBN 0 948540 27 3.
• Marc, V., Robinson, M., 2007. The long-term water balance (1972–2004) of upland forestry and grassland at Plynlimon, mid-Wales. Hydrol. Earth Syst. Sci., 11, 44-60, DOI :10.5194/hess-11-44-2007.
• Neal, C., Kirchner, J.W., 2000. Sodium and chloride levels in rainfall, mist, streamwater and groundwater at the Plynlimon catchments, mid-Wales: inferences on hydrological and chemical controls. Hydrol. Earth Syst. Sci., 4, 295-310, DOI: 10.5194/hess-4-295-2000.
• Neal, C ., Reynolds, B., , Kirchner, J.W., Rowland, P., , Norris, D., Sleep, D.,, Lawlor, A., Woods, C.,, Thacker, S., Guyatt, H., Vincent, C., Lehto, K., Grant, S.,, Williams, J., Neal, M., Wickham, H., Harman, S., Armstrong, L., 2011: Three decades of water quality measurements from the Upper Severn experimental catchments at Plynlimon Wales an openly accessible data resource for research, modelling environmental management and education. Hydrol. Process. 27(17), 2531-2539, DOI: 10.1002/hyp.9814.
• Oborne, A.C., Brooker, M.P., Edwards, R.W., 1980. The chemistry of the River Wye. Journal of Hydrology, 45(3–4), 233-252, DOI: 10.1016/0022-1694(80)90022-0.
• Quinn, P.F., Beven, K.J., 1993. Spatial and temporal predictions of soil moisture dynamics, runoff, variable source areas and evapotranspiration for Plynlimon, Mid-Wales. Hydrological Processes, 7(4), 425–448, DOI: 10.1002/hyp.3360070407.
• Page, T., Beven, K.J., Freer, J., Neal, C., 2007. Modelling the chloride signal at Plynlimon, Wales, using a modified dynamic TOPMODEL incorporating conservative chemical mixing (with uncertainty). Hydrological Processes, 21(3), 292–307, DOI: 10.1002/hyp.6186.
• Robinson, M., Rodda, J.C., Sutcliffe, J.V., 2012: Long-term environmental monitoring in the UK: origins and achievements of the Plynlimon catchment study. Transactions of the Institute of British Geographers, 38, 451–463, DOI: 10.1111/j.1475-5661.2012.00534.x.
• Sklash, M.G., Beven, K.J., Gilman, K., Darling, G., 1998. Isotpe studies of pipeflow at Plynlimon, Wales, UK. Hydrological Processes 10(7), 921–944, DOI: 10.1002/(SICI)1099-1085(199607)10:7<921::AID-HYP347>3.0.CO;2-B.