river case study

• The Conwy Catchment


  The river Conwy is the third largest river discharging into the Irish Sea along the North Wales coast. It drains a catchment of about 590 km2, an area roughly the size of the isle of man. The main channel covering a distance of 55 km long. The river Conwy begins in the Migneint Moor (one of the largest blanket bogs in Wales and a major carbon store) and passes through improved grazing land and conifer plantations). It's source is the Llyn Conwy a reservoir (450 metres above sea level). The lower Conwy flows through extensive flood plains and meets the tidal limit around 20 km inland from the estuary mouth. Three major tributaries (the Machno, Lledr and Llugwy) join the upper Conwy from the west, and drain many of the high mountains Snowdonia.
• Characteristics of the Conwy Catchment

  Physical Characteristics: The maximum elevation of the Conwy catchment is 1050.6m where as the minimum is 9.8 m (so steep terrain). There is a strong climatic gradient across the catchment with annual precipitation varying between 500mm in the north east to more than 3500mm falling in the Snowdonia region. The mean average for the Afron Conwy River is 1700mm. The catchment has a high channel density with many tributaries.
• Geological Characteristics


  Migneint Moor consists of mudstone, some has been metamorphosed into slate. This bedrock is mainly impermeable. The impermeable bedrock means water cannot percolate down. This can reduce lag time for the river and increase the risk of flooding.
• Land use Characteristics


  Land use is predominately rural with 4 towns of a population with 3000-8500. There are 10 villages with around 250 people. The total catchment only holds around 40,000 people. 17% Woodland (coniferous/deciduous), 0.5% Arable land, 65.% Grassland, 15.5% mountain/bog/peatland, 0.5% urban. 340 hectares of the Conwy catchment is defined as urban this makes up 0.5% of the entire catchment. Coniferous woodland makes up around 6000 hectares (or 60km2) of land use in the area.
• Human uses of the Conwy

  Agriculture and forestry dominate the Conwy catchment. Sheep are reared in the upper catchment, with more mixed livestock in the lower sections. The catchment is an important area for: Salmon and sea trout fishery, Recreation and tourism are important to the local economy, with canoeing, walking, climbing in the Conwy Valley.
• Benefits of the Conwy Catchment

  • Carbon capture - blanket bogs of the Migneint at the top of the catchment and forestry, Food production - shellfish in the Conwy estuary, upland lamb, beef and milk production, Recreation and tourism, Forestry - multiple benefits, coniferous and deciduous. Timber production, firewood, recreation, shelter, biodiversity, An ideal research catchment - education and learning, well studied by Bangor University and Centre for Ecology & Hydrology, Energy production – hydropower
• Recent developments in the Conwy Catchment

  The Conwy Catchment contains drinking water supply reservoirs including the Llyn Conwy and the Llyn Cowlyd. They supply some of the water needs of the upper/middle Conwy including Betws-y-coed and Llanrwst. Small sluice gates control the outflow from the lake. A new hydropower scheme on the Afon Conwy approximately 400 metres upstream of Conwy Falls, near Betws-y-Coed, Gwynedd with a generation capacity of up to 5 MegaWatts.
• Conwy catchment measures bare rock and heath, with some forest mainly in lower catchment
• Conwy catchment has an average annual rainfall of 2042mm
• Factors affecting water cycle in Conwy Catchment

  • Land use
  • Geology
  • Moor and Peat bogs
• With reference to a river catchment that you have studied, assess the potential impact of human activity upon the drainage basin
• The Conwy Carbon Capture: Peatlands store about the same amount of carbon that is present in the atmosphere, peat bogs cover more than 420 million ha of the earth's surface and contain 500,000m tonnes of carbon, in the UK peatlands cover ~15% of the land area and store >1400 Mt of carbon
• Carbon Catchments: There are 4 CEH Carbon Catchments in the UK, the aim at Conwy is to find out if UK peatlands are still a sink for carbon, if the sink strength is changing and why, and what processes control the important fluxes
• Data collected so far at Conwy suggests that the peat is a large source of both DOC (around 22 g C m-2 yr-1) and CH4 emissions (around 6 to 8 g C m-2 yr-1)
• Conwy Catchment covers around 200 km2, is the largest area of blanket bog in Wales, has few small lakes, stores water to prevent flooding, has small waterfalls and good views, Conwy Falls runs through a deep gorge called Fairy Glen, set in 10 acres SSSI, is a salmon river with two salmon ladders, has limestone which increases pH, had high historical trout catches, has an average pH of 7.2, is a small market town on the A470 developed around wool trade, harps and clocks, with main industry now being tourism, population 3323
• Betws-y-coed is in the Conwy Catchment, has 28 square miles of national park, lots of outdoor activities including a rollercoaster, and lots of waterfalls