Rivers and reservoirs

The Wharfe is joined by the River Skirfare at Amerdale Dub above Conistone, and by the River Washburn below Leathley. The valleys have very different characters.

The Wharfe itself runs down from Langstrothdale in a narrow valley founded on limestone, which opens out at Buckden and becomes flat-bottomed, with level fields between which the river meanders. The Skirfare, after its constituent becks have dashed down from the fells, also has a slower passage before it joins the Wharfe. Above Kilnsey the valley is wide and level, a former lake bed, but it narrows above Grassington and stays that way down to Ilkley. Here it broadens and again levels out, constricted only by the bridging-point at Otley, and regains a leisurely pace down to Weeton.

The Washburn rises up on the moors near Greenhow but is very soon confined by the reservoir at Thruscross. Released, it has little more than a mile before it flows into first Fewston, then Swinsty reservoirs - then a couple of miles and Lindley Wood reservoir. Below the dam it twists its way down to the Wharfe between Otley and Pool-in-Wharfedale. Many of the hillsides are covered with conifer plantations.

The Wharfe and Skirfare run off the limestone and the scenery is light and open but the Washburn runs off the dark moorland through man-made habitats and the banks are wooded, with a very different atmosphere.

The upper Wharfe has a catchment which includes both limestone and boulder clay and the river bed is variously formed by limestone pavement, loose gravels, cobbles, silt and clay. The flow varies from shallow riffles in the gravel sections to slow-running deep pools over silt.

Mosses characteristic of upland rivers are found on the limestone rocks, including Cinclidotus fontinaloides, Rhyncostegium riparioides and Chiloscyphus polyanthes. Where the river is slow and silty plants such as stonewort, red pondweed and broad-leaved pondweed are found.

On the banks are occasional stands of common reed and reed canary-grass. Willow scrub favours overgrown tributary streams and is accompanied by a variety of sedges, for example bottle sedge, slender tufted-sedge and lesser pond sedge, while the nationally rare northern spike-rush is found in wet hollows and meanders.

In riverside meadows between Buckden and Kettlewell there are stands of a species-poor sedge community, dominated by one or two sedge species, usually the tall lesser pond sedge or bottle sedge.

The contrasting upland/lowland nature of the upper river is reflected in the birdlife, with both dipper and kingfisher present.

The upper Wharfe is important for its population of native white-clawed crayfish which are under threat from ‘crayfish plague’, carried by the North American signal crayfish, a larger and more aggressive species, which is also found in the Wharfe. The signal crayfish have colonised the river near Kilnsey and above Grassington, but good populations of the native species remain, at Kilnsey, Grassington, Burnsall and Appletreewick. Fine lined pea mussel is also to be found.

There are records of water voles, from Grassington and Otley, but unfortunately no recent sightings. There is, however, a healthy population of water voles at Netherby. Otters use the river and there are some artificial holts which have been built to encourage them to stay. If a permanent population can be established, it will do much to discourage the alien mink, which are also present.

Goosander are found in Strid Woods, together with dipper. If lucky, kingfisher can be seen, and grey wagtail is doing well all along the river. Sand martins are an attractive summer visitor and there is a good chance of seeing an oystercatcher anywhere gravel or stones are exposed. The river also supports populations of scarce plants such as stream water-crowfoot, water-speedwell and the Swedish pondweed.

The Washburn is a rich birding area. Heron, grey wagtail, and dipper may be found, and the alder/oak/birch woodland along the banks has the usual tits, mistle and song thrush, treecreeper, wren, great spotted woodpecker, tawny owl, woodcock, sparrowhawk, goldcrest, bullfinch and, possibly, lesser spotted woodpecker. In summer expect spotted and pied flycatchers, common redstart, willow warbler, chiffchaff, blackcap, garden warbler, goldfinch and, rarely, wood warbler.

The string of reservoirs can produce a variety of wildfowl - great crested grebe, heron, mallard, tufted duck, canada and greylag geese and moorhen, plus goldeneye, pochard, goosander and teal in winter. Waders use the mud at Lindley Wood in late summer when the water level has fallen. But the reservoirs are also important for liverworts and mosses which are sufficiently rare to have their own Biodiversity Action Plans - violet crystalwort is found at Fewston and Swinsty reservoirs and dwarf bladder moss can be found at Lindley Wood.