Grimwith Reservoir should be spot on for a bracing Boxing Day blast. I arrived at noon, the temperature was one degree above freezing, the wind was ruffling six-inch waves on the water, and the sun shone in a perfect, cloudless deep blue sky.

Grimwith is not grim, but definitely exposed, high on Wharfedale moorland. Bring your new Christmas hat, because the only certain warmth, apart from the nearby pubs at Pateley Bridge and Grassington, is to be found in the heated loos at the reservoir.

Clockwise or anticlockwise? Which way round the water? The only navigational decision. I'd definitely recommend anticlockwise, for a build up of interest, a movement from the easy 'recreational' end to the surprises of the slightly more wild 'conservation' zone, and it's great to have the dam as a finale. So off we go down to the waterside on Yorkshire Water's super tracks and paths, indeed the circuit is only possible thanks to their permission in places.

Sailing boats were tucked away in a little quarry, they can only use the southeastern half of the water. A few waterside barns are abandoned and in desolate good repair, lucky by a foot or two to be spared a watery grave. Feeder streams come down from the low surrounds of heather, and are nicely ducted under the track. The engineering from splendid dam to neat wooden footbridge is beautiful.

John Mather says in his 'Where to watch birds in Yorkshire' that 'being largely open and exposed, the reservoir is not a particularly good site for waterfowl'. At first all I could see was a small group of little ducks bobbing on the waves and a larger raft of larger ducks further out, and they turned out to be Canada Geese. There was a fieldfare, and a couple of birdwatchers with bigger binoculars and more knowledge than me said they had seen a female sparrow hawk and 30 widgeon. The birds got exciting over the next hour or two.

Meanwhile it was easy warming walking. The sun was a bonus, a quivering, hot ribbon on the water. We leave the track for a single file peaty path into the wildlife area. Up a bit, a little climb through boulders, then back to the track and the far northern part of the reservoir.

I had my sandwich stop on one of the comfy rocks by the bridge over Gate-up Gill. Forbidden but enticing tracks lead north, crags decorate hillsides. The reservoir looked lovely, and for extra seasonal cheer the wind turbines miles away to the south twinkled like fairy lights on the fells.

After an inlet icy in the shade, I noticed the birds. Flock after flock were coming in about every five minutes, low over the dam, skimming the surface, turning into the wind to splash land and join the enlarging raft of white in the middle of the reservoir. This went on between two and three o'clock. There must have been a thousand birds, a mix of species including lots of pochard or tufted duck. Ducks are difficult.

For an ace last half-mile, we walk the grass embankment of the dam. The valve tower is the most stylish cylindrical plughole. Twice jets screamed low over the water, and all the birds lifted a foot or so in fright, then settled down again for a night afloat.

Country Walks will return on January 6.

Fact file

Distance: Four and a half miles.

Time: Two to three hours.

General location: Southern Dales.

Start: Grimwith Reservoir.

Right of way: The route is along public rights of way and permissive paths.

Date walked: Friday December 15, 2000.

Road route: Eight miles from Pateley Bridge on B6265 to Grassington. Two miles west of Stump Cross Caverns.

Car parking: Free car park.

Lavatories: At car park.

Refreshments: Hebden, Stump Cross Caverns, Pateley Bridge and Grassington all nearby.

Tourist and public transport information: Grassington TIC 01756 752774

Map: Based on OS Outdoor Leisure 2, Yorkshire Dales southern and western areas or OS Explorer 298 Nidderdale.

Terrain: Waterside, level plus gentle climbs.

Points of interest: Birds, boats.

Difficulty: Easy/moderate.

Dogs: Suitable, on leads.

Weather forecast: Evening Press and recorded forecast 0891 500 418

Please observe the Country Code and park sensibly. While every effort is made to provide accurate information, walkers set out at their own risk.

Directions

When in doubt look at the map. Check your position at each point. Keep straight on unless otherwise directed.

1. Track uphill from car park, stile/fieldgate, 100 yards, fork left downhill on path (signed Permissive Path). Rejoin track.

2. After roofless ruin and barn, snickelgate to peaty path. Rejoin track and loop around northern part of reservoir.

3. On crest of hill (above barn), path on left between fence and wall (signed Permissive) to grassy dam embankment and back to car park.

Click here to view a map of the walk