The Chew Valley Lake is the most prominent feature of the Chew Valley and is the primary water source for the City of Bristol and an important strategic resource. It is not natural though and wasn’t built until 1956. The lake was constructed by damming the River Chew to the south of Chew Magna and flooding a large area of flat farmland including the villages of Moreton and Denny.
An old linen backed copy of the 1946 edition of the One-Inch Map (“Full Revision 1930 with later corrections”) provides an out of copyright view of what the area was like before the lake was constructed.
The lake is now so familiar that it is hard to imagine the valley without it.
Denny island is the only part of the lake’s area to stand proud of the water but in dry years when the lake level falls parts of the old landscape start to re-emerge.
Apart from the lake itself and some minor realignments of the roads the area remains remarkably similar to how it was in 1946 (and indeed 1930 when the old map was revised). A noticeable difference is an increase in the amount of woodland, much of which is around the banks of the lake itself.
Just across the watershed to the west is the Yeo Valley and the Yeo Reservoir, now known as Blagdon Lake, which opened in 1905.
This area has hardly changed at all since 1946, the road layout is the same and the woodland is largely the same. What has changed is that the railway line, which was used to bring construction materials to the dam and coal to the pumping station, closed completely in 1950.
These areas have remained so unspoiled because of protection by the Town and County Planning Act, The Green Belt and The Mendip Area of Outstanding Natural Beauty and designation of the lakes as Sites of Special Scientific Interest, Special Protection Areas and Groundwater Protection Zones. The area is also home to a number of organic farming industries including Yeo Valley and The Community Farm.
All of these protections are under pressure in 2015 and the area has been identified as potential for Coalbed Methane and Shale Gas exploitation.
The 1946 Ordnance Survey map above is out of copyright. Other spatial information is from the Ordnance Survey Open Data and is covered by the Open Government Licence.