This is Haweswater, a reservoir near Shap south of Penrith that feeds water down to Manchester. The reservoir was made in the 1930s by building a dam and flooding the valley. There used to be a village with a church and a hotel which was demolished and flooded. The village was called Mardale and sometimes reappears when the water level falls a long way. Check out the wonderful Striding Edge website to see what the lake level was like 3 months ago http://www.stridingedge.net/Walks/2014/04.%20Apr/29.04.14.htm I am estimating that the level has fallen by 5 metres. They say it had fallen 23 metres to give the view shown in the bottom picture. The lake is roughly 6km long and 1km wide. That would give a volume of 6 million cubic metres lost in 3 months. It has hardly rained so that suggests Manchester uses about 500 000 cubic metres a week from the reservoir. The catchment area of the streams that feed into the reservoir is roughly a circle of radius 4 km if you measure a map. That gives an area of 48 million square metres. It would need to be filled to 1.5 metres to replace all of that water. Seathwaite in the western Lake District is famously the wettest place in England with about 3.5 metres per year, so that amount of rainfall is not a bad estimate. For photographs and maps of the old Mardale, try http://www.mardale.green.talktalk.net/map%20index.htm The square object in the third photograph is likely to be part of Grove Brae Farm. If it doesn't rain a lot, I suspect it will be worth another visit in September to see if the village has appeared.
