Since 2014, I have measured the depth of the lake on some 400 occasions from a reference point near to the watersports jetty, but calibrated to the crest of the old weir. The minimum depth I found was 13 cm below the old weir crest, at the end of a dry summer period in late July 2018. From historic maps, I was able to establish the lake level in the 1890s, presumably the same as Capability Brown's original depth in 1766. This was around 35 cm below the 2014 weir crest, so about 22 cm lower than the lowest I found in recent years. I have suggested that the new weir constructed for the dam safety works could be set nearer to Brown's original level, but LB Merton rejected this, mainly because they wished to have maximum depth for watersports. The new weir crest is set just 5 cm below the level of the old, a desirable change, but insignificant. The consequence of this is that flooding problems in the public park and drainage problems on the golf course and Wimbledon Club will remain. The good news, however, is that the new weir is a "compound" design, allowing a lowering by a further 30 cm in the future, to bring the lake down to Brown's level.
During the dam safety works, the lake level was lowered to enable access for constructing the new facilities. I have measured the depth of the lake at intervals during the works. The lowest level I found was at the end of March, when the lake was fully 44 cm below the old weir crest, which is 9 cm below Brown's design level. Since then the new weir has been operational and the lake has been filling slowly back up towards the new weir crest. The level rose past Brown's original around 4th April. There were boats out on the lake on 7th April, when the water level had risen only about 3 cm above Brown's level. So, it might appear that a lowering of the lake level to Brown's original design did not preclude watersports use. In early April there was no sediment exposed around almost all of the lake perimeter: just a tiny amount beyond the island in the western arm of the lake. So, lowering the lake to Brown's design level would not reduce the area of open water by a measurable amount. This is quite contrary to the story being spun on escourted walks around the golf course led by AELTC.
Water depth was enough to enable an examination of water clarity on the 23rd. It proved to be mid range and very similar to April readings in the previous five years. So, the drastic lowering seems not to have affected the normal Spring increase in clarity. The real test will come in summer, when disturbance of the sediment has resulted in poor clarity in recent years.
When I did the monthly bird count on the 11th the lake level was still 29 cm below the old weir crest, or 6 cm above Brown's design level. Canada and Egyptian goose numbers were below the historic average for April, but the 42 Greylags were a record April count, suggesting that this species is still doing well in the park. Last year's cygnets seem to have finally departed the lake, leaving the resident Mute swan pair to begin nest construction, this year in full view of the lakeside prominade, in the bed of Yellow and Sweet flag beside the stadium. Great-spotted woodpeckers and Blackcaps were singing in both woods. There was a very vocal Green woodpecker near the crazy golf area, perhaps the works have made the ants there easy prey? A record April count of singing Goldfinches confirms the great increase of this species in recent years.
The flower and leaf buds of the various Oaks in the park come out a different times. One on the south-east edge of Horse Close Wood was half leafed and both Squirrels and Wood pigeons were feeding on this lush young growth. A large old Ash tree, which was spared when many of its fellows were copparded early in 2019, fell in a rainstorm early in the month. This tree was near to a point in the middle of the wood where I do a 10-minute bird count each month so it was known for the nest sites it provided for Stock doves, Wood pigeons, Starlings and Great spotted woodpeckers, making this a significant loss. It fell near, but clear of, the main path and is resting on the ground and no hazard. It was rotten at its base. The management plan would leave it there to rot down over many years, providing habitat for Stag beetles and the like.
In early April, Norway maples come into their own. The trees are covered in bright green flowers and stand out from the drab surroundings, where other species are only just beginning to break bud. There is a fine display of Norway maples along the Home Park Road boundary of the golf course, which is not provided for in the All England proposals, which show newly planted woodland there. Just how sacrificing these mature trees and replacing them with saplings can be seen as a benefit beats me.
