We are getting closer to finishing off the sluice installations that we have been working on for the last three weeks. The first sluice is in and complete and we just need the excavator to remove the dams at the ends of the new channel to connect everything up to the reedbed pools on either side. These sluices control water levels by having wooden boards inserted into the central metal channel within the sluice box. So if we want a different water level on one side of the bank we put boards into the sluice. If we want the water levels the same in each section of the reedbed we take the boards out and fish will treat the open sluice and new ditch just like any other water course on the reserve. As I have said before we have good populations of fish in some areas of the reserve but not in others so these new sluices will allow the fish to colonise areas where they are currently absent on in low number which will then improve the food for otters, bitterns, kingfishers and other fish eating species.
Image - sluice box being dug into the bank - Dave Rogers
Image - The finished sluice with just the dams at the end of the channel to remove - Dave Rogers
As you can see we need to shore up the sides of the sluice with concrete bags to ensure a firm bank and a water tight fit. We overlap the courses of bags like a brick wall to ensure a strong structure. The sandbags are filled with dry mixed concrete which then sets hard in the water. Very many thanks to volunteers Phil, Nigel and Norman for all their hard work in helping Emma, Katherine and myself as we have made over 350 bags so far. To make that many has taken 9 tons of concrete.
The second sluice went into the ground on Wednesday but we have still to complete the bag walls. Another couple of days work this week and we should be finished. Unfortunately as this work has taken longer than expected and we now need to raise water levels for the breeding season so we are going to have to delay installing the bridges until the autumn.
The Thursday volunteer work party was supervised by Suzanne this week as I was away at HQ to present the new management plan to senior staff, Katherine was at a meeting in Norwich and Emma was on a first aid refresher course. Katherine had arranged a list of jobs to do around the visitor centre so the team had a busy day ploughing though the work.
Finally a few sightings from the last few days. Both of our resident crane pairs were seen yesterday and again this morning. Visitors had good sighting of bittern yesterday and this morning three great white egrets were seen on the reserve, with two birds flying together, which hopefully bodes well for the breeding season.
We hope to see you soon.
Dave Rogers - Site Manager
David Rogers Senior Site Manager - Lakenheath Fen