The tree in the picture still is a baby
I have the exact same issue, my neighbour has a sweet chestnut in his garden about 3 metres away from mine. But this one is about 8 to 10 metres high and the trees canopy covers a great deal of my lawn.
I was planning a pond too, but still in doubt if I should. The Sweet Chestnut is an extremely dirty tree, shedding 3 times a year and a lot. In the early summer it sheds the blossoms and pollen, late summer it will shed the nuts and shells and in the fall it will shed its leaves. I'm not sure about yours, but mine is according an expert an American Sweet Chestnut and he told me the fallen leaves of this tree are extremely touch and leathery texture that takes a very long time to decay. And he was right, I'm cleaning it up every year again, if I don't it will suffocate my entire garden with a thick blanket of leaves that about never decay.
Anyway, this will all blow in and pile up in and pollute your pond if you don't clean that out on a daily basis. A skimmer will be pre to have.
I did put a net over my lawn to shield it from all this falling debris and test it how that goes. I'm 3 days t late to take a picture to show the mess it makes because the blossoms have fallen by now and i cleaned it up. But still, a lot falls through the net on the lawn. I'm still not sure if I should make the pond if I do it will be a lot of maintenance to keep it clean.. That I know...
I'm talking about this monster already haunting me the past 20 years.
These are the blossoms.
I guess for now yours is still a baby, but this is what to expect on the long run...
I'm a tree lover and don't advocate taking down trees and not going to bother my neighbour with that. I rather clean up after it.. But if this tree was on my ground i probably would be very tempted to make firewood out of it.