Copper controls mosquitoes.
Metallic copper in the water is good at controlling larva populations. I used to think it was a direct effect on the larvae but experiments showed me that is not it; they do not die. Metallic copper does markedly decrease algae growth and this is the food for the larvae.
Put some scrap copper in the cement thing you have. ...
We see similar things like this quite often.
If the pipe is not overflowing just becoming stagnant.
Get some “summit mosquito dunks” break them in 1/2 and drop a 1/2 in every month. These are fish safe and won’t hurt plants or other animals but will eliminate the mosquitoes by killing the larva.
Depending on where you live 3 or 4 tablets will last a year (...