You use big pumps to fill the lock from the low side instead of just opening a valve or the doors slightly. This would then increase the salinity on the lake side and cause whatever problems that would cause.
What I'm saying is, is there an infrastructure solution that doesn't increase the salinity in the lake? Like can we use gravity up to the last lock, but then pump all the fresh water out back to the lake and then pump seawater into the chamber after it's empty? Or something crazy like that.
