I'm not a doctor.
This still sounds like depression. It's a depression I'm familiar with. It doesn't feel as heavy. Life doesn't lack color. It just doesn't seem any part is as satisfying as it ought to be.
My go-to tactic is to give myself some space to process and then go do free low-stakes things outside the norm. Go to a museum. Walk around a mall. Find the schedule for a local sports league and go watch a game. Visit a local library and see what you can volunteer to help with.
Entertainment isn't enough. We need connection with the world outside of ourselves. Finding ways to engage satisfying that need that aren't taxing is a good first step.
One of the reasons is flow control. You want to be able to move a lot of water slowly until it's where you want it. Many small inlets distributed along the surface is a simple and effective method. I'm sure achieving the design you're speculating on is possible but it would be more complex and expensive for that design to reliably achieve similar goals/metrics.
Permeable pavements like pervious concrete and porous asphalt allow some of what you're interested in without requiring a reinvention of the wheel.