The Main Canal extends westerly 22 miles from the Trinity River Pump Station to the Lynchburg Reservoir located on the north side of the Houston Ship Channel opposite the San Jacinto Monument. The Canal, which is on a gradient of about 0.9 feet per mile, has an average water level at full flow of approximately 100-foot width, a 14-foot flat bottom, and 3 to 1 side slopes.

The canal is unlined, except for a short section near the Interstate 10 siphon, as most of the route is through heavy clay. In those short sections where clay is non-existent, the canal has been undercut and clay lining approximately 2 feet thick has been installed. The total capacity of this canal is over 1.3 billion gallons per day.