Hi GXP, a geographer would look at it this way: all along the coastline ( probably universally) you tend to have a line of coastal cities at the mouths of major rivers and a another line of inland cities at the inland edge of the coastal plain on the major rivers, where the rivers became less navigable and useful for commercial transportation before trains, plains, and automobiles. Exceptions for the Missiissippi, Nile, etc. In Texas those being SA, Austin, Waco, Dallas.
Austin Mueller was about 660’ MSL IIRC. Minor but ~50%. Google says 632’.
We wouldn’t be sending water to Muller you would be sending it to the outlet elevation of Lady Bird Lake which is 425 MSL from there you would mix it with effluent from both Austin treatment plants which are at 410 ish feet just a little down river. Once mixed you would send it via a subsurface pipeline under the south Bank of Lady Bird Lake at 428 feet all the way to Tom Miller dam and Lake Austin. Which right now is 492’MSL once it outfalls in Lake Austin both of Austin existing potable water treatment plants can pull it from Lake Austin just like they pull Travis water. Every acrefoot that gets put in Lake Austin is one less from Travis taken.
Check out hydromet for real time levels.
You are right about port cities and their up river twins. It is easier and cheaper to keep water up hill than pump it back up hill. The plan should always be first stop letting water flow down hill trap it at the upper city and recycle it as much as you can via down river effluent capture and pump back like Dallas does. Since you starved the port city they need to make up for the loss by desal. If the downstream has senior water rights then the up stream must pay for the desal water for them in exchange for keeping the up stream water back.
Some rivers like the ones in South Texas have such little flow in them by the time they reach the coast they are not useable as water sources. The San Antonio river , Guadalupe and Rio Grande in dry years don’t even reach the Gulf with flows. This is why Corpus needs to desal for sure.
The Colorado is special it has a mandate from the legislature for minimum inflow to matagorda bay for crabs and shrimp beds nearly every drop of that mandate is meet with Lake Travis water especially in dry years. This is why the new Arbuckle project is critical and any desal could be dumped there and stored for environmental flows and leave more water in Travis for Austin to use. Austin RR and Georgetown have straws reaching Stillhouse Hollow and soon to be Lake Belton too that’s a good chunk of the while upper Brazos watershed capture area above those two lakes. Austin needs to also teach east for the Trinity and Wilcox aquifers both for raw water and for storage those pipes should be bidirectional. Once you have pipes fast it gets easier to keep going east to the Trinity basin and also the Sabine both in 50-60 inch rain per annum zones vs 20 and under in the upper Hill country. The water is in the east Texas needs to build the pipes to send it west.
East Texas rivers like the Trinity feed Houston with 300000+ acre feet from east Texas rain so Dallas can pump back nearly every drop of effluent it captures down stream in its constructed wetlands.