OK. I'm still optimistic that the ejector would help, and would save a second run of pipe.
Best guess is that the 190' source at 8 GPM will offer 250 watts, and the 240' source at 2 GPM offers less than 100W.
Bearing in mind that no matter how we combine the flows, they won't make more than 350, there are things we can do to get as much of it to your turbine as possible.
My suggestion is to combine the flows by making (or buying, if you can find such a thing!) a section in the large flow tube that has a smaller tube entering it at a very shallow angle like a "y". The small tube would enter not just like a simple T at right angles, but give it an angle so the flows are almost going the same way before the combine. Also, the smaller tube would continue inside the larger tube for some distance, straightening out and running through the center of the larger tube. The mouth of the smaller tube then opens in the middle of the flow of the larger tube, finally mixing the flow. Make the end of the tube have sharp edges, or maybe cut at an angle, so that there's no blunt end to slow the flow down.
I probably need a drawing. My explanations never seem clear when I re-read them. I'm trying to google up a good photo but they all have venturis and nozzles and that's not what you need. All this takes is a gentle introduction of the 2 flow together with the least turbulence added.