We were anchored at:
36º 48.68 N 6º 20.83 W and
36º 59.45 N 6º 10.06 W
sticky mud, good holding in various depths.
The entrance to the river can be a bit rough with wind against current. The bar will always have enough water: big ships go in and out and it's often dredged. At Bonanza the current turns 1-2 hours later than the actual HW/LW.
The ebb runs really fast (much more than f.i. the Guadiana). Some wash from passing cargo ships. Some debris going up and down with the tide, in winter quite a lot.
Nice and quiet anchorages. Only some tourist boats and motor boats and jetski's in the weekend.
The river is charted, so easy to navigate with a plotter. Anchoring can be done anywhere outside the main channel. Safest is just on the inside of a buoy. Our favourite is just N of buoy number 20. Another time we anchored just N of buoy number 28. Between buoy 28 and Gelves/Seville there are less anchoring possibilities because the river gets narrower.
The river forks just before Seville. Turn left for Gelves, right for the lock to Seville. Don't know the lock and bridge opening hours.
According to C-Map there are some patches with very little depths in the part to Gelves, but we had plenty of depth and never noticed any shallows.
Just before Gelves there are high tension wires with a minimum of 16 m. In Gelves we saw several boats with much taller masts than our 15 m.
You can anchor off the outer pontoon at Gelves. Quite deep in the middle of the river but it shallows steeply to the E-shore.
We couldn't find an open wifi signal anywhere. Halfway up the river we only just managed to pick up a dongle signal.
The trip to Seville/Gelves is 50 miles. It's possible to go up all the way on the flood but the ebb won't carry you all the way down in one go. Some call it boring which it might be if you want to do it in one day, very interesting and relaxing if you do it in two days or more and then you can make full use of the tide. Great for bird and other wildlife spotting.