(translation done by GOOGLE translate)
This article describes our Passage of the suspension bridge over the border river RIO GUADIANA separating PORTUGAL from Spain.
Trigger for this article are those different statements with which mast height (better: headroom) you can pass the bridge. We use the guide „ATLANTIC SPAIN AND PORTUGAL“ of IMRAY in the 7th edition of 2015. There, the maximum headroom is described as follows. Quote:
„Note, dass die clearence given on Portugese charts is 18m but this is referenced to Mean Sea Level“.
Well, our STORMVOGEL requires a headroom of 19 meters, which is made up as follows:
(With the Spi-rope = top block on the mast, measured):
1) 16,80 meters from the masthead to mast foot
2) 1.5 meters of mast foot to waterline
3) Subtotal: 18.20 meters
4) In addition, 0.80 meter security buffer for VHF antenna (flexible), top lights and wind sensor (both fixed)
5) Total: 19.00 meters.
OK, 19 meters are not 18 meters. So great internet search:
a) WIKIPEDIA (English)
Speaking of 20 meters headroom, but no indication of the water level.
b) SY BELLA LUNA (English)
Quote: „Our mast is 20.7 m Including antennas The bridge is 18 m accordingly to the charts but our guidebook states 20.5 23 high tide low tide.“. No indication which guide they where using.
c) OFFSHORE SAILING (German)
Has the passage graduated with 18 meters headroom in flood easily.
d) SY MIST OF ROMA GAIR (English)
Hat with 20 meters headroom at low tide, the passage graduated difficulty.
e) CRUISERSWIKI (English)
Speaks even from 23 meters headroom, no details of the Tide.
f) SY SCARLET LADY (English)
This yacht has required a headroom of 19.5 meters – no problem.
Well, so what is right?
No idea. Seems more likely to be judgmental? Due to the above-mentioned references we have assumed for 12 April 2016 that the passage must be possible at low tide.
So travel planning as follows:
r.1) High tide Vila Real de Santo António on April 12, 2016 by 13:22.
r.2) Flood 3.04 meters, 0.98 meters high tide, difference 2.06 meters.
r.3) Leave VILA REAL 13:00 than the short distance up river to arrive to the last ebb tide at the bridge.
r.4) Then with slowly forward under the bridge, ready to turn off when something at the mast begins to scratch. The still ongoing against ebb the boat stops if necessary on very quickly.
That was the plan. In reality, the passage was done without any problems (except for the loud palpitation of the crew!) And it was still clear space between the antenna tip and the bridge concrete. Really hard to estimate, but I think now, that’s the headroom at low water will be 23 meters. This claims two Internet sites and fits our own experience.
So what is actually no grassroots affair but Seemanschaft. In the Baltic Sea we have on the pillars of Fehmarn a level in huge numbers – so you can read the actual, just current maximum headroom before passage – very pretty clever, the Germans 
The RIO GUADIANA is now equipped with fairway markers. Brand new portside and starboard piles after lateral mark. lit even at night.Very reassuring!
On the whole passage to ALCOUTIM (about 18 miles) upriver in the fairway we had a minimum water depth of 4 meters, but often 10 meters or more in accruing water. So really no problem. Only the mooring in ALCOUTIM on the starboard side of the fairway at the northernmost Pontoon we had at the turn at once 1.5 meters in the display. So drive a wide berth, but close to the Pontoon – there are at low water over 3 meters.
A passage in twilight or at night, we would not dare yet. Too many Mooring- and anchor boats in the upper river thirds and fog such a trip would make unnecessarily difficult.
Using the Spi-rope I have drawn a GOPRO in the masthead and made a video recording of the passage. Shown here in YOUTUBE. The noise coming from the bridge – was really loud. Only knock is not, that was the case the GOPRO which struck the mast;-)