Diving in a lake @ 650 mts over sea level

Hi All :

I've been invited to a diving trip which will be done in a lake that is 650 meters (2100 ft) over sea level.
We will done 3 dives the first day and 2 the second. The first day will include a night dive. We have not yet planned the dives, but they will surely be up to 15 mts depth.
The lake is, of course, fresh water.
I have not done yet the speciality course dive in altitude.
How should I correct the diving ND tables for those dives. What additional considerations should I have ?
Please, any help will be much appreciated.

While I don't have the formula in front of me, you could add 10' to your dive and be safe. If you are diving to 60' round your tables to 70'. 2100 ft is not that high but another thing you need to consider is when you go from sea level to altitude you should wait a couple of hours prior to making your first dive. The pressure change will have an affect on your nitrogen loading. If you are using a computer it should have a setting for altitude. It could be automatic (my VT3 is) but my Cobra is not.

This may help: Altitude Dive Table

When I was diving at Lake Atitlan in Guatemala, which is at around 5,000 feet, the ATI divers strongly suggested limiting dives to one a day. I recall reading that as well, so you might want to consult with some experts about your number of planned dives.

It is also critically important that you factor in your travel after your dives. If you must go over a mountain that is at a higher altitude than your dives (which is usually the case because it's really hard to find a lake on the top of a mountain) you will have to wait an appropriate length of time. It is the same as flying after diving. I normally wait 24 hours.

Remember, at altitude there will be less oxygen in the air, meaning your offgassing may take longer. There are also differences in nitrogen loading at depth during altitude dives.

An altitude diving course would be a pretty good idea.

Jeff

Yes. Acclimatise to the altitude before you dive (I would say at least half a day, preferably overnight), dive very conservatively, avoid strenuous exercise directly after diving (I'm thinking here of NOT lugging your gear around) and be very conservative in timing before you ascend from the lake to leave.

Also, expect the water to be very cold, and allow for that as well.

Thanks for the replies.
We will travel to the lake by car, no jet plane travel.
We will arrive to the city over the lake late in the afternoon and will dive next morning.
There is no mountain cross to arrive to the city over the lake, only, maybe, + 200 mts.
The water temperature in the time we will dive is around 18 degrees (64 °F)
I´ve consulted the school where I took my dive courses and Altitude diving is a speciality under the Dive Master course. There is no stand-alone Altitude Diving course.

It's good to be careful, ask, etc - but don't get worried over such a minor change. We routinely dive a spring fed volcano vent at over 4,000 ft to 84 ft deep. Before we got our computers that auto adjusted to the barometric pressure and altitude, but just rounded up to 5,000 and added 20% to the depth for planning our bottom time allowed, if I remember correctly.

Add another 10 ft for the cold water maybe as off gassing is slowed a bit. Waiting a while after arriving is good, but the most important factor is probly good hydration. I reallllllly think that a course on Altitude Diving is not one of the better choices.

Have fun. I'm pretty sure you'll run out of gas well before NDL...!