IMTU, it varies considerably. Most systems have a lot of standing liquid water, but there are 'clumps' of starsystems which have little or no freestanding water.
Again IMTU, the Imperial Empty Quarter is famous for the abundance of desert worlds and the scarcity of liquid water: famous enough so that the very sector is named after Saudi Arabia's "Empty Quarter", a vast sand sea the size of European nations.
(This idea - a sector dominated by desert worlds - is NOT reflected in offical Traveller UWP's: it is only true in my Imperium. As you will discover, I built the Imperial Empty Quarter around the theme of 'scarcity' and 'hard times'.)
The lack of water has crippled development in the Imperial Empty Quarter, keeping populations and tech levels much lower than the Imperial average. Imagine a vast number of Tattonie-like systems (a.k.a impoverished criminal hives) and Arrakis-style worlds (without the Spice to bring in power and money) - sprinkled with a few precious 'oasis worlds' - and you have a basic grasp of my Imperial Empty Quarter.
This alternate Imperial Empty Quarter, the backwater of all Imperial backwaters, is populated by
* tough loners and adventurers
* despised people & hated criminals, fleeing from their enemies (real or imagined)
* species, races and tribes pushed out from more habitable reigions. They tend to be seriously xenophobic, and hostile to visitors...
* Imperial exiles from the Core, 'beached' on a desert world with low-tech primitives ("They drive cars?"), until they learn proper obedience to the Emperor
* a handful of gutsy Imperial colonists, trying to build their dreams on the dry, shifting sands...
* desperate Free Traders, scraping for the dry pickings available in the Imperial Empty Quarter
* even more desperate pirates, trying to make a score... ANY kind of score... from the tiny band of hardy traders and tough merchantmen in the Imperial Empty Quarter.
* The silent steel corpses of dead starships - pirates, traders and merchants alike. Their pathetic, stripped hulks can be spotted here and there, throught the Imperial Empty Quarter.
Interestingly, the cause of death usually isn't related to violence or a hijacking gone wrong: a more insidius and common killer is lack of maintenance, and/or attempting to get by on the substandard equipment & parts available in the Sector. Too many crews try to stretch and make do until something snaps...
"You can always tell an Emptyhead trader - he's the skinny bloke with the faded, patched overalls, sandblasted face, and a haphazard collection of tools and repair gizmos on his utility belt."
"Do they usually carry a weapon?"
"Yep, always - but you got to remember, the Quarter isn't a nice place to be. If you survive long enough, you become a weapon."
"Scrawny poor guys don't seem so tough to me."
"That's because you're looking with the wrong set of eyes. Anyways, I'd avoid the Quarter if I were you - too much sun can burn the soul."
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No survey of the Imperial Empty Quarter is complete without mentioning the Bwaps.
Now, the Bwaps are very interesting. A notable minor race, this group of amphibian bureaucrats are commonly found in the Imperial bureaucracies everywhere. One major reason why they never established a subsector state - not even during the Long Night - is because very few worlds in the Imperial sector is suitable for Bwap colonization. The amphibian Bwaps NEED to live in a humid environment, lest they dry out and perish. They need to wear an enviroment suit when in atmospheres of less than 25% humidity.
The Bwaps thus find most of the Imperial Empty Quarter extremely hostile to settlement. And most Emptyheads have never seen a Bwap....
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The Problem with Ports
One of the crucial chokepoints in the Imperial Empty Quarter are the type and number of ports in the region. IMTU, there are NO high-tech (TL D-F) A-class ports, and only two high-tech B-class port (on opposite sides of the Quarter: one at the sector capital, another in an isolated but crucial, high-pop system)
There *are* three or so A-class starports in the sector (TL A-C), all of which are small ports, making only a few starships a year. Few people in the Quarter can afford a starship, so there is limited production of them within the Imperial Empty Quarter.
More to the point, there are only 4-6 B-class ports, and maybe 6 0r so C-class ports in all of Imperial Space within the Quarter: two decently-sized (on the Bwap homeworld on a pop-8 system), but the others have only limited capasity. Again, this is reflective of the poverty and lack of starship traffic within the Imperial Empty Quarter.
Factoid: there are 134 Imperial systems in the Empty Quarter, both in the OTU and IMTU.
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The observant reader has noticed that I am always mentioning "The Imperial Empty Quarter", not just "The Empty Quarter". That's because the Empty Quarter sector is lateally divided by a lesser rift. Rimward of the rift is Imperial Space, but Coreward lies the Julian Protectorate and the Lorean Hegemony.
These systems are quite different from those in Imperial Space, provided with a more generous amount of liquid water and better systems. Of course, they have their own problems, but they aren't related to the supply of liquid water.