A region with less precipitation than potential evapotranspiration is called arid (from Latin aridus: dry, drouthy). This does not necessarily mean that there are no water sources. For example, when looking at http://commons.wikimedia.org/wiki/File:Klimate-humidität.png it can be seen that Egypt is arid, but of course there is the river Nile as source of water.
The antonym of arid is humid (cf. http://en.wikipedia.org/wiki/Humid#Climate).
When talking about availability of water, also water rights must be taken into account, as pointed out by FumbleFingers. Additionally it might be necessary to distinguish between water and drinking water: think of an island in the ocean – lots of salt water, but maybe no fresh water.
A country without access to the seas is called landlocked country, which is important when considering for example ship transport or fishing.
Note that a wetland is not just wet land and that irrigable means can be irrigated. If you get water from somewhere (e.g. by pipeline), you could also irrigate an arid area, i.e. there exists arid irrigable land. arid and irrigable are not antonyms. Irrigation is even applied to land which needs water, thus arid land gets irrigation but humid land will be seldom irrigated.
Merk mentioned http://en.wikipedia.org/wiki/Water_scarcity for additional thematic information. Also FAO: The arid environments might be of interest.