Ephemeral and endoreic rivers are located in arid, semi-arid and dry sub-humid drylands of the earth. Climate variability, strongly correlated with aridity, is a Major factor influencing ecological, economic and social sustainability of ephemeral and endoreic rivers (Molles et al 1992). Ephemeral rivers, with temporary surface flow that varies between seasons and years, nevertheless support ecological systems that have been used by people and wildlife for millennia. Endoreic rivers, which may be perennial or ephemeral, are also a focus of use and development in otherwise arid landscapes.