With Arizona’s population increasing rapidly many tracts of land in the desert are being developed into urban subdivisions.  Many of these subdivisions are being built along ephemeral streams.  The ecological role of ephemeral streams in the semi-arid southwest might be very important in this water-scarce region as the majority of the streams are ephemeral (> 90%).  The objective of this project is to evaluate how different levels of urbanization can impact the ecological functions of areas along ephemeral streams in the Sonoran Basin and Range ecoregion of Arizona.  Areas along ephemeral streams have in general received less scientific attention compared to areas along perennial streams.  This project will evaluate: a) Microclimatic conditions of riparian areas of ephemeral streams associated with three levels of urbanization, b) Plant composition and structure as affected by microclimatic and disturbance drivers in riparian areas of ephemeral streams associated with three levels of urbanization and c) Decomposition rates as affected by microclimatic and disturbance drivers in riparian areas of ephemeral streams associated with three levels of urbanization.  The levels of urbanization are: a) Heavy urban density along riparian areas of ephemeral streams.  The housing density average is 12 to 14 houses per hectare.  b) Moderate urban density along riparian areas of ephemeral streams.  The housing density average is 4 to 7 houses per hectare. c) Low urban density along riparian areas of ephemeral streams.  The housing density average is less than 1 house per hectare.  Each level of urbanization has three reaches (three replications).  A total of nine reaches have been selected in Marana, Arizona.  These reaches have maximum discharge less than 1000 cfs and are within a radius of 1.5 miles from each other.  The data presented will be from the first six months of the project.