Effect of Urbanization on Surface Water Chemistry in SE Texas, USA.

Bryan/College Station, home of Texas A&M University is a rapidly urbanizing metropolis situated in a post oak savannah biome in SE Texas.   We sampled nine independent watersheds with varying proportions of urbanization plus three watersheds that contained waste water treatment plants (WWTP) upstream from our sampling point.  Our objective was to examine the effect of urbanization on surface water quality.   Grab samples were taken every two weeks between March 2007 and February 2008.  Urban land use was sub divided between urban open, and urban low, medium and high densities and ranged from 6-100% urban in our watersheds without WTTP and 24-67% in watersheds with WWTP.  Sodium, potassium, nitrate, phosphate and DON had significantly higher mean annual concentrations in creeks  in watersheds containing a WWTP than creeks in watersheds without WWTP.  Mean annual magnesium and calcium concentrations were not significantly different between WWTP and non-WWTP creeks.  Thus, we suggest that urbanization per se does not effect surface water chemistry unless point source discharges from WWTP ’s practicing only secondary treatment are within the watershed.