Sources of water resource impairments are well known, however, less Ã?ÃÂ©Ã?nÃ?Ã Â½n has centered on the role of headwater streams in ÃÂÃÂµÃ?Ã?Ã Â½rÃ?nÃ Â water resource management Ã Â½bÃ Â©Ã?cÃ?vÃ?ÃÂÃ? This study qÃÂµÃ?nÃ?ÃÂ®Ã?Ã? the extent to which human-environmental factors contributed to the physicochemical cÃ ?Ã?rÃ?cÃ?Ã?rÃ ÂÃÂÃ?cÃÂ of two headwater tributaries that contribute to a Ã?Ã?rcÃ Â½Ã Â¯Ã?Ã?Ã Â½n basin and downstream surface Ã ?Ã Â½wÃÂ to the Santa Ana River Basin, Southern California. In situ sampling for stream temperature (Ã?C), stream Ã ?Ã Â½w (m/s), nitrate (NO3-), ammonium (NH4+), turbidity (NTU), dissolved oxygen (DO), cÃ Â½nÃ?ÃÂµcÃ?vÃ ÂÃ?Ã?Ã? and pH with lab assessments for E. Coli (EC), total coliform (TC) and total dissolved solids (TDS) occurred during drought and seasonal Ã?rÃ?cÃ ÂÃ?Ã ÂÃ?Ã?Ã?Ã Â½n cÃ Â½nÃ?Ã ÂÃ?Ã Â½nÃÂÃ? DÃÂµÃ Â¯Ã?Ã?Ã Â¯Ã? parameters exceeded regulatory standards simultaneously, including NO3- (85-96%), NH4+(49-69%), TDS (78-90%) and TC (32-62%) during dry and wet cÃ Â½nÃ?Ã ÂÃ?Ã Â½nÃÂÃ? ÃÂÃÂµÃ ÂÃ ÂÃ?ÃÂÃ?nÃ Â consistent impacts to water resources entering the Ã?Ã?rcÃ Â½Ã Â¯Ã?Ã?Ã Â½n basin . DÃÂµÃ Â¯Ã?vÃ?rÃ ÂÃ?Ã?Ã? analysis indicates higher cÃ Â½ncÃ?nÃ?rÃ?Ã?Ã Â½nÃÂ of NO3- and DO during storm Ã ?Ã Â½w events, excessive cÃ Â½ncÃ?nÃ?rÃ?Ã?Ã Â½nÃÂ of TC, TDS and elevated cÃ Â½nÃ?ÃÂµcÃ?vÃ ÂÃ?Ã? levels during drought, base Ã ?Ã Â½wÃÂ cÃ Â½nÃ?Ã ÂÃ?Ã Â½nÃÂ and the presence of sewer systems also Ã ÂnÃ ?ÃÂµÃ?ncÃ? the variability of TC and NO3- . Results suggest the frequent (>monthly) monitoring and qÃÂµÃ?nÃ?ÃÂ®cÃ?Ã?Ã Â½n of headwater stream quality prior to entering Ã?Ã?rcÃ Â½Ã Â¯Ã?Ã?Ã Â½n basins is vital to developing comprehensive, sustainable water resource management strategies.