Kazuhiro Sonoda, J. Alan Yeakley, and Sarah Adams.  2002. Near-stream groundwater correlations with streamwater nutrient concentrations in an urbanizing watershed. In: J.F. Kelly, ed. Ground Water/Surface Water Interactions, American Water Resources Association, pp 67-72.

Abstract

We hypothesized that nutrient concentrations in streamwater within different landuse areas may be influenced by near-stream groundwater.  We sampled streamwater and near-stream groundwater at 8 urban and 5 non-urban locations monthly from December 2000 through December 2001 in urbanizing Johnson Creek watershed in Portland, Oregon.  We compared soluble reactive phosphorus (SRP), total phosphorus (TP), nitrate + nitrite nitrogen (NOx), and total nitrogen (TN) concentrations in both streamwater and near-stream groundwater.  We found significantly higher streamwater and groundwater SRP and TP concentrations within urban areas, while streamwater NOx and TN concentrations were higher in non-urban areas.  NOx and TN were correlated significantly between streamwater and groundwater for both urban (adj. R2=0.873, 0.722) and non-urban landuse areas (adj. R2=0.793, 0.918).  Over 13 month period, we found a strong correlation between streamwater and groundwater SRP (adj. R2=0.975) in non-urban areas.  In contrast, there were no significant correlations between stream water and groundwater SRP and TP in urban areas.  These results suggest that streamwater SRP in non-urban areas was tightly linked to near-stream groundwater.  In urban areas, however, groundwater influence was not the only control on streamwater SRP, indicating that surface water sources were likely also responsible.