NEAR‐STREAM LANDUSE EFFECTS ON STREAMWATER NUTRIENT DISTRIBUTION IN AN URBANIZING WATERSHED¹

Abstract

We investigated spatial and temporal relationships among surface and subsurface watershed attributes and stream nutrient concentrations in urbanizing Johnson Creek watershed in northern Oregon. We sampled stream water at eight urban and five nonurban locations from March 1998 through December 1999. We sampled eight wells distributed over the two primary aquifers in the watershed. Using a Geographic Information System (GIS), percentages of landuse attributes within a radius of 30, 91, and 152 m from each sample site were quantified. We analyzed relationships between (1) nutrient concentrations and percentage cover of different landuse attributes, and (2) nutrient concentrations and underlying hydrologic units. We did not find a significant relationship between ground water chemistry and stream water chemistry. We found elevated levels of phosphorus (P) concentrations correlated with urban landuse, while higher nitrogen (N) concentrations were correlated with nonurban (primarily agricultural) landuse. We concluded that elevated levels of N in nonurban areas of Johnson Creek watershed were associated with agricultural practices. We further concluded that urban development factors such as increases in storm drains, dry wells, and impermeable surfaces may be responsible for higher input of P to the stream in urbanizing areas of the Johnson Creek watershed.

Stormflow Dynamics of Dissolved Organic Carbon and Total Dissolved Nitrogen in a Small Urban Watershed

“…The study area was a small urban watershed (32 ha) drained by a tributary to Johnson Creek, in southeast Portland, Oregon ( (Sonoda et al 2001). The study site lies on the Troutdale Gravel aquifer that dates back to the Pleistocene, ranges from 20 to 120 m thick, and generally is composed of a consolidated sandy gravel layer (Sonoda et al 2001).…”

Using Diatom Assemblages to Assess Urban Stream Conditions

“…The program ArcViewÒ (ESRI, 1997) was used for displaying and analyzing spatial coverage of maps and their corresponding databases created by Metro (1999). Sonoda et al (2001) used GIS analyses to characterize near-stream land use and the relationship with water chemistry in Johnson Creek. They found that nutrients correlated well with near-stream land use characterized within a 30, 91, and 152 m radius around each site.…”

An investigation of water nutrient levels associated with forest vegetation in highly altered landscapes

“…In some studies, urban areas had lower stream NO 3 -N concentrations than in agricultural areas (Coulter et al 2004;Sonoda et al 2001) or were between the extremes of intensive agriculture and intact reference sites (Shields et al 2008). Our study shows urban areas had the highest TN concentrations.…”

“…One explanation for the variability among studies is the obvious differences in type and intensity of agricultural land use and urban development. Baltimore, Maryland (Shields et al 2008), Lexington, Kentucky (Coulter et al 2004), and Portland, Oregon (Sonoda et al 2001) are larger, more heavily urbanized cities than Des Moines, and the agricultural land uses in those studies were more intensive than the cattle grazing in our study. Other factors, such as background levels of nutrients, may be more strongly influenced by natural factors in undeveloped watersheds (e.g., decomposition rates, local N deposition rates) rather than anthropogenic inputs (Clark et al 2000), leading to variability among different study regions.…”

“…In Oregon, urban land use was linked to higher P input to the stream (Sonoda et al 2001), and soil chemistry influenced P levels in stream water. These researchers determined that P-saturated soil could not adsorb additional P and it was lost to the stream (Sonoda and Yeakley 2007).…”