Landscape controls on nitrate removal in stream riparian zones

Abstract

[1] We examined how landscape hydrogeologic characteristics influence groundwater nitrate removal by eight stream riparian sites on glacial till and outwash landscapes in southern Ontario, Canada. During high water table periods in 2000 -N input concentrations from adjacent cropland to the riparian sites ranged from 0.15 to 44.7 mg L À1 . Seven of the eight sites had a mean nitrate removal efficiency of >90%. This removal occurred within the first 15 m of the riparian zone at three sites with loamy sand and sandy loam soils overlying a shallow confining layer at 1-2 m. However, at four of five sites with more conductive sand and cobble sediments the width required for 90% nitrate removal varied from >25 m to a maximum of 176 m at a site with a confining layer at 6 m. Sites linked to an extensive thick (>6 m) upland aquifer with a slope gradient of >15% at the riparian perimeter had high nitrate inputs throughout the year and were large nitrate sinks. Sites with gentle topography (<4-5%) and <2 m of permeable sediments were minor nitrate sinks because of small nitrate inputs that were limited to the late autumn-spring period. A conceptual model linking landscape hydrogeologic characteristics to riparian zone nitrate removal capacity is developed to understand and predict the effectiveness of riparian buffers at the landscape scale.

Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and biogeochemical models

“…This filtering capacity of riparian zones is maximized when the depth of the groundwater flow from upland to stream channel is limited by an impermeable or less-permeable subsoil layer at 1-3 m below the soil surface (Hill, 1996). In these situations nutrients and groundwater move through the biologically active topsoil of the riparian zone before reaching the stream (Sabater et al, 2003;Vidon and Hill, 2004a).…”

Effects of riparian buffers on nitrate concentrations in watershed discharges: new models and management implications

“…Many studies report substantial nitrogen removal along field-to- stream transects (Lowrance al. 1984, Peterjohn and Correll 1984, Jacobs and Gilliam 1985, Cooper 1990, Jordan et al 1993, but other studies report no effect or inefficient nitrogen removal (Denver 1991, Osborne and Kovacic 1993, Altman and Parizek 1995, Hill 1996, Correll et al 1997, Sabater et al 2003, Hefting et al 2004, Vidon and Hill 2004, Mayer et al 2007, Speiran 2010. Because some buffers do not remove nitrogen, the cumulative watershed impact of riparian zones on stream nutrient levels remains poorly understood , Vidon et al 2008.…”

The Characteristics of Riparian Buffer Studies

“…Poole and Berman (2001) and Jackson et al (2001) studied the temperature adjustment function of riparian buffers. Puckett et al (2002) and Vidon and Hill (2004) analyzed the run-off from melting glaciers and its impacts on the environment. Wilzbach et al (2005) studied the interwoven relationship between salmon and the forest, based upon the nitrogen nutrient left behind by the fish.…”