Groundwater cation concentrations in the riparian zone of a forested headwater stream

Abstract

Groundwater cation concentrations in relation to hydrologic flow paths were studied in the riparian forest zone of a small headwater catchment near Toronto, Ontario. Groundwater entering the riparian zone from uplands showed significant differences in cation concentrations between slope-foot and near-stream locations. Mean Ca, Mg, K, and Na concentrations in shallow groundwater at the upland perimeter of the riparian forest were 65.0,11.2,0.7, and 1.8 mg L-' respectively. Mean Ca, Mg, K, and Na concentrations in deep groundwater flowing upwards through glacial sands beneath the riparian zone were 52.1, 15.1, 1.3, and 2.6 mg L-' respectively. Shallow groundwater emerged as slope-foot springs producing surface rivulets which crossed the riparian zone to the streams. Deep groundwater flowed upward through organic soils into the rivulets and also discharged directly to the streams as bed and bank seepage. Springs had higher Ca concentrations and lower Mg, K, and Na values than rivulets entering the streams. Conversely, Mg, K, and Na concentrations were higher and Ca concentrations were lower in bank seeps in comparison to rivulets. These results suggest that differences in cation concentrations in groundwater entering the streams result from initial contrast in the chemistry of shallow and deep groundwater rather than from the effects of riparian soils and vegetation.

Contributions of riparian and hillslope waters to storm runoff across multiple catchments and storm events in a glaciated forested watershed

“…The valley-bottom saturated areas are maintained by deep groundwaters that seep up at these landscape positions. The importance of deep groundwaters in maintaining wetness in valley-bottom areas in glaciated watersheds in eastern North America has previously been highlighted by Hill (1990) and Roulet (1990). The presence of wet valley-bottom conditions further expedites the movement of seep groundwater that traverses the riparian areas via streamlets.…”

“…In many locations in the valley-bottom, seepage areas with reddish-brown iron-oxide deposits were visible. Roulet (1990) indicated that when deep groundwater low in dissolved oxygen (Hill, 1990) emerges to the surface, reduced iron is oxidized, thus producing the reddish brown coloration. Surface-saturation in S2 was also observed in multiple isolated pockets on the hillslope bench along the eastern hillslope flank (Fig.…”

Modelling groundwater-surface water mixing in a headwater wetland: implications for hydrograph separation

“…The Glen Major wetland has been the site of extensive of hydrology and biogeochemical cycling studies (e.g. Roulet, 1989Roulet, , 1990Roulet, , 1991Hill, 1990Hill, , 1991Hill, , 1993Waddington et al, 1993). This research indicates that the relationship between storm characteristics and event-water contributions to storm run-o in headwater swamps of the Oak Ridges moraine is related to the responsiveness of saturated areas to throughfall inputs over relatively short time periods (c. 30 min.)…”

“…Previous research (e.g. Hill, 1990Hill, , 1991Hill, , 1993 has identi®ed a local and regional source of groundwater into the wetland. We have adopted the terms`intermediate' and`regional' to represent the dierent portions of regional groundwater to the subsurface and stream reservoirs, respectively (see Roulet, 1990).…”

The distribution of solute processes on an acid hillslope and the delivery of solutes to a stream: I. Exchangeable bases

“…Various field investigations have shown that the spatially differentiated physico-chemical properties of soils on hillslopes may play a central role in the determination of water quality (e.g. Hill, 1990;Mulder et al 1991;Chappell and Ternan, 1992;Billett and Cresser, 1992). In addition, some geomorphologists have emphasized the importance of the spatial variation of solute processes in the determination of chemical denudation rates over hillslopes (Burt, 1986;Trudgill et al, 1996).…”