Abstract:SUMMARY1. A review is presented of the literature on riparian vegetated buffCT strips (VBS) for use in stream-water-quality restoration and limitations associated with their use are discussed. The results are also presented of recent investigations on the effectiveness of a forested and a grass vegetated buffer strip for reducing shallow subsurface inputs of nutrients from agriculture to a stream in central Illinois, U.S.A. 2. Because riparian zones link the stream with its terrestrial catchment, they can modi… Show more
“…These zones have been shown to function effectively as mechanical filters for sediment-bound phosphorus in surface runoff (Osborne and Kovacic, 1993). This is particularly true in agricultural settings where shallow groundwater systems are often the primary transport pathway for phosphorus (P) to surface water bodies (Sharpley et al, 2002).…”
Riparian wetlands can act as both phosphorus (P) sources and sinks depending upon a range of factors that affect hydrological and biogeochemical processes that govern P mobilization. Stream flow, groundwater levels and water chemistry (total P (TP), soluble reactive P (SRP)) were measured in a series of nested piezometers along three transects located in a riparian zone prior to and throughout a flood event resulting from the release of water from an upstream reservoir. Results of the study show that the stream was influent on all sampling dates, and groundwater flow through the riparian zone was longitudinal to the channel, rather than transverse to the stream. This drainage pattern affected riparian zone biogeochemistry. The riparian zone was a source of TP and SRP to the shallow groundwater system under both pre-flood and flood conditions, as P levels were higher in piezometers at the downstream end of the riparian zone (p B0.001). Flooding induced a brief increase in TP concentrations in shallow groundwater due to mixing with surface runoff following overbank flooding; however, these concentrations quickly returned to pre-event levels. In contrast, SRP concentrations in shallow groundwater decreased during flooding, likely resulting from mixing with oxygen-rich stream water. A large pulse of TP (12,000 mg L(1 ) was observed in the creek on the peak flood date. This P did not originate from the reservoir and was more likely due to the mobilization of P from the riparian zone surface when overbank flooding occurred. The results indicate that autumn flooding of riparian zones downstream from impoundments may mobilize phosphorus if overbank flooding occurs, thereby reducing the nutrient retention potential of riparian zones in some settings.Ré sumé : Les milieux humides riverains, sous l'influence des facteurs hydrologiques et biochimiques, responsables de la mobilisation du phosphore (P), peuvent agir en tant que source et puits de P. Dans le cadre de cette étude, des données sur la position de la nappe phréatique, le débit, ainsi que la chimie de
“…These zones have been shown to function effectively as mechanical filters for sediment-bound phosphorus in surface runoff (Osborne and Kovacic, 1993). This is particularly true in agricultural settings where shallow groundwater systems are often the primary transport pathway for phosphorus (P) to surface water bodies (Sharpley et al, 2002).…”
Riparian wetlands can act as both phosphorus (P) sources and sinks depending upon a range of factors that affect hydrological and biogeochemical processes that govern P mobilization. Stream flow, groundwater levels and water chemistry (total P (TP), soluble reactive P (SRP)) were measured in a series of nested piezometers along three transects located in a riparian zone prior to and throughout a flood event resulting from the release of water from an upstream reservoir. Results of the study show that the stream was influent on all sampling dates, and groundwater flow through the riparian zone was longitudinal to the channel, rather than transverse to the stream. This drainage pattern affected riparian zone biogeochemistry. The riparian zone was a source of TP and SRP to the shallow groundwater system under both pre-flood and flood conditions, as P levels were higher in piezometers at the downstream end of the riparian zone (p B0.001). Flooding induced a brief increase in TP concentrations in shallow groundwater due to mixing with surface runoff following overbank flooding; however, these concentrations quickly returned to pre-event levels. In contrast, SRP concentrations in shallow groundwater decreased during flooding, likely resulting from mixing with oxygen-rich stream water. A large pulse of TP (12,000 mg L(1 ) was observed in the creek on the peak flood date. This P did not originate from the reservoir and was more likely due to the mobilization of P from the riparian zone surface when overbank flooding occurred. The results indicate that autumn flooding of riparian zones downstream from impoundments may mobilize phosphorus if overbank flooding occurs, thereby reducing the nutrient retention potential of riparian zones in some settings.Ré sumé : Les milieux humides riverains, sous l'influence des facteurs hydrologiques et biochimiques, responsables de la mobilisation du phosphore (P), peuvent agir en tant que source et puits de P. Dans le cadre de cette étude, des données sur la position de la nappe phréatique, le débit, ainsi que la chimie de
“…Much of the N released from agricultural lands can be intercepted by adjacent downhill riparian forests (Lowrance et a/., 1984;Osborne and Kovacic, 1993;Hill, 1996: Correll, 1997. The effectiveness of riparian forests as N sinks may strongly influence watershed discharges of N (Jordan et ul., 1997).…”
“…As such, "extra" reduction capacity must be present in the sediments for appreciable amounts of nitrate reduction to occur. Organic carbon is the most common electron donor, and its role in the reduction of nitrate has been studied in both field [e.g., Trudell The ability of stream riparian zones to remove nitrate has been promoted as a way to reduce the effects of pollution from nonpoint sources [Osbourne and Kovacic, 1993;Mengis et al, 1999]. Stream riparian zones are defined as those areas which have direct interaction between terrestrial and aquatic ecosystems with boundaries of the riparian zone extending outward to the extent of flooding [Gregory et al, 1991].…”
Abstract. The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third-order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N 2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N 2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon-based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from <0.01 to 0.14 mM of N per year; rates at the redoxcline along the shallow flow path range from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.
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