Assessment of the Impact of Nutrient Management Practices on Nitrate Contamination in the Abbotsford-Sumas Aquifer

Abstract

The impact of recent changes to nutrient management practices in raspberry fields on the loading and subsequent transport of nitrate through the vadose zone of the Abbotsford-Sumas aquifer is investigated numerically. Previous studies have shown that nitrate concentrations in the aquifer have remained relatively stable despite a shift in nutrient management practices. Using an estimate of net annual available nitrogen in fields that are fertilized using synthetic fertilizer, nitrate concentrations as a function of time and depth through the vadose zone are simulated from spring to late fall. Results indicate rapid leaching of nitrate owing to the permeable nature of the aquifer and suggest that nitrate loading to the water table may occur earlier than previously thought, possibly due to spring rains. For an average fertilizer application rate of 90 kg of N/ha, the simulated nitrate concentration on Oct 1 within the top 1 m of soil is 33 mg of N/kg, while the residual soil nitrate measured in late September was 37 mg of N/kg. Taking into account the effects of dilution within the saturated zone, the simulated peak nitrate concentration is similar to average observed peak concentrations in a shallow monitoring well. A solution is offered for estimating nitrate concentration at the water table as a function of the rate of synthetic fertilizer applied to raspberry fields.

The atmospheric transport of iodine‐129 from Fukushima to British Columbia, Canada and its deposition and transport into groundwater

“…The figure shows the water table located at 7 m depth with a capillary fringe of ∼0.5 m. The saturation is initially at 75% in the soil column; however, as soon as the simulation starts the saturation drops to ∼15–18% and remains in this range for the duration of the simulation. This is indicative of a soil that has a very low field capacity and this scenario agrees well with previous efforts to model the vadose zone of the ASA [ Chesnaux and Allen , ; Chesnaux et al ., ]. This rapid drainage of the vadose zone has a great effect on the mobility and velocity of 129 I.…”

“…The input data are provided in supporting information Table S2. Porosity, hydraulic conductivity, residual moisture content were obtained from literature and K d was calculated [ Chesnaux and Allen , ; Chesnaux et al ., ]. All other hydraulic parameters were default values.…”

“…border between southern British Columbia, Canada, and Washington State, USA and supplies ∼120,000 people with drinking water (Figure ). The hydraulic properties of the ASA have been studied in the context of nitrate leaching and transport as the primary land use in the region is agriculture with a high density of berry farming (raspberries and blueberries), poultry production and some dairy farms [ Wassenaar , ; Cox and Kahle , ; Wassenaar et al ., ; Chesnaux et al ., ]. NO 3 contamination throughout much of the aquifer is attributed to the intensive nature of agricultural activities in this area [ Hii et al ., ; Chesnaux and Allen , ; Zebarth et al ., ].…”

Landscape indicators of groundwater nitrate concentrations: an approach for trans‐border aquifer monitoring

“…The aquifer supplies drinking water for 100,000 residents of Canada in the city of Abbotsford and the township of Langley (Chesnaux et al. ) as well as nearly 10,000 people in the United States (towns of Sumas, Lynden, Ferndale, Everson, Nooksack, and scattered rural areas). The unconfined, highly permeable sand and gravel aquifer is recharged primarily by direct precipitation (Fraser Valley Soil Nutrient Study 2005) and consists of mostly coarse‐grained sediments of glaciofluvial drift origin.…”

The unbearable fuzziness of being sustainable: an integrated, fuzzy logic-based aquifer health index

“…concentrations and (given a predominant flow direction toward the south) contribute to transboundary contaminant transport, with implications to users on both sides of the border. Detailed background information on the ASA can be found, for example, in Zebarth et al (1998), Hii et al (1999), Mitchell et al (2003), Wassenaar et al (2006) and Chesnaux et al (2007). Due to this strong relevance, and the unusually long groundwater quantity and quality data sets available here, three groundwater monitoring wells at different locations in the aquifer on the Canadian side of the international boundary were chosen as an initial proving ground for our index.…”