Publication (Technical report): Groundwater nutrient concentrations in riparian zones of agricultural catchments

Publication Type:	Technical report / Consultancy
Publication Name:	Groundwater nutrient concentrations in riparian zones of agricultural catchments

Reference Information

Udy, J.; Hunter, H.; Bunn, S.; Browne, C.; Fellows, C. (2000) Groundwater nutrient concentrations in riparian zones of agricultural catchments. Final report ScB4.

Optional Information

Attached document(s):

- Grdwater Nutrients.pdf

Other information:

PDF report attached below.

Groundwater Nutrient Concentrations in Riparian Zones of Agricultural Catchments. Final Report. ScB4.

Udy, J., Hunter, H., Bunn, S., Browne, C. and Fellows, C.

Aim:

To provide preliminary data for a proposed joint CRC project on “Transport and transformation of nitrogen in riparian zones.”

Context:

Increased stream loadings of nitrogen are now recognised as a significant impact of upstream land use in many catchments, both in Australia and overseas (see Burt et al. 1993; Hunter and Walton 1997). Nitrogen (rather than phosphorus) has been identified as the major problem nutrient in coastal systems in eastern Australia (e.g. Moreton Bay – Dennison and Abal 1999; Port Phillip Bay – Murray and Parslow 1999). Furthermore, recent Australian research suggests that algal growth in some

Australian river systems is also limited by nitrogen supply (Mosisch et al. 1999; in press). That is, an increased delivery of nitrogen to these systems is likely to boost algal growth, to the detriment of ecosystem health (Bunn et al. 1999). This is particularly the case for bioavailable forms of nitrogen such as ammonia and nitrate, which can constitute a significant proportion of the total nitrogen flux.

The presence of riparian zone buffers is considered to be the most important factor controlling entry of non-point source nitrate to surface waters (Burt and Haycock 1996). Fluxes of nitrate through the riparian zone are intrinsically linked to water
movement (both over and through the soil) and are also strongly influenced by biological processes occurring in that zone. Nitrogen and organic carbon dynamics in riparian zones are closely interrelated. Nitrogen loss to the atmosphere through the
process of denitrification, and its uptake by riparian vegetation are two important means by which nitrate loads can be reduced (Haycock and Pinay 1993). While many of the factors that can potentially influence nitrogen and carbon fluxes through
riparian zones are broadly known, there is presently no quantitative information on the relative importance of these various processes, and their interactions, in the variety of climatic and physiographic settings typical of Australian catchments.
This project was designed to provide a preliminary assessment of nutrient concentrations in the groundwater in the riparian zone to identify if nitrate was attenuated along sub-surface water pathways in riparian zones. We also planned to identify likely processes that could be occurring in the riparian zone that would contribute to observed changes in nutrient concentration. For example, if a decrease in groundwater nitrate concentrations were detected along a gradient from the riparian zone to the river, stable isotope analysis of the nitrate might indicate denitrification as a possible mechanism for this gradient.

The specific activities of the proposed scoping study were:

•install piezometers and water table wells at up to 4 study sites

•collect hydrologic and geochemical data

•collect additional samples for isotopic analysis where warranted by geochemical data.

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