Coupling of surface water and groundwater nitrate-N dynamics in two permeable agricultural catchments

Mellander, P. - E. and Melland, A. R. and Murphy, P. N. C. and Wall, D. P. and Shortle, G. and Jordan, P. (2014) Coupling of surface water and groundwater nitrate-N dynamics in two permeable agricultural catchments. The Journal of Agricultural Science, 152. S107-S124. ISSN 0021-8596

Abstract

The current study investigated the coupling of groundwater and surface water nitrogen (N) dynamics over 3 years, and considered intensive agricultural land-management influences over this period where the risk of N loss to water was considered high. Groundwater N (as nitrate) was monitored monthly in different strata and zones in four hillslopes, two in each of two agricultural catchments of c. 10 km2, and stream water N flux was monitored sub-hourly in the catchment outlets. Field nutrient sources were connected to surface water via groundwater; the groundwater along hillslopes was seen to be influenced spatially and temporally by management, geology and weather as observed in the concentration variability of nitrate in groundwater. Based on spatio-temporal averages of nitrate-N concentration, groundwater status was considered good (at least below a maximum acceptable concentration (MAC) of 11·3 mg/l). However, zones coincident with land-use change (ploughing and reseeding, typical of a management event in intensive landscapes), showed high spatio-temporal variability in nitrate-N concentration, exceeding the MAC temporarily, before recovering. This spatio-temporal variability highlighted the need for insight into these differences when interpreting groundwater quality data from a limited number of basin-scale sampling points and occasions. In both catchments the 3-year mean nitrate-N concentration in stream water was similar to the spatio-temporal mean concentration in groundwater. The magnitude and variability of loads, however, were more related to changes in annual runoff rather than changes in annual groundwater nitrate-N status. In one wet year, nitrate-N loads exceeded 48 kg/ha from an Arable catchment and 45 kg/ha from a grassland catchment (close to double the loss in a dry year).


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published Version restricted in accordance with copyright policy of publisher (CUP)
Faculty / Department / School: Current - USQ Other
Date Deposited: 17 Feb 2015 12:39
Last Modified: 25 Mar 2015 05:00
Uncontrolled Keywords: groundwater; water composition; water quality; agricultural catchment; concentration (composition); intensive agriculture; land use change; nitrogen cycle; permeability; spatiotemporal analysis; water chemistry
Fields of Research : 07 Agricultural and Veterinary Sciences > 0701 Agriculture, Land and Farm Management > 070101 Agricultural Land Management
05 Environmental Sciences > 0502 Environmental Science and Management > 050206 Environmental Monitoring
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences
D Environment > 96 Environment > 9606 Environmental and Natural Resource Evaluation > 960608 Rural Water Evaluation (incl. Water Quality)
Identification Number or DOI: 10.1017/S0021859614000021
URI: http://eprints.usq.edu.au/id/eprint/26652

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