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New Zealand Journal of Marine and Freshwater Research abstracts
Sediment, phosphorus, and nitrogen in channelised surface run-off from a New Zealand pastoral catchment
CHRISTINE M. SMITH
Water Quality Centre
Ministry of Works and Development
Private Bag, Hamilton New Zealand
Abstract Surface run-off derived from 94 m (20°) and 230 m (15°) long hillslopes in a pastoral catchment was collected along a 15.8 m total intercepting face between 1 July 1983 and 31 March 1985; run-off subsamples were analysed chemically. Surface run-off occurred on 49 occasions, these "events" ranging from 0.2 to 115 m3. About 50% of the total run-off occurred in six events. In 20 months the eight individual 1.5-2.4 m long collectors intercepted 4-333 m3 of water. This uneven spatial run-off pattern, the measured flow rates, and total event volumes indicated that extensive areas on both hillslopes produced run-off, and that extreme channelisation occurred during movement downslope. Mean flow weighted run-off concentrations were for total phosphorus (TP) 1053 mg/m3, total dissolved phosphorus (TDP) 300 mg/m3, Kjeldahl nitrogen (TKN) 5898 mg/m3, dissolved Kjeldahl nitrogen (DKN) 1413 mg/m3, NO3-N 69 mg/m3, suspended sediments (SS) 472 g/m3, and volatile suspended sediment (VSS) 115 g/m3. Estimated catchment surface run-off yields in 1984 were: TP 0.75 kg/ha, TDP 0.15 kg/ha, TKN 4.43 kg/ha, DKN 0.74 kg/ha, NO3-N 0.03 kg/ha, SS 374 kg/ha, and VSS 90 kg/ha. Virtually all phosphorus and nitrogen was transported downslope in winter and spring. Controlling these run-off nutrient inputs to the catchment stream is briefly discussed.
Keywords channelised surface run-off; overland flow; sediment yields; phosphorus; nitrogen
New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 627-639 0O28-8330/87/2104-0627$2.50/0 © Crown copyright 1987 Received 3 November 1986; accepted 13 March 1987
PDF file of entire paper: medium quality (906K); (scanned from paper original: notes about this process)
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