Managing pollutant inputs from pastoral dairy farming to maintain water quality of a lake in a high-rainfall catchment

Wilcock, Robert J.; Monaghan, Rachel; McDowell, R. W.; Verburg, Piet; Horrox, J.; Chagué‐Goff, Catherine; Duncan, Maurice J.; Rutherford, Alison; Zemansky, Gil; Scarsbrook, Mike R.; Wright‐Stow, Aslan E.; Howard‐Williams, Clive; Cotton, Sue

doi:10.1071/mf12296

Cited by 13 publications

(9 citation statements)

References 28 publications

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“…Such long-term cycles in rainfall can result in long-term cycles in transparency and productivity in lakes (Gaiser et al 2009). However, there was no evidence for an increase in rainfall in the catchment affecting Lake Brunner's water quality through increased export of nutrients from the catchment to the lake (our results and Wilcock et al 2013). Therefore, increased intensification of land use through development of dairy farms, coupled with rapid drainage from humping-and-hollowing is likely to be the major cause of increased nutrient concentrations and algal productivity in Lake Brunner.…”

Section: Discussionmentioning

confidence: 49%

“…The two major streams draining dairy farms contribute 85% of the lake's total P load. A monitoring study (Wilcock et al 2013) has been underway in one of the dairying subcatchments of the Lake Brunner catchment since 2004. Results have shown very high catchment losses of P and N towards the lake that are well above average for intensively farmed land elsewhere in New Zealand.…”

Section: Discussionmentioning

confidence: 99%

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Effects of nutrient loading on the trophic state of Lake Brunner

Verburg

Horrox

Rutherford

et al. 2013

Mar. Freshwater Res.

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Abstract. Lake Brunner, an oligotrophic monomictic lake on the West Coast of the South Island of New Zealand, is under pressure from urban expansion and increased farming activity, which has led to concern for the effects on water quality in the lake. Epilimnetic nitrogen, phosphorus and chlorophyll a concentrations have increased since 1992, and Secchi depth decreased. This suggests an increased algal productivity caused by increased nutrient inputs, further supported by increased hypolimnetic oxygen depletion since 1992. These observations are likely to have resulted from enhancement of pasture drainage and effluent inputs from expanding dairy farms. The Vollenweider model predicted a mean phosphorus concentration in the lake close to that observed, from estimated catchment loading, suggesting that the Vollenweider model adequately estimated the retention of phosphorous. With the Vollenweider model the effects of potential future loading scenarios were explored. Modelling suggested that a 70% increase in phosphorus loading could turn the lake into a mesotrophic state. Trend analysis of total phosphorus suggests that, with present land uses in the catchment (intensive dairy farming) continuing to develop at the same rate using the same land management practises, this transition to a mesotrophic state will occur by 2040.

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Section: Discussionmentioning

confidence: 49%

Section: Discussionmentioning

confidence: 99%

Effects of nutrient loading on the trophic state of Lake Brunner

Verburg

Horrox

Rutherford

et al. 2013

Mar. Freshwater Res.

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“…Likewise, the effectiveness of the stream fencing, stream bridging, and low‐rate FDE irrigation mitigations are 65, 55, and 29%, respectively. These percentage reductions are averages based on the pooled data, and actual reductions in individual catchments will vary (Wilcock et al, 2013a). …”

Section: Resultsmentioning

confidence: 99%

A Farm-Scale Risk-Index for Reducing Fecal Contamination of Surface Waters

Muirhead

2015

J. Environ. Qual.

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There is increasing recognition of the adverse impacts of agricultural practices on microbial water quality leading to increased expectation on farmers to manage environmental impacts on water quality. Therefore, farmers require a tool to help them prioritize mitigations targeted at reducing fecal contamination of surface water. A farm-scale risk-index was developed from modeled data on the predicted losses of from selected farm practices. The farm-scale data were then converted to a catchment scale risk value and calibrated against stream concentration data measured in five catchments. The data from the five catchments indicate that there is a relationship between the risk of losses from some farm practices and the resulting levels in the streams. The results show that the adoption of existing mitigation options for fecal contamination should result in a substantial reduction of concentrations in streams flowing through catchments used for intensive dairy farming. However, the relatively high concentrations in the stream when the calculated risk-index values are low indicate that currently available mitigation practices may not be sufficient to achieve contact recreational water quality standards in many catchments due to other sources of . This risk-index approach can be incorporated into existing decision support tools to enable farmers to manage fecal contamination impacts from their farming operations.

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“…The study by Verburg et al (2013) assessed the relative of these contaminants on an oligotrophic lake (Brunner). Wilcock et al (2013b) found that while trends were decreasing (i.e. improving) for some water-quality contaminants, much of the load of suspended sediment, N and P came from storm flows or was from groundwater that was not encaptured in surface water inflows into the lake.…”

Section: Linking Nutrient Losses To Effects and Management Across Scalesmentioning

confidence: 99%

“…The study by Wilcock et al (2013b) examined catchment sources and pathways for water-quality contaminants. The study by Verburg et al (2013) assessed the relative of these contaminants on an oligotrophic lake (Brunner).…”

Section: Linking Nutrient Losses To Effects and Management Across Scalesmentioning

confidence: 99%