Trends in water quality of five dairy farming streams in response to adoption of best practice and benefits of long-term monitoring at the catchment scale

Abstract

Abstract. Five streams in catchments with pastoral dairy farming as the dominant land use were monitored for periods of 7-16 years to detect changes in response to adoption of best management practices (BMPs). Stream water quality was degraded at the start with respect to N, P, suspended solids (SS) and E. coli concentrations, and was typical of catchments with intensive pastoral agriculture land use. Trend analysis showed a decrease in SS concentration for all streams, generally increasing water clarity, and lower E. coli concentrations in three of the streams. These are attributed to improved stream fencing (cattle exclusion) and greater use of irrigation for treated effluent disposal with less reliance on pond systems discharging to streams. Linkages between water quality and farm actions based on survey data were used to develop BMPs that were discussed at stakeholder workshops. Generic and specific BMPs were developed for the five catchments. The 3-7 year periodicity of major climate cycles, as well as market forces and a slow rate of farmer adoption of simple BMPs mean that monitoring programs in New Zealand need to be much longer than 10 years to detect changes caused by farmer actions. Long-term monitoring is also needed to detect responses to newly legislated requirements for improved water quality.

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

“…Regarding the effect of the land management practices on stream E. coli concentrations and instantaneous yields, the Toenepi, Inchbonnie, and Bog Burn catchments seemed to show a similar relationship (Fig. 3 and 4), which is possibly a reflection of the high level of connectivity between the poorly drained soils in these catchments and their streams (Wilcock et al, 2006; Monaghan et al, 2007; Wilcock et al, 2013b). The strongest relationship was observed in the Waikakahi catchment, which likely reflects the high connectivity between the flood irrigation outwash and the stream (Monaghan et al, 2009).…”

“…The risk‐index calculation is based on dairy farm practices that we can change and from which we can estimate a daily load of E. coli (Muirhead et al, 2011). Other environmental sources of E. coli during base‐flow conditions that are not included in the risk‐index calculation are wetlands and seeps (Collins, 2004), birds (Muirhead et al, 2011), groundwater (Close et al, 2008), stream sediments (Stott et al, 2011), and the small number of nondairy farms in the five studied catchments (Wilcock et al, 2013b). These high stream concentrations and yields shown at low risk‐index values indicate that further work is needed on quantifying E. coli sources and loads in agricultural catchments.…”

“…Water quality data from each of the catchments and continuous flow monitoring from the catchment outlet had been collected on a monthly or fortnightly basis over a period of 7 to 16 yr (Wilcock et al, 2013b). From this water quality database, the time each water quality sample was collected was compared with the hydrograph of the stream flow rate to determine if the sample was collected during storm‐ or base‐flow conditions.…”

“…This lack of farm‐scale data of FIO losses is attributable to the difficulty of trying to measure these losses and the high variability of the data (Muirhead and Monaghan, 2012; Bradford et al, 2013). However, a focus on the environmental impacts of dairy farms in New Zealand has seen the development of strong databases of information available for this industry at a small catchment scale (Wilcock et al, 2013b). Therefore, it would be an option to attempt to calibrate a farm‐scale risk‐index tool to catchment scale data because the aim of farm‐scale environmental tools is to improve catchment‐scale water quality outcomes.…”

Nutrients and eutrophication: introduction

“…In an effort to detect the influence of best management practices over the long-term, Wilcock et al (2013a) examined trends in water-quality indicators within streams of five dairy farm catchments across New Zealand. Although only inferences could be made (i.e.…”