• About this site|
• Site index|
• Contact us|
• Jobs

Water Quality in Selected Dairy Farming Catchments: A baseline to support future water-quality trend assessments

Executive Summary

Introduction

Methods

Catchment Characteristics

Water-quality Baseline

Summary and Recommendations

References and Information Sources

Appendix 1: Monitoring Catchment Details

Appendix 2: Water-quality Summary Data

Appendix 3: Regression Analyses

Appendix 4: Current Monitoring Programmes

Appendix 5: Recreational Values

Catchment Characteristics

This section contains information about the characteristics of the Tier 1 and Tier 2 catchments discussed in this report (see table 1 and figure 1 for a description of the catchments). It also outlines progress towards the Dairying and Clean Streams Accord targets in each catchment.

Table 3 provides a summary of the geographical, geological and hydrological features of each Tier 1 and 2 catchment as well as an indication of land-use characteristics. Table 4 provides a summary of farm information and Accord actions for each Tier 1 and 2 catchment. This information was predominantly supplied by Fonterra, with supplementary information supplied by regional councils. Further information about each catchment, including location maps, is provided in appendix 1 (figures A1-A to A1-M).

Catchment geography, geology and hydrology

The Tier 1 and 2 dairy catchments generally lie in flat to rolling farmland and range in size from 6 km2 (Inchbonnie) to 211 km2 (Rai) (see table 3). They also span a range of latitudes and climatic conditions, as indicated by the River Environment Classification descriptions in appendix 1.

Average annual rainfall in catchments in the drier eastern areas of New Zealand (600–700 mm/yr across the Waikakahi, Rhodes–Petrie and Washpool catchments in Canterbury and Otago) is less than half that of catchments in the wetter central and northern regions and almost 5–10 times lower than the rainfall received in the Inchbonnie catchment on the West Coast of the South Island (4825 mm/yr).

Annual total rainfall for the year(s) of the monitoring programme in each catchment has been compared with long-term rainfall records (generally 1950 to the present) from the nearest rainfall recorder site (NIWA CliFlow Database). The data and plots are provided in appendix 1 (tables A1-A to A1-M) and show that for most monitored catchments the rainfall received during the period of water quality monitoring was reasonably close to the long-term average (ie, monitoring was not conducted during unusually wet or dry periods); for example, see Figure 2. The exceptions are the Waikakahi (table A1-C) and Rhodes–Petrie (table A1-L) catchments in Canterbury, where rainfall during the monitoring periods was lower than the long-term average by approximately 30 per cent. The extent to which this might have had an effect on stream flow and water quality in these catchments is unknown.

Figure 2: Comparison of annual rainfall totals during the water-quality monitoring period (grey bars) with the long-term record (black bars), Waiokura catchment

View graph|View text description

Year starting	Annual mm
Average 1950 - 2008	1634.54
Average 2001 - 2006	1694.55
1950	1658.2
1951	1678
1952	1830.3
1953	1536.1
1954	1587.9
1955	1809.3
1956	2155.4
1957	1869
1958	1774.4
1959	1257.4
1960	1700.6
1961	1573.2
1962	1878.9
1963	1330.3
1964	1971.6
1965	1771.4
1966	1602.5
1967	1849.3
1968	1729.3
1969	1347.2
1970	1669.3
1971	1942.3
1972	1272.5
1973	1308.1
1974	1963.8
1975	1905.7
1976	-
1977	1453.9
1978	1554.3
1979	1991.9
1980	1568.7
1981	1558.3
1982	1458.4
1983	1282.9
1984	1259.9
1985	1533.2
1986	1589.9
1987	1155.7
1988	1607.3
1989	1613.8
1990	1553.7
1991	-
1992	1672.8
1993	1427.5
1994	1835.8
1995	1545.6
1996	1578.6
1997	1571.3
1998	1833.9
1999	1790.5
2000	1322.5
2001	1693.3
2002	1446.3
2003	2047.1
2004	1677.1
2005	1595.8
2006	1707.7
2007	-

Source: CliFlow Database administered by NIWA.

Notes: The dashed lines are averages for the two periods. The rainfall record is taken from the closest available NIWA rain gauge (8.5 km from the Waiokura catchment).

Stream flow in the catchments is highly variable, which is typical for small waterways in deforested areas. Three of the nine catchment streams for which flow-range data is available had no flow for a time during the monitoring periods, while some catchments had peak flows (following rainfall) well in excess of 20 times their mean flow. Annual flows⁵ varied across catchments from 25 L/s (mean; Powell) to 4842 L/s (median; Rai).

Soils and geology are also variable, both within and between catchments. Catchments with predominantly alluvial sediments, such as the sands and gravels in the Rhodes–Petrie catchment on the Canterbury plains and the pumice in the Taharua catchment in Hawke’s Bay, are relatively free-draining. By contrast, the weathered soils of the Puwera catchment in Northland and the mudstone and siltstone substrates of the Washpool catchment in Otago are relatively poor-draining.

Land-use and farm information

Table 3 shows that, with the exception of Taharua (Hawke’s Bay) and Mangapapa (Manawatu), dairy farming is the predominant land use in all Tier 1 and 2 catchments. The extent of dairy land ranges from 37 per cent of the Bog Burn catchment (Southland) to 100 per cent of the Inchbonnie catchment (West Coast). Dairying accounts for at least twice the land area of the next largest land use in seven of the 12 catchments (including four of the five Tier 1 catchments). Sheep and beef farmland makes up the majority of land not used for dairying in each of the Tier 1 and 2 catchments.

Although the number of dairy farms per catchment varies from three in the Powell (Tasman) and Taharua (Hawke’s Bay) catchments to 21 in the Toenepi catchment (Waikato), the dairy cow stocking rate is fairly consistent, ranging from 2.5 to 3.5 cows per hectare across nine of the catchments. The stocking rate is lower in the Inchbonnie and Enaki catchments (2.0 and 1.6 cows per hectare, respectively) and could not be estimated for the Mangapapa and Rai catchments from the data available.

Dairy farming has a long history in most of the catchments (seven) for which information is available, has been introduced since the early 1990s in two catchments (Waikakahi and Bog Burn), and has undergone rapid and recent expansion in two catchments (Taharua and Washpool).

Progress towards Accord targets

Fonterra on-farm survey records from 2007 (summarised in table 4) indicate that the following progress has been made in the monitored dairy catchments.

• The proportion of streams fenced (that meet Accord criteria) ranged from 66 per cent in the Enaki catchment to 100 per cent in the Powell, Rhodes–Petrie, Waikakahi and Bog Burn catchments. Fonterra survey data was not available for four of the catchments. Northland Regional Council have estimated that less than 10 per cent of the Puwera Stream has stock exclusion, although the extent to which this stream is considered to meet Accord criteria is uncertain.

• All, or almost all, of the Accord stream crossings were bridged or culverted in seven of the catchments (Waikakahi, Bog Burn, Inchbonnie, Mangapapa, Powell, Rhodes–Petrie and Washpool). Six crossings (almost half) were not bridged or culverted in the Toenepi catchment, seven in the Enaki catchment, and 37 in the Rai catchment. Survey data was not available for the remaining four catchments.

• Nutrient management plans are in place on all farms in eight of the catchments and on 85 to 90 per cent of farms in two further catchments. No information is available on the extent to which these plans are being actively used to manage nutrient application.

With respect to the first two bullet points, we recognise that the presence of a fence, bridge or culvert does not always mean that stock are excluded from waterways. For example, while
on-farm survey figures for the Rhodes–Petrie catchment indicate 100 per cent of Accord streams have stock exclusion and that there are no outstanding crossings to be bridged or culverted, an Environment Canterbury (2007) report showed places in these catchments where fencing and culverting was likely to be ineffective. In these places, stock were likely to be able to gain access to the waterways. Also, although the statistics above (and in table 4) on fencing and crossing removal indicate progress on the main catchment waterways, it is not possible to use them to draw conclusions about progress in the catchment as a whole, particularly on smaller headwater streams.

Information on non-compliance with stock effluent disposal rules was provided by councils and is given in table 4. Few recorded incidents occurred over the period of intensive water-quality monitoring.

Table 3: Catchment features and land-use characteristics

Source: Unless otherwise stated, from Wilcock, Monaghan et al, 2007; Monaghan et al, 2004; and Muirhead et al, 2002 for Tier 1 catchment information, and regional councils for Tier 2 catchment information.

Notes:

1 Rainfall is the long-term (1950 to the present in most cases) average annual total for the rainfall recorder closest to each catchment as well as the average total for the period coinciding with the monitoring of water-quality data. The source is the CliFlow Database administered by NIWA. These totals have been presented in favour of totals provided by regional councils to ensure a consistent method is applied across regions and comparisons between short- and long-term averages for each catchment are done using the same rainfall recorder.

2 Flows are means and ranges (unless otherwise stated) for periods coinciding with water-quality monitoring in each catchment.

3 REC = River Environment Classification analysis undertaken by the Ministry for the Environment using the most downstream point of the main catchment stream.

4 Marlborough District Council considers that the large majority of this 23% is made up of dairying and it is the single largest land-use type (by area) in the catchment.

Table 4: Catchment dairy farm information

Source: Unless otherwise stated, Accord actions information is from the Fonterra on-farm survey (provided by Fonterra to regional councils during 2007 and 2008); all other information is supplied by regional councils.

Notes:

1 A complete data set is not available for this catchment. A dairy farm survey due to be undertaken in March 2009 will address areas of incomplete data.

2 The Accord is not in place on the West Coast of the South Island so no Accord-related data exists for the Inchbonnie catchment.

3 Fonterra data is not available for this catchment. The number provided has been estimated by Northland Regional Council.

4 This is the total number of crossings in the Rai catchment. The large majority will be on Accord waterways but some are on smaller streams.

5 This number was provided by Greater Wellington Regional Council from compliance data so may not fit with Accord criteria for a stream crossing.

The number of dairy farms and stocking rates in Tier 1 catchments is from Muirhead et al, 2002. Stocking rates for Tier 2 catchments were estimated by the Ministry for the Environment using cow numbers (provided by councils) and dairy land area.

ND = No data. A complete data set is not available for this catchment.

[ Previous| Next