Nitrate Contamination of Groundwater in the Ashburton-Hinds Plain

Nitrate contamination and groundwater chemistry – Ashburton-Hinds plain

Report No. R10/143 ISBN 978-1-927146-01-9 (printed) ISBN 978-1-927161-28-9 (electronic)

Carl Hanson and Phil Abraham

May 2010

Report R10/143 ISBN 978-1-927146-01-9 (printed) ISBN 978-1-927161-28-9 (electronic)

58 Kilmore Street PO Box 345 Christchurch 8140 Phone (03) 365 3828 Fax (03) 365 3194

75 Church Street PO Box 550 Timaru 7940 Phone (03) 687 7800 Fax (03) 687 7808

Website: www.ecan.govt.nz Customer Services Phone 0800 324 636

Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Executive summary

The Ashburton-Hinds plain is the sector of the Canterbury Plains that lies between the Ashburton River/Hakatere and the Hinds River. It is an area dominated by agriculture, with a mixture of cropping and grazing, both irrigated and non-irrigated. This report presents the results from a number investigations conducted in 2004 to create a snapshot of nitrate concentrations in groundwater across the Ashburton-Hinds plain. It then examines data that have been collected since 2004 to update the conclusions drawn from the 2004 data. In 2004, nitrate nitrogen concentrations were measured in groundwater samples from 121 wells on the Ashburton-Hinds plain. The concentrations ranged from less than 0.1 milligram per litre (mg/L) to more than 22 mg/L. The highest concentrations were measured in the Tinwald area, within an area approximately 3 km wide and 11 km long where concentrations were commonly greater than the maximum acceptable value (MAV) of 11.3 mg/L set by the Ministry of Health. Concentrations above the MAV were also measured in samples from some wells outside the Tinwald area, most of them located southeast of State Highway 1. Concentrations indicating anthropogenic nitrate contamination (>3 mg/L) were found at depths of over 60 m below the water table in the upper part of the plain. Higher nitrate nitrogen concentrations were found in the middle and upper parts of the plain, where the soils are lighter, the sediments are highly permeable and the groundwater is well oxygenated. In contrast, reducing conditions were found in the groundwater near the coast, resulting in lower nitrate nitrogen concentrations. This area was formerly covered by swamp and is characterised by heavy soils and low-permeability sediments. The highest nitrate nitrogen concentrations, including those in the Tinwald area, were found near the transition zone between high-permeability sediments beneath the upper plain and the lower-permeability sediments near the coast. Since 2004, concentrations have been monitored annually or quarterly in eight wells on the plain. The data from this monitoring suggest that concentrations have risen in some locations. In particular, strong increasing trends have been measured in one well (K37/0358) in the Tinwald area and another to the southwest of Tinwald (K37/0468). Diffuse nitrate leaching from agricultural land is the main source of nitrate in the groundwater. Cropping and winter fallow activities on soils with low nitrate uptake have probably contributed to the high concentrations in the Tinwald area, while the dilution of nitrate in soil drainage water caused by flood irrigation in the Valetta irrigation scheme area may help to account for the lower concentrations outside the Tinwald area.

Environment Canterbury Technical Report i Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

ii Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Table of Contents

Executive summary ...... i

1 Introduction ...... 1 1.1 Background ...... 1 1.2 Objective of this report ...... 1

2 Description of the investigation area ...... 1 2.1 Location ...... 1 2.2 Topography and rainfall ...... 3 2.3 Soils ...... 3 2.4 Surface water drainage ...... 3 2.5 Irrigation and stock water ...... 5 2.6 Hydrogeology ...... 5 2.7 Land use ...... 6 2.8 Potential nitrate sources ...... 8 2.9 Pre-2004 groundwater quality data...... 10

3 Nitrate nitrogen concentrations in groundwater in 2004 ...... 12 3.1 Summary of investigations ...... 12 3.2 Nitrate nitrogen results ...... 14 3.2.1 General summary...... 14 3.2.2 Tinwald area ...... 14 3.2.3 Wider Ashburton-Hinds plain ...... 17 3.2.4 Nitrate nitrogen concentrations and well depth ...... 17 3.2.5 Reducing conditions in the coastal groundwater ...... 18

4 Update on the 2004 results ...... 21 4.1.1 Overview ...... 21 4.1.2 Long-term monitoring ...... 21 4.1.3 2009 investigation ...... 24 4.1.4 Summary ...... 25

5 Discussion ...... 26

6 Conclusions ...... 28

7 Recommendations ...... 28

8 Acknowledgements ...... 29

9 References ...... 29

Appendix 1: Analytical results for groundwater samples collected from the Ashburton-Hinds plain, 1988 to 2009 ...... 33

Environment Canterbury Technical Report iii Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Appendix 2: Construction details for wells of the Ashburton-Hinds plain where groundwater samples were collected between 1988 and 2009 ...... 43

Appendix 3: Summary of 2004 investigations, sampling procedure and determinands analysed ...... 50

Appendix 4 Procedure G002_02 - Collection of Groundwater Quality Samples...... 52

List of Figures Figure 2-1: Ashburton-Hinds plain investigation area, including topography, surface water drainage, springs and irrigation schemes ...... 2 Figure 2-2: Soils of the Ashburton-Hinds plain investigation area ...... 4 Figure 2-3: Land use on the Ashburton-Hinds plain (Agribase, 2005) ...... 7 Figure 2-4: Cropping land on the Ashburton-Hinds plain estimated to have low nitrate uptake due to successive years in winter fallow ...... 9 Figure 2-5: Map showing maximum nitrate nitrogen concentrations measured in groundwater samples collected on the Ashburton-Hinds plain prior to 2004 ...... 11 Figure 3-1: Map showing the locations of wells on the Ashburton-Hinds plain where groundwater samples were collected during surveys conducted in 2004 ...... 13 Figure 3-2: Nitrate nitrogen concentrations in groundwater, Ashburton-Hinds plain, 2004...... 15 Figure 3-3: Vertical cross section of nitrate nitrogen concentrations in groundwater along a line through the Tinwald area ...... 16 Figure 3-4: Well depth versus nitrate nitrogen concentrations in samples collected in the Ashburton-Hinds Investigation ...... 18 Figure 3-5: Iron and manganese concentrations and the area where reduced groundwater is likely to occur beneath the Ashburton-Hinds plain ...... 20 Figure 4-1: Wells on the Ashburton-Hinds plain that were sampled from 2005 to 2009, showing the maximum nitrate nitrogen concentrations measured during that period...... 22 Figure 4-2: Nitrate nitrogen concentrations over time, measured in eight long-term annual monitoring wells on the Ashburton-Hinds plain...... 23

List of Tables Table 2-1: Nitrate nitrogen concentrations measured in groundwater samples collected on the Ashburton-Hinds plain prior to 2004 ...... 10 Table 4-1: Summary of nitrate nitrogen concentrations measured in samples from eight long- term monitoring wells located on the Ashburton-Hinds plain ...... 21 Table 4-2: Comparison of nitrate nitrogen concentrations in groundwater from nine wells sampled in both 2004 and 2009 ...... 25

iv Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

1 Introduction

1.1 Background In the autumn (April) of 2004, groundwater sampling near the town of Tinwald on the southern Canterbury Plains identified an area where nitrate concentrations were found to be above the drinking- water standard set by the New Zealand Ministry of Health. In their initial report on the sampling, Abraham and Hanson (2004) wrote that the zone of contamination was at least 7 km long and 2 km wide, but they acknowledged that these dimensions did not outline the full extent of the contamination.

The high nitrate concentrations caused concern because groundwater in the area is used extensively as a source of drinking water. High concentrations of nitrate in drinking water can pose a health risk, particularly to bottle-fed babies whose formula is made from the water. The main concern is the development of an acute condition called methaemoglobinaemia, which reduces the oxygen-carrying capacity of the blood. Based on the short-term health risk for bottle-fed babies, the Ministry of Health (2008) has set a maximum acceptable value (MAV) of 50 milligrams per litre (mg/L) for the concentration of the nitrate ion in drinking water. When expressed as nitrate nitrogen rather than the nitrate ion, the MAV is equivalent to 11.3 mg/L nitrate nitrogen.

High nitrate concentrations in groundwater can also threaten streams, lakes, and coastal waters that are fed by groundwater, increasing the risk of eutrophication from excessive growth of plants and algae and potentially resulting in toxicity to aquatic ecosystems. A recent review (Hickey and Martin, 2009) has suggested guideline values of 1.0 to 3.6 mg/L nitrate nitrogen for chronic toxicity in New Zealand fresh waters, while guideline values of 0.01 to 0.295 mg/L (soluble inorganic nitrogen) are used to control excessive periphyton (algae) growth (Biggs, 2000; ANZECC, 2000). The Ashburton- Hinds plain has a number of groundwater-fed streams and drains, and a man-made recreational lake (Lake Hood), all of which ultimately discharge to the coastal waters of the Pacific Ocean. Concerns about water quality in the coastal streams of mid-Canterbury have been reported in Meredith et al. (2006). As a follow-up to the Tinwald investigation (documented by Abraham and Hanson, 2004), a more extensive investigation was conducted in the winter months of July and August 2004 to better delineate the full extent of nitrate contamination in the Tinwald area. The investigation also aimed to characterise nitrate concentrations in groundwater across the wider Ashburton-Hinds plain. The results of this follow-up investigation have not been published until now.

1.2 Objective of this report This report combines the results of the two investigations, autumn and winter, along with the results of other sampling conducted in the area, to create a snapshot of nitrate concentrations in groundwater across the Ashburton-Hinds plain in 2004. It then examines data that have been collected since 2004 to update the conclusions drawn from the 2004 data.

2 Description of the investigation area

2.1 Location The Ashburton-Hinds plain investigation area encompasses about 600 km2. It is located in the southern part of the Canterbury Plains between the Hinds River and Ashburton River/Hakatere. The plain is bounded to the northwest by the foothills of the Southern Alps and to the southeast by the Pacific Ocean (Figure 2-1).

Environment Canterbury Technical Report 1 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

As A hb s u h r b to u n Mount Somers r R t iv o er n /H a R ka iv te e e r r c e anch / a South Br # H R # # a # k # a t n ## e o # r i ## e INVESTIGATION s r AREA e

D # N # o ta # a H # rt it ind # h g s R # B n iv # a er ### # ra R ## # n Mayfield c # # h ## ## # # # #

Ashburton ## Valetta # # Irrigaton Scheme # # # # # # # # Tinwald A ## s # # h b # u r # to n #

H # d # # oa ### in 1 ## R # # ## y ### ry ## # d a # da # ## s ### w # ## n # ### # ### ou R #### h # # ## B # ig # ## # # Lake Hood i ## H #### # v # # # # e # te # r # # a # # R # t # S # i # # # v # e # r Hinds # / Lynnford # H # a # # k Irrigaton Scheme a t # e # r # springs e

state highways Eiffelton Irrigaton Scheme # roads

rivers and streams N

land surface contours Pacific Ocean (contour interval 20 m) surface water irrigation schemes 0 5 10 15 20 Kilometers

Figure 2-1: Ashburton-Hinds plain investigation area, including topography, surface water drainage, springs and irrigation schemes

2 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

2.2 Topography and rainfall The plain has very little surface relief, but it has an average slope of approximately 0.6%, sloping downward toward the coast from an elevation of about 300 m above sea level near the base of the foothills. Along the coast, the plain terminates in a cliff approximately 10 to 20 m high, which is dissected by steep gullies and has a narrow, stony beach at its base. Average annual precipitation ranges from 700 mm at the coast to 1000 mm near the foothills at the top of the plain. The precipitation is distributed fairly evenly throughout the year. Climate records from the Winchmore Irrigation Research Station (25 km inland from the coast and approximately 10 km northeast of Tinwald) indicate that potential evapotranspiration varies from 597 mm/year to 868 mm/year, with an average of 767 mm/year (Engelbrecht, 2005). Climate trends indicate that evapotranspiration is generally highest in December/January and lowest in June/July (Mosley, 2001).

2.3 Soils Approximately twenty main soil types (Figure 2-2) are recognised on the Ashburton-Hinds plain (DSIR, 1968; Webb et al., 2000). The most common soils are stony silt loams, which are generally less than one metre thick and are mapped as members of the Lismore and Ruapuna soils series. The Lismore stony silt loam, a shallow, free draining soil with low water-holding capacity (profile available water, or PAW, of 40-75 mm), dominates the central part the plain. Soils along the river margins tend to be deeper and more varied in soil type, depth and quality. Along the south bank of the Ashburton River/Hakatere and in the coastal margin of the plain, the area formerly covered by swamp, Waterton gley soils and Wakanui deep silt loam soils dominate. These soils are much deeper and contain more clay and organic material than the soils further inland, and they have higher water holding capacities (PAW up to more than 150 mm).

2.4 Surface water drainage The upper Ashburton-Hinds plain is crossed by the Hinds River, the South Branch of the Ashburton River/Hakatere and other tributary streams that drain the foothills of the Southern Alps. There is no natural drainage in the middle portion of the plain, but the lower plain is crossed by numerous spring- fed streams and drains. The springs emerge in the area between Boundary Road and State Highway 1 (Figure 2-1), near the interface between the deep, clay-rich soils of the lower plain and the shallow, stony soils of the upper plain (Davey, 2003). Meredith et al. (2006) reported that nitrate nitrogen concentrations in these spring-fed streams and drains are high, with median concentrations generally greater than 3 mg/L and in some cases greater than 6 mg/L. Short-term concentrations greater than 10 mg/L have been measured in some of the streams. The concentrations show no clear seasonal pattern, suggesting a consistent source, probably groundwater, rather than surface runoff, which would tend to be more seasonal. Flow records for the spring-fed streams have not been analyzed in this report to confirm this. The lower part of the plain was originally a swamp that was fed by the Hinds River and numerous groundwater-fed springs. The swamp was naturally drained by a number of streams and eroded gullies, locally known as ‘dongas’, that extend up to two kilometres inland from the sea through coastal sea cliffs (Meredith et al., 2006). In the 1850s and 1860s, European settlers channelised and diverted the spring-fed streams in order to drain the land for farming, and tile drains were constructed to provide conduits for groundwater to discharge into the modified streams. The Hinds River was opened by a direct cut to the ocean in 1870 (Mitchell, 1980). Although the drainage of the land has been successful, drainage in places has lead to significant reductions in soil moisture, and some of the former swamp area now requires irrigation (Engelbrecht, 2005).

Environment Canterbury Technical Report 3 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s s hb h ur b to u n r R Mount Somers t i o ve n r/H R a iv e k c at e a e r r ch / R e Bran H outh a S k a t e n r o e i

N o ta r a t it Hin h g ds n Ri B a ver ra R n Mayfield c h

Ashburton

Tinwald A s h b u r to n

H 1 in ay d hw s ig R H iv te e ta r S d oa R R ry i da v un e o r Hinds B / H a k a t e r SOILS e - profile available water (PAW) 0 - 75 mm 76 - 110 mm 111 - 150 mm 151 - 250 mm

investigation area N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 20 Kilometers

Figure 2-2: Soils of the Ashburton-Hinds plain investigation area

4 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

2.5 Irrigation and stock water Three community irrigation schemes service the Ashburton-Hinds plain (Figure 2-1). The largest of these is the Valetta irrigation scheme, which is supplied with water from the Rangitata River via the Rangitata Diversion Race (RDR). The Valetta scheme serves an area of over 7000 hectares (ha) in the northwestern part of the plain. Both flood and spray irrigation are used in the Valetta area. In recent years, increasing demands for water and reductions in the reliability of water supply for irrigation have resulted in moves to re-contour flood borders and convert to spray irrigation in order to improve water use efficiency (Engelbrecht, 2005). Two smaller schemes, the Eiffelton (2290 ha) and Lynnford (541 ha) schemes, operate in the south- eastern part of the Ashburton-Hinds plain. These schemes use water from the Hinds River, local drains and groundwater, and irrigation is by spray only (Figure 2-1). Much of the land outside the scheme areas is spray irrigated by individual farms using groundwater, and there is some land that remains under dryland farming practices. Stock water supplies are provided to farms by the Mt Somers/Willowby stock water race network, administered by the Ashburton District Council (ADC). Race water is taken from the South Branch of the Ashburton River/Hakatere and various tributaries and is augmented by RDR water and other drains (Ryan, 2001). Flows are often very low (in the order of 10 litres per second) and fluctuate significantly with rainfall events. At the bottom of the network, quantities of race water are discharged to rivers, drains, soak pits, or directly to the ocean through piped ocean outfalls.

2.6 Hydrogeology The Ashburton-Hinds plain is part of the Canterbury Plains, which were formed during the Quaternary period by braided river systems carrying large volumes of gravely sediment eroded from the Southern Alps. The rivers deposited the sediment as a complex alluvial fan network up to 600 m thick. Underlying the fan deposits are Tertiary sediments and Cretaceous greywacke basement of the Torlesse Group (Brown and Weeber, 2002). The Quaternary fan sediments are dominated by sand and gravel, deposited in discontinuous lenses and channels as the braided rivers continually changed their courses across the plains. The Canterbury Plains sediments host significant quantities of good quality groundwater, which is used extensively for drinking, irrigation, and stock water supply. As described in papers by Davey (2006a) and Dann et al. (2007), the groundwater largely flows within highly permeable lenses of course, matrix-free gravel, surrounded by less permeable gravel with sandy or silty matrix. The lenses have vertical thicknesses on the order of centimetres to tens of centimetres, and horizontal widths on the order of tens of centimetres to a few metres. The spacing between these lenses is highly variable. The lengths and interconnectedness of the lenses is not well understood. On a larger scale, there is evidence for some broad-scale layering within the sediments (Wilson, 1973, 1985; Scott, 1980; Davey, 2006b), but this layering is unlikely to constitute separate, laterally extensive aquifers (Lough and Williams, 2009; Hanson and Abraham, 2009). Recharge to groundwater comes from rainfall, irrigation, seepage from both the Hinds River and the Ashburton River/Hakatere, and water losses from the Valetta irrigation scheme. Davey (2004) demonstrated that flood irrigation events from the Valetta scheme can be observed as a recharge wave increasing groundwater levels in downgradient wells by around two metres. Piezometric maps presented by Davey and Ettema (2004) indicate that the general direction of groundwater flow is from northwest to southeast, roughly parallel to the flow of the Hinds River and Ashburton River/Hakatere. In the upper plain there is a downward hydraulic gradient with values around 0.01 (Smith, 2008). The hydraulic gradient decreases and becomes neutral near the coast, although Davey (2006c) presents some evidence for upward hydraulic gradients around State Highway 1. Discharge from the groundwater system has not been quantified, but it is known to occur via springs between State Highway 1 and Boundary Road, at the interface between the heavy soils of the lower plain and the more shallow stony soils of the upper plain (Figure 2-2). Groundwater discharge may

Environment Canterbury Technical Report 5 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

also occur along the coast or through the sea floor off the coast, but this discharge has not been well investigated or documented. The permeability of the sediments, that is, the ease with which water can flow through them, is highly variable from one location to another. Two parameters recorded by Environment Canterbury can be used to compare permeabilities between well locations. Transmissivity is a measure of the rate at which groundwater flows through a unit width of an aquifer under a unit hydraulic gradient, and it is calculated from an aquifer test. Values from the 26 aquifer tests recorded on the Ashburton-Hinds plain vary considerably, ranging from 150 to 7,000 m2/day. There is no clear spatial pattern to these test results. Specific capacity is a more commonly recorded estimate of aquifer permeability because it does not require a full aquifer test. It is calculated as the well yield divided by the drawdown in the well during pumping. Environment Canterbury has specific capacity values for 751 wells on the Ashburton-Hinds plain, ranging from 0.013 to 78 litres per second per metre of drawdown (L/s/m). Again, there is little spatial pattern to these results, although the highest results, those greater than 10 L/s/m, generally occur only to the northwest of Boundary Road.

2.7 Land use Farming is the main land use on the Ashburton-Hinds plain, with a mixture of pastoral farming (sheep, beef, and/or deer), dairying, and cropping. Land use in 2005 is shown in Figure 2-3, which is land use data nearest to the time when the investigation was conducted. There has been a general trend of intensification over the years, and many farms throughout the plain have converted to irrigated dairy farming since the mid 1990s (Engelbrecht, 2005). Cropping, much of it not irrigated, is most common in the coastal area and in areas along the river margins above State Highway 1, particularly along the southwest side of the Ashburton River/Hakatere. These are areas where soils are thicker and have greater water holding capacity. Above State Highway 1 in the centre of the plain, farming activity is controlled by the availability of water from the Valetta irrigation scheme. Most farms within the scheme area involve intensive livestock production on fully irrigated units, dominated by dairying. Outside the Valetta scheme area, farming at the top of the plain is dominated by sheep and other pastoral farming, with a general trend of conversion to more intensive farming practices. Some farms outside the scheme area have developed irrigation from groundwater, but many dryland farms remain as well. Tinwald is the only township on the Ashburton-Hinds plain. It is situated immediately south of Ashburton, which is the largest town in mid-Canterbury.

6 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s s h h bu b r u to r n Mount Somers t R o iv n e r/H R a iv e k c a e a t r e ch / R re Bran H outh a S k a t e n r o e i

N ta a o it Hin r g ds t n R h a ive B R r Mayfield ra n c h

Ashburton

Tinwald A s h b u r to n 1 H ay w in h d ig s H R te ta iv S e d R r oa R i LAND USE (Agribase, 2005) ry v da e un r Bo / Cropping - including arable, vegetable Hinds H a or seed production k a t Dairy cattle farming or support, e r minor pig/poultry farming e Mixed pastoral - Beef, deer, sheep and other stock Lifestyle/residential or unspecified farm type Sheep farming Forestry/native bush

investigation area N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 Kilometers

Figure 2-3: Land use on the Ashburton-Hinds plain (Agribase, 2005)

Environment Canterbury Technical Report 7 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

2.8 Potential nitrate sources Natural nitrate nitrogen concentrations in groundwater probably do not exceed 3 mg/L and may not exceed 1 mg/L (Close et al., 2001; Hanson, 2002; Daughney and Reeves, 2005), but higher concentrations can result from human activities such as agriculture and wastewater disposal. Agricultural activities are the most widespread source of nitrate contamination on the Ashburton-Hinds plain, but there are potential sources of localised contamination as well. Diffuse nitrate leaching from agricultural land use is the subject of much study and debate (Haynes and Williams, 1993; Di and Cameron, 2002). Generally speaking, any farming activity will result in some nitrate leaching in excess of what would occur naturally. In order to achieve pasture and crop production, farm soils must maintain greater storage of mineral nitrogen, primarily in the form of nitrate, than would occur naturally. Where nitrate concentrations in the soil exceed plant uptake, nitrate can readily be leached from the soil and contaminate groundwater. In grazed pasture systems, urine patches are the greatest source of nitrate leaching, because the amount of nitrogen applied in a urine patch is far more than plants can use (Haynes and Williams, 1993; Di and Cameron, 2002). In cropping systems, nitrate leaching potential is highest in fallow periods between crop cycles, when there is no plant growth to remove excess nitrogen from the soil (Francis, 1995). Cultivation can also result in high leaching rates because it produces a large input of nitrate to the soil, associated with mineralization of organic components, followed by a period of low plant growth before the next crop is established. Finally, in any farming system, nitrate leaching is greatest in the winter period, when plant growth rates are low and soil moisture levels most commonly exceed soil water holding capacities. On the south bank of the Ashburton River/Hakatere, northwest of Tinwald, there is an extensive area of cropping land with deeper soils (Figure 2-2 and Figure 2-3). Interpretation of time series satellite imagery by Lilburne and North (2010) shows that much of this area could be fallow over winter for more than three years in a six year period (Figure 2-4). Fallow land is estimated to have low nitrate uptake and could result in high nitrate leaching rates (Bidwell et al., 2003). The satellite imagery analysis was not done for other parts of the Ashburton-Hinds plain. Possible point sources of nitrate contamination on the Ashburton-Hinds plain include a fertiliser store and the stock sale yards in Tinwald. There has also been a truck wash on Frasers Road, across from the Tinwald golf club.

8 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Figure 2-4: Cropping land on the Ashburton-Hinds plain estimated to have low nitrate uptake due to successive years in winter fallow

Environment Canterbury Technical Report 9 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

2.9 Pre-2004 groundwater quality data This report focuses on sampling conducted in 2004, but prior to that year, groundwater quality data were available from sixteen wells on the Ashburton-Hinds plain. The oldest data came from two samples collected from well K37/0222 in 1988, but most of the data came from Environment Canterbury’s annual regional groundwater quality survey. The survey first included wells on the Ashburton-Hinds plain in 1991, and by 2003, thirteen wells in the area had been sampled at least once as part of this survey. In addition to the annual survey, five wells near Tinwald were sampled once in April 1995 as part of a survey of Ashburton groundwater. The analytical results for all of these samples, as recorded in Environment Canterbury’s water quality database, are listed in Appendix 1, and well construction details are listed in Appendix 2. Nitrate nitrogen concentrations measured in these pre-2004 samples ranged from 0.6 mg/L to 13 mg/L. This data is summarised in Table 2-1, and Figure 2-5 plots the maximum nitrate nitrogen concentration recorded in these wells. The highest concentrations were measured in two of the annual survey wells, K37/0147 and K37/0358, and it was the results from these wells that initiated further investigation in the area. Nitrate nitrogen concentrations above the MAV had been measured in two samples from well K37/0147 (collected in 2001 and 2002) and in six samples from well K37/0358 (every year from 1998 to 2003). Both of these wells were located in the Tinwald area.

Table 2-1: Nitrate nitrogen concentrations measured in groundwater samples collected on the Ashburton-Hinds plain prior to 2004

Well Samples collected Nitrate nitrogen Well No depth (m) Count First Last (mg/L) K36/0118 11.3 12 1992 2003 2.2 - 8.1 K37/0028 5.1 1 1994 1994 1.9 K37/0087 16 1 1995 1995 3.5 K37/0088 10.1 1 1995 1995 11 K37/0114 9.3 7 1991 1997 5 - 8.5 K37/0147 9.8 10 1995 2003 0.6 - 13 K37/0216 9.5 12 1992 2003 4.5 - 10.3 K37/0222 18.7 5 1988 1993 1.6 - 3.9 K37/0358 15.6 9 1995 2003 11 - 12.8 K37/0466 6 13 1991 2003 1.3 - 6.3 K37/0467 8.2 7 1991 1997 1.1 - 4.3 K37/0468 9.1 13 1991 2003 1.6 - 6.5 K37/0516 46.9 1 1995 1995 0.6 K37/0563 0 2 1994 1995 0.9 - 1.9 K37/0619 55 7 1997 2003 2.6 - 3.3 K37/0833 10 6 1998 2003 4.3 - 8

10 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s s hb h ur b to u n r R Mount Somers t i o ve n r/H R a iv e k c at e a e r r ch / R e Bran H outh a S k a t e n r o e i

i D K36/0118 #

N o ta r a H t it in # K37/0833 h g ds n Ri B a ver ra R n Mayfield c h

# K37/0222

Ashburton

## K37/0114 K37/0216

Tinwald K37/0028 A s K37/0563 # h K37/0358 # b #### K37/0516 u K37/0088 K37/0147 r to K37/0087 n 1 H ay w in h d ig s H R te ta # K37/0468 iv S e r d oa R R ry i da v un e o r Hinds B / H a Pre-2004 - maximum nitrate k a t nitrogen concentration (mg/L) e r e # 0 - 2.8 mg/L # K37/0466 # K37/0467 # K37/0619 # 2.9 - 5.6 mg/L # 5.7 - 8.4 mg/L # 8.5 - 11.3 mg/L # > 11.3 mg/L

investigation area N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 Kilometers

Figure 2-5: Map showing maximum nitrate nitrogen concentrations measured in groundwater samples collected on the Ashburton-Hinds plain prior to 2004

Environment Canterbury Technical Report 11 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

3 Nitrate nitrogen concentrations in groundwater in 2004

3.1 Summary of investigations Three groundwater sampling surveys were conducted on the Ashburton-Hinds plain in 2004: • the Tinwald investigation in the autumn (April), documented by Abraham and Hanson (2004), • the investigation across the wider Ashburton-Hinds plain in the winter (July and August), and • the annual survey in the spring (October-November). In addition, quarterly sampling from two monitoring wells installed on a dairy farm began in May. In total, 121 wells on the plain were sampled at least once during the year. The location of the wells and well number is shown in Figure 3-1. The analytical results and detection limits for all of these samples, as recorded in Environment Canterbury’s water quality database, are listed in Appendix 1, and well construction details are listed in Appendix 2. Summaries of the individual surveys and the sampling procedures followed are presented in Appendix 3 and 4, respectively.

12 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A %U K37/2246 s s hb h ur b to u n r K37/0201 R Mount Somers t %U i o v n %U K37/2242 er /H R K37/2245%U ak iv e a e %U K37/1972 c t K37/0643 a e r %U r ch / R e h Bran H K37/2244 %U Sout a k %U K37/0819 a K37/2253%U t K37/0455 e K37/0358 %U n $T K36/0108 r %U K37/0724 K37/1004%U K37/0622 o $TK36/0282 e #S%U i $T %U Tinwald K36/0055 K37/1807 #S K37/0147 s %U K37/2254 K37/0088 %U K37/0476 r %U

e K37/0685 %U %U $TK36/0056 $TK36/0220 K37/0490 %U K37/0439 v

i D #S %U K37/1008 K36/0118 $TK36/0656

K36/0231$T $T K36/0027 %U K37/2126 $TK36/0540 %U K37/0810 ta $T K36/0780 $T K36/0577 a it Hin $TK37/0759 #S K37/0833 g ds n Ri a ver R Mayfield #S K37/0468 INSET $TK37/2307 $TK37/0219 $TK37/0689 $TK37/2299 $TK37/0222 $TK37/2302 $TK37/1006 $TK37/0224 $TK37/0443 %U $T Ashburton $TK37/1444 $T K37/2301 K37/1587 $TK37/1748 %U #S K37/0204 %U K37/0216 %U $TK37/0693 %U $T %U K37/1749 Tinwald%U $TK37/0188 K37/1661 %U A $T K37/0561%U s $T%U K37/0336 h $T K37/2297 %U %U #S%UK37/0358 $T b %U %U%U#SK37/0147 u $T K37/1061 %U %U r $T K37/0175 %U $T%U $T K37/2333 to $TK37/1711 K37 1/1789$T K37/0697 $TK37/0371 n ay %U w $TK37/0885 hK37/1939 $T K37/1767 $TK37/0060 $T K37/2311 g $T $T H $TK37/0736 i K37/0503 $TK37/1189 i H%U$TK37/0613 %U n te K37/0702$T $T L37/1187 d ta K37/0723 $T s $T K37/0155 S K37/0483$T K37/0474 $T L37/0794 R $T K37/1705 $TK37/0366 #S K37/0468 $TK37/2156 iv K37/0726 e $T$T r K37/0415 d $TK37/2310 oa $TK37/0018 L37/0711 $T R R ry $T i $T K37/0049 da v $T K37/0034 un $T L37/1356 e Bo K37/1745 K37/2325 r Hinds $T$T / K37/1733 H a k Sampling Investigation K37/1177 K37/1178 $T$T K37/1908 a t $T$TK37/2323 e Tinwald investigation well $T r %U $TK37/0680 L37/0852 e $T K37/0550 $TK37/2313 (well numbers labelled in inset only) #S K37/2390 K37/0619 $T K37/2315 $TK37/2314 #S $T K37/1153 Ashburton-Hinds plain investigation well $TK37/1162 $T $T (wells numbers labelled in main map) K37/2322 $TK37/2316 #S $T L37/0379 Annual survey well K37/2317 $T $T K37/1160 K37/0547 $T Consent monitoring well $T K37/1157 K37/2318 investigation area N

state highways Pacific Ocean roads rivers/streams 0 5 10 15 Kilometers

Figure 3-1: Map showing the locations of wells on the Ashburton-Hinds plain where groundwater samples were collected during surveys conducted in 2004

Environment Canterbury Technical Report 13 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

3.2 Nitrate nitrogen results

3.2.1 General summary The nitrate nitrogen concentrations recorded in 2004 are mapped in Figure 3-2. For wells that were sampled more than once during the year, the map reflects the concentration measured during the winter, in the Ashburton-Hinds plain investigation. The concentrations ranged from less than 0.1 mg/L (the detection limit) to 22.4 mg/L. The samples from 20 of the 121 wells sampled had concentrations greater than the MAV (11.3 mg/L), and the samples from 60 wells had concentrations above half the MAV (5.6 mg/L). Four of the samples had concentrations less than the detection limit of 0.1 mg/L.

3.2.2 Tinwald area Based on the results from all 121 samples collected in 2004, the area where concentrations exceeded the MAV was approximately 3 km wide and 11 km long (Figure 3-2). This was larger than the area (2 km wide and 7 km long) that had been delineated initially during the Tinwald investigation by Abraham and Hanson (2004) based on the April 2004 results. Figure 3-3 shows nitrate nitrogen concentrations in a vertical cross section through the Tinwald area. The section line, shown in Figure 3-2, starts at the South Branch of the Ashburton River/Hakatere near the top of the plain. From there, it follows a path south eastward to the coast, following the general direction of groundwater flow. Wells within 1.5 km either side of this line were included in the cross section. The brown line on the cross section represents the ground surface. Along most of the section, the ground surface is relatively featureless with a consistent slope, but near the coast, the section line crosses the lower Ashburton River/Hakatere where it has eroded a steep-sided channel into the plain. At the coast, the cross section shows the sea cliff described in Section 2.2. The blue line on the cross section represents the estimated water table. Note that the cross section is drawn with considerable vertical exaggeration, with the vertical scale approximately 80 times the horizontal scale. Figures 3-2 and 3-3 show a general increase in nitrate nitrogen concentration in a southeast direction from the top of the Ashburton-Hinds plain to the Tinwald area. At the top of the plain, near the South Branch of the Ashburton River/Hakatere, concentrations were less than 2.9 mg/L (wells K36/0055, K36/0108 and K36/0282). Moving down the plain toward the coast, concentrations were between 2.9 and 8.4 mg/L (between ¼ and ¾ of the MAV) over a distance of about 14 km, and then from about 5 km northwest of Tinwald, they were greater than 8.4 mg/L. Downgradient of Tinwald, near Boundary Rd, concentrations changed abruptly to values less than 2.9 mg/L. The change to low concentrations occurred with depth as well as location. An example of this is shown by the results from three wells located near Boundary Road, southeast of Tinwald. The sample from well K37/0810, 10 m deep, had a concentration of 14.4 mg/L, while the sample from K37/0723, 18 m deep, had a concentration of only 1.9 mg/L and the sample from K37/0702, 34 m deep, had a concentration of less than 0.1 mg/L. Similarly, the sample from well L37/1356, a 10 m deep well south of Lake Hood, had a concentration of 22.4 mg/L, while the sample from well L37/0711, a 23 m deep well only 580 m away, had a concentration of only 2.6 mg/L. Another 10 m deep well about 1.5 km to the southwest, K37/2325, had a concentration of 0.7 mg/L (well numbers shown on Figures 3-2 and 3-3). There is evidence that at least some of the low concentrations in the lower part of the plain are associated with reducing conditions in the groundwater. This will be discussed in more detail in Section 3.2.5.

14 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s s hb h ur b to u n r R Mount Somers t i o ve n r/H R a iv e k c at e a e r r ch / R e Bran H outh a S k a t # e n # K36/0108 # r o # K36/0282 # e i # K36/0055

r e ## ## v

# # ##

## ## N # # # o ta ## # K36/0577 K36/0540 r a # t it Hin # ## h g ds n Ri B a ver ra R n Mayfield c ## h ##

# ## # ## K36/0222 ## ## ## K36/1006 # # ##

# Ashburton # # # # # # # # ## # # # ## ## ## ## ## # # ## # # ## A # # ## # Tinwald s ## h # # # # # # ### ## b # # # # # # # # u # # # # K37/0175 # # r # ## ### ## ## t # o ## # ## n # # ## 1 # # # y # # # a # # H # ## w # ## # h ## K37/0810 # i # # n ig K37/0723 ## ## d H K37/0702 ## s ## te ## ## a # t # Lake S # # R # # ## iv Hood # e ## # ## # L37/0711 r d # 2004 - nitrate nitrogen oa # # R R ry ## i # v concentration (mg/L) ## da # # n K37/2325 # e ou L37/1356 B # r Hinds ### / # 0 - 2.8 mg/L H a # k 2.9 - 5.6 mg/L ## ## a # # t ## e # # 5.7 - 8.4 mg/L # # r # e ## ## # ## # K37/2390 8.5 - 11.3 mg/L # # # # # ## # > 11.3 mg/L ## ## K37/2322

## Tinwald area ## # ### #

investigation area ### Cross section (see Figure 3.3) N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 Kilometers

Figure 3-2: Nitrate nitrogen concentrations in groundwater, Ashburton-Hinds plain, 2004. The Tinwald area with concentrations above the MAV and the location of the cross section, Figure 3-3 are shown. Also shown are selected well numbers discussed in the text

Environment Canterbury Technical Report 15

NW SE

Ashburton River/Hakatere South Branch 250 Nitrate contamination groundwater and chemistry K36/0055

200

Tinwald Boundary Rd 150 SH 1 K37/0810 - 10m, 14.0 mg/L K37/0723 - 18m, 1.9 mg/L K37/0702 - 34m, < 0.1 mg/L

Elevation (m asl) 100 L37/1356 - 10m, 22.4 mg/L K37/2325 - 10m, 0.7 mg/L L37/0711 - 23m, 2.6 mg/L

Ashburton River/ 50 Hakatere

Environment CanterburyTechnical Report coast

vertical scale approx. 80 times horizontal L37/0852

0 -

Ashburton 0 5 10 15 20 25 30 35 40 Distance (km) - ground plain Hinds water 0 - 2.8 2.9 - 5.6 5.7 - 8.4 8.5 - 11.3 > 11.3 surface table nitrate nitrogen concentration (mg/L N)

Figure 3-3: Vertical cross section of nitrate nitrogen concentrations in groundwater along a line through the Tinwald area

Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

3.2.3 Wider Ashburton-Hinds plain The nitrate nitrogen concentrations found across the wider Ashburton-Hinds plain ranged from less than 0.1 mg/L to a maximum of 22.4 mg/L (Figure 3-2). Concentrations above 8.4 mg/L were found only in the middle of the plain, within about 5 to 8 km either side of State Highway 1. Farther up the plain, the concentrations were somewhat lower, in the range of 2.9 to 8.4 mg/L, with even lower concentrations (less than 2.9 mg/L) at the top of the plain and along the Ashburton River/Hakatere and the Hinds River. Concentrations were also low in the coastal area, and in fact, all four samples with concentrations less than 0.1 mg/L came from wells located within about 12 km of the coast. In the upper half of the plain, there was a distinction between the areas within and outside of the Valetta irrigation scheme (refer to Figures 2-1 and 3-2). Within the scheme area, nitrate nitrogen concentrations did not exceed 5.6 mg/L. Outside the scheme area, concentrations in the range of 5.7 to 8.4 mg/L were common, particularly to the northeast, between the scheme area and the Ashburton River/Hakatere. In both areas, however, concentrations generally increased in a southeasterly, downgradient direction, reaching levels in the range of 8.4 to 11.3 mg/L downgradient of the Valetta scheme, and reaching concentrations above 11.3 mg/L in the Tinwald area to the northeast of the scheme. The samples from two wells outside the Tinwald area also had nitrate nitrogen concentrations above the MAV. One of these was well K37/2322 (6 m deep), located approximately 14 km southwest of Tinwald and approximately 1 km from the Hinds River (Figure 3-2). The sample from this well had a concentration of 22.4 mg/L, which was equal to the concentration recorded in well L37/1356, located within the Tinwald area. The other well with a concentration above the MAV was the annual survey well K37/2390 (10 m deep), located approximately 2 km northeast of K37/2322. The sample had a concentration of 12.7 mg/L. This well is discussed further in Section 4.1.2.

3.2.4 Nitrate nitrogen concentrations and well depth As discussed in Section 3.2.2, nitrate nitrogen concentrations decreased dramatically with well depth in the area near Boundary Road, to the southeast of Tinwald. However, this trend was not seen throughout the investigation area. In the central part of the plain, low nitrate nitrogen concentrations were found in three relatively shallow wells: K37/0175 (12 m deep, 2 mg/L), K37/0222 (19 m deep, 2.7 mg/L) and K37/1006 (10 m deep, 0.7 mg/L). This was in contrast to the deeper wells in the same area, which had concentrations greater than 2.8 mg/L (Figure 3-2). Overall, the concentrations were more variable in shallow groundwater than in deeper groundwater (Figure 3-4). All of the samples with concentrations greater than the MAV, as well as all of the samples with concentrations less than 0.1 mg/L, came from wells less than 40 m deep. In contrast, the concentrations from wells deeper than 40 m were much less variable, ranging from 3.2 to 8.5 mg/L. As discussed in Section 2.8, natural concentrations of nitrate nitrogen in groundwater are probably less than 3 mg/L (Hanson, 2002; Daughney and Reeves, 2005). Therefore, the results discussed in this report indicate that anthropogenic nitrate contamination has reached considerable depths in groundwater beneath the Ashburton-Hinds plain. The deepest well sampled in the 2004 investigations (K36/0577, located near the upper part of the plain) was approximately 116 m deep, and the nitrate nitrogen concentration in this well was 5.7 mg/L. Another deep well approximately 3.5 km to the east (K36/0540, 113 m deep) had a concentration of 5.3 mg/L. Both of these concentrations are indicative of anthropogenic contamination. Based on unpublished water level data held by Environment Canterbury, the depth to the water table in the area around this well probably lies somewhere in the range of 20 to 50 m below ground surface. Therefore, anthropogenic nitrate has reached depths of at least 60 to 90 m below the water table in the upper part of the Ashburton-Hinds plain.

Environment Canterbury Technical Report 17 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

10 Nitrate nitrogen (mg/L) nitrogen Nitrate

0 0 40 80 120 well depth (m)

2004 Nitrate result MAV 1/2 MAV

Figure 3-4: Well depth versus nitrate nitrogen concentrations in samples collected in the Ashburton-Hinds Investigation

3.2.5 Reducing conditions in the coastal groundwater The low nitrate nitrogen concentrations in the lower part of the Ashburton-Hinds plain (Figure 3-2) coincide with an area where reducing conditions occur in the aquifer. Reducing conditions occur when dissolved oxygen is removed from the groundwater, generally through the breakdown of organic material in the aquifer sediments. Once the dissolved oxygen is gone, chemical reactions that require oxygen must find other sources. Nitrate is typically the next source, followed by the oxides of iron and manganese, and then by sulphate (Langmuir, 1997). The removal of oxygen from these compounds is called "reduction". Nitrate is reduced to nitrogen gases. The oxides of iron and manganese, which are generally insoluble in an oxidised environment, are reduced to more soluble compounds. Sulphate is reduced to hydrogen sulphide. Therefore, under reducing conditions, groundwater typically has little or no nitrate, but relatively high concentrations of dissolved iron and manganese. Strongly reduced groundwater tends to have a hydrogen sulphide odour. The groundwater may also have relatively high concentrations of ammonia nitrogen, because any ammonia derived from the breakdown of organic material cannot be oxidised to nitrate. In the lower part of the Ashburton-Hinds plain, near the coast, the data suggest reducing conditions in the groundwater. Iron and manganese concentrations were relatively high compared to concentrations found farther up the plain (Figure 3-5), and there was a strong correlation between the highest iron and manganese concentrations and the lowest nitrate nitrogen concentrations (refer to Figures 3-2 and 3-5). For example, there were three samples with iron concentrations greater than 1 mg/L. All of these samples had manganese concentrations greater than 0.5 mg/L and nitrate nitrogen concentrations less than 0.1 mg/L, and all were located within about 10 km of the coast. Based on Figures 3-2 and 3-5, the zone of reducing conditions extends inland from the coast for about 10 to 12 km. Along the northeast side of the plain, the zone extends further inland as far as the Tinwald area.

18 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Further up the plain, the concentrations of iron and manganese measured in the groundwater were very low, usually less than analytical detection limits (see Figure 3-5 and Appendix 1). At the same time, nitrate nitrogen concentrations in samples from this area were relatively high, and the concentrations of dissolved oxygen measured in the field during well purging were also high. All of this evidence indicates that the groundwater in these samples was well oxidised. The coastal zone of reduced groundwater coincides with the area of heavier soils near the coast (Figure 2-2) and the line of springs near Boundary Road (Figure 2-1). It also coincides with an area where "blue" sediments and occasional peaty organic material are recorded in well logs (unpublished data held by Environment Canterbury). Blue sediments often reflect reducing conditions because the reduced forms of iron oxides are blue-grey in colour, in contrast to the rusty colour of the more oxidised forms. Not all samples within this zone had high iron and manganese concentrations, nor were all nitrate nitrogen concentrations low. Many samples had nitrate nitrogen concentrations in the range of 2.9 to 5.7 mg/L, and a few had even higher concentrations. Some samples had both high iron and high nitrate nitrogen concentrations, suggesting that the chemistry of the groundwater sample was not at equilibrium. It may be that the well drew water from different parts of the aquifer, such that the sample was a mixture of some reduced groundwater and some oxidised groundwater. This suggests that the oxidation-reduction conditions in the groundwater can vary considerably over very short distances. Such variability was also evident when comparing results from adjacent wells. For example, wells L37/1356 (10 m deep) and L37/0711 (23 m deep) were discussed in Section 3.2.2. The wells are located south of Lake Hood and only 580 m apart (Figures 3-2 and 3-5). The shallow well had a nitrate nitrogen concentration of 22.4 mg/L and iron and manganese concentrations both below detection limits, indicated well-oxidised groundwater. The deeper well had a nitrate nitrogen concentration of only 2.6 mg/L and iron and manganese concentrations both at 0.11 mg/L, indicating partially reducing conditions.

Environment Canterbury Technical Report 19 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s sh h b b ur u to r n Mount Somers t R o iv n er R /H i e a v c k e a a r te / R re Branch H outh a S k a t n ## e o # r i # # e s # r e # v # i # #

D ## ## N ## ## o ta # # r a H ## # # t it in # # h g ds # # n Ri B a ver ra R n Mayfield c ## h ## # # # # # # # # # # # # # # # # Ashburton ## # ## # # ## ## # # # ## # # # # # # # # # A # # s # ## h # ## Tinwald b # # # # # # u # # ### # # # # ## ### rt # # # #### # # o # # ## ## n # 1 # # # y # # a ## # # H # hw # # # # i # # ig # # # n # H ## ### d te ## ## # s ta # # # # # # # R # S ## # Lake i # # # v # # ## Hood e # r ### ## R d # L37/0711 # i oa # v Manganese and iron - 2004 data R ## # ry # e ## da # r # n # L37/1356 / Hinds u H Manganese concentration (mg/L) Bo ## ## a # k 0.005 - 0.01 a t # ## e ## ## 0.011 - 0.4 # r # # ## e 0.41 - 0.57 # # # # # # # # ## ## # Iron concentration (mg/L) ## # # 0.015 - 0.03 ## # # 0.031 - 0.2 # # # # # 0.21 - 2.4 ## # ## investigation area N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 Kilometers

Figure 3-5: Iron and manganese concentrations and the area where reduced groundwater is likely to occur beneath the Ashburton-Hinds plain

20 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

4 Update on the 2004 results

4.1.1 Overview Groundwater sampling has continued on the Ashburton-Hinds plain since 2004, and new samples have been collected from several of the wells that were sampled in the 2004 investigations. The results from these samples indicate that nitrate concentrations have increased in some areas. The data come from Environment Canterbury’s long-term groundwater quality monitoring programme (Abraham and Hanson, 2010) and from a 2009 investigation into changes in groundwater quality with depth (Hanson and Abraham, 2011). The locations of the wells on the Ashburton-Hinds plain that were sampled between 2005 and 2009 are shown in Figure 4-1, grouped according to the maximum nitrate nitrogen concentration that was measured in each well during that period. The full analytical results from the samples collected from these wells are included in Appendix 1, and the well construction details are included in Appendix 2.

4.1.2 Long-term monitoring In 2009, Environment Canterbury’s annual groundwater quality survey included eight wells, all of which were sampled in 2004. In addition, five of these wells (K37/0216, K37/0468, K37/0147, K37/0358 and K37/0833) were sampled quarterly from 2005 to 2009, and two of them (K37/0147 and K37/0358) were sampled monthly for five months after a large snowfall event in 2006. The nitrate nitrogen concentrations from these long-term monitoring wells are summarised in Table 4-1 and shown graphically in Figure 4-2.

Table 4-1: Summary of nitrate nitrogen concentrations measured in samples from eight long-term monitoring wells located on the Ashburton-Hinds plain

Nitrate nitrogen Nitrate nitrogen Nitrate nitrogen 1988 - 2003 2004 2005 - 2009 Depth Well No (m) samples mg/L samples mg/L samples mg/L K36/0118 11.3 12 2.2 - 8.1 2 1.8 - 4.2 6 2.3 - 8.6 K37/0147 9.8 10 0.6 - 13 3 7.8 - 18.4 20 1.0 - 18.3 K37/0216 9.5 12 4.5 - 10.3 2 3.6 - 6.3 18 2.2 - 12.3 K37/0222 18.7 5 1.6 - 3.9 1 2.7 2 3.4 - 3.7 K37/0358 15.6 9 11.0 - 12.8 3 13 - 14.5 20 11.5 - 18.2 K37/0468 9.1 13 1.6 - 6.5 1 7.3 18 4.2 – 14.0 K37/0619 55 7 2.6 - 3.3 1 2.9 5 2.1 - 3.2 K37/0833 10 6 4.3 – 8.0 2 4.8 - 5.5 18 4.3 - 9.5

Values in red indicate concentrations greater than the MAV.

The concentrations measured in two of the wells, K37/0358 and K37/0468, show clear increasing trends over the period of record (Figure 4-2). The data from a third well, K37/0833, also suggest an increasing trend, but a high concentration early in the record makes the trend less clear (Figure 4-2). The data from the other wells show no clear trends of either increasing or decreasing concentrations over the period of record. Note that none of the wells show decreasing trends. In 2004, nitrate nitrogen concentrations exceeded the MAV in samples from two of these eight wells, K37/0147 and K37/0358. Since then, concentrations above the MAV have been observed in two more wells, K37/0216 and K37/0468.

Environment Canterbury Technical Report 21 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

A A s s hb h ur b to u n r R Mount Somers t i o ve n r/H R a iv e k c at e a e r r ch / R e Bran H outh a S k a t # # e n r o e i

r e # v i # D #U K36/0118 # N o ta # K36/0577 r a t it Hin #U K37/0833 h g ds n Ri B a ver # ra R # n Mayfield c h # # K37/0689 #U K37/0222 # # # K37/0443 # Ashburton # # # #U K37/0216 # # # # # A s # # Tinwald h b K37/0358#U #U u K37/0147 r ## to # K37/1711 n

H in # d # s 1 R ay w #U K37/0468 iv gh e Hi r e 2005 - 2009 - maximum nitrate at # # R t i S v nitrogen concentrations (mg/L) e r Hinds d / oa H # R ## K37/1792 y a 0 - 2.8 mg/L ar nd k # ou a 2.9 - 5.6 mg/L B t # K37/1908 e # # r 5.7 - 8.4 mg/L K37/0466 ## K37/0680 e # K37/2390 #U# 8.5 - 11.3 mg/L K37/2314 ## #U K37/0619 # # K37/1010 > 11.3 mg/L # # U annual monitoring well # K37/0547 # ## 2009 investigation transect # # investigation area N

state highways Pacific Ocean roads rivers/streams/drains 0 5 10 15 Kilometers

Figure 4-1: Wells on the Ashburton-Hinds plain that were sampled from 2005 to 2009, showing the maximum nitrate nitrogen concentrations measured during that period. Also shown are selected well numbers that are discussed in the text

22 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

K36/0118 K37/0147 - Q, M 20 20

15 15

10 10

5 5

0 0 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

K37/0216 - Q K37/0222 20 20

15 15

10 10

5 5

0 0 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

K37/0358 - Q, M K37/0468 - Q 20 20

15 15

10 10

5 5

0 0 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

K37/0619 K37/0833 - Q 20 20

15 15

10 10

5 5

0 0

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 Figure 4-2: Nitrate nitrogen concentrations over time, measured in eight long-term annual monitoring wells on the Ashburton-Hinds plain. The M and Q represent wells monitored monthly and quarterly

Environment Canterbury Technical Report 23 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Comments on data from individual wells Concentrations in samples from well K37/0147, located at the Tinwald stock saleyards, have exceeded the MAV on numerous occasions, but they have been highly variable, ranging from 0.6 mg/L to 18.4 mg/L between 1995 and 2009 (Figure 4-2). The variability has led to some question about the validity of the results, and in fact, it is possible that some of the earlier samples with low nitrate nitrogen concentrations were collected from a public water supply rather than from the well. Samples since 2004 have been collected directly from the well with a portable pump and purged according to Environment Canterbury procedures, yet the results continue to vary widely. The reason for the variation is not known. The well is on the upgradient side of the property, so it is probably not affected by the saleyard activities. Only one sample from well K37/0216 has had a nitrate nitrogen concentration greater than the MAV. That sample was collected in September 2008, after a wet winter that might have contributed to the high concentrations. Concentrations in samples from some other wells in Canterbury, including wells K36/0118 and K37/0833 on the Ashburton-Hinds plain (Figure 4-2), also showed significant increases after the winter of 2008. An earlier sample from well K37/0216 (collected in 1999, again after a wet winter) had a concentration of 10.3 mg/L, which was close to the MAV, and the rest of the data from this well do not show a clear trend of either increasing or decreasing concentrations over time. Nitrate nitrogen concentrations in samples from well K37/0358 (Figure 4-2) have shown a fairly steady increasing trend since the well was first sampled in 1995. Concentrations in the first three years of sampling were close to 11 mg/L, but samples collected since 2006 have had concentrations in the range of 16 to 18 mg/L. Well K37/0468, located outside the Tinwald area, has also shown an increasing trend in nitrate nitrogen concentrations (Figure 4-2). In the early 1990s, concentrations were in the range of 5 to 6 mg/L, and at the time of the 2004 investigation, they were about 7 mg/L. More recently, all of the samples collected since March 2008 have had concentrations greater than 11 mg/L, including a concentration of 14 mg/L recorded in September and December 2009. Well K37/0833 was sampled annually from 1998 to 2005, and it has been sampled quarterly since 2005. Peaks in nitrate concentrations occurred after heavy winter rain or snowfall events in 2000, 2006 and 2008, but if these peaks are ignored, it appears that the baseline concentrations have increased over the period of record, from around 5 mg/L in the late 1990s to roughly 7 to 8 mg/L in 2009. Concentrations above the MAV have been noted in another annual survey well, K37/2390 (10 m deep), but that well was only sampled three times and gave highly variable results. It was added to the annual survey in 2004 after a nearby well (K37/0466, 6 m deep) was abandoned. The sample collected in that survey had a nitrate nitrogen concentration of 12.7 mg/L. The well was sampled again in September 2005, and the sample had a much lower concentration of 3.9 mg/L. A third sample was collected in December 2005, with another high concentration at 12.9 mg/L. The well was abandoned after that, so further investigation into the variations in chemistry was not possible. For comparison, the highest concentration in the original survey well, K37/0466, was only 6.3 mg/L (Appendix 1).

4.1.3 2009 investigation In January to April 2009, 49 groundwater samples were collected along a transect oriented from northwest to southeast through the middle of the Ashburton-Hinds plain. The samples were collected from a variety of depths to provide a cross section of groundwater chemistry through the plain. A technical report summarising this investigation is in preparation (Hanson and Abraham, 2011). Nitrate nitrogen concentrations exceeded the MAV in the samples from two of the wells along the transect, K37/1010 (10 m deep, 12 mg/L) and K37/1792 (6 m deep, 12 mg/L). Neither of these wells had been sampled previously. Both were relatively shallow and both were located below State Highway 1. Significantly, both were located outside the Tinwald area. That is, they were located outside the area of highest nitrate nitrogen concentrations that was delineated after the 2004 investigations (Figure 4-1). Nine of the wells sampled along the 2009 transect had also been sampled in 2004 (Table 4-2). The differences in concentration recorded between the two investigations ranged from -0.6 mg/L (lower in

24 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

2009) to +3.7 mg/L (higher in 2009). In all but one of the wells, the concentration was higher in 2009 than in 2004.

Table 4-2: Comparison of nitrate nitrogen concentrations in groundwater from nine wells sampled in both 2004 and 2009

Nitrate nitrogen Nitrate nitrogen Difference 2004 2009 Well No Depth (m) date mg/L date mg/L mg/L K36/0577 115.9 20/07/2004 5.7 22/01/2009 5.1 -0.6 K37/0222 18.7 14/07/2004 2.7 28/01/2009 3.7 1 K37/0443 69.3 15/07/2004 3.8 23/04/2009 5.1 1.3 K37/0547 10 21/07/2004 4.4 10/03/2009 6.7 2.3 K37/0680 13.8 12/08/2004 0.8 24/02/2009 2.3 1.5 K37/0689 91.5 15/07/2004 3.3 28/01/2009 3.7 0.4 K37/1711 48 27/07/2004 3.8 10/02/2009 4.8 1 K37/1908 24 12/08/2004 2.9 23/02/2009 4.2 1.3 K37/2314 9 5/08/2004 3.7 25/02/2009 7.4 3.7

When these results are combined with the long-term monitoring data discussed in Section 4.1.2, they support a conclusion that nitrate concentrations in groundwater beneath the Ashburton-Hinds plain have increased since the 2004 investigations.

4.1.4 Summary When the comparison of the 2004 and 2009 investigations is combined with the long-term monitoring data discussed in Section 4.1.2, the results support a conclusion that nitrate concentrations in groundwater beneath the Ashburton-Hinds plain have increased since the 2004 investigations. Moreover, the more recent sampling demonstrates that groundwater nitrate nitrogen concentrations above the MAV are not restricted to the Tinwald area.

Environment Canterbury Technical Report 25 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

5 Discussion There are several factors influencing nitrate concentrations in the groundwater beneath the Ashburton- Hinds plain, including land use, recharge source, aquifer geology and irrigation.

Land use Nitrate nitrogen concentrations in groundwater across most of the Ashburton-Hinds Plain are higher than concentrations that generally occur naturally (Close et al., 2001; Hanson, 2002; Daughney and Reeves, 2005), and therefore they almost certainly reflect contamination from human activities. Based on the extent of this contamination, which covers most of the plain and extends to depths of more than 60 m below the water table, the main source of the nitrate must be diffuse leaching from agricultural land rather than point-source discharges. This situation is comparable to what is observed across most of the Canterbury Plains (Hanson, 2002). However, the concentrations in the Tinwald area are relatively high compared to concentrations that occur elsewhere in Canterbury. Concentrations above the MAV have been recorded elsewhere in the region, but the concentrations recorded in the Tinwald area, and the areal extent of the contamination, are unusual. Extensive areas of groundwater with nitrate nitrogen concentrations above the MAV have been recorded elsewhere in Canterbury. Among these are the area between the Ashburton River/Hakatere and the Rakaia River (Abraham and Hanson, 2004; Hayward and Hanson, 2004), and the area between the Rangitata River and the Orari River (Hanson, 2002; unpublished Environment Canterbury data). While much of the contamination in these areas is probably caused by diffuse leaching from agricultural land, the highest concentrations appear to be associated with specific point sources, particularly wastewater disposal from meat processing plants or dairy factories. In contrast, there is no clear point source that might explain the high concentrations in the Tinwald area. There are no large wastewater discharges in the upgradient area, nor any other specific sources that could cause nitrate contamination across an area 3 km wide and 11 km long. The high concentrations extend upgradient of all three potential point sources (the stock saleyards, the fertilizer store and the truck wash) listed in section 2.8. Therefore the high nitrate concentrations in the Tinwald area must come from diffuse leaching from agricultural land. This means that in the agricultural land upgradient of Tinwald, nitrate nitrogen concentrations in the soil drainage water must exceed the MAV. In fact, the concentrations probably exceed 20 mg/L, based on the highest concentrations found in the Tinwald area. Moreover, these concentrations must be sustained in the soil drainage water throughout the year because the concentrations measured quarterly in wells K37/0358 and K37/0468 do not show substantial seasonal variation. How these concentrations compare with soil drainage concentrations elsewhere in the region is not known. The farm types upgradient of Tinwald are fairly typical for the Canterbury Plains, but cropping and winter fallow land are more concentrated in this area than they are across most of the plains. Field studies have shown a wide range of leaching rates from cropping, with maximum rates much higher than leaching rates from sheep and beef pasture (Di and Cameron, 2002; Bidwell et al. 2003). Therefore, it may be that cropping practices (current and/or historical) are at least partially responsible for the high nitrate nitrogen concentrations in the Tinwald area. This possibility is supported by the occurrence of high nitrate concentrations in groundwater in the Chertsey-Dorie-Rakaia area, between the Ashburton River/Hakatere and the Rakaia River (Hayward and Hanson, 2004; Abraham and Hanson, 2004). This is another area where there is no clear point source to explain the high concentrations, but cropping is widespread in the upgradient area. However, it would be overly simplistic to conclude that crop farming is the only cause of the high nitrate concentrations in the Tinwald area. The land upgradient of well K37/0468, which is outside the Tinwald area, does not have the same intensity of cropping as does the land upgradient of well K37/0358, and yet both wells have similar elevated nitrate concentrations.

26 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Recharge source The two main recharge sources on the plain are alpine river water and soil drainage water. Nitrate nitrogen concentrations in alpine river water are low, generally much less than 1 mg/L, while concentrations in soil drainage water are higher and more variable (Hanson and Abraham, 2009). Alpine river water is the dominant source of recharge in areas adjacent to the Hinds River and the Ashburton River/Hakatere, while soil drainage water is more dominant in areas away from the rivers, especially in relatively shallow groundwater. It is likely that alpine river recharge dominates deeper groundwater as well, though this investigation does not explore that question (it will be addressed in a separate report, Hanson and Abraham, 2011, which is in preparation).

Aquifer geology There also appears to be a link between groundwater chemistry and aquifer geology in the Ashburton- Hinds plain. In the upper part of the plain, which is dominated by light soils and high-permeability sediments, the groundwater is well oxidised and nitrate nitrogen concentrations are moderate to high. In the lower part of the plain, reducing conditions are common in the groundwater, indicated by the presence of dissolved iron and manganese and by low nitrate nitrogen concentrations. This area is characterised by heavier soils and spring-fed streams and possibly by less permeable sediments, suggested by lower specific capacity values as discussed in Section 2.6. The transition zone between the upper and lower parts of the plain is generally located between State Highway 1 and Boundary Road, and this is where the highest nitrate nitrogen concentrations are found. This is particularly the case in Tinwald, but it is also evident outside the Tinwald area. Across the top of the plain, concentrations are relatively low. As one moves down the plain, concentrations increase until one reaches the transition zone, Then in the coastal zone, concentrations are much lower again (Figure 3-2). Within the transition zone, concentrations can vary dramatically over short distances, both laterally and with depth. It is not clear exactly how this geologic transition influences the nitrate concentrations. It may be that the low-permeability sediments in the lower part of the plain restrict the downward movement of soil drainage water into the aquifer. This would prevent the dilution of the soil drainage water, which contains nitrate leached from the ground surface, with deeper, cleaner groundwater, thereby maintaining higher concentrations near the water table. In turn, this shallow groundwater discharges to the spring-fed streams in the area. This accounts for the high nitrate concentrations noted in the streams. It also helps to explain why nitrate concentrations measured in the groundwater of the lower plain have been low in spite of the considerable amount of crop farming there (Figure 2-3). Much of the nitrate that leaches from the soil is diverted to the streams rather than penetrating deeper into the groundwater system where wells are screened. This flow pattern is also consistent with the reducing conditions found in the groundwater near the coast (Section 3.2.5). Low permeability and low groundwater flow rates lead to longer groundwater residences times. As groundwater remains in the ground for longer periods, it loses its dissolved oxygen to reactions with the aquifer sediments.

Irrigation Irrigation practices will also affect groundwater chemistry. In the Valetta irrigation scheme area, water from the Rangitata River, via the RDR, is likely to be an important component of the soil drainage during the summer. RDR water also dominates summer groundwater recharge in the Mayfield-Hinds (Dommisse, 2007) and Ashburton-Lyndhurst scheme (Thorley et al., 2009) areas. The flood irrigation in the Valetta scheme area will tend to dilute nitrate concentrations in the soil drainage water. In comparison, the area upgradient of Tinwald is largely unirrigated, so soil drainage rates will be lower there than in the Valetta scheme area, and nitrate concentrations in the soil drainage will be less diluted. Therefore, even if leaching loss rates in the two areas were equal when considered on the basis of kilograms of nitrogen per hectare, the concentrations would be greater upgradient of Tinwald than in the Valetta scheme area.

Environment Canterbury Technical Report 27 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Summary In summary, there are several factors that contribute to the high nitrate concentrations found in groundwater of the Tinwald area: leaching from cropping land in the area upgradient of the town, a lack of dilution from flood irrigation compared to the Valetta scheme area, the influence of the aquifer geology and the mixing of soil drainage water with alpine river water within the aquifer system. Which of these factors is most important, or whether the Tinwald concentrations are the product of all three factors combined, is not clear.

6 Conclusions • The area around Tinwald where nitrate concentrations in groundwater exceed the MAV is approximately 3 km wide and 11 km long. However, concentrations above the MAV also occur in some wells outside the Tinwald area, most of them located below State Highway 1. • Diffuse nitrate leaching from agricultural land is the main source of nitrate in the groundwater, but the highest concentrations result from a combination of three factors: recharge source, aquifer geology and land use. • The highest nitrate concentrations occur where groundwater recharge is dominated by soil drainage rather than alpine river water, and at the transition zone between high-permeability sediments beneath the upper plain and the lower-permeability sediments near the coast. • Cropping and winter fallow activities are likely to contribute to the high concentrations in the Tinwald area, while the dilution of nitrate in soil drainage water caused by flood irrigation in the Valetta irrigation scheme area may help to account for the lower concentrations outside the Tinwald area. • Reducing conditions in the aquifer near the coast keep nitrate concentrations low in that area. • Anthropogenic nitrate reaches depths of over 60 m below the water table in the upper part of the plain.

7 Recommendations • Additional work is needed to explore the relationship between nitrate concentrations and depth. This has partly been addressed by sampling in the middle of the plain (Hanson and Abraham, 2011), but further sampling of deep groundwater in the Tinwald area is also needed. • Additional sampling in the coastal zone for a suite of nitrogen species, including nitrate, nitrite, ammonia and organic nitrogen, would be useful to better understand and delineate oxidation- reduction reactions in this area. Arsenic should also be included in this sampling because arsenic contamination is seen elsewhere in coastal parts of Canterbury where reducing conditions are found in groundwater. • The relationship between groundwater and surface water interaction should also be considered in the design of future investigations in this area. • A sampling survey of nitrogen isotopes (δ15N) in groundwater could be useful in differentiating sources of nitrate contamination. • Complete satellite imagery and mapping of historical and present land use on the Ashburton- Hinds plain is needed to determine the effects of different land uses on nitrate concentrations groundwater.

28 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

8 Acknowledgements The cooperation and helpfulness of well owners on the Ashburton-Hinds plain is very much appreciated for allowing Environment Canterbury access to their wells. The authors thank Zella Smith for her help in collecting groundwater samples in the winter of 2004, and Robyn Croucher for her contributions to early drafts of this report. The authors also extend their thanks to Matt Smith, Howard Williams and Kathleen Crisley for providing valuable comments and to Vince Bidwell for his external review of this report.

9 References Abraham, P and Hanson C, 2004. Nitrate Contamination observed in Environment Canterbury’s annual groundwater quality survey. Environment Canterbury technical report U04/79. Abraham, P and Hanson C, 2010. Annual groundwater quality survey, spring 2009. Environment Canterbury technical report R10/50. AGRIBASE, 2005. A GIS layer of land use data from Agriquality summarised to the mesh block level for the Canterbury District. ANZECC, 2000 (Australian and New Zealand Environment and Conservation Council), 2000: Australian Water Quality Guidelines for Fresh and Marine Water Australian and New Zealand Environment Council, Melbourne Bidwell, V., Cameron, K., Di. H., and Francis, G., 2003. Discharge of nitrate nitrogen to Groundwater from Land Use Activities – recommendations for a permitted activity rule. Environment Canterbury technical report U03/27. Biggs, B.J.F., 2000. New Zealand Periphyton Guideline: Detecting, Monitoring and Managing Enrichment of Streams. Ministry for the Environment, Wellington, New Zealand, June 2000. Brown, L J and Weeber J H, 2002. Groundwaters of the Canterbury Region. Environment Canterbury technical report R00/10. Close, M E, Rosen, M R, and Smith, V R, 2001. Fate and transport of nitrates and pesticides in New Zealand's aquifers. In Groundwaters of New Zealand, M R Rosen and P A White, editors. New Zealand Hydrological Society, Inc., Wellington. Pages 185-220. Daughney, C J, and Reeves, R. R., 2005. Definition of hydrochemical facies in the New Zealand National Groundwater Monitoring Programme. Journal of Hydrology (NZ), volume 44, number 2, pages 105-130. New Zealand Hydrological Society. Dann, R., Close, M., Pang, L,. Flint, M., and Hector, R., 2008. Complementary use of tracer and pumping test to characterize a heterogeneous channelized aquifer system in New Zealand. Hydrogeology Journal, volume 16, number 6, pages 1177-1191. Davey, G R, 2003. Hinds Plains springs. Environment Canterbury Technical Report U03/79. Davey, G R, 2004. Valetta hearing evidence. Unpublished Environment Canterbury information. Davey, G.R., 2006a. A Contribution to the Understanding of Canterbury Plains Aquifers. Environment Canterbury Technical Report U06/08. Davey, G.R., 2006b. Definition of the Canterbury Plains Aquifer. Environment Canterbury Technical Report U06/10. Davey, G.R., 2006c. The effects of Border Dyke Irrigation on Groundwater Levels in and below the Valetta Scheme. Environment Canterbury Technical Report U06/11. Davey, G. R., and Ettema, M., 2004. Advice from Grant Davey and Marcus Ettema in the mater of 27 applications to take groundwater from the Valetta groundwater allocation Zone. Unpublished report prepared for a Commissioners hearing, 3 November 2004. Environment Canterbury file number CO6C/22053.

Environment Canterbury Technical Report 29 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Di, H. J., and Cameron, K. C., 2002. Nitrate leaching in temperate agroecosystems: sources, factors, and mitigated strategies. Nutrient Cycling in Agroecosystems, volume 46, pages 237-256. DSIR, 1968. General Survey of Soils of the South Island, Soil Bureau Bulletin 27. New Zealand Department of Scientific and Industrial Research. Dommisse, J., 2007. Hydrogeology of the Hinds Rangitata Plain, and the impacts of the Mayfield- Hinds Irrigation Scheme: MSc thesis summary. Environment Canterbury Technical Report U07/3. Engelbrecht R.L., 2005. Land Use History – Ashburton District Plains. Unpublished report for Environment Canterbury. Environment Canterbury, 2004. EMQ-G002-02, Collection of Groundwater Quality Samples. Environmental Monitoring Groundwater Section Procedure, Environment Canterbury. Francis, G. S., 1995. Management practices for minimising nitrate leaching after ploughing temporary leguminous pastures in Canterbury, New Zealand. Journal of Contaminant Hydrology, volume 20, pages 313-327. Hanson, C.R., 2002. Nitrate concentrations in Canterbury Groundwater - a review of existing data. Environment Canterbury technical report R02/17. Hanson, C. and Abraham, P., 2009. Depth and spatial variation in groundwater chemistry – Central Canterbury Plains. Environment Canterbury Technical Report R09/39. Hanson, C. and Abraham, P., 2011. Depth and spatial variation in groundwater chemistry – Ashburton Rangitata plain. Environment Canterbury Technical Report (in preparation). Haynes, R. J., and Williams, P. H., 1993. Nutrient cycling and soil fertility in the grazed pasture ecosystem. Advances in Agronomy, volume 49, pages 119-199. Hayward, S. A., and Hanson, C. R., 2004. Nitrate contamination of groundwater in the Ashburton- Rakaia Plains. Environment Canterbury technical report R04/9. Hickey, C. W., and Martin, M. L., 2009. A review of nitrate toxicity to freshwater aquatic species. Environment Canterbury technical report R09/57. Langmuir, D., 1997. Aqueous Environmental Geochemistry. Prentice Hall, New Jersey. 600 pages. Lilburne, L.R. and North, H.C., 2010. Modelling uncertainty of a land management map derived from a time series of satellite images. International Journal of Remote Sensing, 31: 3, 597 – 616 Lough, H., and Williams, H. R., 2009. Vertical flow in Canterbury groundwater systems and its significance for groundwater management. Environment Canterbury technical report 09/45. Meredith, A., Croucher, R., Lavender, R., and Smith, Z., 2006. Mid-Canterbury coastal streams: assessment of water quality and ecosystem monitoring 2000 – 2005. Environment Canterbury technical report R06/19. Mitchell D.T., 1980. History of the Ashburton-Hinds Drainage District. South Canterbury Catchment Board, Ashburton. Ministry of Health, 2008 Drinking-water Standards for New Zealand 2005 (Revised 2008) New Zealand Ministry of Health, Wellington, October 2008. Mosley M.P., 2001. Ashburton River: In stream and amenity values, and flow management regime. Environment Canterbury technical report U01/46 Ryan, G., 2001. Ashburton District Council – Summary of stockwater intakes and discharges. Ashburton. Scott, G. L., 1980. Near-surface hydraulic stratigraphy of the Canterbury Plains between Ashburton and Rakaia rivers, New Zealand. Journal of Hydrology (N.Z.), volume 19, number 1, pages 68-74. Smith, M., 2008. Section 42A Officer’s Report. Before the Commissioners appointed by Canterbury Regional Council. In the matter of The Resource Management Act 1991, and in the matter of 78 Applications to take water in the Ashburton and Valetta Groundwater Allocation Zones. Thorley, M. J., Bidwell, V. J., and Scott, D. M., 2009. Land-surface recharge and groundwater dynamics – Rakaia-Ashburton Plains. Environment Canterbury Technical Report R09/55.

30 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Webb, T. H., and Savage, T. J., 2000. Explanation of attributes in the soil database for Northern Canterbury Plains and Downs. Landcare Research contract report LC9900/87, prepared for the Canterbury Regional Council, Christchurch. Wilson, D. D., 1973. The significance of geology in some current water resource problems, Canterbury Plains, New Zealand. Journal of Hydrology (N.Z.), volume 12, number 2, pages 103-118. Wilson, D. D., 1985. Erosional and depositional trends in rivers of the Canterbury Plains, New Zealand. Journal of Hydrology (N.Z.), volume 24, number 1, pages 32-44.

Environment Canterbury Technical Report 31 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

32 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Appendix 1: Analytical results for groundwater samples collected from the Ashburton-Hinds plain, 1988 to 2009

Determinands measured in the laboratory Field determinands

Well Date Sample alcium Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water

Number Sampled Number Laboratory Lower Detection Limit <0.005 <0.03 <0.02 <0.1 <0.005

Early samples K37/0222 28/09/1988 SCY880198 4 11.5 2.77 6.52 59.7 12.5 K37/0222 30/11/1988 SCY880417 4.16 7.9 1.61 7.24 34.3 15 Annual survey samples collected prior to 2004 K36/0118 17/12/1992 CQ923169 7.3 13.3 5.2 6.6 9.4 K36/0118 20/10/1993 SCY930900 40 10.5 6.1 12.9 <0.1 3.3 <0.02 4.6 6.4 1 7.8 7 40 K36/0118 18/10/1994 SCY941096 28 <0.005 13 8 16.6 4.1 6.7 6.42 1.1 9.7 13 49 K36/0118 12/10/1995 CQ954804 33 <0.005 14 7 16 0.65 4.4 <0.04 7.9 6.3 1 8.5 13 53 K36/0118 7/10/1996 SCY962910 43 0.008 13 5 15.5 0.61 4.3 <0.04 6.2 6.3 1.1 8 11 50 -6.25 K36/0118 7/10/1997 SCY973850 39 0.005 14 3.7 15 <0.12 3.7 <0.04 5.9 6.3 0.96 14 7.3 9.4 50 -5.95 K36/0118 23/09/1998 CQ987867 38 0.005 12 4.5 8.6 <0.12 3.4 <0.04 4.9 6.3 1.1 13 7.5 6.5 44 K36/0118 21/10/1999 9902110 33 0.008 11 5.4 14 <0.12 3.4 <0.04 5.1 6.3 0.95 13 6.8 8.4 41 9.9 10 6.3 11.3 -6.5 K36/0118 12/12/2000 2010868 33 0.011 13 5.8 15 <0.12 3.9 <0.04 4.9 6.2 1.2 14 8 12 49 10.9 14.9 6.2 11.5 K36/0118 24/10/2001 2105569 34 0.013 8.9 4.7 11.8 0.1 2.9 <0.01 2.2 6.3 0.8 14 6.2 6.3 34 8.36 11.4 5.6 10.8 -6.87 K36/0118 6/11/2002 2205139 37 0.013 9.7 4.7 12 0.1 2.8 0.01 2.2 6.4 1 13 6.7 7.5 36 9.8 11.5 -6.5 K36/0118 23/10/2003 2305898 28 <0.005 14 7.4 17 <0.03 4.4 <0.01 8.1 6.2 1.2 14 8.4 14 53 17.4 6.5 11.4 -3.2 K37/0028 30/11/1994 SCY941202 5 12 1.9 6.4 10 K37/0114 22/10/1991 SCY911460 6 13.7 5 6.7 9 K37/0114 16/12/1992 CQ923162 9.2 18.8 8.5 6.7 13 K37/0114 20/10/1993 SCY930898 37 11.9 7 14.3 <0.1 3.6 <0.02 6.1 6.1 1.1 7.9 9.3 45 K37/0114 18/10/1994 SCY941098 26 <0.005 11 7 14.9 3.7 5.7 6.34 1 8.6 16 43 K37/0114 11/10/1995 CQ954792 32 <0.005 14 7 15.5 <0.12 4.1 <0.04 7.6 6.3 0.98 7.8 11 52 K37/0114 7/10/1996 SCY962909 39 0.009 13 6 15.5 <0.12 4.5 <0.04 7.1 6.3 1.1 8 11 51 -2.27 K37/0114 12/11/1997 SCY973898 41 0.009 13 4.7 15 <0.12 4 <0.04 6.2 6.2 0.96 13 8.5 9.3 49 K37/0147 13/11/1995 SCY951508 14 26 7.2 6.6 18 K37/0147 3/10/1996 SCY961797 66 0.005 22 16 24 <0.12 6.3 <0.04 7.6 6.4 1.1 13 19 81 K37/0147 6/10/1997 CQ972505 70 0.007 24 13 25 <0.12 6.5 <0.04 8.9 6.4 1.3 16 13 18 87 K37/0147 29/09/1998 SCY981811 35 0.009 11 1.9 9.1 <0.12 1.8 <0.04 0.6 6.7 0.96 9.3 3.2 5.3 35 K37/0147 27/10/1999 9901835 49 0.013 16 3.3 11.8 0.16 2.3 <0.04 2 6.6 0.81 11 4.8 7.1 49 4.69 10.1 6.8 12.5 K37/0147 25/10/2000 2007527 41 0.007 10 2.9 9.5 0.34 1.5 <0.04 0.6 6.7 0.9 9.4 4 5.3 31 8.01 9.1 5.8 14.4 K37/0147 16/10/2001 2105559 39 0.006 25 16 28 0.08 7.5 <0.01 13 6.1 1.3 15 14 22 93 3.31 27.7 6.8 12.7 K37/0147 17/10/2002 2204676 45 0.023 24 15 26.8 <0.03 7.4 <0.01 12.2 6.4 1.3 15 14 21 90 8.91 27.6 6.3 10.1 K37/0147 20/10/2003 2306033 45 0.024 12 5 15 0.16 2.5 0.02 2.6 6.8 0.9 11 5.4 7.2 40 3.49 27.1 6.6 12.4 K37/0147 20/10/2003 2306034 43 0.007 12 4.9 13 0.06 2.5 0.02 2.6 6.8 0.9 11 5.3 7.2 40 3.49 27.1 6.6 12.4 K37/0216 16/12/1992 CQ923163 10 16.6 6.9 6.5 10 K37/0216 20/10/1993 SCY930897 37 10.9 7.9 13.8 <0.1 3.6 <0.02 4.5 6.4 1.1 8.3 10 42 K37/0216 18/10/1994 SCY941097 29 <0.005 12 8 15.7 4.1 6.9 6.64 1.1 9.7 16 47 K37/0216 11/10/1995 CQ954793 34 <0.005 13 7 15.5 <0.12 4.2 <0.04 7.4 6.3 1.1 8.5 11 50 K37/0216 7/10/1996 SCY962908 46 0.008 12 6 14.5 0.28 4.3 <0.04 5.1 6.2 1.1 8.1 9.6 48 -3.18 K37/0216 20/10/1997 SCY973860 38 0.005 12 5 15 <0.12 3.5 <0.04 5.2 6.4 1.1 13 8 9 44 -3.26 K37/0216 20/10/1997 SCY973861 38 0.007 12 5.1 15 <0.12 3.5 <0.04 5.2 6.3 1.2 13 8.2 9.1 44 -3.26

Environment Canterbury Technical Report 33 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0216 21/09/1998 SCY981804 31 0.009 11 5.3 14.4 0.34 4 <0.04 6.8 6.3 1.2 13 8.3 8.4 44 -3.48 K37/0216 21/09/1998 SCY981805 29 0.009 11 5.2 14.4 0.15 3.8 <0.04 6.7 6.4 1.2 12 7.9 8.3 43 -3.48 K37/0216 19/10/1999 9901826 31 <0.005 15 8 17.6 <0.12 4.7 <0.04 10.3 6.2 1.1 13 8.6 8.5 57 9.89 13.4 6.1 12.5 -3.1 K37/0216 18/10/2000 2007524 37 <0.005 15 8.1 18.2 0.36 4.8 <0.04 8.4 6.2 1.3 13 10 13 57 8.12 18.3 5.8 10.9 -2.61 K37/0216 16/10/2001 2105556 27 0.005 12 7.4 14.9 <0.03 4 <0.01 7 6.1 0.9 13 7.4 9.3 46 7.74 14.9 5.9 11 -3.85 K37/0216 16/10/2002 2204673 31 <0.005 12 7 14 0.42 3.9 <0.01 5.6 6.3 1 13 7.7 10 46 9.15 15.1 6.3 10.3 -3.66 K37/0216 14/10/2003 2305445 36 0.022 12 7.3 16 0.03 4.3 <0.01 5.9 6.2 1.1 13 8.1 12 48 7.59 14.9 6 10.8 -3.2 K37/0222 22/10/1991 SCY911459 3 11.5 2.9 6.8 7 K37/0222 16/12/1992 CQ923161 3.1 12.2 3.9 7 5.7 K37/0222 20/10/1993 SCY930899 52 10.2 2.7 12.1 0.2 3.3 <0.02 3.4 6.6 1 7.5 5.7 39 K37/0358 24/11/1995 SCY951506 13 21 11 6.6 12 -2.3 K37/0358 3/10/1996 SCY961798 51 0.006 20 13 24 <0.12 6 <0.04 11.2 6.5 1.2 14 14 75 K37/0358 6/10/1997 CQ972506 45 0.006 20 12 24 <0.12 6.1 <0.04 11 6.6 1.3 17 12 13 75 -4.5 K37/0358 29/09/1998 SCY981812 41 <0.005 23 13 25.4 <0.12 6.8 <0.04 12 6.4 1.3 17 14 14 85 -5.61 K37/0358 27/10/1999 9901816 44 0.013 20 13 23.1 <0.12 6.5 <0.04 12.7 6.5 1.2 17 14 15 77 5.79 19.2 6.4 13.1 -5.55 K37/0358 27/10/1999 9901834 45 0.014 21 13 23.1 <0.12 6.1 <0.04 12.8 6.5 1.2 17 14 16 78 5.79 19.2 6.4 13.1 -5.55 K37/0358 25/10/2000 2007526 49 0.008 19 12 25.3 <0.12 6.2 <0.04 12.1 6.5 1.3 17 14 15 73 7.48 24.8 4.8 12.4 -1.75 K37/0358 16/10/2001 2105558 41 <0.005 22 13 25 <0.03 6.4 <0.01 11.7 6.4 1.1 17 13 17 81 6.26 24.5 6.9 12.5 K37/0358 17/10/2002 2204675 42 0.007 22 13 25.1 0.09 6.6 <0.01 12.5 6.8 1.3 17 14 16 82 8.56 24.3 6.4 9.2 K37/0358 14/10/2003 2305447 48 <0.005 19 12 27 0.04 6.5 <0.01 12.3 6.6 1.4 18 14 16 74 6.07 24.2 6.5 12.1 K37/0466 13/12/1991 SCY911434 2.3 K37/0466 13/10/1992 SCY920823 24 26.3 1.3 6.6 23 K37/0466 13/10/1993 SCY930846 95 21.5 26 28.7 <0.1 8.8 0.36 3.3 6.5 1.2 20 23 90 K37/0466 26/10/1994 SCY941103 99 0.006 20 23 25.4 7.8 2 6.6 1.1 18 22 82 K37/0466 12/10/1995 CQ954807 100 <0.005 22 21 25 <0.12 7 0.51 1.3 6.6 0.99 17 19 84 K37/0466 3/10/1996 SCY961800 109 0.006 22 25 29 <0.12 8.4 0.37 3.78 6.5 1.1 20 25 90 K37/0466 15/10/1997 CQ972868 84 0.011 21 5.7 25 <0.12 7.5 0.53 4.8 6.6 1.2 28 16 8.3 83 K37/0466 29/09/1998 SCY981809 77 0.005 25 24 29.1 0.13 7.9 0.36 2.6 6.6 1.2 26 21 24 95 K37/0466 20/10/1999 9901838 82 <0.005 20 23 26 <0.12 7.4 0.33 1.6 6.5 1.2 26 18 21 80 0.22 19.7 6.4 12.1 K37/0466 18/10/2000 2007520 88 <0.005 19 23 26.7 <0.12 7.7 0.44 2.3 6.6 1.1 25 17 20 79 0.27 20 5.8 11.4 K37/0466 15/10/2001 2105548 76 0.006 21 27 28.6 <0.03 8.1 0.31 2.7 6.5 0.7 26 20 23 86 0.24 27.9 6.9 12 K37/0466 23/10/2002 2204682 71 0.007 26 30 33.8 <0.03 10 0.39 6.3 6.5 1.3 24 22 28 106 0.85 12 K37/0466 13/10/2003 2305441 93 <0.005 24 30 29 0.06 9.3 0.33 2.9 6.6 1.3 26 21 27 98 1.18 28.1 6.8 11.9 K37/0467 13/12/1991 SCY911435 1.8 K37/0467 13/10/1992 SCY920822 25 27.7 1.1 6.9 24 K37/0467 13/10/1993 SCY930845 82 23.2 28 29.5 <0.1 7.8 0.02 3.7 6.4 1.4 21 28 90 K37/0467 26/10/1994 SCY941104 85 0.005 20 32 29.3 7.4 2 6.5 2.2 25 33 80 K37/0467 12/10/1995 CQ954808 88 <0.005 23 27 27 <0.12 6.6 <0.04 1.4 6.6 1.4 19 26 85 K37/0467 3/10/1996 SCY961799 98 0.007 23 31 30 <0.12 7.9 0.06 1.5 6.4 2.7 22 24 90 K37/0467 17/11/1997 SCY972020 83 0.073 22 24 25.9 1 7.9 0.05 4.3 6.5 2 15 22 25 87 K37/0468 13/12/1991 SCY911436 5.4 K37/0468 13/10/1992 SCY920821 8 14.3 5.7 7 7 K37/0468 13/10/1993 SCY930844 39 10.1 8.3 14.5 <0.1 3.3 <0.02 6.3 6.4 0.8 11 6.8 39 K37/0468 30/11/1994 SCY941197 40 <0.005 9.7 8 14 3.4 5 6.8 0.77 11 7 38 K37/0468 9/10/1995 CQ954783 40 <0.005 11 7 14 <0.12 3.6 <0.04 5.3 6.8 0.82 11 8.8 42 K37/0468 3/10/1996 SCY961801 33 0.006 10 6 14.5 <0.12 3.7 <0.04 5.06 6.7 0.81 11 8.6 40

34 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0468 15/10/1997 CQ972867 38 0.012 11 21 14 <0.12 3.1 <0.04 1.6 6.7 1 16 11 19 40 K37/0468 29/09/1998 SCY981810 37 <0.005 11 5.7 14.3 <0.12 3.5 <0.04 4.9 6.7 0.96 16 11 8.9 42 -2.81 K37/0468 27/10/1999 9901836 35 0.005 10 6.6 13.7 <0.12 3.1 <0.04 6.3 6.5 0.77 16 11 8 38 7.13 11.1 6.8 12.9 -2.7 K37/0468 18/10/2000 2007523 38 <0.005 10 7.2 15 <0.12 3.3 <0.04 6.4 6.8 0.8 16 11 7.5 39 9.76 15.1 6.3 12.7 -2.1 K37/0468 15/10/2001 2105549 34 0.012 11 8.2 15.5 <0.03 3.3 <0.01 6 6.6 0.3 16 12 7.8 41 7.05 15.1 6.5 12.4 K37/0468 15/10/2001 2105550 34 0.005 11 8.2 15.5 <0.03 3.3 <0.01 6 6.6 0.2 16 12 7.7 41 7.05 15.1 6.5 12.4 K37/0468 23/10/2002 2204680 33 0.014 11 7.8 15.4 0.27 3.5 <0.01 5.9 6.7 0.8 15 11 8.6 42 7.63 12 K37/0468 13/10/2003 2305438 41 0.015 11 8.3 18 <0.03 3.7 <0.01 6.5 6.7 1 16 12 9.4 43 7.09 15.1 6.5 12.3 K37/0563 7/12/1994 SCY941206 7 13 0.92 6.7 <5 K37/0619 15/10/1997 CQ972869 49 0.009 14 10 15 <0.12 3.3 <0.04 2.7 7.2 1.1 17 9.3 3.9 49 K37/0619 15/09/1998 SCY981788 48 0.012 14 13 16.1 <0.12 3.9 0.06 2.9 6.8 1.4 17 11 5.3 51 -3.29 K37/0619 27/10/1999 9901837 49 0.008 12 9 12.9 <0.12 3 <0.04 3.1 7 0.89 16 8 3 42 5.63 11.1 7.6 15.1 K37/0619 18/10/2000 2007521 52 <0.005 12 9.2 14.1 <0.12 3.2 <0.04 3.3 7.2 1 16 8 3.4 43 8.43 14.1 6.5 12 K37/0619 18/10/2000 2007522 51 <0.005 12 9.1 14.1 <0.12 3.2 <0.04 3.3 7.3 1 16 8 3.3 43 8.43 14.1 6.5 12 K37/0619 15/10/2001 2105551 56 0.01 16 15 18.5 <0.03 4.2 0.14 2.6 6.9 0.6 18 12 8.1 57 5.24 18 6.9 13.1 K37/0619 23/10/2002 2204681 44 0.007 12 8.7 13.8 <0.03 3.2 0.02 3.2 7.3 1 16 7.9 3.4 43 6.44 13.2 K37/0619 13/10/2003 2305439 53 0.01 12 11 16 0.04 3.5 0.03 3.1 7.2 1.1 17 8.9 5.1 44 5.21 17.9 6.9 12.9 K37/0619 13/10/2003 2305440 53 0.012 13 10 15 0.03 3.4 0.03 3.1 7.3 1.1 17 8.9 4.7 46 5.21 17.9 6.9 12.9 K37/0833 29/09/1998 SCY981813 41 0.005 12 4.2 13.2 <0.12 4 <0.04 4.3 7.1 0.84 16 6.5 2.6 46 K37/0833 19/10/1999 9901825 46 <0.005 12 4.3 13 <0.12 3.6 <0.04 4.8 6.9 0.84 16 6.8 2.5 45 10.85 9.4 7.5 11.7 K37/0833 18/10/2000 2007525 51 <0.005 15 6.6 17.4 0.32 4.8 <0.04 8 7.1 1 16 8 5.2 57 11.85 17.5 6.4 10.7 K37/0833 16/10/2001 2105557 40 0.008 12 4.7 13.5 <0.03 3.8 <0.01 5 7 0.7 16 6.5 3.3 46 7.4 13.3 7 11.7 K37/0833 16/10/2002 2204674 40 <0.005 12 4.9 13 0.03 3.7 <0.01 4.8 7.2 0.9 16 6.7 3 45 9.99 13.8 6.9 11.1 K37/0833 14/10/2003 2305446 46 0.008 11 4.7 15 <0.03 3.8 <0.01 5 7.3 1 17 6.8 3.2 43 7.11 13.4 7 11.5 Ashburton groundwater quality survey, April 1995 K37/0087 18/04/1995 SCY951308 85 16 9 17.5 0.2 4.9 0.07 3.5 6.8 1.1 12 12 60 K37/0088 18/04/1995 SCY951309 57 19 13 22 <0.1 5.7 <0.02 11 6.6 1.1 15 19 70 K37/0147 19/04/1995 SCY951311 77 23 11 23 0.2 5.4 <0.02 7.5 6.6 1.2 14 18 80 K37/0516 18/04/1995 SCY951307 84 15 15 16 <0.1 5.5 0.18 0.6 7.2 0.75 9.5 7 60 K37/0563 19/04/1995 SCY951312 74 17 13 16.5 0.7 4.5 <0.02 1.9 6.6 1.1 8.1 12 61 Samples collected in the Tinwald investigation, autumn 2004 K37/0088 21/04/2004 2402217 53 0.013 25 15 30 <0.03 7.6 <0.01 14.2 6.4 1.4 15 20 5.6 29.8 6 13.5 -8 K37/0147 21/04/2004 2402216 79 0.047 28 15 34 0.15 6.8 0.04 13.5 6.5 1.5 15 24 2.4 34.5 6 14 K37/0201 27/04/2004 2403030 48 0.005 9.9 2.8 10 <0.03 2.3 <0.01 0.7 6.6 0.7 5.2 5.3 6.4 10 7 13.5 -2.25 K37/0358 21/04/2004 2402218 50 0.018 23 13 27 <0.03 6.8 <0.01 13 6.5 1.3 14 16 8.5 27.7 6.2 12.7 -8.6 K37/0439 22/04/2004 2403023 69 0.015 28 17 32 <0.03 9.6 <0.01 12.8 6.4 1.7 16 21 3.5 33.4 6.4 12.5 K37/0455 26/04/2004 2403024 68 0.031 23 13 29 <0.03 8.4 <0.01 10.8 6.8 1.2 15 18 5.9 29.8 6.4 12.1 -7.8 K37/0476 22/04/2004 2403021 54 0.011 26 16 32 <0.03 7.8 <0.01 15.3 6.4 1.3 17 23 8.6 32.2 6.3 12.5 K37/0490 22/04/2004 2403022 55 0.016 26 15 31 0.04 7.8 <0.01 15 6.4 1.3 16 21 5.9 31.1 6.8 12.5 -6.8 K37/0622 21/04/2004 2402219 56 0.01 23 13 28 <0.03 7.1 <0.01 13.3 6.4 1.2 14 16 5 28.1 6 12.7 -8.8 K37/0643 27/04/2004 2403032 50 0.006 13 5.9 16 <0.03 3.8 <0.01 5.5 6.8 1 10 7.3 7.1 16 7 13.5 -13 K37/0685 22/04/2004 2403020 56 0.012 21 13 27 <0.03 7 <0.01 11.8 6.5 1.3 14 15 5.9 27.3 6.6 12.8 -8.05 K37/0724 29/04/2004 2403254 65 0.015 19 9 22 <0.03 5.6 <0.01 8.6 7 0.9 7.9 12 6.7 22.5 6.6 12.3 K37/0810 29/04/2004 2403257 52 0.011 27 26 34 <0.03 9.7 <0.01 13.6 6.3 1 19 25 7.3 34.9 6.9 13 -4.4 K37/0819 26/04/2004 2403025 78 0.019 16 14 21 0.05 6 0.3 0.2 7.3 0.8 9.8 7.1 4.3 18.6 6.1 12.5 -7.05

Environment Canterbury Technical Report 35 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/1004 21/04/2004 2402220 54 0.01 20 11 25 0.04 6.2 <0.01 11.4 6.5 1.3 13 12 8.2 24.6 6 12.4 -9.43 K37/1008 29/04/2004 2403256 64 0.012 23 15 28 <0.03 7.8 <0.01 11.3 6.5 1.2 16 16 5.5 28.5 6.7 13 K37/1807 22/04/2004 2403019 58 0.029 20 12 25 <0.03 6.7 <0.01 11.8 6.6 1.3 12 12 6.1 25.6 6.7 12.2 -8.7 K37/1972 26/04/2004 2403026 61 0.16 25 15 30 0.08 9.2 0.02 11.3 6.8 1 14 27 7.3 30.8 6.5 13 -7.18 K37/2126 29/04/2004 2403255 44 0.015 15 8.6 18 <0.03 4.2 <0.01 6.6 6.8 1 10 9 8.2 18.1 6.7 12.5 K37/2242 26/04/2004 2403027 62 0.12 21 11 25 0.21 6.7 0.03 10 6.9 1.2 12 16 7.2 25 6.5 12.5 K37/2244 27/04/2004 2403028 68 0.01 15 7.1 19 <0.03 5.3 <0.01 2.9 6.4 0.9 9.7 17 4.4 19 6.6 13 -2.25 K37/2245 27/04/2004 2403029 62 0.012 13 5.3 16 <0.03 4 <0.01 1.9 6.5 0.9 8.9 12 4.7 15.6 6.5 14 -1.55 K37/2246 27/04/2004 2403031 73 0.007 19 9.9 22 0.04 6.5 <0.01 6.1 6.6 1.1 11 12 6.1 21.9 7 13 K37/2253 29/04/2004 2403033 52 0.011 27 17 33 <0.03 9.2 <0.01 16.8 6.5 1.3 17 23 3.2 34.5 6.4 12 K37/2254 29/04/2004 2403253 53 0.012 15 7.6 26 <0.03 4.5 <0.01 6.9 6.6 0.9 10 9.2 6.1 18.5 6.4 12 -8.5 Samples collected in the Ashburton-Hinds Plain investigation, autumn 2004 K36/0027 20/07/2004 2404756 43 0.009 14 5.7 16 0.04 4.6 <0.01 7.2 7.4 1 7 2.8 8.4 15.9 7.1 11 K36/0055 21/07/2004 2404765 33 0.015 10 2.4 11 <0.03 2 <0.01 2.7 6.5 0.7 4.2 5.1 8.4 10.7 6.2 11.5 K36/0056 21/07/2004 2404764 35 0.01 14 4.3 14 <0.03 2.8 <0.01 5.3 6.3 0.9 6.2 9 7.1 14.4 6.2 12 K36/0108 21/07/2004 2404762 31 0.008 9.3 2.6 9 <0.03 1.6 <0.01 1.3 6.4 0.6 3.3 4.3 9.1 8.7 6.5 11 K36/0118 21/07/2004 2404761 36 0.006 8.9 4.3 12 <0.03 2.6 <0.01 1.8 6.3 0.9 6.4 6.2 10 11.1 7 12 K36/0220 16/07/2004 2404754 37 0.006 17 5.6 16 <0.03 3.4 0.02 7.3 6.4 0.9 6.4 8.8 5.5 16.5 6.7 12.5 K36/0231 16/07/2004 2404753 46 0.007 12 4.1 13 <0.03 3.5 0.02 4.2 7.7 0.9 5.9 2.3 8.5 12.8 7.4 12 -12.2 K36/0282 21/07/2004 2404763 34 0.006 9.7 2.6 9 <0.03 1.7 <0.01 1.4 6.5 0.7 3.7 4.1 8.1 9.2 6 11.4 K36/0540 16/07/2004 2404751 51 0.007 15 4.9 15 <0.03 3.3 0.03 5.3 7.3 0.9 7 0.7 8.2 21.5 6.9 12 K36/0577 20/07/2004 2404759 53 0.01 15 5.6 16 <0.03 4.3 <0.01 5.7 7.4 1 7 0.7 6.5 15.8 7.3 12.1 K36/0656 20/07/2004 2404755 48 0.007 14 4.5 16 <0.03 4.2 <0.01 5.6 7.6 0.9 6.4 2 11 18.2 6.9 12 K36/0780 20/07/2004 2404760 33 <0.005 11 5.3 13 <0.03 3.2 <0.01 3.5 6.3 0.9 6.6 8.9 6.8 13.3 6.4 10 -6.7 K37/0018 18/08/2004 2404809 57 0.014 18 15 23 0.07 6.9 <0.01 6.1 6.6 2.4 14 14 0.13 6.45 19.4 7.1 9.1 -1.18 K37/0034 23/08/2004 2404820 52 0.006 11 8.2 15 <0.03 4.4 <0.01 0.6 6.4 1 9 9.9 <0.05 6.04 14.5 6.1 9.8 K37/0049 27/07/2004 2404772 42 <0.005 11 7.6 14 <0.03 4 <0.01 2.4 6.3 1.1 8.3 9.2 3.1 14.3 6.7 11 K37/0060 26/08/2004 2404832 65 0.007 18 12 22 0.06 6.7 <0.01 4.2 6.5 1.2 13 17 <0.05 6.89 21.9 7.1 9.6 K37/0147 28/07/2004 2404774 62 <0.005 22 12 24 0.05 5.2 0.02 7.8 6.5 1.3 12 17 4.5 24.8 6.4 13.5 -5.35 K37/0155 27/07/2004 2404771 28 <0.005 13 8 16 <0.03 4.3 <0.01 7 6.2 1 8.4 13 8.2 16.6 6.8 13.6 K37/0175 27/07/2004 2404768 29 <0.005 6.3 3.3 9 <0.03 2.1 <0.01 2 6.6 0.8 6.5 4.7 7.4 9.3 7.2 12.9 K37/0188 13/07/2004 2404738 37 0.006 13 6.2 15 <0.03 3.8 <0.01 4.9 6.5 0.9 7.7 12 7.2 15.6 6.6 12.9 K37/0204 14/07/2004 2404740 66 0.005 13 3.9 19 <0.03 4.7 0.01 3.9 7.5 1 11 6.3 8.4 17.3 6.5 11.8 K37/0216 13/07/2004 2404736 35 0.015 11 5.5 14 <0.03 3.6 <0.01 3.6 6.3 1 7.2 9.2 6.6 13.5 6.2 12.5 -5.05 K37/0219 14/07/2004 2404743 39 <0.005 15 8.2 18 <0.03 4 <0.01 7.5 6.7 1 10 9.7 6.9 17.9 6.8 12 K37/0222 14/07/2004 2404744 42 <0.005 11 2.2 12 <0.03 3.1 0.01 2.7 6.8 0.9 6.2 6.5 6.8 11.7 6.7 12.9 K37/0224 16/07/2004 2404750 34 0.012 14 6.6 16 <0.03 3.8 <0.01 6.1 6.4 1 8.2 10 9.9 15.3 6 11.1 K37/0336 26/08/2004 2404830 74 0.009 21 12 25 0.06 7.6 <0.01 4.5 6.6 1 15 24 <0.05 5.84 24.9 7.1 6.8 -0.91 K37/0358 28/07/2004 2404777 45 <0.005 22 13 27 <0.03 6.6 <0.01 14.5 6.6 1.3 15 16 7.9 27.5 6.5 11.2 -8.15 K37/0366 19/08/2004 2404814 27 0.008 9.4 6.1 13 <0.03 3.4 <0.01 4.7 6.4 0.8 8.6 9.4 <0.05 6.44 13 6.6 9.5 -5.78 K37/0371 25/08/2004 2404827 52 0.007 25 17 28 0.04 8.7 <0.01 10.4 6.3 1.3 17 26 0.17 6.18 28.5 7.3 10.2 K37/0415 27/07/2004 2404773 33 <0.005 17 13 22 <0.03 5.7 <0.01 10.6 6.3 1 12 15 6.1 22.5 6.9 12.6 K37/0443 15/07/2004 2404746 51 0.006 13 3.5 14 <0.03 3.7 <0.01 3.8 7.2 1.1 8.3 6 8.8 14.5 6.5 12.3 -52.05 K37/0474 24/08/2004 2404821 52 0.008 30 24 42 0.06 10 <0.01 15.5 6.7 1.2 21 25 0.07 5.31 35.3 6.9 6.1 -3.43 K37/0483 26/07/2004 2404794 50 0.011 21 14 26 <0.03 7.2 <0.01 10.7 6.4 1.1 14 16 0.09 6.17 25.7 6.7 9.7

36 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0490 28/07/2004 2404776 48 0.032 24 16 31 0.11 8.2 <0.01 15.4 6.5 1.3 17 21 5.7 31 6.5 11 -6.3 K37/0503 25/08/2004 2404829 50 <0.005 28 23 34 0.05 9.8 0.01 14.1 6.3 1 18 27 <0.05 6.99 33.5 7.1 11.3 K37/0547 21/07/2004 2404784 42 0.014 13 11 17 <0.03 4.5 <0.01 4.4 6.7 0.9 13 13 0.1 4.27 17.5 6.9 12.6 -3.42 K37/0550 22/07/2004 2404790 39 0.033 15 11 20 <0.03 5.8 <0.01 6.8 6.2 1.1 11 15 0.17 7.05 19.6 7.5 10 -1.15 K37/0561 28/07/2004 2404779 65 0.16 22 15 29 0.04 7.8 0.03 8.5 7.3 1.2 14 15 7.3 26.2 7.2 11.6 K37/0613 19/08/2004 2404815 43 0.006 14 9 18 <0.03 4.8 <0.01 7.1 7.1 1.1 13 11 0.42 6.99 18.9 7 9.1 K37/0680 12/08/2004 2404804 76 <0.005 15 12 19 <0.03 5.8 0.04 0.8 7 1 13 5.9 0.06 5.99 18.9 7.1 9 -1.28 K37/0689 15/07/2004 2404748 44 <0.005 11 4.2 11 <0.03 3.4 <0.01 3.3 7.6 0.9 6.5 2.3 8.3 12 7.7 13 -47.4 K37/0693 13/07/2004 2404733 49 0.006 12 3.3 14 <0.03 3.2 <0.01 3.2 7.7 0.9 7.3 5.5 6.4 13.5 7.4 12 K37/0697 24/08/2004 2404825 56 0.008 23 15 28 <0.03 8.6 <0.01 12 6.7 1.2 16 14 0.11 5.81 28 6.7 5.8 K37/0702 23/08/2004 2404817 74 0.005 17 18 22 <0.03 6 <0.01 <0.1 6.9 0.9 12 5.2 <0.05 6.99 18.7 7.2 7.7 K37/0723 23/08/2004 2404818 77 0.007 20 18 24 <0.03 6.7 0.07 1.9 6.9 1 17 17 <0.05 7.41 23.4 7.6 8.9 K37/0726 19/08/2004 2404813 62 0.007 14 10 20 0.04 7.3 <0.01 6.8 7.4 0.9 13 2.4 <0.05 6.38 19.9 7.2 8.7 K37/0736 27/07/2004 2404769 33 <0.005 15 9.7 19 <0.03 5.6 <0.01 8.9 6.2 1.4 9.7 13 6.2 19.9 6.7 11.8 -6.6 K37/0759 16/07/2004 2404752 49 <0.005 12 3.4 13 <0.03 3.4 0.02 3.4 7.3 0.9 7.2 5.2 7.5 13.6 6.8 12.5 K37/0810 28/07/2004 2404775 50 <0.005 25 25 34 <0.03 9.8 <0.01 14.4 6.9 1 19 25 8 34 6.4 11.1 -4.25 K37/0833 20/07/2004 2404757 44 0.012 12 4.5 14 <0.03 3.9 <0.01 4.8 7.3 1 6.7 2.8 8.7 14.8 7.5 11.1 -4.92 K37/0885 25/08/2004 2404828 68 0.009 23 19 26 0.12 8 0.03 5.8 6.9 1.3 16 20 <0.05 7.09 26.8 7.5 9.3 K37/1006 14/07/2004 2404741 26 <0.005 5.5 1.4 7 <0.03 1.6 <0.01 0.7 6.8 0.5 3.7 3.3 8.3 9.5 6.8 11 -6.3 K37/1061 14/07/2004 2404739 26 <0.005 9.9 3.9 13 <0.03 3 0.01 4 6.3 0.8 5.6 9.5 8.2 11.4 6 11.6 K37/1153 21/07/2004 2404786 61 0.007 14 14 19 0.26 5.2 0.05 0.7 6.8 1 14 17 0.26 2.93 17.3 6.9 10.2 -2.19 K37/1157 5/08/2004 2404797 76 0.016 18 34 31 0.09 7.2 0.17 1.6 6.6 1 26 26 0.23 5.43 30.9 6.6 12.4 K37/1160 21/07/2004 2404783 69 0.013 19 24 28 0.21 6.3 0.17 0.7 6.7 1 27 36 0.35 3.33 28.6 7.6 5.1 -0.8 K37/1162 21/07/2004 2404785 39 0.013 11 5.7 12 0.26 3 <0.01 2.5 7.2 1.3 7.2 6.4 1.8 9.77 12.3 7.1 6.2 K37/1177 18/08/2004 2404807 88 0.005 32 32 41 <0.03 11 0.34 3 6.6 12 24 54 0.92 5.79 22.5 6.7 11.1 K37/1178 22/07/2004 2404789 65 0.005 17 12 22 <0.03 7.1 0.01 6.9 6.7 1.2 12 11 0.07 2.59 23.2 8.1 11.7 K37/1189 23/08/2004 2404819 66 0.008 18 12 23 0.04 6.8 <0.01 4.1 6.5 1.2 14 16 <0.05 6.19 21.4 7.2 9 K37/1444 15/07/2004 2404747 42 0.006 10 4.3 12 <0.03 3.8 <0.01 4.4 7.7 0.9 6.8 1 8.7 12.1 6.5 12.7 K37/1587 13/07/2004 2404737 57 0.008 11 3.9 15 0.06 4.2 <0.01 3.5 7.5 0.9 9.5 5.7 6.4 14.8 7 12.8 K37/1661 21/07/2004 2404766 46 0.01 18 9.1 22 <0.03 5.8 <0.01 9.7 6.6 1.1 11 12 6.6 21.9 6.7 12.4 K37/1705 18/08/2004 2404812 46 0.017 24 13 27 <0.03 8.2 <0.01 12.8 6.4 1.1 16 15 <0.05 6.78 24.8 7 9.6 K37/1711 27/07/2004 2404767 44 <0.005 9.9 5 15 <0.03 3.5 <0.01 3.8 7.6 1 8.1 2.2 8 12.8 6.9 12.9 K37/1733 22/07/2004 2404791 41 0.007 14 10 19 <0.03 4.6 <0.01 7.6 6.7 0.9 12 8.9 0.08 8.12 18.8 7.6 12.1 -2.2 K37/1745 18/08/2004 2404808 38 <0.005 16 11 20 <0.03 5.3 <0.01 8.6 6.5 1.3 14 10 0.07 6.19 19.7 7.7 8.6 K37/1767 24/08/2004 2404824 66 0.18 23 13 29 <0.03 8.2 0.04 11.9 7 1.2 14 13 0.22 9.18 27.2 6.7 7.1 -4.7 K37/1789 25/08/2004 2404826 98 0.011 24 13 24 0.03 7.4 <0.01 12.7 6.6 1.3 15 12 0.2 4.98 26.2 7 10.9 K37/1908 12/08/2004 2404805 52 0.009 11 7.5 14 0.09 4.5 0.02 2.9 7.1 0.9 9.7 2.5 0.11 5.17 14.5 7.1 12.8 K37/1939 19/08/2004 2404816 45 <0.005 15 8.7 19 <0.03 5.2 <0.01 7.3 6.6 1 12 8.5 0.1 5.58 18.5 6.4 10.4 K37/2156 26/07/2004 2404793 55 0.012 19 12 25 <0.03 6.4 <0.01 9.2 6.5 1.2 12 13 0.16 4.95 23.7 6.7 12.4 K37/2253 28/07/2004 2404778 47 <0.005 27 17 33 <0.03 8.7 <0.01 17.2 6.6 1.3 17 23 5.5 33 6.4 12.1 K37/2297 13/07/2004 2404735 33 0.007 11 7.2 15 <0.03 4.2 <0.01 4.8 6.2 1.2 8.4 9.9 7.5 14.9 6 12.3 -2.7 K37/2299 14/07/2004 2404742 49 <0.005 15 6.3 17 <0.03 4.7 <0.01 6.6 6.8 1 8 6.6 6.3 17.4 7 11.6 K37/2301 15/07/2004 2404745 53 0.009 21 11 24 <0.03 6.9 <0.01 10.5 6.6 1.1 12 13 6.8 24 6.8 11.3 K37/2302 15/07/2004 2404749 34 0.007 9.1 5.7 11 <0.03 2.9 <0.01 2.1 6.4 1.1 7.1 6.4 4.4 11.3 6.6 12.5 K37/2307 20/07/2004 2404758 44 0.006 14 5.8 17 <0.03 4.6 <0.01 6.5 7 1 8 7.4 7.5 16.6 6.6 11.6 -2.2 K37/2310 26/07/2004 2404792 45 0.012 13 8.6 20 0.03 4.3 <0.01 7.4 6.6 1 11 8.7 0.08 3.94 17.7 7.2 9.6

Environment Canterbury Technical Report 37 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/2311 27/07/2004 2404770 34 0.01 9.7 6.7 13 <0.03 3.6 <0.01 3.1 6.4 1.1 7.7 9.2 6.3 13.1 6.7 13.1 K37/2313 5/08/2004 2404802 66 0.011 22 29 34 <0.03 9.5 0.01 7.1 6.5 2.7 24 30 0.19 4.98 31.4 6.3 11.1 K37/2314 5/08/2004 2404801 83 0.012 22 26 32 0.04 9.5 0.01 3.7 6.7 1.6 23 29 0.14 6.68 31.8 6.5 13 K37/2315 5/08/2004 2404800 81 0.039 16 18 23 1.2 6.6 0.53 <0.1 6.6 0.9 14 13 0.05 4.59 25.3 6.7 11.1 K37/2316 5/08/2004 2404799 95 0.01 25 40 38 0.08 11 0.03 0.8 6.6 1.7 29 35 0.23 6.17 38.1 6.6 12.6 K37/2317 5/08/2004 2404798 62 0.013 18 22 27 <0.03 8.9 0.09 4.6 6.5 0.6 17 23 0.06 5.36 26.8 6.4 10.6 K37/2318 5/08/2004 2404796 63 0.014 17 12 34 <0.03 9.7 <0.01 7.1 6.5 1.4 26 12 0.38 5.14 30.4 6.8 10.5 K37/2322 12/08/2004 2404803 68 0.008 36 31 49 <0.03 16 <0.01 22.4 6.4 1.9 27 39 0.26 6.43 49.5 7.1 11.9 -0.99 K37/2323 12/08/2004 2404806 100 0.017 18 12 21 0.22 7.3 0.55 0.1 6.4 1.1 13 1.1 0.05 6.99 21.1 6.8 10.9 -1.1 K37/2325 18/08/2004 2404811 70 0.008 22 24 26 0.11 5.9 0.29 0.7 6.6 1.1 21 26 0.1 6.02 25.4 6.7 8.4 K37/2333 26/08/2004 2404831 73 <0.005 23 18 28 0.04 9.2 <0.01 6.7 6.5 1.3 16 21 <0.05 4.83 27.9 7 12.4 L37/0379 21/07/2004 2404787 79 0.024 27 46 34 0.04 8.9 0.06 3 6.6 1.4 24 23 <0.05 1.63 27.3 6.7 12.3 L37/0711 18/08/2004 2404810 85 0.01 26 25 29 0.11 8.6 0.11 2.6 6.8 1.1 20 22 0.2 6.13 29.6 7.7 7.7 L37/0794 24/08/2004 2404822 92 0.014 20 15 22 2.2 7.7 0.54 <0.1 7.4 1 12 9.9 0.15 5.19 22 7.1 8 -4.75 L37/0852 21/07/2004 2404788 81 0.028 12 32 28 2.4 5.6 0.57 <0.1 6.7 1.3 21 20 0.12 2.75 30.2 6.7 9.5 -6.95 L37/1187 24/08/2004 2404823 68 <0.005 22 15 26 <0.03 8.8 <0.01 6.6 6.6 1.1 14 18 <0.05 6.94 25.3 6.7 8 L37/1356 26/07/2004 2404795 55 0.011 34 30 42 <0.03 12 <0.01 22.4 6.3 1.3 24 29 0.26 6 43.6 6.6 7 -1.21 Samples collected in the Ashburton-Hinds Plain investigation, autumn 2004 K36/0118 20/10/2004 2406699 33 <0.005 10 5.8 12 <0.03 3 <0.01 4.2 6.5 1 15 7.1 8.5 37 7.6 12.7 6.1 13.1 K36/0118 20/10/2004 2406700 33 <0.005 10 5.8 12 <0.03 3 <0.01 4.1 6.5 1 15 7 8.5 37 7.6 12.7 6.1 13.1 K37/0147 21/10/2004 2406759 47 <0.005 38 15 35 0.25 9.3 0.05 18.4 6.4 1.6 19 15 35 133 1.2 36.1 6.1 14 -4.45 K37/0216 20/10/2004 2405889 32 0.012 12 7.6 15 0.04 4.1 <0.01 6.3 6.3 1.1 14 8 10 47 7.04 13.6 6.1 11.1 -3.43 K37/0358 20/10/2004 2405891 45 0.018 22 13 26 <0.03 7 0.01 13.7 6.6 1.3 18 15 17 84 7.94 27.6 6.4 11.3 -8.11 K37/0468 30/11/2004 2405908 36 0.006 13 8.2 16 <0.03 4 <0.01 7.3 6.8 1 15 14 9 49 7.12 15.3 6.4 12.1 K37/0619 30/11/2004 2405909 49 <0.005 13 9.8 14 <0.03 3.4 <0.01 2.9 7.4 1.2 16 10 4.9 46 5.99 16.8 6.8 12.8 K37/0833 20/10/2004 2405890 44 0.017 12 5.1 14 0.07 3.9 <0.01 5.5 7.3 0.9 17 7 3.2 46 8.62 14.4 7.4 11.2 K37/2390 30/11/2004 2405910 70 0.12 30 41 44 0.45 14 0.06 12.7 6.4 1.4 22 33 42 133 Samples collected for resource consent monitoring purposes, autumn, winter and spring 2004 K37/1748 25/05/2004 2403754 2.8 -13 K37/1748 4/08/2004 2405024 2.2 -15.7 K37/1748 10/11/2004 2407581 2 -14.1 K37/1749 25/05/2004 2403755 7 -10.5 K37/1749 4/08/2004 2405025 7.4 -14.7 Samples collected for resource consent monitoring purposes, summer and autumn 2005 K37/1748 9/02/2005 2500346 4.4 K37/1748 4/05/2005 2503395 3.2 -12.25 K37/1749 9/02/2005 2500347 7.6 K37/1749 4/05/2005 2503396 7.2 -11.05 K37/1749 4/05/2005 2503935 6.5 Long-term monitoring samples collected from 2005 through 2009 - annual survey only K36/0118 31/10/2005 2506948 37 0.007 11 4.1 11 <0.03 2.7 <0.01 2.7 6.6 0.9 13 6.3 5.3 39 9.6 11.5 6.2 13.6 -6.47 K36/0118 14/12/2005 2509958 37 0.017 9.1 4.3 11 <0.03 2.7 <0.01 2.3 6.6 0.9 13 6.9 5.9 34 9.2 10.9 6.1 11.3 -6.48 K36/0118 13/11/2006 2605929 36 0.016 10 6.9 12 <0.03 3.2 <0.01 3.3 6.5 1.2 13 7.1 9.8 38 6.8 10.4 6.8 12.3 -6.75

38 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K36/0118 13/11/2006 2605930 36 0.006 10 6.9 12 <0.03 3.1 <0.01 3.3 6.4 1.1 13 7 9.7 38 6.8 10.4 6.8 12.3 -6.75 K36/0118 21/11/2007 2705996 36 0.005 9.2 6 11 <0.03 2.4 <0.01 2.5 6.6 0.9 13 6.4 6.4 33 10 11.4 6.3 11.1 K36/0118 15/09/2008 2806526 22 0.014 18 13 20 <0.03 5.2 <0.01 8.6 6.8 1.2 14 9 16 66 11.4 20.3 5.9 10.6 K36/0118 16/09/2009 2905832 33 <0.005 11 7.7 14 0.04 3.4 <0.01 4.2 7.2 1.2 14 7.5 10 41 7.09 14.3 6.1 12.3 -6.39 K37/0619 25/10/2005 2506683 49 0.015 13 8.2 14 <0.03 3.3 <0.01 2.9 7.6 1 16 8.6 3.6 46 5.87 14.2 7 12.6 K37/0619 24/10/2006 2605677 73 0.031 19 18 21 <0.03 5.3 0.07 2.1 7.1 1.1 19 12 14 69 5.84 14.6 6.9 12.4 K37/0619 24/10/2006 2605678 74 0.017 20 18 21 0.04 5.8 0.07 2.1 7.1 1.1 19 15 14 74 5.84 14.6 6.9 12.4 K37/0619 7/01/2008 2706137 48 0.016 15 9 14 <0.03 3.7 0.02 3 7.7 1.2 16 9 5 53 K37/0619 19/11/2008 2806606 44 0.009 15 9.1 14 0.04 3.3 0.02 3.1 7.7 0.9 16 8.3 4.9 51 8.74 14.5 7.3 12.5 K37/0619 17/11/2009 2905903 54 0.01 13 8.9 16 <0.03 3.5 <0.01 3.2 7.7 1 16 8.3 4.8 47 7.5 15.3 7.4 12.4 K37/2390 7/09/2005 2506593 82 0.017 25 31 32 0.19 11 0.19 3.9 6.7 1.1 25 23 29 108 6.32 43.1 6.4 11.4 K37/2390 7/12/2005 2510226 77 29 45 45 14 12.8 6.5 1.2 21 32 44 130 6.34 31.8 6.5 11.5 K37/2390 7/12/2005 2510230 77 30 46 45 14 12.9 6.5 1.2 21 32 44 133 6.34 31.8 6.5 11.5 Long-term monitoring samples collected from 2005 through 2009 - quarterly K37/0147 7/09/2005 2506595 47 0.011 21 14 26 <0.03 7 <0.01 13.3 6.8 1.3 18 14 16 81 4.02 35.4 6.2 13.5 -4.12 K37/0147 7/12/2005 2510228 66 12 9.5 15 3.8 1 7.1 1.4 14 9 5.4 46 4.04 29.1 6.4 12.9 -4.4 K37/0147 28/06/2006 2603784 65 21 14 23 6.2 5.6 6.8 1.6 15 11 11 78 3.22 23.7 6.7 13.8 -1.9 K37/0147 26/07/2006 2604797 65 24 18 26 7 8 6.9 1.7 16 13 18 89 3.89 24.1 6.7 13.9 -1.65 K37/0147 28/08/2006 2604820 65 26 18 27 7.3 8.1 6.7 1.7 15 13 20 95 2.13 27.7 6.5 13.3 -1.48 K37/0147 19/09/2006 2605964 61 27 19 29 7.6 9.4 6.6 1.7 16 13 24 99 4.29 28.9 6.3 13.4 -1.73 K37/0147 9/10/2006 2605662 65 0.057 30 18 29 0.6 7.6 0.08 8.4 6.6 1.6 15 13 24 106 -1.83 K37/0147 5/12/2006 2609578 77 31 18 30 7.7 9.7 6.7 1.8 17 14 26 109 3.29 30.8 13.4 -2.85 K37/0147 5/12/2006 2609580 77 31 17 30 7.7 9.7 6.8 1.8 17 14 26 109 3.29 30.8 13.4 -2.85 K37/0147 1/03/2007 2701572 79 30 17 30 7 8.7 6.4 1.6 18 14 24 104 3.6 29.6 6.6 13.6 -3.83 K37/0147 7/06/2007 2704003 84 32 17 33 7.3 12 6.7 1.9 17 14 28 110 2.62 32.9 6.6 13.7 -4.85 K37/0147 18/09/2007 2706038 63 0.12 39 16 33 1.4 8.6 0.06 14 6.7 1.6 17 15 30 133 2.7 34.5 6.4 13.6 -4.46 K37/0147 11/12/2007 2708502 64 30 16 35 8.8 15.4 6.6 1.6 17 14 34 111 2.2 37 6.3 13.5 -6.85 K37/0147 4/03/2008 2801512 62 32 13 35 8.8 18.3 6.6 1.5 17 14 31 116 3.71 36.2 6.4 13.2 -6.52 K37/0147 11/06/2008 2804202 74 31 12 30 6.7 11.5 6.6 1.6 17 13 23 105 1.4 30.9 6.5 13.2 -6.12 K37/0147 10/09/2008 2806522 46 0.046 34 20 33 1.2 8.6 0.06 13.3 6.7 1.5 17 13 32 120 3.42 34.1 6.1 13.1 -0.95 K37/0147 2/12/2008 2810113 48 33 22 35 9.5 14.6 6.7 1.8 16 16 35 122 3.5 36.1 6.1 13.4 -2.89 K37/0147 4/03/2009 2901526 61 30 15 26 6.3 8.1 6.9 1.5 16 14 21 101 4.04 26.7 6.1 13.9 -4.22 K37/0147 4/06/2009 2903811 67 21 13 21 5.1 4.7 6.8 1.4 16 11 13 73 5.5 21.6 6.4 13.6 -3.27 K37/0147 3/09/2009 2905818 75 0.38 23 14 25 3.1 5.7 0.1 6.3 6.7 1.7 15 12 16 81 2.41 24.7 6.1 13 -3.8 K37/0147 8/12/2009 2909132 77 26 15 27 6.5 7.7 6.9 1.5 16 13 21 92 1.98 28.9 6.4 13.7 -5.45 K37/0216 6/09/2005 2506587 40 0.015 9.7 5.7 12 <0.03 3.4 <0.01 2.2 6.4 0.8 14 7.3 8.6 38 6.89 13.9 6.2 11.4 -4.6 K37/0216 6/12/2005 2510215 40 9.2 5.6 12 3.4 2.6 6.5 0.9 13 7.4 8.4 37 6.89 11.9 6.3 11.3 K37/0216 7/03/2006 2601403 40 10 5.4 12 3.4 2.3 6.5 1.1 13 7.9 8.1 39 6.9 11.9 6.4 10.9 -5 K37/0216 7/06/2006 2603774 39 10 5.8 13 3.5 3.6 6.4 1.1 14 7.8 7.8 39 9.22 13.1 6.3 14.8 K37/0216 5/09/2006 2605613 31 0.02 14 11 18 0.07 4.9 <0.01 7.3 6.3 1.3 13 9 12 55 7.09 17.6 6.3 10.9 K37/0216 4/12/2006 2609569 37 14 9.8 17 5 7.3 6.3 1.2 13 8.7 11 56 8.23 17.6 11.3 -4.18 K37/0216 1/03/2007 2701563 38 13 9.5 17 4.5 6.4 6.2 1.2 14 8.8 13 51 7.7 16.8 6.1 12.1 -3.3 K37/0216 7/06/2007 2703994 38 12 8.2 16 4.2 5.6 6.3 1.3 13 8.3 12 47 6.5 15.4 6.3 12.4 -5.09 K37/0216 4/09/2007 2706105 36 0.023 12 7.6 15 <0.03 4.3 <0.01 5 6.5 1.3 13 8.6 11 48 8.25 15.3 6.2 11.5 -4.45 K37/0216 10/12/2007 2708501 36 11 7 14 3.8 4.5 6.4 1 13 7.6 11 43 6.9 14.4 6 11.4 -3.9

Environment Canterbury Technical Report 39 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0216 4/03/2008 2801515 36 10 6.4 14 3.4 4 6.4 0.9 13 6.8 10 39 7.07 14 6.1 12.2 -5.15 K37/0216 11/06/2008 2804206 31 11 8.2 13 3.6 3 6.2 1 13 7.6 10 42 4.73 13.3 5.9 12.7 -5.6 K37/0216 11/06/2008 2804207 38 11 6.8 13 3.5 3 6.3 1 13 7.6 10 42 4.73 13.3 5.9 12.7 -5.6 K37/0216 10/09/2008 2806520 23 0.006 21 17 24 <0.03 6.9 <0.01 12.3 6.4 1.3 13 10 15 81 10.64 24.6 5.8 11.4 -1.4 K37/0216 2/12/2008 2810116 27 17 11 18 5.6 8.8 6.3 1.3 13 9.7 12 66 6.9 18.7 5.9 11.2 -3.92 K37/0216 4/03/2009 2901524 33 19 11 18 5.4 7.9 6.4 1.3 14 9.7 13 70 5.99 18.4 5.6 12.2 -3.88 K37/0216 3/06/2009 2903806 34 18 13 21 5.9 9.3 6.4 1.4 14 10 16 69 21.3 5.9 13 -2.3 K37/0216 3/09/2009 2905814 33 0.017 13 9.8 17 <0.03 4.5 <0.01 6.8 6.4 1.3 13 8.4 12 51 7.07 16.6 5.7 11.2 -3.65 K37/0216 7/12/2009 2909129 43 14 8.9 17 4.8 6.1 7 1.2 13 8.2 12 55 8.52 17.6 5.9 11.1 -3.83 K37/0358 7/09/2005 2506596 46 0.008 20 13 23 <0.03 6.4 <0.01 12 6.8 1.6 25 14 14 76 7.82 26.1 6.5 11.4 K37/0358 7/12/2005 2510229 49 21 14 26 7 13.9 7 1.3 17 15 16 81 7.19 24.8 6.6 11.5 K37/0358 28/06/2006 2603785 51 23 14 27 7.3 14.2 6.8 1.3 17 15 16 87 7.84 28.4 6.5 10.8 K37/0358 26/07/2006 2604798 56 22 14 26 7.5 11.5 6.9 1.3 14 15 15 86 7.8 27.3 6.5 10.6 K37/0358 28/08/2006 2604821 47 22 13 28 7.4 13.8 6.9 1.3 17 15 15 85 7.8 26.8 6.8 10.7 K37/0358 19/09/2006 2605965 47 23 14 27 7.5 14.8 7.3 1.4 17 15 16 88 8.73 27.6 7.3 10.2 K37/0358 9/10/2006 2605661 46 0.044 25 14 29 <0.03 7.8 <0.01 16.3 6.9 1.3 17 15 16 95 K37/0358 5/12/2006 2609579 51 26 15 30 8 16.7 7 1.5 17 16 16 98 9.77 29.9 12.8 -5 K37/0358 1/03/2007 2701573 45 25 15 30 7.9 16.9 6.2 1.4 17 16 18 95 27 6.5 11.9 -5.33 K37/0358 7/06/2007 2704004 50 25 16 31 7.9 17.8 6.6 1.6 16 15 18 95 9.48 30.5 6.5 11.9 -6.58 K37/0358 18/09/2007 2706039 45 0.025 31 15 30 <0.03 8 <0.01 18 6.7 1.3 17 16 17 110 10.3 31.7 6.4 12 -6.55 K37/0358 11/12/2007 2708503 45 23 15 30 8.1 17.8 6.7 1.3 17 15 17 91 8.3 30.1 6.3 12.3 -8.75 K37/0358 4/03/2008 2801513 44 23 15 30 7.7 17.4 6.7 1.3 17 14 17 89 11 31 6.4 11.9 K37/0358 11/06/2008 2804203 45 26 16 30 8.2 16.8 6.5 1.4 16 16 18 99 8.16 31.1 6.4 11.9 -10.4 K37/0358 11/09/2008 2806524 39 0.016 27 16 30 <0.03 8.3 <0.01 16.4 6.5 1.4 17 16 18 102 9.36 31.3 6.2 12 -3.7 K37/0358 2/12/2008 2810114 40 26 16 31 9 17.7 6.8 1.6 16 18 19 102 11.4 31.7 6.2 12.2 -5.75 K37/0358 4/03/2009 2901527 43 32 18 32 9.2 17.8 6.8 1.5 17 18 20 118 10.76 32.3 6 12.2 -8.2 K37/0358 4/03/2009 2901528 43 32 18 32 9.2 17.8 6.8 1.6 17 18 20 118 10.76 32.3 6 12.2 -8.2 K37/0358 4/06/2009 2903809 47 29 17 34 8.8 17.9 6.7 1.6 16 17 20 109 9.01 32.5 6.3 12.1 -7.28 K37/0358 4/06/2009 2903810 46 28 17 33 8.6 17.2 6.7 1.6 17 17 20 105 9.01 32.5 6.3 12.1 -7.28 K37/0358 3/09/2009 2905817 48 0.007 28 17 32 <0.03 8.7 <0.01 18.1 6.7 1.6 17 16 21 106 8.94 31.9 5.9 12.3 K37/0358 7/12/2009 2909131 52 29 17 33 9.3 18.2 7.1 1.5 17 16 20 111 11.16 34.3 6.3 12.1 -8.45 K37/0468 7/09/2005 2506594 38 0.007 12 8.3 17 <0.03 4.2 <0.01 8 6.8 0.8 17 12 8.7 47 7.08 15.8 6.6 12.1 K37/0468 7/12/2005 2510227 39 12 8.2 17 4.3 8 6.8 0.8 16 12 9 48 7.12 16.8 6.7 12.3 K37/0468 8/03/2006 2601412 44 11 5.1 12 3 4.2 7.6 1 16 8.5 2.5 40 7.09 16.9 6.7 12 K37/0468 28/06/2006 2603783 42 14 10 19 4.7 6.6 6.8 1 16 13 9.1 54 7.17 19 6.8 8.9 K37/0468 6/09/2006 2605616 40 0.011 15 11 19 <0.03 4.8 <0.01 9 6.7 1 16 13 9.7 57 8.29 19.6 6.8 12.4 K37/0468 5/12/2006 2609577 48 16 11 20 5.1 8.9 6.8 1.1 16 14 10 61 9.4 20.2 12 -3.01 K37/0468 8/03/2007 2701571 43 16 12 21 5.1 10 6.2 1 16 13 11 61 8.91 13.2 -3.5 K37/0468 8/03/2007 2701757 41 16 12 21 5.1 10 6.3 1 16 13 11 61 8.91 13.2 -3.5 K37/0468 6/06/2007 2704002 47 16 12 21 5.1 10.1 6.8 1.2 16 13 11 61 8.62 22 6.5 12.4 -3.21 K37/0468 4/09/2007 2706100 42 0.02 17 11 21 <0.03 5.7 <0.01 10.1 6.7 1.2 16 15 9.8 66 9.55 22 6.5 11.6 -3 K37/0468 11/12/2007 2708505 41 16 12 22 5.3 11.4 6.7 1 16 13 10 62 8.6 21.9 6.3 12.5 -5.51 K37/0468 11/12/2007 2708506 41 16 12 22 5.3 11.4 6.8 1 16 13 10 62 8.6 21.9 6.3 12.5 -5.51 K37/0468 4/03/2008 2801514 40 16 13 22 5.2 11.9 6.7 1 16 13 11 61 10.14 22.9 6.5 12.3 -7.3 K37/0468 11/06/2008 2804204 40 19 13 23 5.7 11.8 6.6 1.1 15 14 11 71 8.87 23.2 6.5 11 -5.85 K37/0468 10/09/2008 2806521 38 <0.005 19 13 23 <0.03 5.9 <0.01 11.2 7 1 16 14 11 72 10.67 23.9 6.5 12.2 -1.52

40 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0468 2/12/2008 2810111 39 18 14 26 6.8 12.5 6.9 1.2 15 16 12 73 10.8 24.8 6.4 12.6 -3.92 K37/0468 2/12/2008 2810112 39 18 15 24 6.8 12.6 6.9 1.2 15 16 12 73 10.8 24.8 6.4 12.6 -3.92 K37/0468 4/03/2009 2901529 44 26 16 25 6.9 13.1 6.9 1.2 16 17 13 93 9.79 25.7 6 12.4 -3.23 K37/0468 3/06/2009 2903807 46 22 15 26 6.7 13.1 6.8 1.2 16 16 13 83 26.1 6.3 12.5 -4.15 K37/0468 3/09/2009 2905819 46 0.018 21 15 26 <0.03 6.9 <0.01 13.6 6.8 1.3 16 16 13 81 8.35 26.2 6.1 12.5 -3.5 K37/0468 8/12/2009 2909133 50 22 15 27 7 14 6.9 1.2 16 15 13 84 9.65 28.1 6.3 12.4 -5.65 K37/0833 6/09/2005 2506588 46 0.011 11 4.8 13 <0.03 3.9 <0.01 4.9 7.4 0.8 17 6.5 2.7 44 8.63 14.5 7.3 11.2 K37/0833 6/09/2005 2506589 46 0.016 12 4.6 13 <0.03 3.9 <0.01 4.8 7.5 0.8 17 6.7 2.6 46 8.63 14.5 7.3 11.2 K37/0833 6/12/2005 2510216 47 12 4.7 13 3.8 5 7.3 0.9 16 7 2.7 46 8.59 13.9 7.3 11.3 K37/0833 7/03/2006 2601404 47 12 4.8 14 4 5.1 7.3 1 16 7.2 2.7 46 8.62 13.6 7.2 11.1 K37/0833 7/06/2006 2603775 52 16 7.2 18 5.3 9.1 7.2 1.1 17 8.2 3.2 62 9.73 18.2 7 8.4 K37/0833 5/09/2006 2605614 40 0.009 16 6.4 15 0.04 3.2 <0.01 4.7 6.5 0.9 11 5.3 10 53 4.18 14.8 6.3 9.5 K37/0833 4/12/2006 2609570 55 13 4.1 13 3.6 4.3 7.5 0.9 16 5.8 2.6 47 7.6 13 14.4 K37/0833 1/03/2007 2701564 49 16 7.7 18 5.1 7.2 6.8 1.1 16 8.2 5.5 61 7.5 17.5 7.1 11.9 -5.23 K37/0833 6/06/2007 2703995 61 15 6.6 17 4.9 6.6 7.3 1.1 16 7.8 4.7 58 6.53 17.5 7 12.3 -4.57 K37/0833 6/06/2007 2703996 60 15 6.6 17 4.9 6.5 7.2 1.1 16 7.9 4.6 58 6.53 17.5 7 12.3 -4.57 K37/0833 4/09/2007 2706106 53 0.027 16 7.4 17 0.17 5.3 0.08 6.6 7.2 1.2 16 8.4 5.3 62 7.7 17.7 6.9 11.7 -4.74 K37/0833 11/12/2007 2708504 50 13 6 16 4.3 6 7.3 0.9 16 7 3.9 50 7 15.7 6.7 11.9 -7.51 K37/0833 4/03/2008 2801511 55 14 5.3 17 4.5 6.2 7.1 0.9 16 6.9 4.7 53 8.59 17.1 6.8 12.2 -6.21 K37/0833 11/06/2008 2804205 50 15 6.7 16 4.4 5.6 6.9 1 16 7.3 4.1 56 7.01 15.9 6.7 12.1 K37/0833 11/09/2008 2806523 50 0.015 23 9.9 22 0.03 6.8 <0.01 9.2 7.1 1.2 16 9.3 12 85 8.96 22.7 6.4 10.9 -1.77 K37/0833 2/12/2008 2810115 52 24 9.6 22 7.1 9.5 7.1 1.3 16 9.7 9.9 89 8 22.4 6.6 11.7 K37/0833 4/03/2009 2901525 52 17 6.9 17 5.5 6.8 7.2 1.1 16 8.2 6.3 65 7.22 17.8 6.3 13.1 -6.42 K37/0833 4/06/2009 2903808 62 22 8.5 22 6.4 8.8 7 1.3 17 8.9 9.5 81 7.94 21.9 6.7 11.8 -3.75 K37/0833 3/09/2009 2905815 60 0.013 20 6.4 21 0.03 6.2 <0.01 6.7 7 1.3 16 8.8 8 75 8.07 20.8 6.4 11.3 -4.4 K37/0833 3/09/2009 2905816 60 0.012 19 8.1 21 0.04 6.2 0.01 8.3 7 1.3 16 8.7 10 73 8.07 20.8 6.4 11.3 -4.4 K37/0833 7/12/2009 2909130 65 18 6.6 19 5.7 6.8 7.5 1.1 16 7.9 7 68 6.85 19.4 6.8 12.1 -6.64 Samples collected in the 2009 investigation K36/0232 21/01/2009 2900398 33 0.022 12 4.7 12 <0.03 2.3 <0.01 2.9 6.3 0.8 12 4.5 12 39 8.8 12.1 6 11.4 K36/0577 22/01/2009 2900401 50 0.036 13 7.1 15 <0.03 4 <0.01 5.1 7.3 0.8 18 7 1 49 8.1 15.2 7.3 12 K36/0586 21/01/2009 2900397 24 0.023 7.3 3 8 <0.03 1.5 <0.01 1.7 6.3 0.6 8.5 3.1 5.6 24 8.9 7.7 5.8 12.3 -15.18 K36/0694 21/01/2009 2900399 50 0.021 13 7 16 <0.03 4.2 <0.01 5.1 7 0.9 19 7.3 1.1 50 6.9 15.6 6.8 11.7 K36/0781 22/01/2009 2900402 46 0.035 12 5.8 13 0.07 3.3 <0.01 4.3 7.2 0.8 20 6.9 0.8 44 9.7 13.5 7 11.9 K37/0026 13/03/2009 2900438 76 0.036 20 20 24 <0.03 6.7 0.18 2.4 7.5 1.3 19 15 16 78 11 22.9 6.7 12 -6 K37/0073 28/01/2009 2900404 49 0.03 15 8.9 13 <0.03 2.8 <0.01 3.5 8.1 0.9 16 7.2 1.7 49 6.6 13.3 7.4 12.1 K37/0222 28/01/2009 2900406 47 0.02 14 3.4 13 <0.03 4 <0.01 3.7 6.9 0.9 16 6.5 8.6 51 10.3 13.5 6.1 12.7 K37/0443 23/04/2009 2903069 50 0.013 14 5.2 16 <0.03 4 <0.01 5.1 7.2 1.1 15 8.2 8.3 51 10.7 15.4 6.5 12.6 -57 K37/0547 10/03/2009 2900436 47 0.008 18 17 23 <0.03 6.7 <0.01 6.7 6.9 1.1 12 16 20 73 0.35 23.9 6.3 13.2 -2.87 K37/0599 10/02/2009 2900414 34 0.023 16 8.2 18 <0.03 4.6 <0.01 9.2 6.5 1.5 12 8.2 12 59 8.3 19 5.7 14 -5.75 K37/0610 10/03/2009 2900437 88 0.031 25 30 32 0.2 8.6 0.49 0.8 7.2 1.5 23 25 34 98 0.72 31.8 6.4 12.5 -3.9 K37/0634 22/04/2009 2900439 65 0.012 14 12 16 0.04 4.5 0.01 2 7.7 1.1 17 9.4 3.3 53 4.6 15.8 7.1 12.4 K37/0659 9/04/2009 2900441 69 0.017 15 15 19 <0.03 5.3 0.07 2.2 7.5 1.2 17 12 9.4 59 5 13.1 6.6 12.4 -6.3 K37/0663 10/02/2009 2900415 35 0.016 9.4 3.3 11 <0.03 2.6 <0.01 2.6 7 0.8 12 6 10 34 10.6 11.2 6.1 13.2 -6.3 K37/0680 24/02/2009 2900428 90 0.01 23 19 27 <0.03 8.8 0.02 2.3 7.1 1.2 18 17 27 94 0.23 28.1 6.4 12.5 K37/0689 28/01/2009 2900405 45 0.011 12 5.3 12 <0.03 3.5 <0.01 3.7 8 0.8 16 6.8 3.8 44 9.8 12 7.1 12.3

Environment Canterbury Technical Report 41 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Determinands measured in the laboratory Field determinands

Well Date Sample alcium

Number Sampled Number Alkalinity Ammonia Nitrogen C Chloride Conductivity Iron Magnesium Manganese Nitrate Nitrogen pH Potassium Reactive Silica Sodium Sulphate Total Hardness Total Kjeldahl Nitrogen Dissolved Oxygen Field Conductivity Field pH Water Temperature Depth to Water K37/0704 11/02/2009 2900420 31 0.009 14 15 19 <0.03 4.8 <0.01 8.2 6.6 1.2 16 13 15 55 8.8 19.5 6 13.5 -2.9 K37/0722 25/02/2009 2900433 95 0.1 33 45 43 0.89 11 0.79 1.9 7.3 1.8 14 26 53 128 2.4 42.7 6.6 12.6 K37/0735 9/02/2009 2900413 46 0.009 12 5.5 14 <0.03 4 <0.01 5.2 7.7 1.2 17 7.8 4.7 46 11.2 14 6.9 12.3 K37/0832 23/02/2009 2900425 30 0.025 13 9 16 <0.03 4 <0.01 7.2 6.5 0.9 13 9.4 10 49 9.1 16.7 5.7 12.9 K37/1010 25/02/2009 2900435 82 0.016 30 44 49 <0.03 15 0.13 12 6.8 2.4 14 35 52 137 3.6 47.6 6 13.3 -4.4 K37/1397 23/02/2009 2900426 54 0.018 14 8.9 15 <0.03 4.3 <0.01 3.5 7.2 0.9 16 9.1 5.4 53 4.2 15.6 6.5 12.4 K37/1555 29/01/2009 2900411 47 0.015 13 4.6 14 <0.03 3.7 <0.01 4 8 1.1 16 8.2 4.5 48 10.8 14 7.4 12.2 K37/1711 10/02/2009 2900417 45 0.005 10 6 14 <0.03 3.8 <0.01 4.8 7.8 0.9 17 9.3 3.9 41 7.8 13.7 6.9 12.5 K37/1792 25/02/2009 2900431 42 0.027 19 16 24 0.24 6.2 <0.01 11.6 6.7 0.9 17 14 13 73 6.2 24.4 6 13.3 -2.95 K37/1880 29/01/2009 2900408 47 0.009 11 4.3 11 <0.03 3 <0.01 2.2 8.1 1 16 7 1.7 40 17.5 11.1 7.5 12.3 K37/1908 23/02/2009 2900427 59 0.015 14 11 18 <0.03 5.6 <0.01 4.2 7.2 0.9 17 11 7.9 58 1.2 18.3 6.5 12.6 K37/1997 19/02/2009 2900423 50 0.013 13 7.9 13 <0.03 2.4 <0.01 2.5 7.9 1 16 6.7 1.8 42 8.6 12.9 7.4 12 K37/2133 10/02/2009 2900416 42 0.008 10 7.1 14 <0.03 3.9 <0.01 5.6 7.8 0.9 16 9.5 4.4 41 8.9 14.4 6.9 12.8 K37/2151 25/02/2009 2900432 59 0.016 13 7.9 15 <0.03 4.2 <0.01 3 7.8 0.9 17 7.7 2.7 50 5.7 14.8 7.2 12.1 K37/2153 9/04/2009 2900440 64 0.018 15 8.6 16 <0.03 4.5 <0.01 3.8 7.6 1 16 8.5 4.1 56 5.2 15.5 6.8 12.2 -4.35 K37/2159 29/01/2009 2900412 48 0.011 14 5 15 0.05 4.3 <0.01 4.4 8 1.1 17 7.8 3.5 53 9.6 14.4 7.3 12.1 K37/2227 28/04/2009 2903070 72 <0.005 21 17 23 0.05 6.8 <0.01 4 7.2 1.2 17 13 14 80 3.15 22.8 6.6 12.8 -8.68 K37/2303 11/02/2009 2900418 42 0.01 13 11 17 <0.03 4 <0.01 6.7 7.2 1.1 16 10 5.9 49 10.8 16.9 6.7 12.4 -10.3 K37/2314 25/02/2009 2900434 78 0.01 26 30 37 <0.03 10 <0.01 7.4 6.8 1.9 15 26 42 106 0.7 37.2 6 13.5 K37/2384 11/02/2009 2900419 39 0.03 17 16 21 <0.03 5.3 <0.01 9.7 6.9 1.1 16 13 10 64 9.5 20.9 6.3 12.3 K37/2542 29/01/2009 2900409 49 0.008 14 3.6 13 0.06 2.8 <0.01 2.9 8 1.1 15 8 5.7 44 11.2 13.4 7.3 12.4 K37/2728 11/02/2009 2900421 45 0.012 11 7.3 13 <0.03 3.5 <0.01 4.4 7.5 1 16 9.3 2.8 42 6 13.3 6.9 12.5 K37/2750 22/01/2009 2900400 44 0.045 13 7.8 14 0.04 3.7 <0.01 4.9 7.5 0.8 16 6.8 1.2 48 9.8 14.4 7.4 12 K37/2751 27/01/2009 2900403 76 0.02 12 3.5 14 <0.03 4.9 <0.01 0.3 7.8 0.7 18 8.3 1.8 50 4.6 14.3 7.1 12.6 K37/2774 24/02/2009 2900429 65 0.006 14 14 18 <0.03 5.7 <0.01 2 7.3 0.9 17 11 11 58 0.24 18.1 6.5 12.1 -5.7 K37/2871 19/02/2009 2900424 45 0.009 10 6.7 11 <0.03 2.4 <0.01 2 7.9 0.9 16 6.9 2 35 8.8 11.4 7.4 12.6 K37/2905 11/02/2009 2900422 44 0.01 11 8.1 14 <0.03 4.1 <0.01 5.2 7.4 1 16 8.7 3.7 44 6.4 14.2 6.8 12.3 K37/2960 28/04/2009 2903083 56 2.8 6.8 5.5 10 0.04 2.3 0.02 <0.1 9.4 1 0.26 7.9 2.9 26 0.05 10.7 9.1 12.6 -37.95 K37/3016 28/01/2009 2900407 53 0.011 14 3.1 13 <0.03 3 <0.01 3.4 8.1 1 15 8 6.4 47 8.5 13.6 7.4 12.8 K37/3150 29/01/2009 2900410 56 0.012 12 5.6 11 <0.03 2.8 <0.01 0.3 8.2 0.8 17 7.2 1.9 41 7.7 11.4 7.6 12.8 K37/3156 24/02/2009 2900430 98 0.009 25 29 33 0.04 9.7 0.09 3.8 7.1 1.4 21 23 25 102 0.3 33 6.2 12.7 -4 K38/2244 22/04/2009 2903068 74 0.013 20 18 24 <0.03 6.3 0.14 5 7.3 1.2 17 14 12 76 4.1 23.7 6.6 12.4 Samples from wells added to the annual survey after the 2009 investigation K37/0222 7/09/2009 2905820 49 0.007 12 3 13 <0.03 3.7 <0.01 3.4 6.8 1.1 16 6.2 6.9 45 9.35 12.7 5.5 12.5 K37/0689 5/11/2009 2905889 50 0.006 12 5 12 <0.03 3.5 <0.01 3.4 7.7 0.9 16 6.6 2.8 44 9.91 13.2 7.2 12.3 -49.3 K37/1010 17/11/2009 2905904 91 <0.005 31 39 53 <0.03 16 <0.01 12.4 7.1 2.3 13 35 57 143 3.25 50.2 6.2 11.6 -3.35 K37/2871 23/11/2009 2905908 50 0.015 11 6.5 12 <0.03 2.6 <0.01 2.2 7.7 0.8 17 6.9 1.5 38 8.44 11.8 7.8 12.7 K37/2303 23/11/2009 2905909 49 0.008 15 10 19 <0.03 4.3 <0.01 6.8 7.3 1.1 16 11 6 55 -9.75 Other samples collected from 2005 to 2009 K36/0220 3/08/2005 2506290 39 0.064 4.3 4.3 11 0.16 13.7 6.1 13.7 -14.95 K37/2232 8/03/2006 2601896 62 14 5.7 14 4.5 3.8 7.7 1.1 17 8.2 1 53 6.01 12.9 7.1 11.1

42 Environment Canterbury Technical Report

Environment CanterburyTechnical Report

Appendix 2: Construction details for wells of the Ashburton-Hinds plain where groundwater samples were collected between 1988 and 2009

Nitrate contamination groundwater and chemistry

Use Owner (m bgs) samples Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K36/0027 2396743 5710989 13.72 150 steel FECHNEY D J domestic 1 20/07/2004 20/07/2004 K36/0055 2393248 5715037 6.94 100 steel WADDELL, GM & JM domestic 1 21/07/2004 21/07/2004 K36/0056 2391297 5713819 12 83 steel DONALDSON OL & SK domestic 1 21/07/2004 21/07/2004 K36/0061 2389523 5715372 6.95 51 PVC ROY, JW & PC water level observation 1 21/05/2004 21/05/2004 K36/0108 2387077 5715856 10.4 200 steel GALLAGHER G W B 6.4 - 10.4 domestic 1 21/07/2004 21/07/2004 K36/0118 2381923 5712379 11.3 100 steel SPENCER A E domestic 24 17/12/1992 16/09/2009

K36/0220 2394642 5713870 19.5 150 steel LOWE, WJ domestic, irrigation 2 16/07/2004 3/08/2005 K36/0231 2395616 5711010 27.5 150 steel LIFESTOCK HOLDINGS LTD 18 - 27.5 domestic, stock 1 16/07/2004 16/07/2004 K36/0232 2385243 5716174 23 150 steel HA Smith & ME Roysmith 21.5 - 23 domestic, irrigation 1 21/01/2009 21/01/2009 K36/0282 2389528 5715375 11.25 200 steel ROY, J W & P C domestic, stock 1 21/07/2004 21/07/2004 K36/0436 2389225 5715354 111.2 250 steel Roy, JW & PC 90 - 111.2 irrigation 1 20/05/2004 20/05/2004 K36/0540 2393532 5710603 113.4 300 steel QUIGLEY B G & P J 95.61 - 113.4 domestic, irrigation 1 16/07/2004 16/07/2004 K36/0577 2389788 5710363 115.93 300 steel MOONSHINE FARM 102.9 - 115.93 irrigation 2 20/07/2004 22/01/2009 -

K36/0586 2384376 5716115 35.1 203 steel MR & MRS J G K & A J RUSHTON 32.1 - 35.1 domestic, stock 1 21/01/2009 21/01/2009 Ashburton K36/0656 2396691 5712221 47.2 300 steel DELOS DAIRY 43.2 - 47.2 irrigation 1 20/07/2004 20/07/2004 K36/0694 2386263 5711886 105.26 300 steel Wall, G 99.24 - 105.26 domestic, stock, irrigation 1 21/01/2009 21/01/2009 K36/0780 2384374 5710337 20 150 steel SCOTT W M domestic 1 20/07/2004 20/07/2004

K36/0781 2385988 5713082 116.63 300 steel MR S B ROY 109.63 - 115.63 irrigation 1 22/01/2009 22/01/2009 - Hinds plain Hinds K37/0018 2406639 5690831 12.19 127 steel LOVETT W.R. 9.2 - 12.1 domestic 1 18/08/2004 18/08/2004 K37/0026 2405928 5681075 38.4 250 steel JAINE M.A.C. & P.D.J. 32.94 - 38.04 irrigation 1 13/03/2009 13/03/2009 K37/0028 2408198 5698164 5.11 310 steel MILLICHAMP NURSERY irrigation 1 30/11/1994 30/11/1994 K37/0034 2396862 5689672 6.25 125 steel LD & JL Moore 3.57 - 6.25 domestic 1 23/08/2004 23/08/2004

K37/0049 2396780 5689803 8.23 150 steel LOWE W W domestic 1 27/07/2004 27/07/2004 K37/0060 2409335 5695033 10.36 125 steel Mr and Mrs Peck domestic 1 26/08/2004 26/08/2004

43 K37/0066 2397135 5708095 42 250 steel LANGDON J E A 38.98 - 42 irrigation 1 27/05/2004 27/05/2004

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/0073 2389126 5706017 149.8 250 steel STOCKDILL N 132.7 - 146.3 irrigation 1 28/01/2009 28/01/2009 K37/0087 2405980 5697170 16 150 steel MWD TINWALD DEPOT 11.5 - 16 commercial, domestic 1 18/04/1995 18/04/1995 K37/0088 2405550 5697220 10.06 150 steel BEST BF & PM 6.4 - 10.06 irrigation 2 18/04/1995 21/04/2004 K37/0114 2390866 5701609 9.3 150 steel MWD VALETTA COTTAGE 0 - 9.3 domestic, stock 8 22/10/1991 12/11/1997 K37/0147 2406374 5697131 9.75 100 steel TINWALD SALEYARDS stock water 35 19/04/1995 8/12/2009 K37/0155 2398168 5692968 10.15 100 steel DAVIDSON C domestic 1 27/07/2004 27/07/2004 K37/0175 2398227 5696420 12.19 76 steel MONTGOMERY R domestic 1 27/07/2004 27/07/2004 K37/0188 2399489 5698837 9.1 100 steel McKINTYRE JB KA domestic 1 13/07/2004 13/07/2004 K37/0201 2406232 5701851 6 95 steel THOMAS MW & SM domestic, stock 1 27/04/2004 27/04/2004 K37/0204 2399136 5701687 41.14 150 steel Mr & Mrs D B & J H Pike domestic 1 14/07/2004 14/07/2004 K37/0216 2390246 5701380 9.5 300 steel Austin Farms Ltd domestic, stock 35 16/12/1992 7/12/2009 K37/0219 2398297 5706873 9.11 57 steel LANGDON RW domestic 1 14/07/2004 14/07/2004 K37/0222 2393760 5705712 18.69 100 steel STOCKER D domestic 8 28/09/1988 7/09/2009

Environment CanterburyTechnical Report K37/0224 2389200 5704125 6.3 100 steel MORRISON F G domestic 1 16/07/2004 16/07/2004 K37/0316 2399398 5691296 55.1 300 steel R D & J R Jones 42.9 - 55.1 irrigation, dairy, stock 1 28/01/2009 28/01/2009 K37/0336 2407755 5697511 6.5 150 steel Whelan, Mr & Mrs domestic, irrigation 1 26/08/2004 26/08/2004

K37/0358 2405025 5697461 15.56 100 steel TATE A.J. 13.5 - 15.5 domestic 36 24/11/1995 7/12/2009 -

Ashburton K37/0366 2400589 5692243 9.3 200 steel JP McGillen domestic 1 19/08/2004 19/08/2004 K37/0371 2407670 5696050 30.5 150 steel CORNELIUS B J 28.5 - 30.5 domestic, irrigation 1 25/08/2004 25/08/2004 K37/0415 2398480 5691210 12 100 steel SOUFFLET M domestic 1 27/07/2004 27/07/2004 K37/0436 2408000 5694950 10 150 steel EDER WH & DE 7 - 10 domestic 1 20/05/2004 20/05/2004 - Hinds plain Hinds K37/0439 2406659 5696411 34.5 150 steel ALLEN W D 31.5 - 34.5 domestic, irrigation 1 22/04/2004 22/04/2004 K37/0443 2395160 5703646 69.3 150 steel NORDQUEST C & W 66.5 - 69 domestic 2 15/07/2004 23/04/2009 K37/0455 2406158 5698051 22 150 steel TINWALD GOLF CLUB irrigation 1 26/04/2004 26/04/2004 K37/0466 2402560 5685180 6 51 steel GRAY R M domestic 13 13/12/1991 13/10/2003 K37/0467 2408600 5685230 8.2 51 steel GOING, KW & JM water quality sampling 7 13/12/1991 17/11/1997 K37/0468 2403495 5692270 9.1 170 steel Schmack, B & F domestic 39 13/12/1991 8/12/2009 K37/0474 2409289 5693381 9 125 steel Mr Punselie domestic, irrigation 1 24/08/2004 24/08/2004

Environment CanterburyTechnical Report

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/0476 2405850 5696929 14.5 150 steel MURNEY FG & KG 2.4 - 14.5 irrigation 1 22/04/2004 22/04/2004 K37/0483 2407060 5692960 6 150 steel SCOTT R J 4 - 6 domestic 1 26/07/2004 26/07/2004 K37/0490 2405930 5696601 21.4 150 steel TAYLOR DE & MF 20 - 21.4 irrigation 2 22/04/2004 28/07/2004 K37/0503 2408149 5694662 10 150 steel RA & ME Prattley 4 - 10 domestic 1 25/08/2004 25/08/2004 K37/0516 2406819 5697523 46.9 300 steel ASHBURTON DISTRICT COUNCIL 36.5 - 40.7 public water supply 1 18/04/1995 18/04/1995 K37/0547 2404832 5681406 10 125 steel ESKDALE FARM LTD domestic, stock 2 21/07/2004 10/03/2009 K37/0550 2399850 5685570 24 100 steel READ, R.G. 23.5 - 24 domestic 1 22/07/2004 22/07/2004 K37/0561 2405819 5698146 66.8 300 steel KELBURN HOLDINGS LTD 55.3 - 66.8 irrigation 1 28/07/2004 28/07/2004 K37/0563 2406300 5697300 TINWALD MODEL RAIL SOC 2 7/12/1994 19/04/1995

K37/0599 2396780 5701130 10 203 steel Kanally Farm Ltd domestic 1 10/02/2009 10/02/2009 K37/0610 2405456 5682390 36 150 steel Mathews, G.A. 34 - 36 domestic, stock, irrigation 1 10/03/2009 10/03/2009 K37/0613 2402440 5694050 11 125 steel HOSKIN, L.D domestic, stock 1 19/08/2004 19/08/2004 K37/0619 2408617 5684702 55 300 steel GOING, K.W. & J.M. 49 - 55 domestic, dairy, irrigation 16 15/10/1997 17/11/2009 K37/0622 2405084 5697505 10 150 steel CLARKSON RA & LJ domestic 1 21/04/2004 21/04/2004 K37/0634 2406567 5681219 70.6 300 steel TOWNSHEND, K.B.& R.A. 61.6 - 70.6 irrigation 1 22/04/2009 22/04/2009 K37/0643 2401302 5699853 19 150 steel SMITH, MD 18 - 19 domestic 1 27/04/2004 27/04/2004

K37/0659 2405926 5683168 57 300 steel GWENDINGWE LIMITED 52 - 57 irrigation 1 9/04/2009 9/04/2009 -

Ashburton K37/0663 2398663 5698222 11 125 steel POWER, M.R.& L.L. 10 - 11 domestic, stock 1 10/02/2009 10/02/2009 K37/0680 2404154 5685979 13.84 76 steel Mr and Mrs Tulley domestic 2 12/08/2004 24/02/2009 K37/0685 2405309 5696501 17.5 150 steel McINTYRE JR & GA 16.5 - 17.5 domestic, stock 1 22/04/2004 22/04/2004 K37/0689 2391100 5706172 91.5 250 steel MORRISON, A & B.M. 84 - 91.5 irrigation 3 15/07/2004 5/11/2009 - Hinds plain Hinds K37/0693 2395877 5700193 59 150 steel SURRIDGE J 54.16 - 58.74 irrigation 1 13/07/2004 13/07/2004 K37/0697 2406049 5696449 22 150 steel WW and KE Sell 20.5 - 22 domestic 1 24/08/2004 24/08/2004 K37/0702 2408517 5693845 34 150 steel BADGER, GS & HM 32.5 - 34 domestic, stock 1 23/08/2004 23/08/2004 K37/0704 2402036 5690585 9 300 steel B & R Smith irrigation 1 11/02/2009 11/02/2009 K37/0722 2405055 5684629 58.5 300 steel ROSTREVOR HOLDINGS LTD 52.3 - 58.3 irrigation 1 25/02/2009 25/02/2009 K37/0723 2408409 5693756 18 100 steel DAY, G. 17 - 18 domestic 1 23/08/2004 23/08/2004

45 K37/0724 2401610 5697541 16.5 150 steel SPARKS A 15 - 16.5 domestic, stock 1 29/04/2004 29/04/2004

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/0726 2399097 5691403 38 150 steel D & J Jones 35 - 38 domestic, irrigation 1 19/08/2004 19/08/2004 K37/0735 2396678 5698954 60 300 steel YEOMAN, AG 57 - 60 stock, irrigation 1 9/02/2009 9/02/2009 K37/0736 2396191 5694460 10 150 steel FARRELL, A & N.J. domestic, irrigation 1 27/07/2004 27/07/2004 K37/0759 2394933 5709807 48 150 steel CHUDLEIGH HOLDINGS LTD 44.5 - 48 irrigation 1 16/07/2004 16/07/2004 K37/0810 2408718 5693988 9.5 150 steel WILSON, GP & FM domestic, stock 2 29/04/2004 28/07/2004 K37/0819 2406271 5698642 40 200 steel TOPHAM, CJ 38.5 - 40 irrigation 1 26/04/2004 26/04/2004 K37/0832 2398247 5696327 17.9 150 steel BREED, DW 14.9 - 17.9 domestic, stock 1 23/02/2009 23/02/2009 K37/0833 2397948 5709668 10 150 steel LYATT PARTNERSHIP domestic 29 29/09/1998 7/12/2009 K37/0885 2407940 5695410 36 150 steel GIBB, NJ & RM 34.5 - 36 domestic, stock, irrigation 1 25/08/2004 25/08/2004 K37/1004 2404329 5697566 10 150 steel HOSKEN, AG 7 - 10 domestic 1 21/04/2004 21/04/2004 K37/1006 2397415 5704744 9.5 300 steel BRYANT, DW 5 - 9.5 domestic, stock 1 14/07/2004 14/07/2004 K37/1008 2406480 5695580 17 150 steel SCHOONDERBEEK, MW 15 - 17 domestic, stock, irrigation 1 29/04/2004 29/04/2004 K37/1010 2404654 5683794 9.5 315 PVC JD & CM MCKENZIE LIMITED 3 - 9.5 domestic 2 25/02/2009 17/11/2009

Environment CanterburyTechnical Report K37/1061 2395650 5696905 10 160 steel YOUNG, PD domestic, stock 1 14/07/2004 14/07/2004 K37/1153 2409925 5684404 4.9 140 steel Taylor, D. domestic 1 21/07/2004 21/07/2004 K37/1157 2402638 5680000 13.53 51 SP & KM Marsh domestic 1 5/08/2004 5/08/2004

K37/1160 2402000 5681200 6.4 100 Davidson, P domestic 1 21/07/2004 21/07/2004 -

Ashburton K37/1162 2406810 5684086 5.7 51 steel Lovett, R W domestic 1 21/07/2004 21/07/2004 K37/1177 2402308 5687090 1.7 76 steel Smith, B R garden 1 18/08/2004 18/08/2004 K37/1178 2401860 5687140 3.3 51 Smith, R M domestic 1 22/07/2004 22/07/2004 K37/1189 2409400 5694447 5.64 100 steel Mr and Mrs Schikker domestic 1 23/08/2004 23/08/2004 - Hinds plain Hinds K37/1397 2403897 5688498 91 300 steel R M & B R Smith 67.3 - 91 stock, irrigation 1 23/02/2009 23/02/2009 K37/1444 2391307 5702293 92 300 steel LANDCORP FARMING LTD 76 - 92 domestic, stock 1 15/07/2004 15/07/2004 K37/1502 2401643 5695583 51 300 steel D J & S M Williams 45 - 51 irrigation 1 20/05/2004 20/05/2004 K37/1555 2395045 5701026 72.5 300 steel Landcorp Farming Ltd 65.5 - 72.5 domestic, stock 1 29/01/2009 29/01/2009 K37/1587 2396084 5702136 53 150 steel GOSLING, BM & H domestic 1 13/07/2004 13/07/2004 K37/1661 2403468 5698366 11 100 steel HAMPTON PR & ML domestic 1 21/07/2004 21/07/2004 K37/1705 2406420 5692640 6 200 PVC MR F E ALLEN domestic, stock 1 18/08/2004 18/08/2004

Environment CanterburyTechnical Report

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/1711 2399630 5696003 48 150 steel MR & MRS M & R MCKINSTRY 45 - 48 domestic, stock 2 27/07/2004 10/02/2009 K37/1733 2404946 5688713 8.7 170 steel Simon Eddington domestic 1 22/07/2004 22/07/2004 K37/1745 2404624 5688919 6 100 steel Begby, AJ domestic 1 18/08/2004 18/08/2004 water quality, water level K37/1748 2399112 5702040 18 100 PVC GUYON FARM LIMITED, Mr Dewhirst 15 - 18 observation 7 25/05/2004 7/12/2005 water quality, water level K37/1749 2400628 5699514 17.85 150 PVC GUYON FARM LIMITED, Mr Dewhirst 15 - 18 observation 8 25/05/2004 7/12/2005 MR S H LOEFFLER & K37/1767 2405813 5695076 29.5 200 steel MS E L HUISMANS 27.5 - 29.5 domestic, stock 1 24/08/2004 24/08/2004 K37/1789 2405128 5696117 18 150 steel Box Hurst Trust domestic, stock 1 25/08/2004 25/08/2004 K37/1792 2404605 5688436 6.2 76 steel CANTERBURY REGIONAL COUNCIL 4.2 - 6.2 water level observation 1 25/02/2009 25/02/2009 K37/1807 2404602 5697053 24 150 steel MR & MRS A & J M STRACHAN 22.5 - 24 domestic, stock 1 22/04/2004 22/04/2004 K37/1880 2393540 5702802 100.5 150 steel ROLLINSON FARMS LIMITED 94 - 100.5 domestic, stock 1 29/01/2009 29/01/2009 K37/1908 2404065 5686741 24 150 steel MR R I C MACKENZIE 22.5 - 24 domestic, stock 2 12/08/2004 23/02/2009 K37/1939 2404553 5694782 39.15 150 steel A D & G M GREENSLADE 37.65 - 39.15 domestic 1 19/08/2004 19/08/2004 K37/1972 2405377 5700174 20 150 steel MR & MRS B & A LESLIE domestic, stock, irrigation 1 26/04/2004 26/04/2004 K37/1997 2390980 5704407 159 300 steel MR & MS A & B M MORRISON 129 - 159 domestic, stock, irrigation 1 19/02/2009 19/02/2009 K37/2126 2402309 5694130 11.88 150 steel MR & MRS D N & M M HASTINGS 10.88 - 11.88 domestic 1 29/04/2004 29/04/2004 -

K37/2133 2397985 5696353 48 150 steel MR & MRS P D & J M SHEEHAN 46.5 - 48 domestic, stock 1 10/02/2009 10/02/2009 Ashburton K37/2151 2403706 5685876 94.85 300 steel Mr R I C MacKenzie 58.5 - 94.85 irrigation 1 25/02/2009 25/02/2009 K37/2153 2404385 5683300 87 300 steel J D & C M McKenzie Ltd 56.7 - 87 irrigation 1 9/04/2009 9/04/2009 K37/2156 2406107 5692210 10 51 steel M Barltrop domestic 1 26/07/2004 26/07/2004

K37/2159 2395413 5700106 64.41 300 steel Woodside Dairying Limited 59.41 - 64.41 irrigation 1 29/01/2009 29/01/2009 - Hinds plain Hinds K37/2227 2405152 5679810 94.84 300 steel LONGBEACH ESTATE LIMITED 91.84 - 94.84 irrigation 1 28/04/2009 28/04/2009 EIFFELTON COMMUNITY IRRIGATION K37/2232 2402666 5685273 57.8 300 steel SCHEME 48.3 - 57.8 irrigation 1 8/03/2006 8/03/2006 K37/2242 2403610 5701300 20 51 steel ROSS D A domestic 1 26/04/2004 26/04/2004

K37/2244 2407299 5699389 22 150 steel HARVEY I domestic, irrigation 1 27/04/2004 27/04/2004 K37/2245 2406530 5700850 6 200 steel CORNELIUS BR & BV domestic, stock 1 27/04/2004 27/04/2004 K37/2246 2402250 5703560 12 51 ROSS DA domestic 1 27/04/2004 27/04/2004 47 K37/2253 2405833 5698196 8 51 steel TARBOTTON M E domestic 2 29/04/2004 28/07/2004

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/2254 2403386 5696867 22 100 steel PATERSON R W & E M domestic, stock 1 29/04/2004 29/04/2004 K37/2297 2392808 5697577 4 51 MULLIGAN A domestic 1 13/07/2004 13/07/2004 K37/2299 2400533 5706300 4 38 steel BLAIR AJ & JM domestic 1 14/07/2004 14/07/2004 K37/2301 2402115 5702430 25 150 steel WALLS PM domestic 1 15/07/2004 15/07/2004 K37/2302 2386830 5705230 8 51 TAIT A domestic 1 15/07/2004 15/07/2004 K37/2303 2401805 5693512 48 150 steel WINSLOW FEEDS LIMITED 45 - 48 domestic, stock, irrigation 2 11/02/2009 23/11/2009 K37/2307 2399417 5707368 6 100 steel ROBINSON RW domestic 1 20/07/2004 20/07/2004 K37/2310 2404258 5691189 5 76 steel A & A Wilson domestic 1 26/07/2004 26/07/2004 K37/2311 2394124 5694646 11 150 steel MOWAT A domestic 1 27/07/2004 27/07/2004 K37/2313 2403980 5685610 10 76 steel S Pattison domestic 1 5/08/2004 5/08/2004 K37/2314 2404500 5684640 9 51 steel J Scott domestic 2 5/08/2004 25/02/2009 K37/2315 2401720 5684850 7 51 steel G Deal domestic 1 5/08/2004 5/08/2004 K37/2316 2405430 5682360 15 51 steel G Mathews domestic 1 5/08/2004 5/08/2004

Environment CanterburyTechnical Report K37/2317 2401990 5681180 13 51 steel G Barwell domestic 1 5/08/2004 5/08/2004 K37/2318 2402600 5680000 6 51 steel DJ & VM Strong domestic 1 5/08/2004 5/08/2004 K37/2322 2401160 5683490 5 150 steel R F Wilson domestic 1 12/08/2004 12/08/2004

K37/2323 2403950 5686750 5.2 76 steel R I C MacKenzie domestic 1 12/08/2004 12/08/2004 -

Ashburton K37/2325 2409090 5689650 10 76 steel M & T Skevington domestic 1 18/08/2004 18/08/2004 K37/2333 2408296 5696406 10 51 steel J Cain domestic 1 26/08/2004 26/08/2004 K37/2384 2401467 5693942 18 150 steel Mr & Mrs GN & RB Ashton 16.5 - 18 domestic 1 11/02/2009 11/02/2009 K37/2390 2402540 5685190 10 51 R M Gray domestic 6 30/11/2004 28/06/2006 - Hinds plain Hinds K37/2542 2394816 5702072 66 150 steel MR & MRS RM & CA GREER 64.5 - 66 domestic, stock 1 29/01/2009 29/01/2009 K37/2728 2403463 5690521 60 300 steel MR & MRS I R & R D MOORE 57 - 60 domestic, stock, irrigation 1 11/02/2009 11/02/2009 K37/2750 2388832 5708389 131.08 250 steel MOONSHINE FARMS LTD 113.22 - 131.08 irrigation 1 22/01/2009 22/01/2009 K37/2751 2390504 5708733 274.94 300 steel MOONSHINE FARMS LTD 250.88 - 268.92 irrigation 1 27/01/2009 27/01/2009 K37/2774 2404150 5686050 53 150 steel MR & MRS M R & S C HYDE 51.5 - 53 domestic, stock 1 24/02/2009 24/02/2009 K37/2871 2401801 5693318 100.64 300 steel ROSS YOUNG LIMITED 92.61 - 100.64 irrigation 2 19/02/2009 23/11/2009 K37/2905 2403513 5690650 48 300 steel MR D P SAUNDERS 42 - 48 irrigation, domestic, stock 1 11/02/2009 11/02/2009

Environment CanterburyTechnical Report

Use Owner (m bgs) samples Nitrate contamination groundwater and chemistry Depth (m) NZMG East NZMG North Well Number Water quality Last sampled First sampled Diameter (mm) Screen interval Casing material K37/2960 2396493 5698057 107.4 300 steel Ian Hopping 101.3 - 107.3 irrigation 1 28/04/2009 28/04/2009 K37/3016 2394341 5703358 124.4 200 steel KANUKA SYNDICATE LIMITED 118.38 - 124.4 domestic, stock 1 28/01/2009 28/01/2009 domestic, stock, dairy, K37/3150 2395802 5702210 129.5 300 steel MR B GOSLING 123.5 - 129.5 irrigation 1 29/01/2009 29/01/2009 K37/3156 2403923 5685582 29 150 steel MR & MRS P A & A M CUSHNIE 27.5 - 29 domestic, stock 1 24/02/2009 24/02/2009 K38/2244 2406344 5679769 39.55 300 steel RAYNHAM DAIRIES LIMITED 33.55 - 39.55 irrigation, dairy, stock 1 22/04/2009 22/04/2009 L37/0379 2410486 5681937 18 125 steel CHALMERS R G 17 - 18 domestic 1 21/07/2004 21/07/2004 L37/0711 2410407 5690693 23.37 150 steel SKEVINGTON, J.W.& J.A. 22.37 - 23.37 domestic 1 18/08/2004 18/08/2004 L37/0794 2410384 5693016 35 150 steel MILLAR, DA 33.5 - 35 domestic, stock 1 24/08/2004 24/08/2004 L37/0852 2411470 5686205 24 150 steel WILLIAMSON, LE 22.5 - 24 domestic 1 21/07/2004 21/07/2004

L37/1187 2410626 5693765 71.5 300 steel RIVERSDALE PASTURES LTD 63.5 - 71.5 domestic, stock, irrigation 1 24/08/2004 24/08/2004 L37/1356 2410420 5690106 10 100 PVC McGrath, T J domestic 1 26/07/2004 26/07/2004 -

Ashburton - Hinds plain Hinds

Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Appendix 3: Summary of 2004 investigations, sampling procedure and determinands analysed

1. Summary of investigations

1.1 Tinwald investigation - autumn As reported by Abraham and Hanson in 2004, a groundwater quality survey was conducted in the Tinwald area in April 2004, in response to the high nitrate nitrogen concentrations observed in annual survey wells K37/0147 and K37/0358. Groundwater samples were collected from 25 wells, and nitrate nitrogen concentrations ranged from 0.2 to 16.8 mg/L. Samples from 14 of the 25 wells had nitrate nitrogen concentrations greater than or equal to the MAV, and these wells were located within a zone approximately 2 km wide and 7 km long (Figure 3.2). Most of the samples with lower concentrations were collected from outside this zone. 1.2 Ashburton-Hinds plain investigation - winter The Tinwald investigation did not delineate the full extent of the nitrate contamination in the Tinwald area, so a broader investigation of groundwater quality across the entire Ashburton-Hinds plain was conducted in July and August of 2004. In this survey, 96 wells were sampled. For the most part, the survey targeted relatively shallow wells, where nitrate nitrogen concentrations were expected to be highest. The wells ranged in depth from 2 m to 116 m, with 78 of them (approximately 80%) less than 30 m deep, and 18 of them more than 30 m deep. Five of the wells (K37/0147, K37/0358, K37/0810, K37/2253 and K37/0490) had also been sampled in the April 2004 Tinwald investigation. 1.3 Annual survey - spring In 2004, Environment Canterbury’s annual regional groundwater quality survey included eight wells on the Ashburton-Hinds plain. Seven of the wells (K36/0118, K37/0147, K37/0216, K37/0358, K37/0468, K37/0619 and K37/0833) had been sampled in previous annual surveys dating back as far as 1991 (Appendix 1). The eighth well, K37/2390, was a new addition to the survey in 2004, and it is discussed further in Section 4.1.2. The wells ranged in depth from 9 to 18 m, except for K37/0619 which was 55 m deep. 1.4 Resource consent monitoring – autumn, winter and spring Apart from the two investigations and the annual survey discussed above, the only other groundwater samples collected from the Ashburton-Hinds plain in 2004 came from two wells that were sampled as a condition of a resource consent. The consent authorises the taking and use water for the irrigation of a dairy farm near the centre of the Ashburton-Hinds plain. The consent conditions required the installation of two monitoring wells, one (K37/1748) upgradient of the farm and one (K37/1749) downgradient of the farm (Figure 3.1). Environment Canterbury consents monitoring staff collected quarterly groundwater samples from these wells in May, August and November 2004, with the exception that the downgradient well, K37/1749, was not sampled in November because the well was dry.

2. Final dataset In total, 121 wells on the Ashburton-Hinds plain were sampled at least once by Environment Canterbury in 2004. Seven of the wells were sampled in both the autumn and winter, six were sampled in both the winter and spring, and three were sampled in all three seasons. The analytical results from all of the samples are listed in Appendix 1, and well construction details are listed in Appendix 2. Overall, nitrate nitrogen concentrations ranged from less than 0.1 mg/L to 22.4 mg/L. Where samples were collected from the same well more than once in the year, the nitrate nitrogen concentrations were generally similar between the samples, but there were some differences. The greatest differences were in the results from annual survey well K37/0147, which had concentrations of 13.5, 7.8 and 18.4 mg/L in the autumn, winter and spring samples, respectively. This is a range of 10.6 mg/L between the highest and lowest concentration.

50 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Wells K36/0118 and K37/0216 had differences of 2.4 and 2.7 mg/L, respectively, between samples collected in the winter and spring. The three samples from well K37/0358 had differences of 1.5 mg/L, from 13.0 to 14.5 mg/L. For all of the other wells with more than one sample, the concentrations differed by less than 1 mg/L.

3. Sampling procedure and determinands analysed All samples were collected following Environment Canterbury's procedure EMQ-G002-02, Collection of Groundwater Quality Samples (Appendix 3). To ensure that the samples represented ambient groundwater quality, each well was purged by pumping at least three well volumes of water prior to sample collection. Where possible, the water level in the well was measured prior to purging. Conductivity, pH, and dissolved oxygen content were monitored in the field during purging (except for the two consent monitoring wells, K37/1748 and K37/1749), and the sample was collected after the readings stabilised. Samples were analysed at Environment Canterbury’s laboratory for nitrate nitrogen, ammonia nitrogen, major anions and cations, pH, and conductivity. Some samples were also analysed for total kjeldahl nitrogen (TKN), while the samples from the two consent monitoring wells, K37/1748 and K37/1749, were analysed only for nitrate nitrogen and E. coli. A complete list of determinands, analytical methods, and detection limits is provided in Table A3-1. Cation samples (including samples for iron and manganese) were filtered in the field using a 0.45- micron filter and collected in acid-preserved plastic bottles. Samples for anions and ammonia were not filtered in the field and were collected in un-preserved plastic bottles.

Environment Canterbury Technical Report 51 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Appendix 4 Procedure G002_02 - Collection of Groundwater Quality Samples

52 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Environment Canterbury Technical Report 53 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

54 Environment Canterbury Technical Report Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

Environment Canterbury Technical Report 55 Nitrate contamination and groundwater chemistry - Ashburton-Hinds plain

56 Environment Canterbury Technical Report