Proposed Additions to South Canterbury Groundwater Allocation Zones Report No

Proposed Additions to South Canterbury Groundwater Allocation Zones Report No. R08/42 ISBN: 978-1-86937-835-6

Mike Thorley Philippa Aitchison-Earl Jen Ritson Shirley Hayward

August 2008

Report R08/42 ISBN: 978-1-86937-835-6

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

75 Church Street PO Box 550 Timaru Phone (03) 688 9069 Fax (03) 688 9067

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

Proposed Additions to South Canterbury Groundwater Allocation Zones

Executive Summary

The South Canterbury area from Timaru to the Waitaki River currently includes seven groundwater allocation zones in the Proposed Natural Resources Regional Plan (PNRRP). Groundwater abstractions are becoming more common in the Cannington Basin (inland Pareora River) and Timaru areas, which are not currently covered by any of those groundwater allocation zones. In addition, submissions to Variation 4 of the PNRRP have raised the issue of the Timaru area not being part of a groundwater allocation zone.

Environment Canterbury (ECan) is also currently involved in an Integrated Catchment Management (ICM) and Environmental Flow Regime process together with the local community that addresses flow regimes and water allocation for the Pareora River.

This report discusses the options for groundwater allocation, and recommends the creation of two new groundwater allocation zones: Cannington Basin and Timaru. Changes to the existing Pareora groundwater allocation zone are also recommended.

In catchments with a high proportion of groundwater dependant surface flows and surface water abstraction, there is a risk that over allocation of groundwater could cause reductions in baseflow for dependant tributary streams and main stem waterways. These are the major issues when evaluating sustainable groundwater allocation for the proposed Cannington Basin groundwater allocation zone and the connection with the Pareora River. The current surface water and hydraulically connected groundwater allocation for the Pareora River exceeds the interim allocation block calculated for Schedule WQN2 and Policy WQN14 by over 350%. Any further allocation of surface water or significant groundwater takes will reduce flow reliability for existing users and exacerbate detrimental effects of dry reaches and prolonged low flows on instream values.

The proposed Pareora groundwater allocation zone revises the zone boundary by excluding the Pig Hunting Creek catchment area to the north because the Pig Hunting Creek catchment is hydraulically connected to the Timaru area rather than the Pareora River valley. As a result, the groundwater allocation limit is revised downwards. The existing Pareora groundwater allocation zone is more than fully allocated and the proposed revision exacerbates its existing allocation status by approximately 10%.

The proposed Timaru groundwater allocation zone encompasses the area from the northern margin of the lower Pareora River catchment to the southern margin of the Oakwood Stream and Washdyke Creek/Lagoon catchment. Although there is no allocation limit to this area currently, the volume of groundwater allocated is equivalent to fifty percent of land surface recharge (LSR). This report proposes a limit of 4,240,333, meaning the zone is currently less than fully allocated (50.8%).

Environment Canterbury Technical Report 1 Proposed Additions to South Canterbury Groundwater Allocation Zones

2 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

Table of Contents

Executive Summary ...... 1

1 Introduction ...... 5

2 Cannington Basin ...... 6

3 Timaru Zone ...... 9

4 Land surface recharge calculations...... 11

5 Stream recharge/discharge...... 15 5.1 Cannington Basin...... 15 5.1.1 Minimum flows ...... 19 5.1.2 Surface water allocation block ...... 20 5.1.3 Current surface water allocation ...... 20 5.1.4 Reliability of supply ...... 20 5.1.5 Impacts on instream values ...... 21 5.2 Timaru Zone...... 22

6 Proposed groundwater allocation limits...... 23 6.1 Cannington Basin...... 23 6.2 Timaru and Pareora...... 24 6.3 Current groundwater allocation...... 24

7 Further considerations...... 26

8 Main recommendations summary ...... 27

9 Acknowledgements ...... 27

10 References...... 28

Appendix 1: Historic surface water takes used to naturalise the flow record....29

Appendix 2: Current surface water and groundwater takes in the Pareora catchment (where no rate is given for a groundwater take, it is not considered to be hydraulically connected) ...... 30

Environment Canterbury Technical Report 3 Proposed Additions to South Canterbury Groundwater Allocation Zones

List of Tables Table 2.1: Hydrogeology in the Cannington Basin (adapted from Aitchison-Earl et. al., 2006; GNS, 2006)...... 6 Table 4.1: Summary of calculated mean annual land surface recharge ...... 12 Table 5.1: All surface water inflows (L/s) into the Upper Pareora Catchment between the Upper Gorge and the Lower Gorge, measured on five occasions ...... 17 Table 5.2: All surface water inflows (L/s) into the Upper Pareora catchment between the Lower Gorge and Evans Crossing, measured on five occasions...... 18 Table 5.3: All surface water inflows (L/s) into the Upper Pareora catchment between Evans Crossing and the Huts recorder, measured on four occasions ...... 18 Table 6.1: Summary of Groundwater Abstractions...... 23 Table 6.2: Summary of recharge estimates for land-surface and surface water for Cannington Basin ...... 24 Table 6.3: Summary of recharge estimates for land surface and surface water for South Canterbury Zones ...... 24 Table 6.4: Summary of current and proposed allocation in South Canterbury Groundwater Allocation Zones (August 2008)...... 25

List of Figures Figure 1.1: Location of existing groundwater allocation zones and groundwater takes ...... 5 Figure 2.1: Geological map of the Cannington Basin area (from GNS, 2006)...... 7 Figure 2.2: Schematic geological cross sections of the Cannington Basin (Cross section locations shown in Figure 2.1)...... 8 Figure 3.1: Geological map of the Timaru area...... 10 Figure 4.1: Location of irrigated land parcels...... 11 Figure 4.2: Calculated mean annual dryland drainage (land surface recharge)...... 13 Figure 4.3: Calculated mean annual dryland and irrigated drainage (land surface recharge)...... 14 Figure 5.1: Location of gaugings sites in the Cannington Basin...... 15 Figure 5.2: Hydrograph for Pareora River at Huts Recorder (Site number 70105) during period of concurrent gaugings (marked by pink squares)...... 16 Figure 5.3: Changes in flow in the Pareora River downstream from the Upper Gorge to the Huts Recorder...... 16 Figure 5.4: Loss and gain in flow in the Pareora River downstream from the Upper Gorge to the Huts Recorder...... 17 Figure 5.5: Regression of the percentage contribution groundwater to flow at the Huts Recorder ...... 19 Figure 5.6: Flow exceedance curve for Pareora River at Huts Recorder (1982-2008 irrigation season) showing the level of current surface water takes below the Huts Recorder.. 21

4 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

1 Introduction The South Canterbury area from Timaru to the Waitaki River is currently divided into a number of groundwater allocation zones in the Proposed Natural Resources Regional Plan (PNRRP). These include the following: Pareora, Otaio, Makikihi, Hook, Waimate, Waihao, and Whitneys Creek (Thorley and Ettema, 2007). Groundwater abstractions are becoming more common in the Cannington Basin (inland Pareora River) and Timaru areas, which are not currently covered by a groundwater allocation zone (Figure 1.1). Submissions to Variation 4 of the PNRRP have raised suggested that the Timaru area should be assigned to a groundwater allocation zone. Aitchison-Earl and Thorley (2008) provided an initial technical response to these submissions, and that report provided further discussion on the issues raised by submitters.

Consent applications to take groundwater from deep strata in the Cannington Basin area are currently being processed. The potential environmental effects of the proposed takes on Pareora River flows are of primary concern (Ritson and Horrell, 2008).

Figure 1.1: Location of existing groundwater allocation zones and groundwater takes

Environment Canterbury Technical Report 5 Proposed Additions to South Canterbury Groundwater Allocation Zones

2 Cannington Basin

The geology of the Cannington Basin area is mapped in two 1:250 000 scale maps sheets (GNS, 2006). The geology in the Cannington Basin area is shown in Figure 2-1, and schematic cross sections of the geology in Figure 2-2. The extent of the proposed Cannington Basin groundwater allocation zone is derived using geological boundaries and the Pareora River catchment boundary and is shown in Figure 2-1.

A synclinal feature is mapped through the Cannington Gravels in the Basin, running approximately north-south in orientation. Other faults may exist within the basin that do not have a surface expression.

Aquifers are known to occur in several units in South Canterbury, as outlined in Table 2-1. In the Cannington Basin, wells tap both Quaternary gravels and Cannington Gravels and one well taps the White Rock Formation. Outside of this area, in the South Branch Pareora, two wells intersect the Taratu Formation (locally known as the Broken River Formation, the basal terrestrial part of the Onekakara Group).

Table 2.1: Hydrogeology in the Cannington Basin (adapted from Aitchison-Earl et. al., 2006; GNS, 2006)

Strata Typical Description

Sandy gravels with varying quantities of silty/clay. Quaternary Alluvium May be overlain by silty deposits near the coast.

Cannington Yellow-orange/brown rusty or weathered clay Terrestrial bound gravels and sands. Cannington Blue-grey well rounded gravels and sands with Gravels seashells present in many deposits. Higher yielding Cannington aquifers occur in the more gravel dominated layers. Beach/Marine Aquifers can be interbedded with swampy deposits of green-blue silts, clays and sands. Southburn Sand Grey running sand (occasional gravels) and shells. Small quartz gravels, shells and sand with silt. The Taratu Formation presence of lignite is indicative of Taratu Formation. Weak claystone, siltstone and sandstone with minor White Rock Formation conglomerate and scattered lignite seams.

6 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

GEOLOGICAL LEGEND

Fan deposits Fluvial deposits Anthropic and swamp deposits Loess Beach deposits Material placed for hydroelectric Q1-2a Mn_w Q1n and port works; dredge and E Pl_kc mine tailings (Q1n). N Q2a Boulders, gravel, sand, silt and clay forming Deposits of sand and gravel on mQa er sloping alluvial fans and grading into scree Q1f Q1a Gravel, sand and mud of modern and Q1b beaches, seaward of 6000yr seacliff Q2a Q1-2a emQa Mn_w iv postglacial flood plains (Q1a). CE R and valley alluvium (Q1f). (Q1b). LO Q1a ai Boulders, gravel, sand and clay forming w Gravel, sand and silt of low river terraces sloping low alluvial fans (Q2f). Q2f Q2a HO Pl _kc Q1f (Q2a). Yt2A eMn enga Q2a Ee_w T Undifferentiated Late Quaternary fan deposits Q2a Pl_kc Q1a (lQf). lQf Q1-2a Boulders, gravel, sand and clay Gravel, sand and silt of low river terraces with Q1-2a forming sloping low alluvial fans Q4f Q4a patchy loess cover (Q4a). mQa mQa Q6a (Q4f). Undifferentiated Quaternary fan Slightly weathered and cemented gravel of Q1-2a deposits (uQf). Q5a alluvial terraces at Waikouaiti and Shag river Mn_w eMk estuaries (Q5a). Slightly weathered gravel and sand Slightly weathered gravel and sand in alluvial At least 2 loess layers in upward- eMn in sloping alluvial fans (Q6f). uQf Q6f Q6a terraces with some loess cover (Q6a). building "loess-scape" away from Q6e fluvial influence (Q6e).

mQa Moderately to highly weathered Moderately to highly weathered brown gravel RY piedmont fan gravels overlain by up eMk eMk mQf mQa in highly weathered sandy matrix, overlain by Q1-4a to 3 loesses (mQf). up to 3 loesses (mQa). Pl_kc E Q2a Weathered gravel forming high ERNA More than 2 loess layers in upward- T sloping fans (Q8f). Q8f Q8a Weathered gravel and sand in alluvial building "loess-scape" away from Q8e terraces with loess cover (Q8a). fluvial influence (Q8e). Mn_w eMk OCEN Q1-4a QUA Yt1 eMn ST eMn Multiple yellow and brown loess layers Yt2A EI with interbedded paleosols and peat; mQe eMk Ee_w Weathered gravel in high alluvial Weathered gravel and sand in alluvial may span much of mid and late PL Pl_kc Q1-4a fans (Q10f). Q10f Q10a terraces with loess cover (Q10a). Quaternary in age (mQe). eMk lPlt mQe Q12a Weathered gravel and sand in highest alluvial Ee eMn terraces (Q12a). eMk Q4f Q1-2a Yellowish brown, highly eMkMo eQa weathered, river gravel, eMk Plkc Q2a Plkc sand and silt (emQa, eQa).

mQf Plkc Mo REGIONAL UNCONFORMITY Q2a mQf P lPlt areo COASTAL OTAGO AND CANTERBURY ra Q2a R TIMARU BASALT: Olivine and hypersthene basalt i eMk mQe ## Plkc ve Yt2A lPlt Pl_kc KOWAI FORMATION: Deformed brown weathered greywacke r in several flows in Timaru area (lPlt), extending ## slightly offshore (lPlt~). ### Plkc gravel; local names Cannington Gravel (Pl_kc, Plkc), Elephant Q4f Plkc Q1a ##lPlt~ # Hill Gravel (Plke); marine at base (Makikihi and Timaru). NE A' E # # # Plke A Plkc C O

Mo mQe Mo I lPlt UNCONFORMITY PL Mo eMk E

Q2a Ytv2A eMk EN C O WHITE ROCK COAL MEASURES Weak claystone, Siltstone, sandstone, limestone and MI siltstone and sandstone with minor conglomerate Mn_w Mo carbonaceous mudstone (Mo). OTAKOU GROUP P and scattered lignite seams (Mn_w). a Calcareous greensand and cemented eMk KEKENODON re bioclastic limestone (eMk). mQe Q2fPlkc GROUP Plkc or E Y a Q2a N R R MARSHALL REGIONAL PARACONFORMITY E A C r iv I Ee Ee e e T R iv r Q8e GO eMk LI R TE mQe Mo Q1a O a Marine pale grey silty quartz sandstone; olive grey fine sandy EYRE r siltstone or mudstone; medium to dark green quartz sandstone; GROUP mQe Ee o Ee Ee_w pale coloured, fine grained muddy limestone (Ee_w). Plkc re a Marine micaceous sandstone and mudstone, glauconitic B' sandstone and mudstone, marl and impure limestone (Eo). mQe P Eo South of the Waitaki River (KOom(eo)). h Ee eMk KOom(eo) mQf c Note: Eyre and Onekakara are equivalent units lQf n CENE a in Otago and Canterbury. Yt2A EO mQe r Q4a ONEKAKARA B BROKEN RIVER FORMATION: Non-marine quartz sand with GROUP Yti h Eeb clay matrix, lignite seams and carbonaceous mudstone; Plkc t limonite and silica cemented; north of Waitaki River (Eeb). Q2a Ee u E N

o TARATU FORMATION: Non-marine quartz sand E

Plkc S and conglomerate with clay matrix, lignite seams C Ee mQf KEot(e) and carbonaceous mudstone; limonite and silica O Ee cemented; south of Waitaki River (KEot(e)). LE A

mQe S mQf P B Mo U

CEO Plkc A

REGIONAL UNCONFORMITY CRET

Q4a C Yt1 Mo I Ee S eMk Mo Q6e S Q6e A

Q4a R Q1a Eeb JU eMk Q6e IC

Q1a Q4a S Ee S mQf mQe IA

Eeb Q4a Mo TR

Q2a Yti mQf RAKAIA TERRANE: Quartzofeldspathic sandstone ("greywacke") interbedded with mudstone ("argillite") (Yt1); Yt1 volcanic horizons (Ytv, Ytv2A) and thicker mudstone units (Yti). mQe Semischist and schist from this protolith (Yt2A, Yt2B). N A Yt2A Mainly Permian age with some Carboniferous and Triassic. I Ytv2A Ytv M mQf Plkc Q4a PER Yt2A Plkc Yt2B

Figure 2.1: Geological map of the Cannington Basin area (from GNS, 2006). Cross sections A-A’ and B-B’ are shown in Figure 2.2. The red polygon shows the proposed boundary for the Cannington Basin groundwater allocation zone. In the north, the boundary follows the margin of the Pareora River and Te Ngawai catchments. In the east and west, the boundary is defined by the mapped extents of the Cannington and Quaternary gravels. In the southwest, the boundary follows the Pareora River catchment boundary, and in the southeast, it follows the contact between the Tertiary and Quaternary strata.

Environment Canterbury Technical Report 7 Proposed Additions to South Canterbury Groundwater Allocation Zones

400 m A’ Timaru A Loess Basalt White Cannington 300 m Rock Ca nni River Pareora Burnett Taiko ngto 9/0429 G n River St0 ream Stream rave J3 ls 0231 200 m J39/023 J39/ J39/0701 J39/0496 O n e k O a t Otakau Group Greywacke k a a k r K a 100 m a u Cannington e G k G r e r Gravels o n o u o u p d p o n

0 G r o u p

0 3 6 9 12 15 18 km

B B’ O n ek 300 m a k a O Maungati South r ta a k Branch G a u ro Pareora u G Cannington Gordons p ro K 200 m u Gravels e Stream p ke On no eka do kara n G Cannington Gr ro oup up Gravels 100 m Greywacke

Otakau Group 0 Greywacke

-100 m

0 369 1215 18 km Figure 2.2: Schematic geological cross sections of the Cannington Basin (Cross section locations shown in Figure 2.1).

The cross sections (Figure 2.2) show the Cannington Basin as a fault bounded structure with outcropping greywacke basement (blue on map) to the west and up thrust greywacke/Tertiary sediments to the east, where the North Branch of the Pareora River enters the Lower Pareora Gorge. Within the basin, the greywacke is overlain by a sequence of mainly marine Tertiary sediments, including the Onekakara Group (olive-brown), Kekenodon Group (dark orange on map and in cross section – includes Otekaike Limestone) and the Otakau Group (lighter orange on map and cross section). The Tertiary Units are overlain by the Cannington Gravels (equivalent of the North Canterbury Kowai Formation), a Pliocene-Pleistocene deposit (peach colour on map and cross section). The Timaru Basalt (dark pink) overlies this in the far east of the area. Recent Quaternary gravels (light yellow – not shown on cross section) are deposited in river valleys, and Quaternary loess (dark yellow) caps much of the area, obscuring the underlying deposits.

The geological structure indicates that any groundwater within older gravels/Tertiary units would most likely flow with the direction of dip, and topography – from the west to the east. The presence of the up thrust greywacke basement in the east is likely to provide a barrier to groundwater flow, so that any groundwater would be expected to discharge upwards. To the north of the cross section line A-A’ it is possible that another basin exists which may partly discharge to the north (Te Ngawai).

Environment Canterbury Technical Report 8 Proposed Additions to South Canterbury Groundwater Allocation Zones

3 Timaru Zone The geology in the Timaru area is characterised by an extensive basaltic sheet deposit, the ‘Timaru Basalt’ (dark pink on map, symbol IPlt). This Pliocene age rock was extruded subaerially from a vent near Mt Horrible, over a 1-2o southeast slope. The basalt is overlain by Quaternary loess of varying thickness. Cannington Gravel deposits underlie the basalt, and are terrestrial in nature in upper layers, but marine based beds are found at greater depths (Aitchison-Earl, 2005). Aquifers are found in the terrestrial and marine parts of this formation, but the marine units tend to have greater yields. Underlying the Cannington Gravels is the same sequence of Tertiary age units as described for the Cannington Basin. However, these are at greater depths (the Cannington Gravel is > 180 m thick at Timaru, (Gair, 1962)) in the Timaru area such that groundwater from these units is not presently utilised.

The direction of deep groundwater flow is unknown in the Timaru area, due to lack of water level data. However, we have assumed that the groundwater flow direction generally follows topography.

The proposed Timaru groundwater allocation zone is almost wholly capped by loess, which is underlain by the Timaru basalt. This in part, provides a geological basis for defining the zone boundary. It was considered that the Oakwood Creek catchment is likely to contribute recharge toward the north-east rather than the south-east, so it has been excluded from the proposed Timaru groundwater allocation zone.

The southern and south-western boundary of the proposed Timaru groundwater allocation zone is based on the surface water catchment of Pig Hunting Creek, which is entirely included in the Timaru zone. This would require a change in the current Pareora groundwater allocation zone, with the boundary altered to the south, reducing the size of the current zone. The northern boundary is based upon the catchment boundary of Otipua Creek and Oakwood Stream.

9 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

GEOLOGICAL LEGEND Pl_kc eMn osewill Stream Fan deposits Fluvial deposits Anthropic and swamp deposits Loess Beach deposits R Pl_kc Q2a Material placed for hydroelectric lPlt Q1n and port works; dredge and mine tailings (Q1n). NE Q1-4a Q1-4a Boulders, gravel, sand, silt and clay forming Deposits of sand and gravel on mQe sloping alluvial fans and grading into scree Q1f Q1a Gravel, sand and mud of modern and Q1b beaches, seaward of 6000yr seacliff CE eMn and valley alluvium (Q1f). postglacial flood plains (Q1a). (Q1b). O

Pl_kc L

Q6a Boulders, gravel, sand and clay forming O lPlt Gravel, sand and silt of low river terraces Q6a sloping low alluvial fans (Q2f). Q2f Q2a H Q2a (Q2a). Plkc Q6a Plkc Undifferentiated Late Quaternary fan deposits lPlt Q2a (lQf). lQf k/Lagoon Boulders, gravel, sand and clay Gravel, sand and silt of low river terraces with Mo ashdyke CreQ1eb forming sloping low alluvial fans Q4f Q4a patchy loess cover (Q4a). od Stream W (Q4f). PlkcOakwo Plkc Q2f water Undifferentiated Quaternary fan Slightly weathered and cemented gravel of lPlt deposits (uQf). Q5a alluvial terraces at Waikouaiti and Shag river estuaries (Q5a).

Slightly weathered gravel and sand Slightly weathered gravel and sand in alluvial At least 2 loess layers in upward- Q2a in sloping alluvial fans (Q6f). uQf Q6f Q6a terraces with some loess cover (Q6a). building "loess-scape" away from Q6e Q1a lPlt~ fluvial influence (Q6e). Moderately to highly weathered Moderately to highly weathered brown gravel RY eMk piedmont fan gravels overlain by up in highly weathered sandy matrix, overlain by mQf mQa NA water to 3 loesses (mQf). up to 3 loesses (mQa). E ER Weathered gravel forming high N Plkc k More than 2 loess layers in upward- T tipua Cree E ranch O sloping fans (Q8f). Q8f Q8a Weathered gravel and sand in alluvial building "loess-scape" away from Q8e A North B Q1a C Mo terraces with loess cover (Q8a). fluvial influence (Q8e). U O Q T S Multiple yellow and brown loess layers EI with interbedded paleosols and peat; mQe lPlt Q1n Weathered gravel in high alluvial Weathered gravel and sand in alluvial may span much of mid and late PL Ee mQe fans (Q10f). Q10f Q10a terraces with loess cover (Q10a). Quaternary in age (mQe). Q12a Weathered gravel and sand in highest alluvial eMk lPlt terraces (Q12a). So Yellowish brown, highly uth B eQa ranch Oti weathered, river gravel, pua Creek sand and silt (emQa, eQa). lPlt Q2f Q1a S lPlt~ al REGIONAL UNCONFORMITY Q2f Plkc tw a Q1b Ee te COASTAL OTAGO AND CANTERBURY r C TIMARU BASALT: Olivine and hypersthene basalt r lPlt ## Pl_kc eMk e in several flows in Timaru area (lPlt), extending ## KOWAI FORMATION: Deformed brown weathered greywacke e slightly offshore (lPlt~). ### Plkc gravel; local names Cannington Gravel (Pl_kc, Plkc), Elephant k ### NE lPlt~ Hill Gravel (Plke); marine at base (Makikihi and Timaru). P # # # Plke a Q2f lPlt~ CE

Mo O re I o L Q2a P ra UNCONFORMITY Ee R iv P e ig E r H N un E tin g WHITE ROCK COAL MEASURES Weak claystone, Siltstone, sandstone, limestone and C water MIOC r siltstone and sandstone with minor conglomerate Mn_w Mo carbonaceous mudstone (Mo). OTAKOU GROUP ee and scattered lignite seams (Mn_w). k Calcareous greensand and cemented Q1a Q8e eMk KEKENODON lPlt bioclastic limestone (eMk). GROUP E Y N R MARSHALL REGIONAL PARACONFORMITY E C IA O T R G LI TE O Marine pale grey silty quartz sandstone; olive grey fine sandy EYRE siltstone or mudstone; medium to dark green quartz sandstone; GROUP Ee_w pale coloured, fine grained muddy limestone (Ee_w). Marine micaceous sandstone and mudstone, glauconitic sandstone and mudstone, marl and impure limestone (Eo).

Q4a Eo South of the Waitaki River (KOom(eo)). E N KOom(eo) Note: Eyre and Onekakara are equivalent units CE in Otago and Canterbury.

EO mQe ONEKAKARA BROKEN RIVER FORMATION: Non-marine quartz sand with GROUP Eeb clay matrix, lignite seams and carbonaceous mudstone; limonite and silica cemented; north of Waitaki River (Eeb). E

N TARATU FORMATION: Non-marine quartz sand E and conglomerate with clay matrix, lignite seams KEot(e) and carbonaceous mudstone; limonite and silica cemented; south of Waitaki River (KEot(e)). Mo Q4a LEOC Q4a A P US Q6e EO

Q6e ET R water REGIONAL UNCONFORMITY C mQe C I

S S

Mo A Q1a R Q2a JU IC S

Q2a IA

Yti Plkc RAKAIA TERRANE: Quartzofeldspathic sandstone ("greywacke") interbedded with mudstone ("argillite") (Yt1); mQe Yt1 volcanic horizons (Ytv, Ytv2A) and thicker mudstone units (Yti). Semischist and schist from this protolith (Yt2A, Yt2B). N A Mainly Permian age with some Carboniferous and Triassic. I Ytv2A Ytv Q4a RM PE mQe Plkc Yt2A Yt2B Q4a

Figure 3.1: Geological map of the Timaru area. The red polygon shows the proposed Timaru groundwater allocation zone. The proposed allocation zone boundary follows the margin of Oakwood Creek and Otipua Creek catchments in the north. In the west, the boundary is defined by the catchments of Otipua Creek and Pig Hunting near the western extents of the Timaru Basalt. The southern margin of the proposed boundary follows the Pareora River catchment boundary, and loess terrace coastwards of Pareora Township. The coastline defines its eastern margin. From GNS (2006).

Environment Canterbury Technical Report 10 Proposed Additions to South Canterbury Groundwater Allocation Zones

4 Land surface recharge calculations Land surface recharge was estimated for the recommended revision to the Pareora groundwater allocation zone, and the proposed Cannington Basin and Timaru groundwater allocation zones. The procedure described in Thorley and Ettema (2007) was followed to calculate land surface recharge. This involved the mapping of irrigated land parcels, soil profile available water, categories of slope, and geological units. These spatial elements were used to create distinctive ‘hydrological parcels’ which were used as inputs for the land surface recharge model (Scott, 2004, modified in Thorley and Ettema, 2007). This includes the description of limited drainage through loess deposits (constrained to 3 mm/day). The spatial coverage of loess deposits ranged from 25% (Cannington Basin zone) to 77% (Timaru zone). The layer of irrigation parcels used in Thorley and Ettema (2007) was updated to account for those within the proposed Timaru Zone (Figure 3-1) using information from the ECan Consents Database. Other layers used are identical to those described in more detail in Thorley and Ettema (2007).

Figure 4.1: Location of irrigated land parcels

The results of the soil water balance modeling are displayed in Table 4.1. As in Thorley and Ettema (2007), recharge under loess soils is limited by low permeability, thus reducing mean annual dryland recharge. The ‘excess drainage’ is the balance between the unconstrained land surface recharge and constraining land surface recharge to 3 mm/day. The excess component of the land surface recharge is thought to be an approximate description of the surface water runoff in the loess dominated areas of the catchments. The soil water balance model used daily rainfall and potential evapotranspiration data from January 1972 to June 2006.

Environment Canterbury Technical Report 11 Proposed Additions to South Canterbury Groundwater Allocation Zones

Table 4.1: Summary of calculated mean annual land surface recharge Proposed groundwater allocation zone Pareora Cannington Basin Timaru Late Quaternary, Timaru Basalt, Kowai Formation Area (ha) 4,632 5,324 2164 Mean annual rainfall (mm) 633 791 650 Dryland drainage (m3/yr x 106) 8.54 14.46 3.32 Equivalent depth increment (mm) 184 272 153 Dryland drainage as % of mean annual rainfall 29% 34% 24% Loess Area (ha) 6,605 3,015 10,568 Mean annual rainfall (mm) 644 824 655 Dryland drainage - Loess (m3/yr x 106) 2.31 1.81 3.88 Equivalent depth increment (mm) 35 60 37 Dryland drainage as % of mean annual rainfall 5% 7% 6% Dryland drainage excess (m3/yr x 106) 8.41 6.56 12.95 Equivalent depth increment (mm) 127 218 123 Dryland excess drainage as % of mean annual rainfall 20% 26% 19% Dryland Drainage - Total Area (ha) 11,237 8,339 12,733 Mean annual rainfall (mm) 637 798 652 Total dryland drainage (m3/yr x 106) 10.85 16.27 7.20 Equivalent depth increment (mm) 97 195 57 Total dryland drainage as % of mean annual rainfall 15% 24% 9% Irrigation - Late Quaternary, Timaru Basalt, Kowai Frm Irrigated area (ha) 1,762 240 346 Recharge increment (m3/yr x 106) 3.17 0.45 0.68 Equivalent depth increment (mm) 180 189 196 Irrigation - Loess Irrigated area (ha) 762 334 913 Recharge increment (m3/yr x 106) 0.37 0.21 0.60 Equivalent depth increment (mm) 48 62 66 Excess increment - Loess (m3/yr x 106) 0.74 0.62 1.20 Equivalent depth increment (mm) 97 185 132 Irrigation - Total Irrigated area (ha) 2,524 574 1,259 Recharge increment (m3/yr x 106) 3.54 0.66 1.28 Equivalent depth increment (mm) 140 115 101 Total Land surface Drainage Mean annual land surface drainage (m3/yr x 106) 14.39 16.93 8.48

The dryland drainage evaluation results in estimates of land surface recharge which vary from 9% (Timaru) to 24% (Cannington Basin) of mean annual rainfall. The higher land surface recharge in the Cannington Basin is mostly due to the lower spatial coverage of loess. Mean annual dryland land surface recharge calculated from the model is illustrated in Figure 4.2, and combined dryland and irrigated recharge is included in Figure 4.3. The pattern of recharge in these figures clearly shows higher dryland recharge across the Quaternary deposits (e.g. Pareora River Valley) compared with the loess deposits (inland Timaru). In addition, higher recharge occurs in the Cannington Basin zone due to the higher rainfall. Under irrigated conditions, the pattern of high recharge on irrigated parcels is superimposed on the dryland pattern. The land surface recharge for the Levels Plain allocation zone has not been recalculated as the boundary change is very minor.

12 Environment Canterbury Technical Report

Propos

Enviro nment C ed Ad di tions toSouth anterb u ry T e ch Canter nical R bury Groun e p o rt dwat er Allo

cation Z o n e s

Figure 4.2: Calculated mean annual dryland drainage (land surface recharge). 13

Proposed Additions to South Canterbury Groundwater Allocation Zones

ge). r a e rech rfac u nage (land s i and irrigated dra l y al dr mean annu ed t Calcula

Figure 4.3:

14 Environment Canterbury Technical Report

Proposed Additions to South Canterbury Groundwater Allocation Zones

5 Stream recharge/discharge

5.1 Cannington Basin The Pareora River (mainstem) and tributaries flow through the Cannington Basin groundwater allocation zone, toward the Lower Gorge, and then through the Pareora groundwater allocation zone to the sea. As discussed in Section 2, the underlying geology of the basin makes it likely that all groundwater recharge will re-emerge at surface.

Five concurrent gauging runs (site locations shown in Figure 5.1) were conducted to illustrate the interaction between surface water and groundwater in the Upper Pareora catchment. The concurrent gauging runs were carried out on: 30/01/08, 10/03/08, 20/03/08, 30/03/08, and 22/04/08 when the flow at the minimum flow monitoring site (Pareora at Huts) was above the first restriction level (400 L/s), see Figure 5.2. The data are summarised in Figure 5.3 and Figure 5.4, and Table 5.1, Table 5.2, and, Table 5.3. The data have not been naturalised for surface water or groundwater abstractions: it is a snap shot of the current situation. Without a detailed knowledge of the surface water / groundwater interaction, it is not possible to naturalise the spot gaugings accurately.

Figure 5.1: Location of gaugings sites in the Cannington Basin

Environment Canterbury Technical Report 15 Proposed Additions to South Canterbury Groundwater Allocation Zones

10000 9000 Huts recorder Spot gaugings 8000 First restriction level 7000 )

s 6000 / L

( 5000

ow 4000 Fl 3000 2000 1000 0 1/01/2008 21/01/2008 10/02/2008 1/03/2008 21/03/2008 10/04/2008 30/04/2008 Date

Figure 5.2: Hydrograph for Pareora River at Huts Recorder (Site number 70105) during period of concurrent gaugings (marked by pink squares).

The changes in flow in the mainstem of the Pareora River are shown in Figure 5.3. There are seven main inflows to the Upper Pareora catchment between the Upper Gorge and the Lower Gorge (some of which were dry at the time of gauging), and an additional two inflows between the Lower Gorge and the Huts Recorder. The approximate locations of these inflows to the mainstem are illustrated in Figure 5.3.

1400 Inflo w Inflo w Inflo w White Inflow Burnett Inflow Taiko 1200 Unnamed Cannington Rock River and stream and Stream (dry) and stream stream Galway (dry) M otukaika and Pareora South 1000 (dry) Pratt and Branch Elworthy (dry) ) s 800 (L/

ow 600 Fl 400

200 Plus emerging 0 groundwater 30/01/2000 8 5 10 15 20 25 30 10/03/2008 Distance downstream from Upper Gorge (km) 20/03/2008 31/03/2008 Gorge Scotts Cannington Cav e Low er Ev ans Huts 22/04/2008 Road Bend Bridge Pareora Gorge Crossing Recorder

Figure 5.3: Changes in flow in the Pareora River downstream from the Upper Gorge to the Huts Recorder

It would appear from Figure 5.3 that surface flow is lost to groundwater as far downstream as Cannington Bridge. However, in order to more clearly illustrate the gains and losses to and from groundwater in the Upper catchment, the inflows have been subtracted from the flow measured at the top main stem site and the initial flow measured at Gorge Road has been set to zero, as shown in Figure 5.4.

16 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

200

) 150 s (L/ 100 ow Fl

n 50 i n i a 0 G 0 5 10 15 20 25 30 nd -50 a

s Average gain in s groundwater of

Lo -100 114 L / s

-1305/01/2008 10/03/2008 Distance downstream from Upper Gorge (km) 20/03/2008 31/03/2008 Gorge Scotts Cannington Cave Low er Ev ans Huts 22/04/2008 Road Bend Bridge Par eor a Gorge Crossing Recorder

Figure 5.4: Loss and gain in flow in the Pareora River downstream from the Upper Gorge to the Huts Recorder

Figure 5.4 shows that surface water is lost to groundwater all the way down the main stem until the river reaches a point between Cave Pareora and the Lower Gorge where there is a significant surface water gain which continues through to Evans Crossing. Table 5.1, Table 5.2, and Table 5.3 examine the differences in accounted flow taking into account the margins of error in the stream flow gaugings.

Table 5.1: All surface water inflows (L/s) into the Upper Pareora Catchment between the Upper Gorge and the Lower Gorge, measured on five occasions

Tributary 30/01/2008 10/03/2008 20/03/2008 31/03/2008 22/04/2008 Pareora River at Gorge 98 ±8 107 ±13 64 ±9 53 ±7 57 ±8 Road Unnamed stream 0 ±0 0 ±0 0 ±0 0 ±0 0 ±0 Cannington Stream 13 ±1 5 ±1 0 ±0 0 ±0 1 ±0 White Rock River 310 ±26 184 ±13 138 ±10 118 ±10 154 ±12 Galway Stream 0 ±0 0 ±0 0 ±0 0 ±0 0 ±0 Burnett Stream 2 ±0 0 ±0 0 ±0 0 ±0 3 ±0 Motukaika River 74 ±8 67 ±6 48 ±6 38 ±5 53 ±7 Pratt and Elworthy Stream 0 ±0 1 ±0 0 ±0 0 ±0 1 ±0 Total 497 ±29 364 ±19 250 ±15 209 ±13 269 ±16 Pareora River at Lower 588 ±39 453 ±29 295 ±21 283 ±20 292 ±20 Gorge Difference 91 ±49 89 ±35 45 ±25 74 ±24 23 ±26 Note: Each individual gauging error is signified by ±X L/s; the cumulative error is calculated by the square root of the sum of the squares of each individual error.

Environment Canterbury Technical Report 17 Proposed Additions to South Canterbury Groundwater Allocation Zones

On each gauging run there is an unaccounted gain (ranging from 23 L/s to 91 L/s, average 64 L/s) at the Lower Gorge (Table 5.1). In all cases except for the last concurrent gauging (on 22/04/08), the gain in flow exceeds the margin of error. The probable source of this unaccounted flow is emergent groundwater, forced up by basement greywacke exposures towards the Lower Gorge, as described in Section 2.

There is additional average gain of 50 L/s (ranging from a loss of 25 L/s to a gain of 100 L/s) in the short distance (2.4 km) between the Lower Gorge and Evans Crossing (Table 5.2). This gain probably includes an unknown volume of emergent groundwater from the Taiko Stream catchment. The actual amount of emergent groundwater (from a combination of all aquifers, Quaternary, Cannington Gravel and deeper Tertiary) cannot yet be calculated1. However, additional concurrent gauging runs planned in the future will help to confirm the proportion of groundwater contribution to surface water flow through the Lower Gorge. An additional site will also be gauged between the Lower Gorge and Evans Crossing in order to be able to distinguish the proportion of groundwater from the Cannington Basin and from the Taiko Stream.

Table 5.2: All surface water inflows (L/s) into the Upper Pareora catchment between the Lower Gorge and Evans Crossing, measured on five occasions

Tributary 30/01/2008 10/03/2008 20/03/2008 31/03/2008 22/04/2008 Pareora River at Lower 588 ±39 453 ±29 295 ±21 283 ±20 292 ±20 Gorge Pareora River at Evans 563 ±51 484 ±50 396 ±43 341 ±39 376 ±45 Crossing Difference -25 ±64 31 ±57 101 ±48 58 ±44 84 ±49 Note: Each individual gauging error is signified by ±X L/s; the cumulative error is calculated by the square root of the sum of the squares of each individual error.

In addition, the inflow of the Taiko Stream and the Pareora South Branch were measured on the last four gauging runs along with the flow at the Huts recorder. The inclusion of these inflows from Evans Crossing leads to a cumulative flow within the range of flow measured at Huts recorder (Table 5.3).

Table 5.3: All surface water inflows (L/s) into the Upper Pareora catchment between Evans Crossing and the Huts recorder, measured on four occasions

Tributary 30/01/2008 10/03/2008 20/03/2008 31/03/2008 22/04/2008 Pareora River at Evans 563 ±51 484 ±50 396 ±43 341 ±39 376 ±45 Crossing Taiko Stream 0 ±0 0 ±0 0 ±0 0 ±0 Pareora River South Branch 269 ±21 218 ±15 190 ±14* 201 ±14 Total 753 ±54 614 ±46 531 ±42** 577 ±14 Huts Recorder 995 ±71 752 ±59 571 ±50 507 ±45 543 ±49 Difference -1 ±80 -43 ±67 -24 ±61** -34 ±68 * Average value since the data could not be retrieved from the Glogger file. **Dependent on average value, however sensitivity analysis confirmed that the value was not sensitive. Each individual gauging error is signified by ±X L/s; the cumulative error is calculated by the square root of the sum of the squares of each individual error.

1 Quantification would require knowledge of piezometric gradients between aquifers and aquifer storage. There is currently insufficient information from the limited wells in the basin to allow such an assessment.

18 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

The estimated percent contribution of groundwater from the Cannington Basin and Taiko Stream catchment is calculated from the sum of the flow differences in Tables 5.1 and 5.2 divided by the flow at the Hut recorder site. From the five concurrent gaugings, a clear relationship (R2 = 0.9) between the percentage contribution of groundwater from the Cannington Basin and Taiko Stream to the flow at the Huts recorder is visible, see Figure 5.5. Whilst this is only based on five gaugings, the relationship will be investigated further with future work in the catchment. Based on this regression, it would appear that when the flow at the Huts Recorder is at 7 day MALF (479 L/s, recorded), 25% of the flow (119 L/s) is derived from re-emergent groundwater.

30.0%

o y = -0.0004x + 0.4393

ti 2 r 25.0% R = 0.9002 e bu i d r r t n co o e 20.0% c r R s te t a u

w 15.0% e H nd h t ou

at 10.0% gr w o ge l f ta

o 5.0% n t e c r e

P 0.0% 0 200 400 600 800 1000 1200 Flow at Huts Recorder (L/s)

Figure 5.5: Regression of the percentage contribution groundwater to flow at the Huts Recorder

It can be seen from the gauging data that the contribution from localised and deep groundwater storage does support the Pareora River baseflow. Abstraction from groundwater at any depth in the Cannington Basin should therefore be allocated taking account of the downstream water users’ reliability of supply (Section 5.1.4), and instream values (Section 5.1.5), and storage in the aquifer to buffer climatic variation and the impact of groundwater abstraction on surface water flows (Section 6.1).

5.1.1 Minimum flows Minimum flows and allocation blocks have not been set in Schedule WQN1 of the PNRRP for the Pareora River. Environment Canterbury is in the process of gathering the necessary information and undertaking community consultation to enable recommendation of a flow regime for incorporation into Schedule WQN1 by way of a publicly notified variation. It is anticipated this will occur by June 2009.

There is an environmental minimum flow site on the Pareora River at Huts, which was determined for consenting purposes. This allows for three bands of flow restriction and allocation. Band 1 has full restriction at 300 L/s and 50% restriction at 400 L/s. Band 2 has full restriction at 1,500 L/s, and Band 3 full restriction at 2,700 L/s (the majority of abstractions fall within Band 1). Recorded 7 day MALF at Huts is 479 L/s (data from 1982-2008), and a naturalised2 MALF of 525L/s has been calculated for this site.

2 The flow has been naturalised for all the takes except for the Timaru District Council take, since it is an historic take and upstream of all the other takes, so is effectively ‘lost’ to the system.

Environment Canterbury Technical Report 19 Proposed Additions to South Canterbury Groundwater Allocation Zones

5.1.2 Surface water allocation block In the absence of allocation limits in Schedule WQN1, Policy WQN14 and Schedule WQN2 of the PNRRP provide guidance for calculation of interim allocation blocks.

In order to calculate reliability of supply and the size of the interim surface water allocation block, the flow record was naturalised for all the surface water takes that were exercised over the period from 14/02/1985 (when the first surface water take consent was issued) through to 12/10/1999 (when the first groundwater take consent was issued) so that no uncertainty is included by including the groundwater takes. For details of the consented takes used for calculation of the naturalised flow record see Appendix 1. The only exception to this is the Timaru District Council (TDC) take (CRC011399) which has been exercised since 1969. The take is upstream of all the other takes and so is effectively ‘lost’ to the system. This take is continuous at around 200 L/s except when the flow at the Huts recorder is less than 750 L/s where it is a proportion of 200 L/s. It is felt that adding the take back to the flow record would create additional uncertainty. All domestic and stockwater supply takes are considered to be taken at their maximum allowed rate throughout the year. All takes for irrigation purposes are considered to be taken at 50% of their maximum allowed rate throughout the irrigation season in order to account for the variability in actual water usage versus consented quantity.

Potential ‘A’ permit allocation blocks for the Pareora using Policy WQN14 and Schedule WQN2 of the proposed NRRP have been calculated based on the naturalised flow record from 1982 through to 12/10/99.

Using the existing minimum flow of 300 L/s, criteria set out in Schedule WQN2 provides for a surface water allocation block of 199 L/s; Policy WQN14(4)(a) provides for an allocation block of 224 L/s; Policy WQN14(4)(b) provides for an allocation block of 188 L/s .

5.1.3 Current surface water allocation As the Pareora Huts Recorder site is the minimum flow site for the whole catchment (both upstream and downstream users) it is important to consider the surface water allocation for the whole catchment. The majority of current water allocation is in the lower Pareora, below the Huts Recorder site. Surface water and hydraulically connected groundwater allocation from the whole catchment is currently 759.3 L/s (Appendix 2) far exceeding any of the calculated allocation blocks above. Of the 759.3 L/s, 142.4 L/s is currently consented for takes above the minimum flow site, with the remaining 616.9 L/s for consented takes downstream of the Huts Recorder site.

5.1.4 Reliability of supply Ritson and Horrell (2008) noted that currently 50% restrictions occur 5% of the time, or an average of 11 days per year, and full restrictions 1% of the time, or 2 days per year. Under Policy WQN9 (19) it is possible that water users downstream of the minimum flow site will not be able to fully utilise their consented take (i.e. they will be on partial restriction) on average 69 days per irrigation season, see Figure 5.6. The flow exceedence curve in Figure 5.6 represents the current flow regime (from 1982- 2008) i.e. it has not been naturalised since it is showing the actual water available to the downstream users.

20 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

1000

900 Flow (L/s) 1982-2008 800 Current sw takes d/s of Huts Recorder Partial Restriction 700 Full Restriction ) s / 600 (L

ow 500 Fl 400

300

200

100 0 1020304050607080 Number of days flow is not exceeded

Figure 5.6: Flow exceedance curve for Pareora River at Huts Recorder (1982-2008 irrigation season) showing the level of current surface water takes below the Huts Recorder

Below the Huts Recorder site, the Pareora River looses flow along its main stem to about Midgley’s track (approximately 12 km below Huts Recorder), after which the river gains flow again (Aitchison- Earl et al., 2006). At times of low flows, the river can become dry in its middle reaches. Aitcheson- Earl et al., (2006) estimated that when naturalised flows at the Huts recorder were at 525 L/s, the Midgley’s track site would be dry. Clearly, surface and groundwater abstraction increase the duration and extent of the dry reach.

Granting surface water abstraction or significant groundwater takes in the Cannington Basin will make the situation even worse for downstream users and is likely to have a further detrimental impact on instream values.

5.1.5 Impacts on instream values The Pareora River has many attractive features, and has been valued by the local community as a trout fishery and popular swimming and general recreational area. However, recent perception of the river is that low flows in the lower reaches (below the Lower Gorge) have resulted in a decline of those values. In particular, poor fishing and generally poor aesthetic value owing to the dry river bed in places are reported by many locals (Hayward et al., 2003).

The low flows generally result in increased concentrations of contaminants (in particular nutrients and sediment), resulting in increases in plant and/or algal growths. This combined with loss of flowing stream habitat results in changes to the stream biota. Recent research on the impact of flow intermittence on aquatic biotic health has shown strong relationships between loss of flow permanence and decline in fish and aquatic invertebrate abundance and diversity (Davey, A.J., and Kelly, D.J., 2007).

Hayward et al. (2003) noted such impacts on the lower reaches of the Pareora River, with nuisance levels of periphyton and plant biomass developing at times of low flows, and macroinvertebrate communities indicating poor stream health. Therefore, given the already stressed state of the lower reaches of the Pareora River at times of low flows, any further loss of flow is likely to see decreased stream health and further loss of aesthetic/amenity values.

Environment Canterbury Technical Report 21 Proposed Additions to South Canterbury Groundwater Allocation Zones

5.2 Timaru Zone There are very little gauging data for streams that are located in the Timaru Zone. These streams include Pig Hunting Creek, Washdyke Creek, and Otipua Creek (a tributary of Saltwater Creek). A few months of data were collected from a recorder on the Otipua Creek (site 69903) during 1993-94 (Figure 4.3). The creek was often dry, but did record flows over 200 L/s. Median flow for the period of record was 2 L/s.

Observations from Environment Canterbury hydrology staff in Timaru (Horrell, pers. comm. 2008) are that other streams in the Timaru area have little flow except after a major rain event, and have stagnant pools of water in their lower reaches.

There is no clear indication of the interaction between surface water and groundwater in this area. Therefore no contribution or deduction has been made to or from the groundwater recharge estimates for determining the groundwater allocation volume in the Timaru zone. Therefore 50% of land surface recharge has been used to determine the groundwater allocation limit for the Timaru groundwater allocation zone.

22 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

6 Proposed groundwater allocation limits

6.1 Cannington Basin

There are five current groundwater consents in the Cannington Basin area, summarised in Table 6.1. One of these is from shallow hydraulically connected groundwater in recent river gravels, (hydraulic connection = high) and is treated as a surface water take. Three takes (all for the same user and the same area) are from the Cannington Gravels, and one take is from the White Rock Formation. These takes total an effective allocation of 1,312,146 m3/year.

Table 6.1: Summary of Groundwater Abstractions

Average Current Volume/ Maximum Daily Effective Consent Number Day Aquifer Rate (L/s) 3 Rate Allocation (m /day) 3 (L/s) (m /year)

CRC0806551 55 4752 55.00 1,207,170 Cannington Gravels CRC030170.2 15 1296 15.00 104,976 White Rock Formation Total Allocation 1,312,146 1 CRC000379.1 & CRC042573 are included in a cumulative volume condition under consent CRC080655 limiting all these consents to a combined maximum rate of 137 L/s, daily volume of 11,837 m3 and consented annual volume of 1,341,300 m3, and effective allocation of 1,207,170 m3.

Allocation of groundwater in catchments with a high proportion of groundwater dependant surface flows and surface water abstraction risk a reduction in baseflow for dependant tributary streams and main stem waterways. These are the major issues when evaluating sustainable groundwater allocation for the proposed Cannington Basin groundwater allocation zone.

Analysis of possible reductions in surface flow reliability has been presented in Section 5.1.4. Figure 5.6 illustrates the point at which the flow reliability specified in Policy WQN14(4)(b) of the PNRRP is reached. This flow of 488 L/s is used to determine how much water can be allocated from surface water above the current minimum flow of 300 L/s, giving an allocable flow of 188 L/s. The current surface water and hydraulically connected groundwater take from the whole catchment is 759.3 L/s. This indicates the Pareora River is already over-allocated and therefore there is no further surface water allocation or groundwater allocation available.

The recommended annual volume of water available for groundwater allocation in the Cannington Basin is capped at the existing level of allocation, which is 1,312,146 m3.

A further source of uncertainty in the conceptual understanding of the Cannington Basin zone is that some of the groundwater in the Cannington Basin may discharge to the Te Ngawai River. However there is little data to differentiate the respective groundwater contributions to the Pareora River and Te Ngawai River, although it should be noted that there is a very large area north-east of the Pareora River catchment that is potentially the major contributor of groundwater to the Te Ngawai River.

Table 6.2 presents a summary of recharge estimates and recommended groundwater allocation for the proposed Cannington Basin groundwater allocation zone. The adoption of 7.8% LSR as an allocation limit for the Cannington Basin is appropriate given the highly allocated surface water and groundwater downstream of the Pareora River gorge.

Environment Canterbury Technical Report 23 Proposed Additions to South Canterbury Groundwater Allocation Zones

Table 6.2: Summary of recharge estimates for land-surface and surface water for Cannington Basin

Groundwater Land-surface Recommended Groundwater Allocation Limit Zone recharge (7.8% LSR) (m3/year) (m3/year)

Cannington Basin 16,932,457 1,312,146

6.2 Timaru and Pareora

In the Timaru zone, the use of 50% of land surface recharge seems reasonable given the large coverage of loess over the zone that has had the effect of limiting recharge to a relatively modest volume given the total area of the zone. There are uncertainties surrounding the degree to which groundwater contributes to the surface flows in this zone, and no clear indication exists that less than 50% of recharge should be used when adopting a groundwater allocation limit to provide for flow in surface water bodies. Therefore 50% of land surface recharge has been provided for in the proposed Timaru groundwater allocation zone limit (Table 6.3).

The proposed extents of the Timaru groundwater allocation zone include areas currently within the Pareora groundwater allocation zone, i.e. the Pig Hunting Creek catchment. The proposed Pareora groundwater allocation zone area is therefore narrowed by 39% with an associated reduction in the groundwater allocation limit by 23%.

Table 6.3: Summary of recharge estimates for land surface and surface water for South Canterbury Zones

Groundwater Zone Land surface Surface water Groundwater recharge (m3/year) component (m3/year) Allocation Limit (m3/year) Timaru 8,480,665 none 4,240,333 Pareora 14,389,641 none 7,194,820

6.3 Current groundwater allocation

Table 6.4 summarises the status of the proposed allocation for the Cannington Basin, Timaru, Pareora and Levels Plain groundwater allocation zones.

24 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

Table 6.4: Summary of current and proposed allocation in South Canterbury Groundwater Allocation Zones (August 2008).

Proposed Existing In Process Potential Groundwater Effective % Groundwater Zone Allocation % Allocation Allocation Allocated 3 (m /year) Allocated Limit (m3/year) (m3/year) Cannington Basin 1,312,146 1,312,146 100 1,980,751 251 Timaru 4,240,333 2,152,616 50.8 544,455 63.6 Pareora 7,194,820 8,512,456 118.3 none 118.3

The proposed Cannington Basin groundwater allocation zone would be considered 100% allocated for those consents that are already processed. This would increase to 251% allocated if the applications in process were granted. The main factor when considering applications for further allocation in this zone, however, is the connection of the Cannington Basin to the lower Pareora River. The lower Pareora River is located within the existing Pareora groundwater allocation zone, which is currently 106% allocated. The proposed Pareora zone boundary decreases the size of the zone causing the proportion of allocation to increase to 118.3%.

The proposed Timaru groundwater allocation zone would be considered 50.8% allocation based on existing consents. This would further increase to 63.6% taking account of those in process.

The Levels Plain groundwater allocation limit has not been adjusted as the change in area of the zone is considered minor (138 ha or 0.5%). Furthermore, significant work is currently underway to evaluate the surface water and groundwater balance for this zone, which is likely to form the basis of revised limits for this zone in the future.

Environment Canterbury Technical Report 25 Proposed Additions to South Canterbury Groundwater Allocation Zones

7 Further considerations The following considerations, in order of importance are identified as resulting from the information contained in this report:

• A review, in association with an ICM assessment, is required to verify surface water allocation blocks and minimum flows for the Pareora River catchment. An audit of existing surface water and hydraulically connected groundwater takes is also required, with implementation of surface water take rostering and stream depletion protocol for groundwater takes in the Pareora catchment and associated groundwater allocation zones.

• The sustainability of the proposed groundwater allocation limits given in this report may be monitored by assessment of long term water levels. A declining trend may indicate the limit is too excessive. There are currently no monitored deep or shallow wells within the Timaru or Cannington Gravel zones. Investigation of potential monitoring sites should be made, and any consent granted in either zone should include a water level monitoring condition.

• Input of streams in the Timaru Zone: There is only limited flow data for Otipua Creek, and no data for other streams in this zone to assess their contribution to groundwater resources. However, in the overall context of the proposed zone, the total intermittent stream input is likely to be very small compared to land surface recharge (<2%), and the zone is currently < 50% allocated. The resources required to collect the level of information needed to assess appropriate mean/median flows may not currently be warranted.

• Recharge under basalt for the Timaru Zone: Land surface recharge has been calculated taking account of loess coverage where it exists. In the Timaru zone, most of the loess area is underlain by the Timaru Basalt. How this basalt affects drainage to the underlying Cannington Gravel aquifer is unknown. The basalt is likely to be fractured or jointed in some parts, perhaps allowing direct recharge paths, but in other parts may be massive, and land surface recharge may be perched along the loess/basalt interface. The fact that an aquifer exists in the underlying Cannington Gravel, but not within the Basalt suggests that land surface recharge does drain through the basalt.

26 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

8 Main recommendations summary

The following main recommendations for the inclusion and functioning of two new groundwater allocation zones (Cannington Basin and Timaru) and the revision of the Pareora zone in south Canterbury are as presented below:

1. Surface water allocation of the Pareora River is currently over allocated by over 350%. Any further allocation of surface water or significant groundwater takes will reduce reliability of supply for existing users and exacerbate detrimental effects of prolonged low flows and dry reaches on instream values.

2. The Cannington Basin Groundwater Allocation Zone should comprise the aquifer zone area as mapped in this report with a groundwater allocation limited to the existing level of allocation, which is approximately 1.3 million cubic metres per annum;

3. The Pareora Groundwater Allocation Zone should comprise the aquifer zone area as mapped in this report with a revised groundwater allocation of 7.19 million cubic metres per annum;

4. The Timaru Groundwater Allocation Zone should comprise the aquifer zone area as mapped in this report with a groundwater allocation limit of 4.24 million cubic metres per annum.

9 Acknowledgements

This report was first drafted by Philippa Aitchison-Earl. The report was externally reviewed by Tom Heller and redrafted by Jen Ritson (surface water) and Mike Thorley (groundwater). It was subsequently internally reviewed by the Water Allocation Group (a panel of staff members from planning, groundwater, and surface water resources and ecosystems).

Environment Canterbury Technical Report 27 Proposed Additions to South Canterbury Groundwater Allocation Zones

10 References Aitchison-Earl, P. L., 2005 ‘Deep Aquifer Review: Timaru – Waitaki River’ Environment Canterbury Unpublished Technical Report U05/02.

Aitchison-Earl, P., Ettema, M., Horrell, G., McKerchar, A., Smith, E., 2006. ‘Pareora-Waihao River: Water Resource Summary’ Environment Canterbury Published Technical Report R06/20.

Aitchison-Earl, P., Thorley, M, 2008. ‘Submissions on NRRP Variation 4: Southern Zones’ Internal Memorandum to A Veltman, 17 April 2008.

Davey, A.J., Kelly, D.J., 2007. Fish community responses to drying disturbances in an intermittent stream: a landscape perspective. Freshwater Biology 52:1719-1733.

GNS (Geological and Nuclear Sciences), 2006. Forsyth, P. J. (compiler), 2001. Geology of the Waitaki area. Institute of Geological and Nuclear Sciences 1:250,000 geological map 19. 1 sheet and 64p. Lower Hutt, New Zealand: Institute of Geological and Nuclear Sciences Limited. ISBN 0-478-09739-5. Cox, S.C. and Barrell, D.J.A. (compilers) 2007 (in preparation). Geology of the Aoraki area. Institute of Geological and Nuclear Sciences 1:250 000 geological map 15. 1 sheet + 71p. Lower Hutt, New Zealand: Institute of Geological and Nuclear Sciences Limited. ISBN 0-478-09521-X. Provided as electronic shapefiles by GNS to ECan in 2006.

Gair, H. S., 1962., ‘Drillhole evidence of the Pliocene-Pleistocene boundary at Timaru, South Canterbury’ New Zealand Journal of Geology and Geophysics, 4:89-97.

Hayward, S.A.; Meredith, A.S.; Lavender, R.M., 2003: Pareora River: assessment of water quality and aquatic ecosystem monitoring, 1998 to 2003. Environment Canterbury technical report R03/25

Davey, A.J.H.; Kelly, D.J., 2007: Fish community responses to drying disturbances in an intermittent stream: a landscape perspective. Freshwater Biology 52:1719-1733.

Ritson, J and Horrell, G ‘Upper Pareora Catchment Groundwater Take’ Internal memorandum to K Taylor, 25 February 2008.

Scott, D., 2004. ‘Groundwater Allocation Limits: land-based recharge estimates’ Environment Canterbury Unpublished Technical Report U04/97

Thorley, M., Ettema, M., 2007 ‘Review of allocation limits for the South Canterbury downlands’ Environment Canterbury Unpublished Technical Report U07/09.

28 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

on ts is u <400 H

at when o o o o

w conditi N N N N w Min flo 0 when flo <300; 50%

r r r r r r on a a a a a a season season season season season e e e e e e

y n n n n n o o o o o i i i i i t t t t t All y All y All All y All y All y a a a a a Durati g g g g g i i i i i r r r r r r r r r r I I I I I

0 0 0 5 o 0 0 0 0 5 7 5 5 . . . . . d bac 3 5 7 2 . 8.00 2.00 1 1.00 3 5.50 2.00 (L/s) 2 1 2 0 Take t adde

0 0 0 0 0 5 0 0 0 5 0 . 7 . . . . . 0 4 5 8.00 2.00 1 1.00 7 5.50 0 2.00 (L/s) 5 3 4 Max Rate

) y orit

s used to naturalise the flow record y

ly ly ly

p p p n n n n n p p p

o o o o o r i i i i i r Suppl t t t t t e t a a a a a a (Local Auth g g g g g i i y r r r r rri rri rri I I I I I Wate

ter Use y y y y y y a W Stockw Spra Spra Spra Spra Spra Rural Water Su Rural Water Su Rural Water Su Communit Public Water Suppl

5 6 1 4 9 4 nce 6 8 0 7 6 3 4 4 4 3 4 4 ------6 0 9 5 9 5 fere 0 1 1 9 7 3 e 4 4 5 4 4 5 : : : : : : 9 9 9 9 9 9 3 3 3 3 3 3 J J39:433-303 J39:406-465 J39:477-360 J J J J J J39:4055-391 J39:4812-363 Grid R

3 4 9 9 0 0 3 0 9 9 0 0 0 0 9 9 0 0 2 / 2 1 1 2 2 / / / / / 0 To 6 6 6 5 5 1 / 0 0 0 0 0 / / / / / 5 1/06/2009 1/06/1994 1/06/1999 1 1 1 1 1 1 19/12/1995 31/08/2029 Historic surface water take

8 9 9 9 9 2 9 8 8 8 8 9 9 9 9 9 9 9 1 1 1 1 1 / 1 / / / / / 0 6 6 6 5 0 1 0 0 0 0 From / 1 / / / / / 9 4 4 4 0 7/09/1994 2 1 14/06/1989 14/02/1985 14/12/1988 10/05/1989 1 1 1 1

B 2 1 7 5 1 8 4 03 0 9 7 5 4 0 1 3 er 0 0105 0028 0032 0 0 0 b 0274B 0 6 5 8 0 2 2 3 5 7 7 8 8 8 8 8 8 Y Y Y Y Y Y Y Y Record Num SC SC SC SC SC SC CRC9215 CRC9501 CRC9903 SC SC Appendix 1:

Environment Canterbury Technical Report 29

Proposed Additions to South Canterbury Groundwater Allocation Zones

Appendix 2: Current surface water and groundwater takes in the Pareora catchment (where no rate is given for a groundwater take, it is not considered to be hydraulically connected)

30 Environment Canterbury Technical Report Proposed Additions to South Canterbury Groundwater Allocation Zones

Record Rate From To Grid Reference Source Name Number (L/s) CRC000183 14/02/2002 27/04/2015 J39:4101-4807 Un-named Tributary 50.00 CRC950103 7/09/1994 31/08/2029 J39:477-360 South Branch Pareora River 2.00 CRC950386 17/03/1995 15/03/2030 J39:632-348 Pareora River 60.00 CRC990342 19/10/1998 15/10/2033 J39:406-465 Cannington Creek 1.50 CRC990820 6/12/1999 5/11/2014 J39:653-334 Un-named Tributary 30.00 CRC990880 1/05/2000 27/04/2015 J39:61868-36002 Pareora River 38.00 CRC991282 1/05/2000 27/04/2015 J39:554-411 South Branch Pareora River 30.00 CRC991286 1/05/2000 27/04/2015 J39:535-434 Pareora River 45.00 CRC992192 1/05/2000 27/04/2015 J39:617-379 Pareora River 10.00 SCY760105 14/06/1989 1/06/2009 J39:4055-3919 White Rock River 5.50 CRC032086 3/10/2003 3/10/2038 J39:519-401 South Branch Pareora River 7.00 CRC950292.2 17/05/2001 5/10/2029 J39:583-399 Pareora River 30.00 CRC950390.1 12/09/2001 15/03/2030 J39:620-353 Pareora River 42.00 CRC063184.1* 17/12/2007 28/07/2016 J39:5658-4103 J39/0339 100.00 CRC971810.2 18/10/2004 19/03/2032 J39:58716-39660 J39/0529 90.7 CRC990818.1 14/06/2001 5/11/2014 J39:65277-35151 J39/0049 66.7 CRC991400 1/05/2000 27/04/2015 J39:6363-3624 J39/0053 12.9 CRC991468 6/12/1999 5/11/2014 J39:64073-35751 J39/0236 36.4 CRC991281 1/05/2000 27/04/2015 J39:638-339 J39/0340 31.8 CRC990943.1 30/09/2004 27/04/2015 J39:475-466 J39/0336 28.4 CRC991284.2 22/06/2006 27/04/2035 J39:5658-4103 J39/0339 25.5 CRC991239.3 18/10/2004 27/04/2015 J39:59750-38794 J39/0338 23.0 CRC980553.2 5/08/2003 10/12/2032 J39:6308-3653 J39/0407 10.0 CRC990697 1/05/2000 27/04/2015 J39:64670-33627 J39/0218 12.1 CRC020599 7/01/2002 27/04/2015 J39:6193-3740 J39/0228 11.6 CRC991283 1/05/2000 27/04/2015 J39:66410-32959 J39/0154 9.6 CRC991982 1/05/2000 27/04/2015 J39:6380-3410 J39/0162 9.5 CRC991279 1/05/2000 27/04/2015 J39:66444-34642 J39/0337 8.4 CRC991310.1 3/06/2004 27/04/2015 J39:6453-3525 J39/0341 6.6 CRC991443 18/06/1999 16/06/2034 J39:66919-32016 J39/0176 4.7 CRC010393 30/10/2000 27/10/2035 J39:66300-33075 J39/0095 4.2 CRC991278 12/10/1999 8/10/2034 J39:6590-3300 J39/0067 3.7 CRC991280 12/10/1999 8/10/2034 J39:6615-3278 J39/0254 3.6 CRC990633 26/02/1999 23/02/2034 J39:650-332 J39/0072 2.9 CRC010392 30/10/2000 27/10/2035 J39:67000-34441 J39/0135 2.8 CRC991384 25/05/1999 22/05/2034 J39:65372-32857 J39/0098 1.9 CRC991682 23/03/1999 16/03/2034 J39:66273-32184 J39/0191 0.8 CRC011907 7/01/2002 24/12/2036 J39:5530-4205 J39/0460 0.5 CRC070367 30/05/2007 24/05/2017 J39:65779-34848 J39/0669 0.0 CRC070367 30/05/2007 24/05/2017 J39:65779-34848 J39/0669 0.0 CRC072257 5/06/2007 31/05/2017 J39:61190-38843 J39/0565 0.0 CRC080655 17/12/2007 12/12/2017 J39:48151-45450 J39/0701 0.0 CRC030798.2 13/02/2008 9/12/2037 J39:61645-34292 J39/0442 0.0 CRC042573.1 10/06/2008 8/10/2034 J39:48036-45380 J39/0496 0.0 CRC071956.1 9/06/2008 31/05/2017 J39:59931-36656 J39/0686 0.0 CRC021932 4/06/2002 30/05/2037 J39:60602-36379 J39/0412 CRC041067 22/12/2003 22/12/2038 J39:63835-33932 J39/0489 CRC041487 20/05/2004 20/05/2039 J39:64393-33753 J39/0473 CRC041568 12/07/2004 9/07/2039 J39:65668-33201 J39/0516 CRC050870.1 J39:59790-38189 J39/0485 CRC054403 17/11/2005 15/11/2040 J39:6590-3224 J39/0158 CRC030170.2 21/04/2006 16/08/2037 J38:4731-5013 J38/0521 CRC081699 29/11/2007 31/12/9999 J39:4871-4706 J39/0490 TOTAL 759.3 *Not included in allocation as take only commences at a flow of 2,700 l/s in the Pareora River (Huts Recorder).

Environment Canterbury Technical Report 31