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​3   Paparua Water Races

3.1       Scheme Summary

Description​	​	Quantity
Scheme area (within scheme boundary) ​		35,837 ha
Scheme Coverage (as at 1 Jan 2021)	Area of Full Charges
	Unit Charge (No.)	1355
	Irrigators	59
Systems components ​​ ​​ ​​ ​	Intakes	1
	Main Race	114.79 km
	Local Race	218.64 km
	Lateral Race	99.59 km
	Other	2 settling ponds
Water Source	via River	Waimakariri River (Paparua intake)
History	Install date	Installed progressively from 1885
Value ($) ​	Replacement Cost	$23,140,131
	Depreciated Replacement Cost	$20,281,143
​Financial	Annual maintenance cost % of total water race maintenance spend	$876,741/year 41% of total water race maintenance spend​
Water Take ​	Annual average (from Management Plan)	41.3 million m3
	Consented Take	2,031 Lts/sec (including irrigation)
Sustainability ​	Biodiversity	Groundwater recharge and natural habitat
	Amenity	Urban features

 

3.2       Key Issues

The following key issues are associated with the Paparua Water Race system.  A list of district wide issues are located in 5Waters Activity Management Plan: Volume 1.

Table 3‑1 Paparua Scheme Issues

What's the Problem​	What we plan to do
Vandalism at the Paparua intake.	The Paparua intake is subject to ongoing vandalism which will be monitored and onsite improvements made where practical.
Health and Safety Risk	Health and Safety inspections and improvements
Operating race for biodiversity values will add financial pressure.	Review options for alternative funding.
Operating race for biodiversity values will add financial pressure.	An alternative rating structure is proposed which takes into account benefits of the race network other than stock water.  The alternative rating structure is one of the matters included in the 2018-28 consultation document.

 

3.3       Overview & History

The Paparua scheme serves a variety of smaller farms and a large number of lifestyle blocks.  It consists of an intake on the southern bank of the Waimakariri River at Intake Road feeding into races, which fan out across the plains towards Christchurch in the East and Burnham in the south.

The intake although still within the flood plain of the river is a simple concrete weir with a vertical sluice gate on the protected southern branch of the river.  The water is led to this channel as necessary after each major fresh or flood in the river.  In a flood the intake is protected by a combination of willow plantings and the mechanism of the river in the active main flood plain area overtopping the low bank of the dozed channel and washing the weak portion downstream.

From the river, water is fed through an intake race for some 500 metres.  This race then divides into two races leading to two sedimentation pond areas where most of the sand and silt is allowed to settle out before the water feeds into the scheme. 

The scheme from here consists of a series of main and subsidiary races feeding water to properties throughout the scheme area which generally covers the area of the old Paparua County totalling approx. 35,000 hectares with 2,966ha of Christchurch City area served.

Figure 3‑2 Scheme Schematic

Figure 3‑3 Intake Scheme Schematic

 

3.4       Resource Consents

The Paparua water race scheme has a number of resource consents. Table 3‑2 shows that water takes permitted by the resource consents at the three intakes and Table 3‑3 details the resource consents for this scheme.

Table 3‑2 Allowable Take

Intake​	Base Minimum Flow (Lts/sec)	Maximum Take (Lts/sec)
Intake Rd – Stock water	1231	1331
Intake Rd - Irrigation	800	800
Total	2,031	2,131

 

Table 3‑3 Resource Consents

Consent Number​	Description	Location	Date Issued	Expiry Date	Application Status
CRC012005	To disturb the bed of the Waimakariri River to maintain intake and discharge structures	Stockwater Race Network	10/12/2002	10/12/2037	Issued - Active
CRC012006	To take a maximum flow of 1430 litre per second from the Waimakariri River at the Waimakariri Gorge intake and to take a maximum flow of 800 litres per second from the Waimakariri River at the Paparua intake for stockwater and irrigation supply	Stockwater Race Network	10/12/2002	10/12/2037	Issued - Active
CRC012007	To discharge water and water containing contaminants into land and/or water from the stockwater scheme at several points into drains and soakpits	Stockwater Race Network	10/12/2002	10/12//2037	Issued - Active
CRC201738	Global Consent - To discharge contaminants into water and onto land in circumstances where they may enter surface water	Global Consent (Spraying)	25/01/2021	25/01/2036	Issued - Active
​CRC212849	​Global Consent - To discharge contaminants to air	​Global Consent (Spraying)	​25/01/2021	​25/01/2036	​Issued - Active

 

3.5       Water Quality

Under resource consent CRC012006 Council were required to undertake water quality sampling from May 2003 to December 2004. A summary of the results, sampled on 14 December 2004, is below in Table 3‑4.

Table 3‑4 Sampling Results

Map sample location​	E.coli Count	Nitrate Nitrogen g/m3	Temp C	Turbidity g/m3
Marshes Road NZMS 260 M36:7265-3663	2100	0.5	14	12
Marshes Road NZMS 260 M36:7265-3664	Dry	Dry	Dry	Dry
Marshes Road NZMS 260 M36:7265-3665	Dry	Dry	Dry	Dry
Tosswill Road NZMS 260 M36: 7151-3512	300	<0.05	13	28.4
Tosswill Road NZMS 260 M36: 7151-3512	Dry	Dry	Dry	Dry
Tosswill Road NZMS 260 M36: 7151-3512	Dry	Dry	Dry	Dry
Lincoln Township NZMS 260 M36: 6832-3017	350	0.06	14	6.84
Lincoln Township NZMS 260 M36: 6832-3017	Dry	Dry	Dry	Dry
Lincoln Township NZMS 260 M36: 6832-3017	Dry	Dry	Dry	Dry
Ellesmere Road NZMS 260 M36: 7036-3002	Dry	Dry	Dry	Dry
Ellesmere Road NZMS 2​60 M36: 7036-3002	Dry	Dry	Dry	Dry
Ellesmere Road NZMS 260 M36: 7036-3002	Dry	Dry	Dry	Dry
Days Road NZMS 260 M36:6474-2834	4100	0.08	12	49.6
Days Road NZMS 260 M36:6474-2834	400	0.19	11	14.17
Days Road NZMS 260 M36:6474-2834	1600	0.09	10	42.1

 

3.6       Scheme Assets

3.6.1   Silt Ponds

There are two silt ponds, which are used to settle out river silt from the Waimakariri River in times of flood.  The ponds are accessed through a locked gate about 100 metres from the river end of Intake Road.  These ponds are situated about 1 kilometre below the Main Race Intake Control gates.

The first pond (1.23ha) is situated above the start of the Harewood Race and is the larger of the two ponds.  The silt progresses down the main race to a wider channel section just before the pond and silt settles out in the channel.

The second pond (0.44ha) is smaller in size and the silt is allowed to settle in the pond itself and is cleaned out to bank.  Pond number two has minimal storage.  The race, known as the Sandy Knolls, leads away from this pond and supplies water to the Rolleston and Burnham area.

If there is a total outage, or gates are closed completely at the intake and there is no flow into the race system within 24 hours, the upper half of the Paparua Race system drops to a very low flow.  After 24 hours of outage at the intake the whole upper half of the scheme will be out of water.  The lower half of the Paparua scheme starts to be affected by lack of flow into the scheme.

3.6.2   Control Structures

Divides are on the main races below the main intake control gates.  The divides are a mixture of single or multiple control gates sited where the main race flow requires splitting into equal or different flows.  Each split race then goes on to serve a different area of the scheme.

3.6.3   Monitoring Points

Monitoring structures are sited below intakes to measure the quantity of water taken from the source. The main monitoring site is located immediately downstream of the intake and fish screen. The only other monitoring structures on the Paparua Water Race System are approximately 400 metres downstream of the main intake where there are two control gates that divide the flow into two races. They are used to measure flows to ensure compliance with resource consent requirements and to compile a history of the intake flow.

Each of these races has a section of race that has had its cross-sections calibrated by a certified hydrologist to enable measurement of the flows.

3.6.4   Emergency Discharge Points

There are discharge points on main races, and on some minor races, to dump surplus water from the race system.  These are used in an emergency, or when work is required on a section of race, and can be dewatered using the emergency discharge point.

An emergency is when water has got into the race system from heavy rain causing.  This water is required to be quickly removed from the system to prevent flooding at downstream culverts or overtopping and affecting roads, property, crops or buildings.  This water can be removed from one discharge point or several, up to 3 to 4, depending on the amount of water to be removed.  Also excess water may be taken from the race to buffer additional usage such as high irrigation and sudden shut down of the irrigation systems.  Flood discharge points on the race system are sited at:

• Scout Camp on West Coast Road and Buchannan's Road intersection
• Old West Coast Road and Main West Coast Road intersection
• Sandy Knolls Road and Railway Road
• Newton's and West Melton Road intersection

3.6.5   Soakholes

Soakholes allow excess water to be taken from the intake to buffer additional usage such as high water use.  Maximum flow to each soakhole is 10 L/sec.  The Paparua scheme has 104 soakholes (including privately owned).

3.6.6   Pipe Summary

A summary of material and diameter for pipes (culverts and aquaducts), where known, is shown below in Figure 3‑4 and Figure 3‑5.

​Figure 3‑4 Pipe Material - Paparua

​Figure 3‑5 Pipe Diameter - Paparua

 

3.7       Operational Management

Presently the scheme is operated in two sections, being the western area, including the intake, and the eastern area.  The boundary between the two being the Main South Road along Sandy Knolls Road to Newtons Road and then to the airport area.

The Western Operator checks the main intake gates, river flows, cleans intake grills and when required adjusts intake gates and adjustable weirs.  Contact with the Eastern Operator then occurs to ascertain flow requirements in the eastern area.  Adjustments then can be made at either the main intake or the other major divides located at Bells Divide, SH73/Sandy Knolls, SH73/Weedons Ross Road, SH73/Langdales Road, SH73/Kirk Road to ensure the correct flow into the eastern area. When there is a total outage of the intake, flows in the upper half of the Paparua race scheme fall away in 6- 8 hours.

 

3.8       Irrigation

There are 56 property owners on the Paparua Scheme that have authorisation from the Selwyn District Council for use of water from the water race system for irrigation.  Irrigation agreements are required with each user. The agreement covers individual water allocations, monitoring responsibilities and details recommended water management practices.

Due to consent conditions, restrictions occur when the flow in the Waimakariri River is less than 63 cubic metres per second.  In the event of this occurring rosters are developed to assist irrigation when restrictions are imposed on irrigation.  A graph is also sent to the irrigators detailing the steps down in the river and indicating how many litres are available at any one time.  When the river reaches 41 cumecs all irrigation ceases.  The Council has instigated in conjunction with all irrigators a system that allows irrigators to call Council and receive information on River levels, any restrictions imposed and the appropriate “roster".

 

3.9       Environmental Management

3.9.1   Water Quality Issues

Water quality in races is largely affected by runoff and stock activity in races. Runoff containing fertiliser and organic nutrients is difficult to manage. Stock activity (especially cattle, horses and deer) can affect water quality by increasing sedimentation from bank erosion and disturbance of the bottom of the race channel. Direct defecation and surface runoff can also add to elevated faecal coliform levels.

Improved management of the water race network will need to address stock movement in races.  Maintenance contractors and users need to be aware of the effect of operation and maintenance activities on water race quality.

3.9.2   Management Approach

The Council will use a combination of the following to address water quality issues:

• Watering bays are being promoted for water races that serve all stock farming properties (excluding sheep).  This will allow limited and controlled access to races for stock drinking purposes.  The remaining length of races to be fenced off/hot wired so that animals only have access to the race for drinking purposes.  This is 'best practice' for managing stock access to races.
• The Council will provide guidance to race users on design/layout of watering bays
• Maintenance contractors will ensure that subcontractors use clean and sound machinery when working in riverbeds.
• Maintenance Contractors will be required to monitor and minimise discharge of surplus water from the race network

 

3.9.3   Demand Management

Environment Canterbury as the consenting authority are requiring demand management practices to be implemented as part of new or reviewed consent conditions.  This is due to water allocations in most areas of the district being assumed as fully committed.

Selwyn District Council has integrated a demand management plan into the existing Water Race Management Plan.

An Efficiency Audit of the Paparua Scheme dated January 2004 indicated potential improvements to the Water Race scheme.  A summary of the potential improvements are detailed in the table below:

Table 3‑5 Potential Improvements

Improvement​	Description	Comment
Reducing infiltration or Leakage	Most of the obvious leakage areas have been rectified and any new ones are fixed once they become apparent.	Without committing to large scale lining of channels with clay, concrete or bentonite, it is unlikely that the chronic infiltration losses can be substantially reduced with current technology Suggested Action: Continue the development of a leakage measurement system and use it to obtain  more accurate data about infiltration losses
Race Rationalisation	There are races that could be decommissioned as they are either not required or could be replaced with short pipe feeds from adjoining races.	SDC Policy W107 allows the race network to be rationalised from the extremities of the Water Race. Suggested Action: Investigate the possibility of rationalisation further with a view to optimising the network to meet current consumers.
Control Improvements	Installation of additional automated control and monitoring points.	Suggested Action: Investigate the installation of monitoring stations with automated/remote controls at key points within the system.
Management Improvements	Most of the easy gains in scheme operation have been made. The Water Race Management Plan provides an improved framework for managing the schemes.	Suggested Action: Fully implement the Water Race Management Plan as soon as possible.

 

3.10       Photos of Main Assets

​ Photo 1: Intake gate, control building and fish screen	​ Photo 2: Control Gate
​ Photo 3: Inlet Weir	​ Photo 4: Sediment Pond 1
​​ Photo 5: Sediment Pond 2

3.11       Risk Assessment

A risk assessment has been undertaken for the Paparua scheme. The key output from the risk assessment is the identification of any extreme and high risks which need to mitigated. In order to mitigate these risks they have been included and budgeted for in the projects within this LTP. Table 3‑6 details the risk priority rating and Table 3‑7 outlines the risks for this scheme.

Table 3‑6 Risk Priority Rating

Risk Score​	Level of Risk	Risk Response
> 50	Extreme	Awareness of the event to be reported to Council.  Urgent action to eliminate / mitigate / manage the risk. Document risk and action in the AMP.
35-50	Very High	Risk to be eliminated / mitigated / managed through normal business planning processes with responsibility assigned.
14-35	High	Manage risk using routine procedures.
3.5-14	Moderate	Monitor the risk.
< 3.5	Low	Awareness of the event to be reported to Council.  Immediate action required to eliminate / mitigate / manage the risk. Document risk and action in the AMP.

Table 3‑7 Risks – Paparua

Risk​	Action/Project	Year Identified	2014 Risk Rating	2017 Risk Rating	Residual Risk Rating
Collapse of old tunnels Kowai	Condition inspection of water race tunnels	2014	10	3.5	3.5
Public Health and Safety risks at intakes	Health and Safety improvements	2014	10	10	10
Sink holes are developing	Develop standard soak hole repair procedures	2014	9	9	9
Siphons are a risk	Condition inspection of water race siphons	2014	12	12	10
Public Health and Safety risks at intakes	Health and Safety improvements	2014	10	10	7
Siphons are a risk	Condition inspection of water race siphons	2014	12	12	10
Non-consented activities	Renewal of consents	2014	27	27	6
Collapse of old tunnels Waimak	Tunnel repairs	2017		20	10

The list of district wide risks can be found in 5Waters Activity Management Plan: Volume 1.

3.12       Asset Valuation Details

The total replacement value of assets within the Paparua Scheme is $23,140,131 with further details in Table 3‑8 below. 

Table 3‑8 Replacement Value, Paparua

Asset Class 1​	Asset Class 2	Sum of Replacement Value
Plant and Equipment​		$67,808
Water Race Reticulation ​​ ​​ ​​ ​​ ​	Channel	$21,196,384
	Divide	$643,598
	Gate	$56,744
	Inlet-Outlet-Point	$1,113,713
	Instruments	$12,360
	Structure	$49,525

Channels are broken down into open channels: culverts, lateral, locals, mains, siphons and culverts. Main races are have a larger cross sectional area in comparison to locals and laterals. 

 

3.13       Renewals

The renewal profile has been taken from the 2019 5 Waters Valuation. A graph showing the renewals for this scheme are shown by Figure 3‑6 below. The majority of assets requiring renewal are culverts which occur in the period 2019-2023.

The open race channels are taken as having infinite lives (renewal by maintenance) and therefore renewals are not budgeted for these assets types.​

​Figure 3‑6 Paparua Water Race Renewal Profile

There are many aging structures within the water race network these include gates, intake structures, tunnels, siphons, aqueducts and culverts. These assets are near the end of their life and will require increased funding moving into the future.

 

314       Critical Assets

The criticality model for Paparua has been updated for the 2021 AcMP. The methodology of the criticality model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the criticality has been calculated for the reticulation assets. Table 3‑9 and Figure 3‑7 below show the level of criticality for all of the assets within this scheme that have a recorded known length.

​Table 3‑9 Length of Assets per Criticality Level

Criticality Bands​	​	Length (m)
5	Low	323,496
4	Medium-Low	101,760
3	Medium	5,645
2	Medium-High	11
1	High	49

​3.15       Asset Condition

The asset condition model was run for Paparua in 2021. The methodology of the model can be found in 5Waters Activity Management Plan: Volume 1 and it provides details of how the model has been calculated for the reticulation assets (particularly pipes). Figure 3‑8 below shows the level of asset condition for all of the assets within this scheme that have a recorded known condition.​

Table 3‑10 provides a description of the condition rating used within the condition model.

Table 3‑10 Asset Condition Grading

Condition Rating​	Grading
1.0	Excellent
2.0	Good
3.0	Moderate
4.0	Poor
5.0+	Fail

 

3.16       Funding Program

The 10 year budgets are shown by Table 3‑11​. Bu​dgets are split into expenditure, renewals, projects and capital projects. Expenditure and renewals have been reported on a district-wide basis in Volume 1. 

All figures are ($) not adjusted for CPI “inflation".  They are calculated on historical data, and population growth where relevant.​

Table 3‑11 Budget Summary

Years​	Projects	Capital Projects
2021/2022	-	-
2022/2023	-	-
2023/2024	-	-
2024/2025	-	$40,000
2025/2026	-	$200,000
2026/2027	-	$200,000
2027/2028	-	-
2028/2029	-	-
2029/2030	-	-
2031/2032	-	-
Total	-	$440,000

An explanation of the categories within the budgets are as follows below:

• Expenditure consists of operation and maintenance costs;
• Renewals are replacement of assets which are nearing or exceeded their useful life;
• Projects are investigations, decisions and planning activities which exclude capital works; and
• Capital projects are activities involving physical works.
  

​Table 3​‑12 Key Projects​

Account Label	GL	Description​	Year 1($)	Year 2($)	Year 3($)	Years 4 to 10	Funding Split *
​Capital Projects	-	Bells Divide upgrade	​-	-	​-	​$440,000	100% LoS

 * Where LoS refers to Level of Service and G refers to Growth

The list of district wide projects can be found in 5Waters Activity Management Plan: Volume 1.

Discussion on Projects

Projects​​​ have been determined based on their:

• Relevance to the scheme
• Requirement to be completed under legislation
  
• Ability to bring the scheme up to or maintain the Level of Service required under council's Asset Management Policy. 

Many projects are jointly funded by more than one scheme and activity.  Each scheme pays a pro-rata share only, equivalent to the number of connections.

Discussion on Capital and Projects

Where relevant, Capital (Levels of Service) and Capital (Growth) projects have been included in the scheme financial details. 

Levels of Service Projects and growth splits have been provided to ensure the costs of population driven works are clear.​​​​

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