upstream and downstream of the oxidation ponds, and of the
effluent from the oxidation ponds during late autumn under relatively low river flow
conditions. This survey was delayed due to no discharge from the system under very
dry late summer-autumn conditions. The sampling sites are shown in Figure 2 (Section
3) of this report. The samples were analysed for temperature, pH, conductivity,
chloride, dissolved oxygen, total and filtered uninhibited biochemical oxygen demand,
turbidity, suspended
Waitotara Coast 13 76.6 60 341.2 94 30 Sep 2015
page
Table 2: River Flow at 9 sites throughout the region
River and Site
Recorded Flows (m3/sec)
Records
Began
Maximum Minimum Mean
April 2021
April all
previous
years
April 2021
April all
previous
years
April 2021
April all
previous
years
% of
normal
Waitara at Bertrand Rd 222.290 915.735 14.916 4.587 37.197 45.080 83% Feb 1980
Manganui at Everett Park 176.714 634.905 6.660 2.825
Waingongoro River water quality low flow data
for the period 1992 to 2010 coincident with Eltham WWTP
discharge to the Mangawhero Stream and in March 2011,
following wastes diversion to Hawera WWTP 24
Table 7 Summary of selected water quality results from two sites in
the Waingongoro River (N = 125 samples) above and below
the Mangawhero Stream confluence and one site in the
lower Mangawhero Stream (N = 114 samples) for the pre-
wastewater diversion period January 2001 to June 2010 26
Table
during the regular survey season 19
Figure 8 Flow in the Waiwhakaiho River during the survey period 20
Figure 9 Box and whisker plots for all summer SEM surveys of E.coli
bacteria numbers in the Waiwhakaiho River at Merrilands
Domain 22
Figure 10 LOWESS trend plot of median E.coli numbers (per 100ml) at
the Waiwhakaiho River, Merrilands Domain for the 1996 to
2017 period 23
Figure 11 E. coli numbers for the Waiwhakaiho River at Merrilands
Domain for the 24-sample extended survey 24
106
List of figures
Figure 1 Location of freshwater contact recreation survey sites in 2017-2018 8
Figure 2 E. coli results for Lake Rotomanu 14
Figure 3 Box and whisker plots of E. coli for all summer SEM surveys at Lake Rotomanu 16
Figure 4 LOWESS trend analysis of median E. coli data at Lake Rotomanu 16
Figure 5 Cyanobacteria bio-volume at Lake Rotomanu 18
Figure 6 E. coli results for the Waiwhakaiho River at Merrilands Domain 19
Figure 7 Flow in the
effluents and stormwater.
• Sludge removed from the clarifiers is allowed to settle in the sludge lagoons. The water from this
process is either allowed to evaporate or is discharged via the outfall.
• Naturally occurring dissolved salts in the abstracted river water are removed using ion exchange
resins. Process boiler condensates for reuse also go through ion exchangers to remove trace
minerals. The resins are regenerated using sulphuric acid and sodium hydroxide. The waste flow is …
figures, fish pass water level and Punehu Stream flow between 1
February 2017 and 6 February 2017 16
Figure 5 Fish pass water level data, July 2016 – June 2017 17
List of photos
Photo 1 The Waiaua River, weir, intake, canal, fish pass and Lake Opunake, as viewed from the State
Highway 45 Bridge, Opunake. 4
Photo 2 Opunake Power Limited scheme on the Waiaua River 5
page
1
1 Introduction
1.1 Compliance monitoring programme reports and the Resource
to the consent was granted in December 1986, permitting
an additional 130 litres per second. Consent 0820-1 was due to expire on 12 March 2009
and was superseded by renewed consent 0820-2.
This consent provides for the abstraction of water from the Waitara River. The point of
abstraction is on the eastern bank, 10 kilometres from the sea. The maximum permitted
rates of abstraction allowed by consent 0820-1 varied according to the river flow
volumes, as measured at the Bertrand Road
underestimates due to the nature of the
rock riprap structure which reduced visibility of the total flow at the outfall. The rock
page
9
rip-rap was free of debris. There were no particularly noticeable visual impacts of the
effluent discharge under moderate winter flow conditions. However, there was some
noticeable visual discolouration beyond the mixing zone under lower river flow
conditions on the other three inspection occasions.
The adequacy of the mixing characteristics of
observations 9
4.7 Recommendations 10
5. Rainfall information for the June event 11
6. Soil moisture levels 13
7. Impacts of the June 2015 event - Waitotara 14
7.1 Flood levels 14
7.2 River management and flood information 14
7.2.1 Data restrictions 14
7.2.2 Background to the river level and flow recording 15
7.3 How the scheme held up 15
7.4 Mitigation of adverse flooding effects 17
7.5 Scheme Review 18
7.6 Recommendations 18
8. Impacts of the June 2015