Piha R&R undertook to open the mouth of the Piha Stream in May, to release the sand blockage that was causing the lagoon to overflow and to allow the accumulated algae to be released. Below is a report on the status as at September 1st.
Update , Graeme Carrie, 1/Sept/2020
Last update 2/July/20 : Log of Lagoon Opening 18/May 20 .
At the Piha R&R committee meeting 7.Aug.20 comment was made re the unusually high clarity noticed recently in the Lagoon and Piha stream. The committee decided to measure current pollution levels and check out conditions 3 months after the Lagoon was opened to clear stagnant water, algae pollution and allow natural flow input from the ocean.
Tests were conducted by GBC at 1.00pm at similar depths of 500mm 10-15 steps from the shore, water temperature 14/15 degrees C measured at the same locations as all previous testing viz East side Lagoon by domain 20 metres south of table (Lagoon) and south side of Lagoon entrance opposite Little Lion. (Mouth). Bird life and water fowl numbers have been consistent during this period of time. Testing used 1ml samples on E.coli coliform differential counting templates
Date Tues 18th Sat 22cnd
High Tide 9.10 am/3.9m 12.12pm/4.2m
Clarity V Good Low
Inflow at HT Nil +500mm at Lagoon., In flow at FB bridge
Outflow at mouth 1m/20sec 1m/10 sec
Ecoli/ Lagoon 0 0
Ecoli /Mouth 1 (100/100ml) 0
The results are well within the 250/100ml safe swim standard at both locations. The small samples will need larger sampling in the Lab for verification.
It is likely that favourable conditions for the two main pollution drivers produced this result.
Firstly effluent overflows from domestic and public systems have with less visitors been markedly reduced over lockdowns.
Secondly there has been consistent flow since the Lagoon was opened 18/May . The Lagoon is breathing again, naturally reducing pollution and flood risk. This pattern is continuing at the time of writing this report.
The two independent sets of results were taken in very different conditions, the first being no inflow from the sea or run off from rain and the second with strong tidal movement which moved sand but did not cause high readings indicating a cleaner environment on the Lagoon base.