Braided River Bird Monitoring – how it works

Braided rivers are a common in Alaska, Canada, New Zealand’s South Island, and the Himalayas, which all contain young, rapidly eroding mountains. They are a unique environment inhabited by equally unique birds.

They simply cannot contain a river in a straight line. In floods especially they carry sediment, and in places where the flow slows down this settles on the bottom, thus raising it. And the water flows off to the side of least resistance. This will happen constantly during floods.

The technique for gathering bird numbers on these sort of rivers is quite simple: a team of four people spread out, in radio contact with each other, walk downstream counting every bird they see in front of them. On the ground or airborne.

And at that point the simplicity vanishes! Very finely tuned river crossing skills are needed, as well as “an eye” for the line that will give the best results. Plus physical stamina.

The tools of the trade are: a radio each, walking pole to aid crossings, binoculars, sun-cream, sun hat, good boots and gaiters [to stop gravels getting in the socks], GPS each, and a pen/paper/clipboard. Plus lunch, warm clothing, a camera etc. Warm dry socks also help at the end of the day.

A view upstream of the Hunter River that feeds Lake Hawea in Otago, New Zealand
Preparation. In this case to get into the very remote Hunter Valley. In the Wanaka area two other rivers, the Matukituki and Makarora are also done, and they don’t require a helicopter drop in. There is 25 years now of history – each river being monitored every third year.

The three year cycle is sometimes hard to maintain. The work has to be done in the spring when the birds are breeding, and this is when there is a high frequency of floods, with high levels due to snow melt.
After a short but steep climb in the helicopter from Makarora town-ship, on popping over the ridge the large and rugged Mckerrow Range come into full panoramic view [actually named after a close friend’s grandfather who did lots of surveying and exploring.
Dropping the over-night gear off by a hut, before flying further up the valley to begin the survey.
On the left [note the silt in the grass!] where we only go to avoid a complex river crossing; and where we do – the gravel on the right.
One species of many that we’re looking for. The ‎nationally vulnerable banded dotterel / tūturiwhatu, is the most common small plover of New Zealand seashores, estuaries and riverbeds.

This one is feigning a broken wing to lead the surveyor/photographer away from a nest.

After breeding, they either remain at the nesting area or move relatively short distances to nearby estuaries.
Typical nesting surface, and one of the team striding it out. Being very careful to not stand on eggs!
On the wing. A black fronted tern. Not in the Hunter though, but the Tasman River near Mt Cook. The blue colouring of the very cold water is caused by rock ground up by glaciers.

There are about six species that are primarily dependent on the braided river habitat: wrybill, banded dotterel, south island pied oyster-catcher, black-fronted tern, black-billed gull, black stilt) as well as the caspian tern and the pied stilt. The villain of the piece though is the black-back gull, as they predate on the eggs of the others.

Teaming up – linking arms for mutual support. Lots of concentration is required so it’s harder to observe what maybe in the air ahead. However the most experienced person leading the crossing, which is nearly done, has in this instance time to look. River crossing is best done by not looking down, which upsets balance, and with great care – there is no Plan B if people get swept away.
When not to cross at all – just too big and not braided into smaller channels.
The job is going well!
What we don’t want to see, but if we do, weeds are recorded as Way Points on a GPS, so that DOC staff can return later to deal to them. The most often encountered on the above mentioned rivers is this area, is often broom.

We don’t encounter many lupins in the above mentioned rivers. This photo is in the nearby Ahuriri. Lupins, which the birds don’t like, offer cover to predators. Foolishly seeds were spread many decades ago by well meaning people wanting to add some colour to the grey landscape. And the seeds can remain for years until uncovered by a flood as they’re coated with a protective oil.
A sad aspect of some surveys is that we know that after a bank-to-bank spring flood hundreds of these young birds are washed away. These are a few surviving gulls after such an event in the Matukituki a few years back.
Knock off time – a classic old-time hut.
Every hut has one
Evening and time for sleep. Tomorrow morning the survey will resume tidying up the riverbed to the right.
Job over and pickup
The long and sometimes bumpy drive home beside Lake Hawea

Obviously the results of such monitoring give a good guide as to the health of the environments concerned.

However the data as regards where breeding colonies are located, can be used for the most efficient locations for a new trapping lines. There is an attrition of traps though – during floods despite them being anchored by a chain to a long steel stake hammered in, they get washed away. Often the best compromise often considered, is for them to be near a bank that exhibits a history of stability, and place them with a shorter distance apart than the 200 mt standard in the bush, so as to create a fence of sorts.

In reply to a recent article (“Is our water quality testing of Lake Hawea proactive enough?”)

In reply to a recent article (“Is our water quality testing of Lake Hawea proactive enough?”), the Guardians of Lake Hawea would like to reassure readers that the change in lake colour this summer is not due to an algal bloom.

The change from clear to bright or milky blue is caused by an influx of sediment from the lake’s major tributary, the Hunter River, at the head of the lake (photos 1 & 2).

Photo 1:  Lake Hawea adjacent to the Hunter River delta on March 10 2018.  Delta of Big Hopwood Burn visible near top of picture. The water is discoloured with sediment near the river mouth. Trevor Chinn photo.

Photo 2: The lower Hunter River on March 10 2018. The water is milky with sediment. Delta of the High Burn at lower left of the picture. Trevor Chinn photo.
Chinn photo 2

This occurred on and following 1 February with heavy rainfall from ex-tropical cyclone Fehi, and is unlikely to be related to warm summer temperatures in the Queenstown-Lakes district.

Photo 3: Flight over Lake Hawea on March 29 2018. Sediment-laden water flows from the Hunter River. Highburn Delta on left and Big Hopwood on right. John Taylor photo. Chinn photo 3

Chinn photo 4

Even if the colour does not return to clear in the near future, this is not an issue of poor water quality or the health of the lake. People who have lived near Lake Hawea for many years say that such colour changes after rainstorms have happened in the past.

So the short answer is that there should be no concern that warm weather and algal blooms have been a concern at Lake Hawea.

In the longer answer, below, the Guardians deal with some of the other questions in the article.

Is our water quality testing of Lake Hawea proactive enough?

The water quality testing is carried out by Otago Regional Council (ORC), which is currently 18 months into a “3 years out of every 10” State of the Environment Reporting Exercise. This means that the Regional Council are currently doing substantially more than they would normally be doing to monitor Lake Hawea water quality.

Following is a list of what ORC are currently doing:

On a monthly basis, samples at one site in Lake Hawea (4.5-5kms from the dam) and one site further north on a quarterly basis.

At each of these sites the following is undertaken:
Lake Hawea: Open Water “Surface” Sample

–  Sonde profiles – chlorophyll fluorescence, dissolved oxygen, pH, and temperature.

– Secchi depth (shaded side of boat with bathyscope)

–  Lake Snow tows

–  algal biomass and community  composition

– Zooplankton tow (drop net to 150m and slowly retrieve). These samples are being preserved and archived – not being analysed.

• Pooled sample from 0.5, 15, 30 and 45 metres

• Total nutrients, total dissolved nutrients and dissolved nutrients
• Total Organic Carbon / Dissolved Organic Carbon
• Chla (2 litre sample)
• Phytoplankton cell counts
• Suspended and volatile solids

Lake Hawea:  Open Water “10m” Sample

• Sample AT 10m

• Total/dissolved nutrients
• Chla (2 litre sample)
• Sonde profiles / Secchi depth

–  algal biomass only

Lake Hawea: Open Water “Deep” Sample

• Sample AT 150m

• Total/dissolved nutrients only

These samples are taken by Regional Council staff and are analysed by Watercare Laboratory, who are contracted by the Council to undertake this work.

Otago Regional Council are currently considering an increased monitoring programme for lakes Hawea, Wanaka, Wakatipu and Hayes (Otago Daily Times, April 23 2018).

Is the change in water quality only temporary?

Yes, water clarity will recover when sediments settle out and or flow through the lake. Another event like this has occurred on Lake Wakatipu, where the whole lake (right down to Kingston) changed colour in January 2014 after a massive landslide into the Dart River. The upper part of Lake Wakatipu is still cloudy when the Dart River floods, but much of the lake is clear much of the time

If the lake water clarity does return to normal, will the deterioration be repeated with increased hot weather spells in future summers?

As the cloudiness of the water is caused by sediment, any future hot weather should have no effect. The lake water clarity will be continue to be impacted by heavy rain (as at Lake Wakatipu).

Are our current tolerances of nitrogen levels within the lake too high given the probable increase in mean summer water temperatures resulting in risk to further and perhaps more serious algal blooms?

There have not been any “serious algal blooms”. Lake Hawea nutrients (nitrates and phosphates) are shown by ORC sampling to be very low.  Phosphorus is at the limits of detection and total nitrates are only around 0.06mg/litre, with ammonium nitrogen around 0.005mg/litre.

In fact, the small cyanobacteria observed are some of the primary producers in the lake ecosystem – like the grass at the bottom of the food chain. They are not the larger forms such as Phormidium, which occur in warmer and more nutrient-rich water, and can give rise to toxic algal mats. It is incorrect to suggest that serious or toxic algal blooms occurred in Lake Hawea in the past summer.


Jane Forsyth

Don Robertson

on behalf of Guardians of Lake Hawea

Categorized as Hawea

Is our water quality testing of Lake Hawea proactive enough?

Anthony Coote, local Geo-scientist reports: 

Is our water quality testing of Lake Hawea proactive enough, and are any measured tolerances of deemed good quality appropriate, given climate change.

If you thought that Lake Hawea hasn’t looked right for about a month now, you are not alone and probably not mistaken: pale blue green in colour rather than the normal pale to dark blue. The water is not clear around the edges.

A panorama of the lake last night shows the colour change quite clearly. Of special significance is the drop off in clarity from the, milky look (unusual) in the immediate foreground, going out a few meters to where obscurity now reigns…
Lake Hawea water clarity compromised

This is how it used to look regrading colour and clarity, for years gone by…
Lake Hawea water clarity

The change appears timed with the end of the really hot weather during mid to late January with resulting increased lake water temperatures.

The poor water clarity can’t be explained by suspended mud (clay and mica mineralogy) as the lake has been low all summer with little in-flow. A sudden increase in water inflow, resulting in minimal lake level rise, in relation to the down-graded cyclone Fehi rain event took place after the change in lake water appearance. Furthermore, the lake water quality remained high all last 2016-2017 summer when high lake levels were sustained by north-westerly rain in tributary catchments.

Working on the suspicion that an algal bloom is the cause of the lake colour change, water samples were analysed under a microscope. As a possible cause to the change in lake water quality, a range of micro-organisms were identified including algae, dynoflaggellates and possible cyanobacteria. Whilst the preliminary study is only semi-quantitative, alarmingly the most abundant identified micro-organism is the possible cyanobacteria, the “blooming” of which is mostly likely to cause the current lake water discolouration.

The questions are:

Is the change in water quality only temporary and that it will revert to normal conditions once water temperature stratification is lost resulting in termination of the algal bloom (assuming it is the cause)?

If the lake water clarity does return to normal, will the deterioration be repeated with increased hot weather spells in future summers?

Are our current tolerances of nitrogen levels within the lake too high given the probable increase in mean summer water temperatures resulting in risk to further and perhaps more serious algal blooms.

Anthony Coote MSc (1st Class Hons) MBA, member AIG & SEG

Hawea kiteing
Lake Hawea kite surfer

Read a reply to the above by the Guardians of Lake Hawea ~ dated 11 May 2018 >>

Letter: Aquifer concern |

Trevor and Barbara Chinn, friends of mine who live by Lake Hawea, may have become very mindful of water quality by the proximity of many thousands of dairy cattle at nearby Hawea Flat.

New Zealand Dairy Cows
Photo by Southern Light

Trevor’s letter below should be read in the context of his lifetime’s work as an internationally acknowledged glaciologist

The South Island has been blessed by massive supplies of gravel spread from the Southern Alps down to the coasts to form fertile valleys and plains holding pristine aquifers.

I have been concerned about the effects of the recent explosive spread of dairy irrigation in the catchments feeding these aquifers.Over the gravel plains of Canterbury, Mackenzie Country, Upper Clutha and Southland, with annual rainfalls of around 800mm

Read more at the source: Letter: Aquifer concern |



The nearby Cardrona Valley and a weather change

We’ve just had many days of settled weather in Wanaka and in winter this equates to either an inversion cloud base hanging over the town [where the temperatures actually are higher as one ascends – proved by going up to a ski area], or the skies stay clear and we have wicked frosts…
Hawea River frost and sunrise

And it’s when the weather is on the cusp of change that other possible scenarios present themselves as landscape photography opportunities. In this case it’s warmed up as cloud with accompanying wind comes in from the north west.

For this image, just a 20 min drive up the Cardrona Valley was all it took to capitalise on the change photographically speaking…
Mt Cardronai