Catchment Update Summer 2010

The ‘eofys’ (end of financial year) monster will and should be used by all as an all round excuse for things being late. I will of course use this same excuse for as long as I can get away with it.
Here, finally, in mid winter, is the report for autumn.

In General:
Well above average rainfall for February, March and May, has had a big impact on our region over autumn. The dams topped up to about 56% for the first time since 2006 (ActewAGL data) and the long suffering Murrumbidgee River also managed a clean out and a top up during this time.

Admittedly, most of this rain was experienced in February and ‘Little Dry Creek’, way up in Namadgi NP, had water flowing in it for the first time in nearly two years. Winter will be interesting, as so far the rainfall has been below average (even though it’s drizzling outside as I write this!) Our base flow (‘permanent’) creeks will be watched closely as indicators of how well our ground water storage levels are fairing.

I am now including an overview of algae assessments as well as RARC and macros surveys (signal 2 score) where they are recorded. The RARC need only be undertaken annually and macros need only be conducted in autumn and spring. These are important indicators of catchment health and form part of the reporting we provide to the ACT government. It’s great to see volunteers becoming more confident in their use and this feed back is in appreciation of your efforts.

Here is how the season treated our waterways:

Water Temp:
The general pattern was for creeks in the higher altitudes to be several degrees cooler than the main rivers and lakes in Canberra. No surprises here. Urban drainways, such as Wanniassa and Village Creeks, also had much warmer water than elsewhere.

This varied little between 6.0 to 9.0 over most of the region. Some of the higher altitude creeks showed quite low (acidic) readings. See below.

Salinity readings were all well below 1000uS (level of concern) around the whole region.

The Murrumbidgee showed a remarkable drop in NTUs at all monitored sites. The urban sites were much cloudier, probably as a result of disturbance to sediment in the silt traps from increased urban runoff this season.

Dissolved Oxygen:
Readings of lower than 4.0mg/L indicates water may be considered ‘stagnant’. There was one upland creek in the Gudgenby sub-catchment with this issue. All other sites gave acceptable readings.

Phosphates, Nitrates and Nitrites:
Generally well below the level of concern at most sites. There were high readings at known ‘hot spots’ which where around ponds and lakes.
RARC: This was conducted at several sites in the Upper Murrumbidgee catchment and one site in the Gudgenby catchment. See below.

This was conducted at several sites in the Upper Murrumbidgee catchment and one site in the Gudgenby catchment. See below.

Signal 2 Score:
This was carried out at 5 sites in the upper Murrumbidgee catchment, 3 sites in the Tuggeranong catchment and one site in the Gudgenby.

There has been a transitional period this season as training and support for the new recording method has got under way. The resulting measurements have been quite varied around the sub-catchments. See below.

Lower Molonglo:
Coppings Crossing had a welcome flush in March. Never the less, salinity levels at Coppins Crossing remain 3 times higher than most sites in the southern catchments. Development on the new suburbs of Wright and Coombs will be the biggest impact on this sub-catchment especially on the remnant yellow and apple box woodland. For more details on issues relating to the Molonglo River and surrounds see the Molonglo Catchment Group at or phone 6299 2119.

Lower Murrumbidgee:
This sub-catchment has been a hive of construction as work has intensified on the dam. Volunteers have recorded much larger levels of noise and activity in the region as a result. Water levels have shown overflows at all sites this season as well as a reduction in turbidity in the Murrumbidgee R. which is good news. Algae readings at the Cotter campground indicate the site is ‘degraded’ based on the type and quantity of algae observed. Not such good news.

Upper Murrumbidgee:
The drop in turbidity was the big news this autumn. Many groups added comments saying this was the clearest they had seen the river in many years. Macros surveys in April gave good results with both Point Hut and Angle crossings indicating ‘good habitat and water quality’. The algae readings from the site where this was recorded also suggest good water quality.

The Riparian Assessments completed gave good scores (35/50) for sites near the ‘Gigerline’ reserve, but less impressive in built up areas (e.g.20/50 for Conder Wetlands). Lack of canopy trees (native or otherwise) over 5m in height, native regrowth, and dead trees providing nesting sites are a big contributing factor to low assessments.

Conder Wetland looking west into the sunset.

On the news front there has been a lot of commitment and organizational activity focusing on the upper Murrumbidgee recently. Tanya Noakes, our ACT facilitator, is to be congratulated as being at the centre of most of these initiatives. Highlights include the appointment of a Waterwatch coordinator for the Cooma/Monaro region with ActewAGL’s support, the UMDR’s continued growth and the MCMA’s injection of funds into land improvement work in the Numeralla and Murrumbidgee catchments.

A warm welcome to Kim and Caroline to the monitoring of this sub-catchment. They join Marg Peachey in filling a substantial gap we had in keeping an eye on Lake Tuggeranong, our biggest urban water body in the southern ACT.
There were some ‘spikes’ in nutrient readings around the lake in April. These had dropped by May, possibly as a result of the month’s flushing rains.

Josh crossing Lower Tuggeranong Ck in May.

Macro’s surveys at Village Ck and Lower Tuggeranong Ck gave woeful scores, suggesting poor water quality, confirmed as well by a poor algae score for lower Tuggeranong Ck.

Upper Tuggeranong Ck faired a little better in the bug stakes. Interestingly, it gave us the highest salinity reading in the southern region, consistently above 400 uS. The testing is done 50m or so above the concrete channel, raising questions about the possible source.

I had recorded the Cotter campground site under this heading in the first update. My mistake, it is actually part of the Lower Murrumbidgee sub-catchment and is discussed as such above.
There are 3 sites that are intermittently monitored in the Cotter catchment, however no data was submitted for the 3 months of autumn this year.

The creeks running into Paddy’s River have enjoyed the same flushing as elsewhere in our region. Lots of reports came in about bent over vegetation on banks and piles of debris as a result of high flows. .

Debris from high flows at lower Gibraltar Ck in March

Hospital Creek in the Namadgi NP gave some very acidic readings in its lower reaches combined with very low oxygen levels. Looking back at the historical records the acidity of the lowest site on Hospital Creek has been increasing steadily over time from around pH 7 in 2003 to around pH 6 in 2008 and down to around pH 5 for all the tests this year. I will keep you informed of any investigations that arise.

The bogs of Lower Hospital Creek

A huge thank you to all those groups and individuals involved in collecting data for this update. Waterwatch volunteers provide vital and immediate information on the state of our waterways which is being increasingly used by government and corporations locally and nationally.