Southern ACT Catchment Group

Waterwatch Words – May 2008

            How is the General Condition of Your Site?

    Why do it now?:  Now that the autumn is upon us and the main weeds have died back for the winter - even the willows and poplars have turned yellow - it’s time to have a good look at the site itself and see if it looks better than it did this time last year.  With a quite gentle summer behind us and a moderate amount of rainfall, much of it at opportune moments, many places along the Murrumbidgee are looking good. 

At your site the native upper storey (that’s the trees), and middle storey (that’s the shrubs over 1 m high) will now be clear to see in the autumn and winter landscape.  The upper and middle storey weeds like willows, blackberry and Hawthorn, colour up at this time of the year.  The grasses, local and exotic, are usually in seed, and are then a little easier to identify.  The annual weeds have died down, and while they aren’t much fun to identify to species, their impact can be contrasted with the still green locals.

    What are these storeys?: In the scheme of things woodland, whether it is along waterways or in open country, is characterised by having plenty of trees, scattered or in clumps –the upper storey – with a generous layer of shrubs between 0.5 and 3m tall – the middle storey – and much of the ground is covered with smaller shrubs but mostly softer plants such as grass, daisies and other annual plants – the understorey.  Grassy woodland has large areas of grass between widely scattered trees; tall woodland has many trees over 20m in height; Black cypress woodland has mostly black cypress trees; apple box woodland has mostly Eucalyptus bridgesiana trees; and so on

    What are our waterways supposed to be like?: The riparian vegetation, and the near-riparian vegetation at our sites, depends on quite a few things. The first is the actual form of the river at the site: Angle Crossing is on a sweeping bend with steep spurs of hill-slope on both sides; Tharwa Bridge is half way down a long, wide reach through a simple flood-plain of sand bars and flood runners, with terraced banks on both sides, and higher terraces beyond; the Point Hut Crossing to Pine Island area is a complex flood plain with plenty of bedrock outcrops and sandbars enclosed by sloping banks with rock outcrops and rolling hills beyond; while Kambah Pool is once again in narrow gorge country with a narrow riparian fringe and steeply rising hill-slopes.  In short, Angle Crossing should have a wattle and bottlebrush riparian fringe, backed by the Eucalypts of the hill-slope; Tharwa Bridge should have a grand forest of Manna Gums with occasional sheoaks; Pine Island has graceful tall sheoaks but should have cypress pine woodland behind; and the narrow fringe of sheoaks at Kambah Pool should have the hill-slope eucalypts behind it. But that was once upon a time, and long ago…

We have constructed or deconstructed much of the urban riparian areas.  The creek-lines have been much changed, sometimes disappearing completely to become open or covered drains.  The lakes and ponds may have been built in once swampy hollows, but now have fixed depths and margins with partly manicured vegetation.  Some areas have been crafted to mimic the natural systems, but all are radically changed.  That doesn’t mean they cannot be assessed for the health of their vegetation, it just means that some adjustments have to be made to how things get scored.

    How is riparian vegetation health assessed?: The Rapid Appraisal of Riparian Condition (RARC) approach to vegetation and habitat along rivers and creeks is designed for less rugged country than most of our sites.  The designers are always ready to hear what we found useful and what we didn’t think was appropriately weighted for our waterways, but they do ask that we trial it at as many sites as we can.  It is a good template and gives us all a comparable score for our site both to compare in time and over a catchment.  You can find it on the Land & Water website at
    http://products.lwa.gov.au/products_list.asp
and select title No.1.

There are a couple of tricky bits at the very start of the scoring sheet  Here are some categories that require careful interpretation.

            Longitudinal Continuity of Riparian Canopy greater than 5m wide.  You are asked to make an estimate of the tree cover (upper storey) along your 200m + creek or river bank.  Stick to what is actually there…if it is bare, score it that way!  And don’t be too precise…sometimes there may only be room for one line of trees and a narrow, but real shade crown,…use your common sense.

            Channel Width: this is the part, wet or dry at the time you do your appraisal, that doesn’t have terrestrial or bank plants.  So it’s the river or creek bed, or the high water mark in the dam.

            Vegetation Width: this is the overstorey cover, which could be sapling sheoaks and River Bottlebrush or even (horror of horrors) blackberry bramble in patches between trees, or where trees cannot grow.  In most of our sites, the channel width isn’t more than 10m for much of the length of the waterway, dams and river reaches being the exceptions.

            Native and non-native: here we are being very parochial, Cootamundra Wattle, Tasmanian Bluegums and any Melaleuca species are considered exotic, as are some revegetation patches in places where they just were not before we put them there (river sheoaks above Point Hut Crossing are very probably planted, as are many up creek lines in urban areas … especially on the dry east side of Tuggeranong valley).  Silver Wattle, Red-Stemmed Wattle and Burgan are locals, even though they are invasive after fire.

            Tussock Grasses:  River Tussock (Poa labilliardieri) holds on to its flower heads and has rolled leaves, while the exotic African Love Grass (Eragrostis curvula) looses its flower heads at the end of the season (its main means of seed dispersal!) and has broader, open leaves that coil at the drying tips.

Describe what you actually see, to the best of your judgement.  I’d like to have us put together two things about the sites we Waterwatch:

1)      use the RARC as set out in version 4A; and

2)      make a list of as many of the plants, from the reeds to the trees for your sites, weed and all!

If you would like a helper with the RARC, Tanya or myself will be happy to oblige or we may be able to ask Fleur Horan or Joan Goodrum to give you a hand.  Getting 4 spots with 40m of vegetation can be a challenge in deep gullies, but do give it a try.  If you are clearly out of the riparian zone before 40m just note it.

For the plant lists, use whatever names you know…botanical, polite common, vulgar or your own ‘stuff with the grey feather-dusters on a long rod’ name. We will sit down and get the appropriate names in the end. The record is the thing! Don’t forget, we love collecting photos of your sites!

Stephen Skinner

                                    Waterwatch Coordinator,

                                    Southern ACT Catchment Group

                                    (02) 6296 6400; Waterwatch@sactcg.org