Farrer Memorial Agricultural High School: Cockburn River
Bottle number: 37
Collected at: Cockburn River weir/fish ladder, Kootingal, NSW.
Site is east of Kootingal one kilometer along the 'Back Kootingal Road' downstream from a concrete bridge.
31° 03 '48.64S, 151° 03'17.98E.
Collected by: Farrer Memorial Agricultural High School
Teacher: Mark Treneman
The site was chosen because:
a. There was no data on water quality for this major tributary of the Peel/Namoi.
b. There was an easily accessible weir and fish ladder.
c. It's the only river in NSW that was destroyed (?) by cars ... cars need roads ... roads need gravel ... duh
Water quality (as at 24 November 2009, 1.30pm EST):
Also tested temperature: 26 degrees Celsius
ACT Waterwatch says:
This group really know their stuff. The raised salinity could be a symptom of irrigation in the area. Turbidity is also a bit higher than one would want, but considering the massive changes that have gone on in the system, it's not too surprising. Fish passages in the weirs are great to see, and quite forward thinking. Water quantity is a big problem in this river, as it is throughout the whole Murray Darling, and a problem that each and every one of us has some control over in our own home and garden.
About the site
The Cockburn River was used as the major source of gravel for the construction of roads and for the production of cement in the Tamworth area. The unsustainable gravel extraction lowered the bed of the river by over three meters in parts. These practices substantially altered the fluvial dynamics of stream flow (speed of flow increased) to such an extent that there was a real danger of all the timber and concrete bridges being undermined by bed lowering. To avoid this possibility a number of experimental weirs (in bed structures) were created both upstream and downstream of major bridges. These weirs were designed to slow down water and build up gravel under the bridge supports. These weirs were all constructed with fish ladders.
The site is surrounded by small farms mostly irrigated lucerne with the upper valley slopes dryland grazing for sheep, cattle and horses. The town of Kootingal (population 1400) is one km from the site. Town water comes from alluvial (local water) bores. This is happening more often due to increasing population and low flow rates. Recently Kootingal has been connected to Tamworth potable water supply by pipeline. Kootingal's sewage treatment plant is located in close proximity and discharges onto alluvial soils downstream of our site. Bore water and river water are highly interconnected. Irrigators are issued with a notice to quit pumping if the gauging station shows a flow depth of less than 50cm.
The riverene environment is not pristine in any area nearby. There are some remnant River Red Gums (pre gravel extraction) and some Casuarinas but mostly introduced species especially Willow trees and other weed species especially grasses. Goats and cattle constantly graze both sides of the river at our site.
The major threat is unsustainable usage of water for irrigation for agriculture and town usage. During summer there is often no flow.
What's going on:
The weir has stopped bed degradation. Locals still use it as a swimming hole and for fishing. The upstream bridge is a major roosting site for swallows.
The Farrer Waterwatch group measures up to six water quality characteristics at this site (and at two other sites). We always measure temperature, pH, salinity and turbidity. We can also measure phosphates and dissolved oxygen. These measurements are entered into the Waterwatch website.