Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Friday, June 15, 2007

Kangaloon Hills - leaking like a seive.

Regular readers will have seen me talking about the rich red basalt soil of the Kangaloon Hills (left).

The soil of these hills soaks up water - then leaks it back out from springs, into the streams (see below).

This process is groundwater generating "base flows" as they are called, which form rivers.

East Kangaloon -
above the road
In the Kangaloon Ridge, these hills are less than 1 Km long (in catchment length) before they form permanent streams (see left). In other words, permanent streams, such as these headwater streams of the Nepean River, form less than 1 Km from the top of the Kangaloon Ridge. They are fed by springs in the tops of the red basalt hillsides.

East Kangaloon -

Permanent stream
between Kangaloon Rd,
and Kirkland Road
Yesterday, Robertson recorded 96 mm of rain (approx 3 and 3/4 inches). This follows even heavier falls over last weekend. The hills are soaked. So, rainfall becomes "run-off", and it is "run-off" which puts water into dams.

East Kangaloon -

permanent stream
beside Kirkland Road
Just near the old Forestry Station, at East kangaloon, this permanent stream was racing today, with a considerable flow.

Dairy Pastures with

flow - East Kangaloon
On the Watman Dairy Farm, this gently sloping pasture, with a catchment of less than 300 metres, below the basalt hilltop, was "flowing".

In the wet, the springs in the basalt hills form streams in as little as several hundred metres distance from the ridge-tops. Those tiny flows are not permanent streams, but they are important to the flow of the real streams, none the less, at times of heavy run-off.

As someone said to me today:
"It is such a shame it all goes to Sydney where they waste it!"

It is worth noting that unlike the rain which fell in the Central Coast and much of the Hunter, at least this rainfall run-off goes to dams in the Upper Nepean River system, where it can be utilised. See my comments earlier this week on the wasted water flowing, unharnessed, through those systems, last week. And worse, the Mangrove Mountain dam with inadequate catchment, to utilise the rain which did fall.
Wingecarribee Dam -
from the air

The rain which fell on the other side of these hills (see top photo) flows into the Wingecarribee Dam ( a mere 3 Km away, over the back of these hills) and then into the Wollondilly River, before going to the Warragamba Dam.

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