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This section is divided into two parts. The first deals with the Shoalhaven River, Tallowa Dam and the transfer of water into the Sydney Catchment system. In the Shoalhaven region most of us depend on the Shoalhaven River for the supply of our household water; St Georges Basin residents certainly do. However, we are not the only consumers of Shoalhaven water; the Tallowa Dam and some pumps allow Shoalhaven water (which includes that of the Kangaroo River) to be fed into the Sydney Catchment system.

The second part deals with four particular matters (feral animals, phytophthora, caulerpa, and pollution) which should concern those of us who live in the St Georges Basin area. It should be noted that these matters are not necessarily specific to the Basin area.

The Shoalhaven River and Tallowa Dam

In the news in recent times is the heavy use by Sydney of Shoalhaven River water from the Tallowa Dam. The ecological condition of the river downstream is deteriorating. The ever increasing population of Sydney means that this situation will continue and worsen with time, and will be more marked in times of drought. In July 2006 the level of Sydney water catchments was just above 40% of capacity in spite of water restrictions. If you want to check the level of the Sydney water supply go to the Sydney Catchment Authority (SCA) website. Here one can find daily information such as temperature and rainfall (for Sydney), the amount of water supplied, as well as the storage level for the total catchment. Only weekly statistics are available for Tallowa. However, what are not given to us are environmental flows - daily or weekly. According to the SCA website the daily environmental flow from the Tallowa Dam equals the inflow up to a maximum of 90 ML (a ML is a million litres). Above this level the water presumably is retained in the dam or sent into the Sydney system. Plotting (shown in a new window) the storage data shows us that the Tallowa Dam got as low as 20% at the beginning of October 2003, in mid-February 2004, and in the middle of August 2004 it was down to about 15%. Most certainly 15% is an extremely low value; a result of sending water into the Sydney catchment area. We can also see that the last time Tallowa Dam was full was at the beginning of July 2003. This means that the full 100% operating storage of 35,300 ML was available (when full the dam actually holds 90,000 ML). Since then the graph is characterised by very rapid increases and decreases in the available storage. The rapid increases are due to natural flows into Tallowa Dam following periods of significant rainfall in the catchment of the Shoalhaven River. The rapid decreases are unnatural, occurring when water is transferred (pumped) to the Sydney catchment area.

Over the past decade the rainfall in the Sydney catchment area has dropped to about half the long term average and this situation is expected to continue. This behaviour is a result of the warming of our planet due to greenhouse gases. But it is still a matter of debate as to whether the greenhouse gases are a result of human activity or are a natural cycle, or a bit of both. Whatever the explanation, Sydneysiders need to better manage their water useage - install water tanks, recycle their water, etc; and the levels at which mandatory restrictions apply need to be raised. The first mandatory restrictions since November 1994 came into force on the 1st of October 2003. Level 2 restrictions began on the 1st of June 2004, and Level 3 on 1st June 2005.

NB The intention is not to indefinitely maintain details of the storage situation in Tallowa Dam; rather it has been to show the very rapid, and unnatural, reductions in the water level due to Sydney's thirst for Shoalhaven water. Details are not provided beyond August 2005 but can be obtained from the SCA website which is provided above.

Four Particular Concerns

In this section we highlight four concerns. Two of these, cats and other ferals, and phytophthora cinnamomi, are of a general nature, in no way specific to the St Georges Basin area. Caulerpa taxifolia refers to a marine plant infesting some NSW coastal lakes, including a few on the South Coast (unfortunately the Basin is now one of them -see the news page). The Henry Kendall disaster refers to a local accident which had a significant affect on the Basin. But something similar could occur at other coastal lakes where development is taking place. Click on your choice below for more information.

While these points have been chosen for amplification there are many areas which concern environmentalists, and indeed should concern everyone. All over the planet 'progress' continues, usually at the expense of the natural world. Buildings, industries, and other developments, invade and cover the land. Rivers are dammed for water and power, swamps and marshes drained, forests cut down and bush cleared for stock and crops. Many creatures and plants have been made extinct and many more are threatened. Much to our shame Australia has one of the worse records in terms of extinctions, most occurring since white man arrived. In lakes, seas and oceans commercial fishing has become so sophisticated with modern technology that fish stocks become exhausted.

The first two points on the list above refer to exotic 'invaders' in Australia but there are many more. Rabbits, rats, cane toads, foxes, starlings and Indian mynahs of course are well known. But there are others not so well known - such as fire ants, carp in our rivers and plague minnows (gambusia) in our creeks. Of course, there are many, many floral invaders (weeds) as well - blackberry, prickly pear, bitou bush and lantana, for example. The third point is closely associated with another problem in Australia, viz. the problems arising from feral domesticated animals. In this category, in addition to cats and dogs, are pigs, buffalo, camels, goats, deer, and even horses and bees.

bushcare Basin wildlife heritage Florance Larmer cedar plants problems news

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