A Bunch of Negatives & A Big Postive

In this, the third part of the Mpofana River Report, Penny Rees writes about Alien Invasive Plants.

It was extremely encouraging to see the sterling job that the Balgowan Conservancy and some landowners have done by clearing invasive plants in the 32 metre buffer along the Mpofana River.  Thus far a total of 6 kilometres (both sides of the river for three km in total) have been cleared of Bugweed,

P1430854

wattle

P1430868

and some bramble.

P1440279

This is only the beginning as there are still many more areas that have been targeted. This will go a long way towards improving the health of the river, and all those concerned are heartily congratulated. Of the eight rivers that DUCT staff have walked, this is the largest private invasive control effort we have seen. Well done to all concerned.

Sadly, that’s where the good news ends!

Some of the negative impacts on the Mpofana are found along the entire length of the river. These include pastures, timber, gardens and lawns – not only in the buffer but often up to the rivers edge.

P1440508

Thriving in the buffer are also invasive alien plants: bramble, self seeded wattle and bugweed

P1440025

Construction of two different types was observed in the buffer – Downstream of the outfall this was undertaken by a landowner,

P1440553

whilst upstream of the outfall, construction was for the new Mooi uMngeni Transfer Scheme pipeline at river and wetland crossings.

P1430919

P1430833

At these points, the meagre mitigation measures seen during the walk did not raise our hopes that enough care was being taken to minimise impacts on the Mpofana.

P1440043

Of concern is the potential lack of post pipeline construction rehabilitation and monitoring which could lead to silt loads entering the Mpofana in places where up to now there have been no siltation impacts.

ms site 1

Additionally, the disturbed soils will be an ideal sprouting ground for invasive species such as wattle and bug weed

P1440028

On the other hand, upstream of the outfall cattle trampling of river bank and wetland edge was far more prevalent

P1440195

 

P1440329

There were plenty of signs of nutrification:

Algal blooms – 5 sites: 4 on livestock farms, 1 residential

P1430767

Oxygen weed – 10 sites: 2 in dams, 2 near residential, 6 at livestock watering points

P1430948

Seen only upstream of the outfall: one rubbish pit only metres from the river

P1440741

And the highly invasive Pickerel Weed – 2 sites: dams

P1430929

Finally there were two impacts which were clearly different up and downstream of the outfall. They are as follows:

Reduced Flows:

Upstream of outfall: The first water extraction point on the Mpofana is approximately 100 metres below the source spring. This is followed by dams which do not release any water into the stream,

P1430778

plantations across the stream that have dried up the water,

P1430844

water extraction pumps,

P1440562

extraction for the pipeline construction

P1440314

and a small non-permanent irrigation furrow for subsistence vegetable farming.

P1440088

All of which, combined with the lack of rainfall over the last few months, have caused the river level to be either non–existent or very low.

P1440074

Downstream of outfall: the amount of water slowly increases downstream as water from tributaries enters the Mpofana and the number of dams and plantations are fewer.

P1440947

Siltation of river bed and submerged rocks:

Upstream of outfall: Occasional areas of elevated silt in the river from cattle trampling and erosion from paths accessing the river.

P1440181

Mpofana banks are extremely vulnerable to water or wind erosion at pipeline construction points due to insufficient cover on exposed river banks.

P1440037

P1440039

Downstream of outfall: Almost constant elevated silt levels on the river bed and submerged rocks have the effect of smothering the life in the Mpofana.

P1440737

As this was not observed upstream of the outfall, we have concluded that the silt is a direct result of the erosion caused by the inter catchment transfer.

Advertisements

About Nikki Brighton

I live in Howick, between the river and the hills. I enjoy pre-dawn walks in the streets with my dog, sitting on the veranda with crochet and tea, and harvesting vegetables outside the kitchen door.
This entry was posted in Uncategorized and tagged , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s