Waters & words

Posts tagged “Ngeli mountain

Lessons from the landscape: the 1600m contour

Here in the KZN midlands, altitude is accepted as a defining criteria for Trout water. It has long been held that trout will survive above 1200meters above sea level, and there is very little fishable water above 1800metres.   So within that band of 1800m down to 1200m, there are a few critical bands, and I would argue that one of them is the 1600m band.  I say that because every listed trout stream in these parts rises above 1600m.

So here is where that contour runs along the front of the Drakensberg:

The 1600m contour in KZN

Interesting isn’t it!

For me what makes it fascinating is that:

  • It shows deeply incised valleys where streams cross the line remarkably close to the escarpment
  • It shows that ridge of high ground that runs out into the province from the end of Giants Castle to Inhlosane mountain, very clearly
  • And from the few spot heights I threw in on the map above, you will see that there are many islands of ground above 1600m, many of which are a long way “from the mountains”.

One also  quickly concludes that the altitude alone is a poor measure of where trout thrive.  In studying a map in detail, you come to realise that trout will survive and indeed thrive in stretches of river at low altitudes where the valley sides rise to much higher altitudes, and cool short tributaries contribute to the river (Examples, The Inzinga and the Umgeni).  Also, if the drainage upstream of where you are standing is overgrazed or densely inhabited, or intensely farmed, then altitude becomes a less significant measure ( Example, The Bushmans below 1400m …below the clinic).  Also, if the stream is on a steeply drained area, where the cold fronts coming from the south west are forced up to generate orographic rainfall, the trout are better off.  So, for example, south of Giants Castle, the 1600m contour averages about 130 kms from the sea. North of the Hidcote ridge, where the berg tracks north, north-west, the sea is an average of 175 kms from the sea, and over 200kms in many cases.  Here it is drier, there are a lot fewer trout streams, and those that there are, have just a short run in the berg before they spill out onto flatter, warmer plains where they don’t hold Trout.  In fact, down south (and off below the limits of the map above), we know that in the Ingeli mountain area, trout are found as close as 80km from the sea at altitudes of under 1000m.  There the slope from the sea to Ngeli mountain is 25m per km.   From a similar altitude on the Mlambonja at Cathedral Peak, to the sea, the slope is under 8m per km.  Those southern areas get more life-giving mist and drizzle.  Did you ever notice how there are no thorn trees along the N3 from Maritzburg to Hidcote, then on the Estcourt side of Hidcote (the dry side), you can draw a line where the thorns start. Thorns like drier , and/or warmer climates.

Returning to our 1600m contour:  At a glance, it is encouraging to see how much land above this contour is in the Drakensberg park, and therefore conserved as catchment area.  The exception is where the land juts out from Giants Castle.  Parts of that area (top end of Dargle, Inzinga, Fort Nottingham, Western side of Kamberg etc) have at times been threatened by proposed developments. (I hope you will join me at the protests if they try again). 

 

See you in the highlands……above 1600 metres perhaps….