Drought …or not?
Just when you thought we have had so much rain the drought has broken…think again. Although the rainfall during October and early November was the best for many years, it was so dry beforehand that much of it has simply been absorbed by the parched ground and the depleted water table. Remember also that Grahamstown has been dependent on only one source of water, the James Kleynhans Dam, which is fed by the Orange and Fish Rivers.
Drought …or not?
Just when you thought we have had so much rain the drought has broken…think again. Although the rainfall during October and early November was the best for many years, it was so dry beforehand that much of it has simply been absorbed by the parched ground and the depleted water table. Remember also that Grahamstown has been dependent on only one source of water, the James Kleynhans Dam, which is fed by the Orange and Fish Rivers.
Additional allocation of Orange River water to the Fish River is almost certainly out of the question, as South African water law stipulates that inland water may not be used in coastal areas. A morning’s wander around the countryside on the morning of Tuesday, 16 November tells the story. The best news is that Howison’s Poort Dam, which lies upstream of Settlers Dam, has gone from nearly dry just six weeks ago, to almost full.
When visited last Tuesday, the dam was only two metres from maximum water level. Once it spills, it will overflow into Settlers Dam, which is still at an all-time low. Many people don’t understand why some dams are so dry after such good rains, yet others are almost full. Here are the reasons.
Settlers Dam lies on the confluence between the Kariega River, which arises from catchments on the Lothians road, and the Oldenburgia, Berg and Palmiet Rivers of Howison's Poort. Upstream of Settlers, on the Kariega River side, is the large farm dam on Mosslands, which is still largely empty.
Howison's Poort Dam lies above Settlers Dam up the other arm, and this dam is probably easily 80% full now. Only when the Mosslands and Howison's Poort Dams are full, will Settlers Dam receive any significant inflow.
Along the Highlands road, and in the New Year’s River upper catchment, are Grahamstown’s two older water-supply dams, Jameson and Milner, on the farm Slaaikraal. Despite the good spring rains, both are virtually empty.
Jameson overflows into Milner, but Jameson Dam itself receives very little water until the large dam upstream on Coldsprings Farm overflows. Both these dams are a sorry sight, with hectares of dry, cracked mud, and the rusty eight metre iron water extraction towers, built in the early part of the 20th century, standing gaunt, a reminder of wetter times gone by.
The three streams of the Howison's Poort area (the Oldenburgia stream from the Conservancy of that name, the Palmiet River that flows adjacent to the N2, and the Berg River from the Highlands road area) are all flowing strongly. It is interesting to see these latter streams that arise from the more pristine mountain catchments in the grassland fynbos-covered hills to the west of Grahamstown are those that contribute most water to our water-supply dams.
The grassland fynbos-covered slopes have a thick but low aspect vegetative cover, with a layer of acidic soil overlying a deep clay layer and underlying hard, impermeable quartzitic rocks. These steep slopes, with their sponge-type covering, absorb rainfall until it reaches the clay layer, and then release copious quantities of clean, filtered water once this is saturated.
However, streams that arise from the thicket-covered catchments, such as the Kariega River, are not yet flowing well, and this may be partially attributed to both interception of rainfall by the vegetation type, as well as the underlying geology.
The more permeable shales of these thicket-covered slopes (such as the Kariega River catchment) require much more, and heavier rains, before streams begin to flow. In Featherstone Kloof, the headwater catchment of the Kowie River, springs and oozes have come alive again after months of near, but not total desiccation.
Being a grassland-fynbos valley, and having been so well-cleared of alien vegetation by Working for Water, this catchment is now working as it should do, and acting as a slow-release sponge feeding the lower Kowie River. A strong flow is passing under the bridge on the gravel road to Southwell, however further downstream (in the thicket zone) this flow is much-reduced . Hopefully soon, summer thunderstorms will augment the soft spring rains we have had, and get these streams really flowing!
Do your bit
If life in Grahamstown is to be sustained, water usage will have to be reduced at every level. Our municipality urgently needs to upgrade its water reticulation infrastructure, to minimise water loss through leaks. In every home, business and institution, responsible water use and grey water re-use play a vital role. New developments should consider the option of waterless toilets, where appropriate, and installation of rainwater tanks should be standard for every building.
Howison's Poort Dam in early October, and from the same spot on 16 November 2010 Settlers Dam wall, and the dry dam at the picnic site on 16 November 2010. The almost dry Milner Dam (left) and Jameson Dam (right) on 16 November 2010. Inflow from the Berg and Palmiet Rivers (left) and the Oldenburgia stream (right) to Howison's Poort Dam after the strong Spring rains.
Contacts for Makana Enviro-News: Nikki Köhly: n.kohly@ru.ac.za, 046 603 7205 / Lawrence Sisitka: heilaw@imaginet.co.za, 046 622 8595 / Jenny Gon: j-gon@intekom.co.za, 046 622 5822 / Dan Wylie d.wylie@ru.ac.za, 046 603 8409 / Nick James: nickjames@intekom.co.za, 046 622 5757 / Strato Copteros: strato@iafrica.com, 082 785 6403
