Compiled by Nick James
Drought or not?
Venture outside your air-conditioned office or lab. What do you see? A very green and lush landscape. So are we experiencing a drought or not? Grahamstown’s water supply dams (Settlers and Howisons Poort) are still very low. The level in Howisons Poort is fairly irrelevant as this dam is largely silted up and has water pumped into it from Settlers Dam, before that same water is pumped to the water works at Waainek. Despite recent ‘good’ rains, Settlers Dam is still at around 19%.
Rainfall is measured at four points in, or near town: two points in Oatlands, one in Sunnyside, to the south, and one 5km from town in the hills to the SW. Typically, the Oatlands sites record more rain from thunderstorms, which build up over the Fish River Valley and then move southwards, and at the more southerly sites, more rain comes from orographic rain (moist air that ‘bumps up’ against a mountain). Rivendell, the most southerly site, receives on average 25% more annual rain than town, due to the higher ‘drizzle type’ rain on the hills facing the sea.
In the most recent rainy spell (10-15 February), Rivendell received 64.5mm rain, compared to the 55mm in Oatlands, and around 37mm in Sunnyside. But Rivendell did not experience the 15mm thunderstorm on 14 February which caused considerable runoff in town. This runoff drains into the Kowie ‘ditches’ and ends up in the Bloukrans River, so does not fill our dams. Despite 64mm rain to the south west, there was very little runoff in the Settlers Dam catchment. The moral of this is that low intensity showers, interspersed with sunny periods, have little effect on raising dam levels, but make for a green landscape. For those concerned with global warming, a piece of good news is that increased intensity weather events such as thunderstorms are expected to be more common…and will fill our dams!
Spring into action
Three cheers for Makana Parks Dept staff who weeded the garden beside Fairview Spring on the Port Alfred road last Friday. And a big thank you to Tobias de Vlamingh, who runs Grahamstown Market. He has generously offered to keep the area clean and assist in maintaining this community facility.
It would be great if everybody could show respect by not littering, dumping, weeing or worse, around this valuable source of drinking water!
http://www.grocotts.co.za/2018/03/06/council-zones-in-on-water-crisis/
