File:Not Your Usual Flooding In Botswana - NASA Earth Observatory.jpg
Die oorvloei van 2012 was anders as die tipiese seisoensvloede wat die delta jaarliks beleef, en Guido van Langenhove van Namibië se Hidrologiese Dienste het dit as “'n buitengewone hidrologiese gebeurtenis” beskryf.
Die reëns wat die Okawango vul, val eintlik nie oor die delta self nie, maar wel oor die Angolese hooglande vanwaar die neerslag sowat 450 km (280 myl) ver met meanderende riviere oor 'n baie effense gradiënt afgevoer word. Gevolglik bereik die reënwater wat tipies van Oktober tot Maart in Angola val, gewoonlik nié voor Julie die bekken van die Okawangodelta nie. In Mei 2012 het water egter reeds die Okawango bereik en het dit na ander waterweë soos die Sawoetirivier oorgevloei.
“Die Okawangodelta ervaar nou reeds 'n paar jaar lank rekordvloede,” het Frank Eckardt van die Universiteit van Kaapstad gesê. “Ons het gevind dat die Botetirivier sedert 2009 oorstroom word, en het ook water in Xau-meer, suidoos van die delta, opgemerk. Verder sien ons nou water in die Selindakanaal, op pad na die Mababe-laagte, noordoos van die delta. Sommige van hierdie laagtes word net na dekadelange droogte met water gevul.”
Van Langenhove beaam dat die vloede waterweë in die streek herstel het wat deur sommige waarnemers as “fossielriviere” gereken is.
Hierdie beeld van NASA se Aardobservatorium is deur Jesse Allen en Robert Simmon verskaf, met EO-1 ALI-data wat goedgunstiglik deur NASA se EO-1-span verleen is. Die byskrifte is deur Michon Scott verskaf, met inligting deur Frank Eckardt, Universiteit van Kaapstad, en Guido van Langenhove, Hidrologiese Dienste Namibië.
One of the waterways linked to the Okavango Delta is the Savuti River, roughly 80 kilometers (50 miles) northeast of the sprawling inland delta. On May 26, 2012, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of water flowing through the Savuti River and into Savuti Swamp. The swamp sits inside the larger Mababe Depression within Botswana’s Chobe National Park.
Unlike the seasonal flooding that affects the Okavango Delta every year, the flooding in 2012 was unusual. Guido van Langenhove of Hydrological Services Namibia characterized it as “an exceptional hyrological event.”
The rains that fill the Okavango don’t actually fall over the delta itself. Instead, the rains fall in the Angolan Highlands and travel about 450 kilometers (280 miles) through meandering rivers and over an extremely shallow gradient. As a result, rains that typically fall over Angola from October through March don’t usually reach the bottom of the Okavango Delta until July. But in May 2012, water had already arrived in the Okavango and was overflowing into other waterways such as the Savuti River.
“The Okavango Delta has had record floods for a few years now,” said Frank Eckardt of the University of Cape Town. “We have seen the Boteti River in flood since 2009, and have also seen water in Lake Xau, southeast of the delta. Now we are seeing water in the Selinda Channel, heading into the Mababe Depression northeast of the delta. Some of these depressions only fill with water after decades of dryness.”
Van Langenhove concurs, remarking that the flooding had reactivated waterways in the region regarded by some observers as “fossil rivers.”
The Earth Observatory's mission is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models.
To download the full resolution and other files go to: earthobservatory.nasa.gov/IOTD/view.php?id=78166&src=...
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