地理漫步·世界地理英语30篇（4）

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奥卡万戈三角洲：构造抬升与季节性泛滥塑造的内陆三角洲

Unlike most deltas, the Okavango flows inland onto the Kalahari sands instead of reaching the sea.
Tectonic uplift in the Angola Highlands diverts the river eastward, while a regional fault line blocks further drainage.
Annual floodwaters arrive six months after local rains, peaking in June when evaporation rates are lowest.
Papyrus and reed beds stabilize channels while filtering nutrients, creating rich habitats for elephants and sitatunga antelope.
Islands form where termite mounds elevate ground above seasonal inundation levels, enabling tree growth.
Water chemistry varies spatially: upstream channels carry more sediment, while distal floodplains accumulate dissolved minerals.
Climate models project reduced Angolan rainfall may shrink peak floods, stressing aquatic vegetation and fish spawning grounds.
Traditional pastoralists time cattle movements with flood recession to access nutrient-rich grazing lands.
Satellite imagery shows channel migration patterns shifting over decades due to sediment deposition and vegetation encroachment.
Hydrological connectivity between wetland patches sustains biodiversity despite increasing aridity across southern Africa.