一根掉落的树枝开始堵塞狭窄的小溪，导致上游积水。
A fallen branch began to occlude the narrow creek, causing the water to pool upstream.
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解释
堵塞（水道），自然物体阻塞狭窄水流通道
A fallen branch began to occlude the narrow creek, causing the water to pool upstream.
堵塞（水道），自然物体阻塞狭窄水流通道