This gallery is part of a special news series on global water issues.
这个图册是关于全球水问题的物种新闻系列的一部分。
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This gallery is part of a National Geographic News series on global water issues.
图片是国家地理杂志有关全球水资源问题的新闻系列的一部分。
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Normally, the cumulated water in top cover is drained to cumulated water well by gravity drainage, in emergency situation, the water would be drained by the self-priming pump installed in gallery.