💧 水资源：地球上能喝的水很少💧 Water Resources: Little of Earth's Water Is Drinkable
上一片烧的是地下的油，这一片数的是地上的水：蓝色星球向导翻开蓝星镇的水账本——地球水很多，能喝的却很少。Last leaf burned underground oil; this leaf counts the water above ground: our blue-planet guide opens Blue Planet Town's water ledger — Earth holds lots of water, yet little is drinkable.
第 1 步：能喝的水很少Step 1: Drinkable water is rare
先看总数：咸水占大头，能喝的只是零头。Totals first: salty water takes almost everything; drinkable water is just a sliver.
地球水里 97.5% 是咸水，不能直接喝。剩下 2.5% 淡水中，三分之二冻在冰川里。真正顺手能喝的，只有江河湖水一小勺。Of Earth's water, 97.5% is salty and undrinkable straight away. Of the 2.5% that is fresh, two-thirds sit frozen in glaciers. What we can readily drink is just one small spoonful of rivers and lakes.
水本来就少，还偏心眼：都挤在南方。Water is scarce — and unfair: it crowds into the south.
第 2 步：南多北少，南水北调Step 2: Wet south, dry north — move water north
中国人均水资源只有世界四分之一。南方多雨水漫田，北方少雨麦喊渴。南水北调就是修长渠，把南方水送往北方。China holds only a quarter of the world's water per person. The rainy south floods its paddies while the dry north's wheat thirsts. The South-to-North project is a long canal carrying southern water north.
调水来了还是不够：地里的水，一半都白流了。Even moved water is not enough: half the farm water runs to waste.
第 3 步：把每一滴都省下来Step 3: Save every single drop
农业最费水。大水漫灌泡黄了苗，还浪费大半。滴灌把水送到根边，中水回用让洗过的水再干活。Farming drinks the most water. Flood irrigation yellows the crops and wastes over half. Drip lines feed each root precisely, and recycled water (reclaimed water) lets used water work a second shift.
🎮 你来当水账先生（30 秒）🎮 Your turn: water accountant (30 seconds)
道理讲完了。打开蓝星镇的水账本：点开节水措施，把 4 关的缺水指数都降到 0。Theory done. Open Blue Planet Town's ledger: switch on saving measures and bring all 4 levels' shortage index down to 0.
一句话记住它：能喝的水很少（咸水占 97.5%）＋ 中国水南多北少（人均世界四分之一）；调水加节水（滴灌、中水回用）才够喝。Remember it in one line: drinkable water is rare (97.5% is salty) + China's water sits in the south (a quarter per person); moving water north plus saving it (drip, recycled water) keeps everyone drinking.
很少：咸水 97.5%，淡水大半冻在冰川里Rare: 97.5% salty, most fresh water frozen in glaciers不均：中国人均世界四分之一，南多北少，南水北调Uneven: a quarter per person, wet south vs dry north — move water north省水：农业滴灌、中水回用，每滴都算数Saving: farm drip lines, recycled water — every drop counts
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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