英検は社会問題、環境問題、国際問題などのトピックはよく取り上げられます。What can be done to help solve the world wide fresh water shortage? （世界的な水不足の問題をどのように解決することが可能か？）は旺文社の問題集にあったトピックですが、2011年にIs it acceptable to treat water as a private commodity?というトピックが出題されているようですし、水に関する問題は日頃から考えておくのが良いでしょう。

ウィキペディアで水不足の問題が説明されています。面接で使えるキーワード、語句、英語表現が満載です。一部を紹介します。

• Water scarcity is the lack of sufficient available fresh water resources to meet water demand. (Water_scarcity)
• The essence of global water scarcity is the geographic and temporal mismatch between freshwater demand and availability.(Water_scarcity)
• Climate change, such as altered weather-patterns (including droughts or floods), deforestation, increased pollution, and wasteful use of water can cause insufficient supply.(Water_scarcity)
• Physical water scarcity results from inadequate natural water resources to supply a region’s demand, and economic water scarcity results from poor management of the sufficient available water resources. (Water_scarcity)
• Economic water scarcity is caused by a lack of investment in infrastructure or technology to draw water from rivers, aquifers or other water sources, or insufficient human capacity to satisfy the demand for water. (Water_scarcity)
• Large parts of Africa suffer from economic water scarcity; developing water infrastructure in those areas could therefore help to reduce poverty. (Water_scarcity)
• the human right to water entitles everyone to sufficient, safe, acceptable, physically accessible, and affordable water for personal and domestic use (Water_scarcity)

BBCの記事Is the world running out of fresh water?でも、水不足の解決策について議論されていて、役立つ表現が多く見つかります。

• Water demand globally is projected to increase by 55% between 2000 and 2050.
• Much of the demand is driven by agriculture, which accounts for 70% of global freshwater use, and food production will need to grow by 69% by 2035 to feed the growing population.
• Of the world’s major aquifers (gravel and sand-filled underground reservoirs)(帯水層;地下水が蓄えられている地層), 21 out of 37 are receding, from India and China to the United States and France.
• Some hypothesise that increased water shortages around the world will lead to wars.
• The key was putting a price on water and making it a tradable commodity.
• Another ‘gold standard’ is Israel, which views water availability as a national security issue.
• By recycling effluent water（排水）, including household sewage（下水）, the Shafdan Wastewater Treatment Facility near Tel Aviv supplies approximately 140,000,000 cubic metres of water per year for agricultural use, covering 50,000 acres of irrigated （灌漑）land.
• Israel is also a global leader in desalination（脱塩；淡水化）– turning seawater into potable drinking water.
• A simpler and cheaper solution is rainwater capture.

水不足問題の解決に関してはTEDでも議論されています。
A Global Solution to Water Scarcity（59秒）

下の動画は募金に関する内容。
Solving the water crisis | Olivia Andersen & Maria Oszova Johnson | TEDxTacoma

飲料水は英語でdrinking water または　portable water。海水を脱塩して淡水化する方法の動画。
How Seawater Desalination Works