chap 2 Summary水資源要覽

Water

Summary
1. Approximately 0.024% of the earth’s water supply is available as liquid freshwater. Management of the world’s water supply is a huge 21st century challenge.

2. Freshwater shortages are caused by dry climate, droughts, desiccation, and water stress. Solutions for this problem include building dams and reservoirs, transporting freshwater between locations, withdrawing groundwater, and desalination.

3. Advantages of dams and reservoirs include cheap electricity, reduction of downstream flooding, and year-round water for irrigation. Disadvantages include displacement of people and disruption of aquatic systems, and the hydrological cycle.

4. Transferring large amounts of water from one area to another can give stream runoff from water-rich areas to water-poor areas and aid in irrigation of farmland. It can also cause ecological, economical, and health disasters.

5. The advantages of withdrawing groundwater include water for drinking and irrigation; availability and locality; low cost, no evaporation losses; and it is renewable. Disadvantages include aquifer depletion from over pumping, subsidence, pollution, saltwater intrusion, and reduced water flow. Desalination increases the supply of fresh water but is expensive and produces large quantities of wastewater.

6. We can waste less water by lining canals, leveling fields, irrigating at night or using new irrigation techniques, polyculture or organic farming, seasonal farming, irrigating with treated waste water, and importing water-intensive crops and meat.

7. Flooding is caused by heavy rain or melting of snow within a short time. To reduce flood damage or the risk of flooding we can avoid building on floodplains, removing water-absorbing vegetation, or draining wetlands.

8. Methods for achieving more sustainable use of the earth’s water include not depleting aquifers, preserving aquatic systems and water quality, integrated watershed management, agreements among regions and countries sharing surface water resources, outside party mediation of water dispute nations, marketing of water rights, raising water prices, wasting less water, decreasing government subsidies for reducing water waste, and slowing population growth.

1。大約地球上的水供應的0.024%,為液態淡水。管理全世界的水供應是21世紀的一個巨大挑戰。

2。淡水短缺的原因主要是氣候乾燥,乾旱,乾燥,水的壓力。這個問題的解決方案,包括建設水壩和水庫,不同地點之間運送淡水,抽取地下水和海水淡化。

3。水壩和水庫之優勢,包括廉價的電力,減少下游洪水和提供全年的灌溉用水。缺點包括人民流離失所和破壞水生系統,水文循環。

4。從一個地方轉移大量的水到另一個地方,可以將河水的徑流從水資源豐富的地區,移向缺水地區,以幫助農田灌溉。它還可能導致生態,經濟和健康的災難。

5。抽取地下水的優勢,包括:提供飲用水和灌溉,具有可用性和地區性,成本低,沒有揮發性損失,並且是可再生能源。缺點包括:超抽會使含水層枯竭,沉降,污染,鹽水入侵,減少水流量。海水淡化增加淡水供應,但價格昂貴,產生大量的廢水。

6。我們可以少浪費水,這可透過建造運河,整平田地,在夜間灌溉或使用新的灌溉技術,以多元栽培式或有機耕作,季節性農作,用經過處理的廢水灌溉,及進口用水密集型的作物和肉類。

7。洪水是由於在短期內下大雨或積雪融化所致。為了減少洪水損毀或浸水的風險,我們應該避免在洪水平原建設房屋,消除吸水植被,濕地或排水。

8。實現更加可持續地利用地球的水之方法,不僅包括不要使含水層枯竭,保護水生系統和水質,流域綜合管理,協議各區域和國家共享地表水資源,由局外者調解國家之間的水事糾紛,建立水權市場,提高水價,檢少水的浪費,減少政府補貼以減少水的浪費,減緩人口增長。
Last modified: Sunday, 1 November 2009, 8:36 PM