The Yellow River is indicative of the problems affecting many of China's rivers. Pollution, hydropower, and intensive water extraction for human consumption, agriculture, and industrial use are all taking their toll on the river.

The Chinese government estimates that around two-thirds of the Yellow River's water is too polluted to drink and according to the Institute of Public and Environmental Affairs, a Beijing-based NGO, 4.3 billion tonnes of waste flowed into the Yellow River in 2005.

Huang He, Wade-Giles romanization Huang Ho, also spelled Hwang Ho, English Yellow River , principal river of northern China, often called the cradle of Chinese civilization. It is the country’s second longest river, with a length of 3,395 miles (5,464 km), and its drainage basin is the third largest in China—an area of some 290,000 square miles (750,000 square km). The river rises in Qinghai province on the Plateau of Tibet and crosses six other provinces and two autonomous regions in its course to the Bo Hai (Gulf of Chihli), an embayment of the Yellow Sea. In its lower reaches it is a shifting, turbulent, silt-laden stream that often overflows its banks and sends floodwaters across the North China Plain. For this reason, it has been given such names as “China’s Sorrow” and “The Ungovernable.” The word huang (“yellow”) is a reference to the fine loess sediments that the river carries to the sea. The Huang He basin has an enormous population—exceeded by only a small number of countries—and the river and its tributaries flow past some of China’s oldest cities, including Lanzhou, Baotou, Xi’an (Sian), Taiyuan, Luoyang,Zhengzhou, Kaifeng, and Jinan.

Around 30% of fish species in the river are believed to have become extinct and the river's fish catch declined by 40%.

The river is extremely prone to flooding and accounts for some of the deadliest disasters in human history. In 1931 an estimated 1 million died in a massive flood. A key reason for the severity of the floods is deforestation up river and the embankment of tributaries for irrigation. These practices date back thousands of years.

all about rivers

Coming a close second after the Nile as the world’s longest river, the Amazon River sets the record in terms of the sheer volume of water that it carries – a mind-boggling average discharge of 219,000 m3/sec of water.2

It is estimated that approximately one-sixth of all fresh water that drains into the world's oceans goes through the 320-km-wide delt of the Amazon, where it meets the Atlantic Ocean.

As the seasons change, so does the river. During the dry season, the width of the Amazon River can be 4 km to 5 km in places – and in the wet season, this can increase to 50 km! At the height of the wet season, the current can reach a speed of 7 km/hr.

Major roles of the Amazon River
As the drainage system of the Amazon Basin, the Amazon River and its approximately 1,100 tributaries play major roles in the ecology of the basin.

Before roads and airstrips started appearing in the basin, these waterways were the major access routes to the interior areas of Brazil and the northern half of South America.

For example, the only way you can get to Iquitos, Peru, which is right on the Amazon River, is to board a plane or a boat. There are no roads to get there.3

Origins and course of the river
The Amazon River has its source high in the Peruvian Andes, at an elevation of 5,598 m. There, at a mere 192 km from the Pacific Ocean where it once flowed into, the Amazon River begins as a small tributary called the Carhuasanta.

As it heads east, it flows into and becomes the Hornillos, which merges into the Apurimac, a major tributary that eventually joins the Ene, the Tambo and then the Ucayali.4

The ecosystems of the Danube River Basin are highly valuable in environmental, economic, historical and social terms, but they are subject to increasing pressure and serious pollution from agriculture, industry and cities.

The river flows (from upstream to downstream) through 11 countries: Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Montenegro, Romania, Bulgaria, Moldavia and the Ukraine. Additional basin countries are Poland, Czech Republic, Switzerland, Italy, Slovenia, Albania, Bosnia‑Herzegovina and FYR of Macedonia.

The Danube is one of Europe’s richest rivers with regard to fish species with seven fish species found nowhere else in the world, 10 diadramous fish including five sturgeon species, and altogether 103 fish species. The basin has 90 freshwater molluscs and over 30 amphibian species.

Current threats
The past years there have been an increasing human impacts, pressure and serious pollution from agriculture, industry and municipalities affect the water supply for communities, tourism and fishing.

Examples of threats are: new infrastructure for shipping, eight proposed large dams (including hydropower), diffuse pollution (use of pesticides), gravel extraction/dredging, flood protection and invasive species.