Oroville Dam Crisis: Potential Emergency Spillway Breach (February 2017) - Part I

The Oroville Dam in Northern California is the tallest dam in the United States, rising ~770 feet (235 m) high. It was built on the upper Feather River in 1968, serving mainly for water supply, hydro-electric power generation and flood control. The dam impounds Lake Oroville, the 2^nd largest man-made lake in California, capable of storing more than 3.5 million acre-feet (4.4 km³), almost 1.1 trillion gallons of water for supplying farms and cities across the state. It’s a vital piece of infrastructure located in the Sierra Nevada foothills east of the Sacramento Valley.

Storms in early February, 2017 caused significant damage to the primary spillway when flood was released at 50,000 cubic feet per second (cfs), hindering the safe release of floodwater. The threat of uncontrolled release of water from the dam threatened more than 180,000 people living downstream along the Feather River. To alleviate the flood risk, there are four intended routes that engineers can use to allow water to pass downstream, from most to least preferred:

1.   Through the hydro-electric generators, which allow a maximum flow rate of 16,950 cfs.

2.   Through a river outlet or bypass valve, when operational it has a capacity of 5,400 cfs. The outlet was damaged during an accident in 2009 and has not been used since.

3.   Through the main (primary) spillway, which is used to quickly release large amounts of excess water down a concrete channel and control the height of the reservoir. It is controlled by gates and has a maximum capacity of 150,000 cfs. Based on the dam operator's contracted agreement for flood control, reservoir engineers lower the height of the reservoir before storms arrive. The practice allows the dam to capture storm runoff, reduces spillway flows, and lessens the likelihood of flooding below the dam.

4.   Over the top of an ungated emergency spillway, a 1,700-foot long and 30 ft high weir built several feet below the height of the main dam. Once the lake reaches an elevation of 901 ft, this emergency spillway naturally flows over the weir and down the unprotected natural hillside, which is used as the spillway channel.

 

Improving China’s Yellow River: Why Business and Government Need to Work Together

The Yellow River has played a critical role in the growth and prosperity of Chinese civilization for thousands of years. But today, the Yellow and the people who depend on it face severe challenges. Stress of limited water resources, pollution, and flooding pose significant risks to communities and businesses that rely on the river. As these stresses grow, China’s water managers and users face the daunting challenge of implementing policies that balance economy, ecology, and community. 

At the Yellow River Commission’s annual Forum in September, water experts from government, research institutes, the private sector, and NGOs gathered to discuss problems facing the Yellow and potential solutions for better water management. One sentiment that came through loud and clear is that the only way to improve the Yellow is for government and business to collaborate—not clash.

The Role of Government: Set a Clear Agenda

At the Forum, it was clear that the relationship between Chinese companies and government is evolving when it comes to water issues. The government is dealing with the complex and pressing challenge of water resource management by setting ambitious goals, adopting a set of “three red lines” in its 2011 No.1 Policy document for achieving water security. 

Full paper can be read from World Resources Institue website at: http://www.wri.org/blog/2012/10/improving-china%E2%80%99s-yellow-river-why-business-and-government-need-work-together.

Credit: World Resources Institute, 10 G Street NE Suite 800, Washington, DC 20002, USA

The Yellow River: a History of China’s Water Crisis

During the hot, dry month of August 1992 the farmers of Baishan village in Hebei province and Panyang village in Henan came to blows. Residents from each village hurled insults and rudimentary explosives at the other across the Zhang River – the river that feeds the Red Flag Canal Irrigation System and forms the border between the two provinces. 

Centuries of state investment in a massive system of dykes along the Yellow River has left China’s water planners with a difficult legacy today (Image by Teruhiro Kataoka)

The emotions of that afternoon were fuelled by events of the previous night when 70 Baishan villagers had waded into the river to build a barrage to divert water to their fields. Upon hearing of the treachery, Panyang villagers assembled to drive the dam-builders away.  

Two days later, Baishan villagers crossed the river to the Henan side and dynamited an irrigation canal that watered Panyang’s fields.    

Struggles over water are not new in China or around the world.  But these struggles have their own unique historical and cultural contexts. Climate, geography, and social forces all combined to escalate tensions over water resources on the North China Plain during the 1990s.   

In the early 1960s when the Red Flag Canal was constructed water was plentiful. The canal was a showpiece of Chinese hydraulic engineering that was begun during the Great Leap Forward, and celebrated as an exemplar of massive surface water irrigation development.  But after the 1980s, upstream withdrawals for irrigation and local industry dramatically expanded competition for water downstream.  

Full article can be read from here (中外对话): https://www.chinadialogue.net/culture/8134-The-Yellow-River-a-history-of-China-s-water-crisis/en.

Effect of Perennial Sediment Regulation in Xiaolangdi Reservoir on Reduction of Deposition in the Lower Yellow River

Article in International Journal of Sediment Research 12(2) · August 1997

Full text can be found at: https://www.researchgate.net/publication/262935877_Effect_of_Perennial_Sediment_Regulation_in_Xiaolangdi_Reservoir_on_Reduction_of_Deposition_in_the_Lower_Yellow_River.