Title: Down Go The Dam
Author: Jane C. Marks
A:
B:
today about 800,000 dams operate worldwide, 45,000 of which are large—that is, greater than 15 meters tall. Most were built in the past century, primarily after World War II. Their benefi ts are clear. Hydroelectric power makes up 20 percent of the globe’s electric supply, and the energy is largely clean and renewable, especially when contrasted with other sources. Those plants powered the mining operations that fueled Arizona's economic growth and helped support the rapid expansion of the city of Phoenix. By 2001, however, the Fossil Creek generating stations were providing less than 0.1% of the state's power supply.Societies will continue to balance the pros aand cons of dams, weighing their urtility and benefits against their destructive costs.
C:
After I read this article, I have learned a lot of things. First is that the dams is have pro and con. Dams were originally built before understanding of their impacts on rivers were widely known. While beneficial to humans, dams cause stress on a river system, stopping the flow of sediment and nutrients downstream and negatively impacting fish species that spawn in upstream areas. The nutrients contained within this sediment gets caught behind the dam and downstream areas can suffer increased erosion from the lack of sediment already held by the water. Areas downstream of dams generally have differing temperatures from the rest of the river depending on the size of the dam. For instance, a dam that forms a reservoir or lake behind it still must let some water pass through the dam. The water that passes through is the water from the bottom of that reservoir and is colder than the rest of the river. The deconstruction of dams, while not perfect, can aid in the restoration of a river's natural state, including biodiversity and fertility of nearby soils. "The most important positive outcome of dam removal is the re-connection of river reaches so that they can operate as an integrated system, which is the basis of a river with restored physical integrity."
So What?
Hydroelectric power makes up 20% of the globe’s electric supply, and the energy largely clean and renewable, especially when contrasted with other sources.
Say Who?
Jane C. Marks
What If?
The release of sediments trapped behind a dam’s walls can choke waterways
This Remind Me Of?
Dams are used around the world for numerous purposes, including flood prevention, irrigation, hydroelectric power, water supply, and more. However, in recent years, the scientific community has become more aware of environmental issues and hazards represented by the presence of dams on river systems worldwide.
Author: Jane C. Marks
A:
- The wild river and lush riparian ecosystem attracted fish and a host of animals and plants that could not survive in other environments.
- attracted prospectors and settlers to the Southwest
- support the rapid expansion of the city of Phoenix
- utility workers retired the dam and the flumes and in so doing restored most of the flow
- to the 22.5 kilometers of Fossil Creek riverbed that had not seen much water in nearly a century
- Decommissioning dams is becoming a regular occurrence as structures age, provide an inconsequential share of a region’s power, become unsafe or too costly to repair
- as communities decide they want their rivers wild and full of fish again
- today about 800,000 dams operate worldwide, 45,000 of which are large—that is, greater than 15 meters tall
- In the previous two years alone, about 80 dams have fallen
- researchers following the trend expect that dams will continue to come down, especially small ones
- biologists observed with some surprise the return of scores of striped bass, alewives, American shad, Atlantic salmon, sturgeon, ospreys, kingfishers, cormorants and bald eagles
- the water became well aerated and that populations of important food-chain insects
- such as mayflies, stoneflies and caddisflies grew
- Water clarity and oxygen levels increase as flow comes back, and aquatic insects thrive again
- the water moves freely, its temperature falls and cold-loving fish species
- such as trout, proliferate or return
- muddying the environment and wiping out insects and algae, which are important food for fish
- the mud that had been held back by the structures is rife with contaminants
- dams have blocked invasive species from moving upriver and into zones above the dam
- the government computerized data on weather patterns, rainfall and river levels so
- flood warnings could be released at least four hours before danger arrived
- biologists decided to actively manage the native fish
- doused the creek with fish poison to kill exotic species
- returned the natives to the water once the poison had dissipated
- made of travertine, formed naturally as the calcium carbonate–rich water of the springs interacts with algae to form layers of lime- stone
- the legacy of releasing PCBs downstream in the Hudson River,
- scientists now routinely test these materials for toxicity
- the sediment load is very high and the river’s flushing capacity low, engineers might opt to remove the dam in stages, allowing small amounts of sediment to be released at a time
- the downstream beaches are starved of sediment: they badly need dirt
- sand to stave off ongoing erosion from wind and rain
- using all available information about dam removal and restoration ecology
- as well as what they know of the entire water- shed, to make decisions
- using computer simulations and are conducting indoor studies.
- The National Center for Earth-surface Dynamics in Minnesota has created a model ecosystem of miniature streams, dams and reservoirs
B:
today about 800,000 dams operate worldwide, 45,000 of which are large—that is, greater than 15 meters tall. Most were built in the past century, primarily after World War II. Their benefi ts are clear. Hydroelectric power makes up 20 percent of the globe’s electric supply, and the energy is largely clean and renewable, especially when contrasted with other sources. Those plants powered the mining operations that fueled Arizona's economic growth and helped support the rapid expansion of the city of Phoenix. By 2001, however, the Fossil Creek generating stations were providing less than 0.1% of the state's power supply.Societies will continue to balance the pros aand cons of dams, weighing their urtility and benefits against their destructive costs.
C:
After I read this article, I have learned a lot of things. First is that the dams is have pro and con. Dams were originally built before understanding of their impacts on rivers were widely known. While beneficial to humans, dams cause stress on a river system, stopping the flow of sediment and nutrients downstream and negatively impacting fish species that spawn in upstream areas. The nutrients contained within this sediment gets caught behind the dam and downstream areas can suffer increased erosion from the lack of sediment already held by the water. Areas downstream of dams generally have differing temperatures from the rest of the river depending on the size of the dam. For instance, a dam that forms a reservoir or lake behind it still must let some water pass through the dam. The water that passes through is the water from the bottom of that reservoir and is colder than the rest of the river. The deconstruction of dams, while not perfect, can aid in the restoration of a river's natural state, including biodiversity and fertility of nearby soils. "The most important positive outcome of dam removal is the re-connection of river reaches so that they can operate as an integrated system, which is the basis of a river with restored physical integrity."
So What?
Hydroelectric power makes up 20% of the globe’s electric supply, and the energy largely clean and renewable, especially when contrasted with other sources.
Say Who?
Jane C. Marks
What If?
The release of sediments trapped behind a dam’s walls can choke waterways
This Remind Me Of?
Dams are used around the world for numerous purposes, including flood prevention, irrigation, hydroelectric power, water supply, and more. However, in recent years, the scientific community has become more aware of environmental issues and hazards represented by the presence of dams on river systems worldwide.