water resource 留学生作业

保证足够的水供应-Assuring adequate water supplies

 

What does a swimming pool in Phoenix, an eight acre lake in front of the Bellagio hotel in Las Vegas, drinking water San Diego, and a grass sprinkler in Denver all have in common? Most likely all of that water came from the same source, the Colorado River. If Arizona has a weakness, it would be our insatiable need for water. But with proper planning, conservation, and cooperation by the competing states, cities and customers we will be able to learn to survive with our static water supply.

 

In Arizona, as in most of the southwest and California, the demand for water is exceeding our supply. We are used to turning on the faucet, running the sprinklers or filling the pool with no regard to water being an exhaustible resource. We wash our cars and let the hose run; brush our teeth while leaving the faucet running not being concerned since water is so inexpensive here. Most residents here come from somewhere else in America where in the past they didn't have any concerns for water. Here in Arizona, during years of low rainfall or snowpack we hear some talk about a shortage or drought, most of the time it is not a concern.

 

Where does our water come from that fills our pools, our ice trays and keeps our lawns lush and green? In Arizona we have three main sources of water: ground water, surface water and water from the Colorado River.

 

水的来源-Sources of Water

 

Our ground water comes from what is called basin and range aquifers that cover over 200,000 square miles in the arid west. In Arizona our largest aquifers cover most of the southern half of the state. They are made up many different aquifers that are not connected because of how our fault lines were formed during creation. These aquifers have been filled over thousands of years from runoff coming from our mountain watersheds, which feed into our river systems in the state. Most of the runoff is evaporated before it is able to infiltrate into the aquifers, so our recharge rate is only about 5 percent a year of our runoff which is determined by our annual rain or snowfall totals. Recharge rate is?

 

Our surface water is the runoff from our mountain watershed areas that run through our major river systems in the state. Up until the mid 1800s all of runoff just flowed through the river systems and evaporated; and what didn't evaporate eventually made its way through the state into the Colorado River. In 1868 a man named John Swilling built the first canal following the imprints of the old Hohokam Indian canals. It became known as the "Salt River Valley Canal" (SRP; Our Water History). This helped start the growth of Phoenix into a large agricultural community by creating a dependable supply of water to irrigate farmland. But even with the canal systems, they experienced drought conditions in most summer months which led to crop failures. So in 1901 a group of men started lobbying the federal government for ways to borrow money to fund projects for water storage. In 1902 they found an ally in President Theodore Roosevelt and he signed the National Reclamation Act on June 17, 1902. In 1903 the construction of Roosevelt Dam began and was completed in 1910. Now with a dam they could regulate the flow of the river and have water year round for crops. "As Phoenix grew, the land available for farms shrank and water use shifted. As recently as 1965, 80 percent of the water delivered by Salt River Project was used by agriculture. Today, that number is just 15 percent" (McKinnon, 2009). With all of the other dams built on the Salt River and the Verde River, Phoenix has very good surface water system to draw water from.

 

Today the Central Arizona Project, CAP, is the main source of water for the Tucson and Phoenix metropolitan areas. The CAP came about from the Colorado River Compact?

 

Phoenix is in a better position for water since it also relies on water from the Salt River Project's reservoir lakes. If current trends hold and the runoff is under average levels and a shortage on the Colorado River Compact is declared, Arizona would be hurt the most. The Colorado River Compact was structured so that Arizona would lose all of the water that is currently allocated to the CAP, which supplies about a third of Arizona's needs. This would mean California would still receive all of the water allocated to them because of their 'grandfather' rights. Meaning that California was first in line, a law that is precedent in the west. This same law also gives farmers, mines in Arizona unlimited water first over municipal users if there was a shortage of water in state.

 

我们的水需求-Demand for our Water

 

In the past demand for water came primarily from agriculture and mining business purposes, with their use of water consuming approximately 80 to 90 percents of the water pumped yearly from our aquifers. Agricultural users are able to pump all of the water they need at no cost to them, except for what it cost to get out of the ground or deliver it to their farm because of there "grandfather" rights that comes with the land they own. Farming is still the largest user of water in the state in Arizona today. However, because of all of the extensive growth in urban areas the percentage has dropped to around 70 percent. Farms are still pumping water out at record levels from our aquifers at a rate that they cannot naturally recharge, and the water tables are lowering.

 

The largest sector for new demand of water will come from our extensive growth and demand from Phoenix and Tucson metropolitan areas. The Phoenix metropolitan area has grown from "a population of 750,000 in 1960 to over 3.5 million people in the year 2000" (Census scope). Today it is has an estimated population of around 4.6 million people. The Tucson metropolitan area has gone from "a population of 250,000 in 1960 to almost 850,000 in the year 2000" (Census scope). Today the Tucson areas population is estimated to be "1 million residents" (Pima Association of Government). Phoenix growth rate is estimated to double again by the year 2025, and Tucson is estimated to grow by another 40 percent by 2025.

 

The CAP isn't the only supply source draining water from the Colorado River. There are six other states and dozens of Indian tribes along with Mexico that have vested rights to water from the Colorado River. With all of the demand already putting a strain on the Colorado River we need to start conservation sooner then later. With all of the development and growth in the southwest over the last 50 years and the recent drought conditions Lake Meads level has dropped by 50 percent. It would take over 20 years of above average conditions to bring the lake back up to capacity. "Lake Mead, an immense reservoir that dams the Colorado to supply most of Phoenix's water, has a 50-50 chance of running dry by 2021, according to a study by the Scripps Institution of Oceanography"( Power, 2008 ). Because of the water level drop of the lake, Nevada has had to start a project to drill through bedrock to install inlet tubes to the bottom of the lake so they will still be able to draw water.

 

保护需要-Need for Conservation

 

Water is a valuable resource in the desert and though we don't face any immediate water shortages, if we fail to take action now and encourage conservation we will be in trouble in 20 years from now. We are already taking our full allotment of CAP water and pumping more water out of the ground than our aquifers can recharge. "For example, in two southern Arizona areas groundwater levels have dropped more than 500 feet. One area occurs southwest of Casa Grande near Stanfield, and the other is located south of Chandler near Chandler Heights"(Gelt, 1992). Due to what is called over draft, pumping out water faster then it can be replaced naturally; the Arizona Department of Water Resources, ADWR, formalized in 1980 the Arizona Groundwater Management Code. 'The 1980 Groundwater Management Code has three primary goals: to Control severe overdraft occurring in many parts of the state: Provide a means to allocate the state's limited groundwater resources to most effectively meet the changing needs of the state: Augment Arizona's groundwater through water supply development" (Arizona Department of Water Resources). The state legislature in 1986 established a program run through ADWR called the Underground Water Storage and Recovery program. This program allows users by permit to use their surplus water to recharge the aquifers for storage to use at a later time. There are over 60 permitted users doing this today, including cities using there surplus CAP allotment; and corporations doing it by processed waste water treated to drinking quality water. In the city of Chandler "the city banks as much excess CAP water as it can, pumping it underground along with Intel's contribution. Thanks to this so-called recharge, the local aquifer is actually rising a few feet a year" (Arizona Department of Water Resources).#p#分页标题#e#

 

We as well need to work on our per gallon per capita use per day to lower our water use. "In Phoenix our average use per day is over 226 gallons, compared to Tucson where it is only 160 gallons" (Copenhaver, 2003). Santa Fe New Mexico has a per capita daily use of only 120 gallons. If we could match our water use with what they are doing in Santa Fe, Phoenix could double in size using the same amount of water that we are using today.

 

总结-Conclusions

 

Water in Arizona is a valuable but exhaustible resource that we need to manage through conservation and careful planning on how we use or water. If we do not do this we won't be able to attract new business here willing to make long term investment assuring high paying jobs to make Arizona a desirable place to live. Water is critical in every segment of our economy, farming, mining, electronics, to making energy in our power plants. Our future here depends on everyone using our water wisely to secure a reliable stable supply of water.