TOEFL Experts Reading Practice 15
The Bitterroot Valley in the Western state of Montana in the United States has two largely separate water supplies: irrigation from ditches fed by mountain streams, lakes, or the Bitterroot River itself in order to water fields for agriculture; and wells drilled into underground lakes, called aquifers, which provide most of the water for domestic use. The valley's larger towns provide municipal water supplies, but houses outside those few towns all get their water from individual private wells. Both the irrigation-water supply and the well-water supply are facing the same fundamental dilemma: an increasing number of users for decreasing amounts of water.
The ultimate reason for decreasing amounts of water is climate change: Montana is becoming warmer and drier. While global warming 'will produce winners as well as losers in different places around the world, Montana will be among the big losers because its rainfall was already rnarginally adequate for agriculture. Drought has now forced abandonment of large areas of farmland in eastern Montana. One visible effect of global warming in western Montana is that snow in the mountains is being confined to higher altitudes and often no longer remains there throughout the summer as it did 50 years ago.
The most visible impact of global warming in Montana is on Glacier National Park. While glaciers all over the world are in retreat, the phenomenon has been especially well studied in Montana because its glaciers are so accessible to climatologists. When the area of Glacier National Park was first visited by naturalists in the late 1800s, it contained over 150 glaciers. Now there are only about 27 left, mostly at just a small fraction of their first-reported size. At present rates of melting, Glacier National Park will have no mountain glaciers at all by 2030. Such declines in the mountain snowpack (the seasonal accumulation of snow) are bad for irrigation systems, whose summer water comes from the melting of the snow that remains in the mountains. It is also had for well systems tapping the Bitterroot River's aquifer, whose volume has decreased as a result of recent drought.
As in other dry areas of the North American West, agriculture would be impossible in the Bitterroot Valley without irrigation because annual rainfall in the valley bottom is only about 13 inches per year. Without irrigation, the valleys vegetation would be sagebrush, which is what explorers Lewis and Clark reported on their visit in 1805-1806, and which travelers can still see today as soon as they cross the last irrigation ditch on the valley's eastern side. Construction of irrigation systems fed by snowmelt water from the high mountains forming the valley's western side began in the late 1800s and peaked in 1908-1910. Within each irrigation system or district, each landowner or group of landowners has the right to take for his or her land a specified quantity of water from the system.
Unfortunately, in most Bitterroot irrigation districts the water is overallocated. That is, the sum of the water rights allocated to all landowners exceeds the flow of water available in most years, at least later in the summer when snowmelt is decreasing. Part of the reason is that allocations are calculated on the assumption of a fixed water supply, but in fact water supplies vary from year to year with climate, and the assumed fixed water supply is the value for a relatively wet year. The solution is to assign priorities among landowners according to the historical date on which the water right was claimed for that property, and to cut off water deliveries first to the newest water-right and then to earlier water-right owners as water flows decrease in the ditches. That is already a recipe for conflict because the earliest farmers with the earliest water rights are often downhill, and it is hard for uphill farmers with lower-ranking rights to see water that they desperately need flowing merrily downhill past their property, and yet to refrain from taking the water. But if they did take it, their downhill neighbors could sue them.
The Bitterroot Valley in the Western state of Montana in the United States has two largely separate water supplies: irrigation from ditches fed by mountain streams, lakes, or the Bitterroot River itself in order to water fields for agriculture; and wells drilled into underground lakes, called aquifers, which provide most of the water for domestic use. The valley's larger towns provide municipal water supplies, but houses outside those few towns all get their water from individual private wells. Both the irrigation-water supply and the well-water supply are facing the same fundamental dilemma: an increasing number of users for decreasing amounts of water.
The ultimate reason for decreasing amounts of water is climate change: Montana is becoming warmer and drier. While global warming 'will produce winners as well as losers in different places around the world, Montana will be among the big losers because its rainfall was already rnarginally adequate for agriculture. Drought has now forced abandonment of large areas of farmland in eastern Montana. One visible effect of global warming in western Montana is that snow in the mountains is being confined to higher altitudes and often no longer remains there throughout the summer as it did 50 years ago.
The most visible impact of global warming in Montana is on Glacier National Park. While glaciers all over the world are in retreat, the phenomenon has been especially well studied in Montana because its glaciers are so accessible to climatologists. When the area of Glacier National Park was first visited by naturalists in the late 1800s, it contained over 150 glaciers. Now there are only about 27 left, mostly at just a small fraction of their first-reported size. At present rates of melting, Glacier National Park will have no mountain glaciers at all by 2030. Such declines in the mountain snowpack (the seasonal accumulation of snow) are bad for irrigation systems, whose summer water comes from the melting of the snow that remains in the mountains. It is also had for well systems tapping the Bitterroot River's aquifer, whose volume has decreased as a result of recent drought.
As in other dry areas of the North American West, agriculture would be impossible in the Bitterroot Valley without irrigation because annual rainfall in the valley bottom is only about 13 inches per year. Without irrigation, the valleys vegetation would be sagebrush, which is what explorers Lewis and Clark reported on their visit in 1805-1806, and which travelers can still see today as soon as they cross the last irrigation ditch on the valley's eastern side. Construction of irrigation systems fed by snowmelt water from the high mountains forming the valley's western side began in the late 1800s and peaked in 1908-1910. Within each irrigation system or district, each landowner or group of landowners has the right to take for his or her land a specified quantity of water from the system.
Unfortunately, in most Bitterroot irrigation districts the water is overallocated. That is, the sum of the water rights allocated to all landowners exceeds the flow of water available in most years, at least later in the summer when snowmelt is decreasing. Part of the reason is that allocations are calculated on the assumption of a fixed water supply, but in fact water supplies vary from year to year with climate, and the assumed fixed water supply is the value for a relatively wet year. The solution is to assign priorities among landowners according to the historical date on which the water right was claimed for that property, and to cut off water deliveries first to the newest water-right and then to earlier water-right owners as water flows decrease in the ditches. That is already a recipe for conflict because the earliest farmers with the earliest water rights are often downhill, and it is hard for uphill farmers with lower-ranking rights to see water that they desperately need flowing merrily downhill past their property, and yet to refrain from taking the water. But if they did take it, their downhill neighbors could sue them.
- The Bitterroot Valley in Montana has too little water for those who need it.