Example Project 1: Create a Virtual Poster for Your Project
How Has the Aral Sea Changed Over Time?
By Sally Student, Sam Student
Circle High School, Ms. Teacher, grades 6-8
Team Project (2-10 students)
Image that Represents the Project
We analyzed NASA satellite images of the Aral Sea, making distance and area measurements to characterize changes in the size of the lake over time. We used eleven Moderate Resolution Imaging Spectroradiometer (MODIS) images, each taken in August for the years 2000 through 2010. The images also display a line that represents the 1960 shoreline of the Aral Sea. Based on the spatial resolution of the image, we set a scale so that pixels in the image represent actual kilometers on Earth. We graphed the change in distance and area measurements over time to investigate the rate of change and to predict when the Aral Sea might disappear completely. Our research has implications for other similar environmental situations.
irrigation, pollution, environmental impact
Until quite recently, the Aral Sea was similar to North America's Great Lakes—it was a huge body of fresh water, filled by rivers that brought rain and snow melt to it from distant mountains. Though it was once the fourth largest freshwater lake in the world, it has shrunk dramatically since 1960. In fact, the Aral Sea in central Asia is drying up. Rivers that once flowed into the lake have been diverted to irrigate crops. With the decrease in the amount of water flowing into the lake, evaporation has become the dominant process. As fresh water evaporates from the lake and is not replenished, the amount of dissolved minerals (salts) in the water increases and the area of land covered by the water decreases.
The environmental changes in the lake and surrounding region have been dramatic and difficult. The change in water chemistry (increased salinity) wiped out huge populations of fish. The decline of the fish populations, in turn, wiped out the commercial fishing industry on the lake. Today, fishing boats sit in the desert many kilometers from the water's edge. The lakebed sediments (fine-grained sand and dirt) that are now exposed on the desert floor can be picked up by wind quite easily, contributing to large dust storms in the region. In our research project, we studied the Aral Sea, investigating the rate at which it is changing and considering implications for its future and that of similar environmental situations.
How has the Aral Sea changed over time?
We think that the loss of water in the Aral Sea has occurred at a steady, linear rate through time and that it could dry up completely within 10 years.
Materials & Equipment
- NASA MODIS satellite images
Geospatial Technology ToolsImageJ
Data Collection Steps
- Download Images from World of Change collection at the NASA Earth Observatory: http://earthobservatory.nasa.gov/Features/WorldOfChange/aral_sea.php
- Read related NASA Earth Observatory Articles:
Data Analysis Steps
- Import all eleven images into ImageJ to create a stack.
- Animate the stack to observe the change in the area of the lake through time.
- Make the 2000 image active and use it to set a scale in ImageJ.
- Propagate the scale to the remaining images.
- Starting with the 2000 image, use the straight line selection tool to measure the distance across the lake at two recognizable points.
- Repeat this procedure for the other ten images (2001 through 2010).
- Then use the free hand selection tool to measure the area of the lake in each of the images.
- Save and open results into Excel.
- Graph results with measurements on the y-axis and years on the x-axis. Create two graphs, one showing the change in distance across the lake through time and the other showing the change in area of the lake through time.
- Calculate the average annual rate of change in the width and the area of the Aral Sea from 1960 to 2009.
Image that Highlights Data or Analysis
In 1960, the width across the Aral Sea was 235.625 km. By 2009, that width was reduced to 20 kilometers. In a similar manner, the area of the Aral Sea was 66,784.3 kilometers squared in 1960, but only 4049.74 kilometers squared by 2009. We took the difference between the 2009 widths and areas and the 1960 measurements, dividing this difference by the number of years (50) to calculate average yearly rates of change. Between 1960 and 2009, the Aral Sea shrunk at a rate of approximately 4.3 kilometers in width per year and at a rate of approximately 1,255 kilometers squared in area per year. See our graphs and results in the Excel file attached below.
From our graphs, it appears as if the Aral Sea is shrinking at a steady rate through time. However, because we are missing data from the years 1961 through 1999, it is not possible to characterize the loss as either a linear or exponential rate. The last 10 years exhibit a linear trend, but we do not know what this looked like during the missing years.
The width across the Aral Sea was 20 kilometers in 2009. Based on our calculated rate of change (4.3 kilometers loss in width per year), we project that the Aral Sea will dry up within 4.6 years. The time for the Aral Sea to dry up is projected to be sooner than that based on the area measurements. In 2009 the area of the Aral Sea was 4049.74 kilometers squared. At our calculated rate of change (1255 squared kilometers loss in area per year), the Aral Sea could be dry in as few as 3.2 years. These results support our initial hypothesis that the Aral Sea could be dry within 10 years.
Our projections have limitations. Through the years, the distance loss across the left side of the lake is less than on the right side, perhaps because the left side of the lake is deeper. Changes in the volume of a three-dimensional shape such as a lake cannot be characterized very accurately by measuring only one dimension, such as width or area.
Furthermore, our projections are based on the assumption that the lake will continue to lose water in future years. In fact, in 2010, both the width and the area of the Aral Sea increased. We measured the width and came up with 126 kilometers. The area was 9437 kilometers squared. If steps are taken to replenish the water, then the sea might not dry up after all.
Summary and Reflection
Based upon the data we collected and the graphs we produced, the Aral Sea is shrinking at steady rate of change. At its current rate of loss, it will take approximately 3 or 4 years for the lake to disappear. This calculation is only theoretical because distance across the lake at only one location as well as area of the lake is not a direct proxy for the volume of the lake. Furthermore, the projection assumes that the lake will not gain water. Our 2010 measurement shows the Aral Sea beginning to increase in size. Further study of this lake is needed in additional years.
Implications for the Future
If the Aral Sea continues to shrink, it is in danger of completely drying out. Further loss of the Aral Sea could have significant negative impacts on agriculture and human health in surrounding communities and beyond as sand full of salts, minerals, and toxins gets swept away from the dried up lake bed. This environmental situation is not limited to the Aral Sea. We need to monitor our lakes to ensure an adequate supply of water for the future.
Right-click(PC) or control-click(Mac) any of the links below to download files to your computer.
Excel SpreadsheetsAral Sea Data and Graphs (Excel 237kB Apr27 11)
Geospatial Data: Images, Shapefiles, KML files, etc.Aral Sea ImageJ Stack (TIFF 16.3MB Apr27 11)
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