How Does Human Activity in Watersheds Affect the Water Quality of Lakes?
Essay by review • February 13, 2011 • Research Paper • 1,346 Words (6 Pages) • 1,786 Views
Essay Preview: How Does Human Activity in Watersheds Affect the Water Quality of Lakes?
How does human activity in watersheds affect the water
quality of lakes?
Water is a vital resource that sustains all living things. In Michigan, people value this
abundant resource and are attractive to the thousands of inland lakes which provide aesthetic, as
well as recreational opportunities throughout the year. The health of our lakes is directly
impacted by the amount of recreational use they receive, shoreline development, and water
quality. Water quality covers many aspects of lake chemistry and biology. Both natural and man-
made features of watersheds impact the quality of aquatic habitats. Examining the relationship
between land use and water clarity in lakes can help us to understand what negatively impacts
the health of our lakes. This in turn will lead us to finding solutions to improve and maintain the
quality of our lakes and waterways.
I expect aquatic habitats in watersheds with more man-made features to have lower water
quality and clarity. I expect this because runoff from man-made features will contain chemicals
and particles that reduce clarity through biological and physical processes.
Begin the lab by saving the 12 maps of the six lakes (six color coded by land use and the
same six in grayscale) along with a Legend file on the website. The Legend file explains the
color coding of land uses in the map files. Open up each map and Legend in the ImageJ program
and move the mouse cursor over the different areas of the grayscale image and looking in the Menu window, a numerical value (between 0 and 255) for each level of gray can be determined.
A list of numerical values was obtained for each color image by comparing the numerical value
in the grayscale image with the corresponding color image. By using the Legend. it was possible
to match the numerical values to each land use type and then determine the area of each land use
type in the grayscale image. Take the maps that are in black and white and have ImageJ analyze
the pixels into a histogram. Take the histogram and turn it into a list so that you know how many
pixels are to each land use. Then take that data and put it in excel so that you can determined
which land uses are most prevalent in each of the lakes. To do these take only the land uses that
occur prevalently on the graphs and use those to find the percentages of each, for each watershed
(leave out 255 because that is the white area around the map). Also, you should not include
water in the estimate of total watershed area because a watershed is the area of land that catches
rain and drains into the lake. You need to add up the total pixels to get an estimate of total
watershed area in order to determine the percentage of each land use type.
Water quality data for these lakes can be obtained from the Michigan Department of
Environmental Quality website. For this analysis of water clarity, parameters of Secchi disk,
total Phosphorous (Spring data), and Chlorophyll (mean) were used. Data can then be analyzed
in terms of water quality and how the percentage of surrounding watershed may have impacted
the data that was given. The six lakes can then grouped according to two categories: high water
quality or low water quality.
Moon, Indian, and Margrethe Lakes were determined to be of high quality and Devils,
Christina, and Pleasant Lakes were determined to be of low quality. The Secchi Disk readings
were highest for Indian Lake at 22.1 feet, Moon at 19.8, Margrethe at 16.7 feet. The total
Phosphorous level was relatively low for Moon at 9 and Margrethe at 4 which explains why their
corresponding Chlorophyll levels were low. Although Indian Lake had a Phosphorous level of
14, its Chlorophyll level was only 3.3.
I don't think this relationship is that accurate between open field and wetlands to water
clarity because those should make the water clearer. Since those two land uses aren't very
prevalent it's not even a big percentage to make a positive impact on the water clarity because
there are other water uses that affect the water clarity more since they are more prevalent. The
graph for urban isn't very strong, but the less urban area then generally the lake would be clearer.
I do feel that the agriculture did affect the lakes a lot, because the less agriculture the higher the
Secchi Disk depth, which would be a clearer lake. I also believe that the forested area's had a big
impact on the water clarity. The more forested area the greater the water clarity.
The percentages compared to the Secchi Disk information seemed to show more of a
trend in most cases. Although the data from the three parameters seemed contradictory in some
cases, data from the Secchi Disk seemed to be the best indicator of the overall
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