Analysis of Water Clarity in Lake Superior using MODIS Images Yan Wang, Beth Peterson Forest Resources 3262 / 5262 Remote Sensing of Natural Resources and Environment 12/10/12 Background Satellite imagery has been used effectively to estimate water clarity levels. Improving the application of satellite data for analyzing water quality is an important issue because it would reduce the cost of gathering on site data in remote locations, and allow for the analysis of water quality from historical images when field data is not available. Water clarity can be analyzed from satellite by measuring how much light in reflected in different bands. Water reflects a small range of light compared to most surfaces, but good data can still be acquired by comparing the return in different parts of the spectrum. The most reflection occurs near the blue end of the visible spectrum, while less light is reflected near the red portion of the spectrum. Water clarity is an important measure of water quality. Measures of water clarity are often included in the standards for safe drinking water. There are several ways of measuring water clarity, one method is to measure turbidity. Turbidity can be measured in Nephelometric Turbidity Units (NTU), by using a nephelometer which measures the amount of light reaching a detector after passing through the water. In this way the amount of suspended particles scattering the light can be found. Clear water will have a low NTU, while murky water will have a high NTU. Many human activities, mining in particular, have impacted the clarity of water in Lake Superior. Average water clarity for Lake Superior is 8m when measured using a secchi disk, which is very good relative to most lakes. Because it is such a large lake, clarity can vary in different places, and clarity may not be as good in all locations. Reduced clarity comes from suspended sediments or algal growth from eutrophication. In Lake Superior eutrophication is very low due to the relatively low amount of organic matter input. Most of the land cover surrounding Lake Superior is forested. There are logging roads and other logging activities that could pollute the basin. There are several mining operations within the Mesabi Iron Range that could also be contributing contaminants to the lake, as well as other point and non-point sources in local communities. Objectives
Analysis of Water Clarity in Lake Superior using MODIS Images Yan Wang, Beth Peterson Forest Resources 3262 / 5262 Remote Sensing of Natural Resources and Environment 12/10/12 Background Satellite imagery has been used effectively to estimate water clarity levels. Improving the application of satellite data for analyzing water quality is an important issue because it would reduce the cost of gathering on site data in remote locations, and allow for the analysis of water quality from historical images when field data is not available. Water clarity can be analyzed from satellite by measuring how much light in reflected in different bands. Water reflects a small range of light compared to most surfaces, but good data can still be acquired by comparing the return in different parts of the spectrum. The most reflection occurs near the blue end of the visible spectrum, while less light is reflected near the red portion of the spectrum. Water clarity is an important measure of water quality. Measures of water clarity are often included in the standards for safe drinking water. There are several ways of measuring water clarity, one method is to measure turbidity. Turbidity can be measured in Nephelometric Turbidity Units (NTU), by using a nephelometer which measures the amount of light reaching a detector after passing through the water. In this way the amount of suspended particles scattering the light can be found. Clear water will have a low NTU, while murky water will have a high NTU. Many human activities, mining in particular, have impacted the clarity of water in Lake Superior. Average water clarity for Lake Superior is 8m when measured using a secchi disk, which is very good relative to most lakes. Because it is such a large lake, clarity can vary in different places, and clarity may not be as good in all locations. Reduced clarity comes from suspended sediments or algal growth from eutrophication. In Lake Superior eutrophication is very low due to the relatively low amount of organic matter input. Most of the land cover surrounding Lake Superior is forested. There are logging roads and other logging activities that could pollute the basin. There are several mining operations within the Mesabi Iron Range that could also be contributing contaminants to the lake, as well as other point and non-point sources in local communities. Objectives
superior_clarity.docx