Water quality is vital to corn production and agriculture. Healthy water supports a diverse ecosystem, while nutrient imbalances restrict sensitive organisms and let tolerant organisms grow out of control. In this unit, learn how to test for physical, chemical and biotic factors to determine water quality.
Water quality
Unit level:
Phenomenon
Students make observations of water health on aquatic ecosystem cards and/or water samples.
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Understanding watersheds
How might we model a watershed? What are the impacts of various human activities on a watershed?
What do students do? Students develop an understanding of what factors impact water quality within watersheds.
What do students figure out? A watershed is all of the land that drains into a water source. The human activities that take place within a watershed impact the health of the watershed
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Watersheds and soil profiles
What soils are most vulnerable to erosion?
What do students do?Students develop an understanding of what soil types/profiles are most susceptible to erosion.
What do students figure out? The most susceptible soil profiles have the slowest percolation rates allowing for more water to runoff carrying soil particles, rather than those that have faster rates of percolation.
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Watersheds and erosion
What is the impact of water on land surfaces? How might we prevent erosion impacts?
What do students do? Students develop an understanding of what factors impact water quality within watersheds and how to mitigate erosion on susceptible soils.
What do students figure out? Erosion is dependent on slope. There are land management practices that may be used to lessen erosion on slopes.
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Effect of nutrients on water sources
What is the effect of added nutrients on water sources? What is the source of these added nutrients?
What do students do? Students investigate the effects of nutrients on water quality.
What do students figure out? Water quality is negatively affected by excess nutrients. Some water sources are more affected than others due to depth and temperature.
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Chemical and physical testing
How can we analyze the abiotic components (chemical and physical tests) of the stream in order to determine the stream’s overall water quality?
What do students do? Students perform temperature, pH, Dissolved Oxygen, Nitrogen and Phosphorus of water samples.
What do students figure out? Students determine nutrient profile and the health of an aquatic ecosystem. Students make connections between climate, land use, and biotic capacity of an aquatic ecosystem.
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Biotic sampling
How can the health of an aquatic ecosystem be determined by the macroinvertebrates present in the ecosystem?
What do students do? Students collect and identify macroinvertebrates from a freshwater system to analyze the taxonomic groups that live in a habitat annually.
What do students figure out? Students determine the sensitivity of collected macroinvertebrates and the overall health of the aquatic ecosystem.
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Freshwater plankton biodiversity investigation
Can human impact affect freshwater plankton biodiversity? How can Simpson’s Index of Diversity help to determine the species richness of freshwater systems?
What do students do? Students will be able to understand and explain the importance of biodiversity in a freshwater plankton ecosystem and calculate the Simpson’s Index of Biodiversity to determine how human impact can alter the biodiversity in a freshwater plankton ecosystem.
What do students figure out? Students learn how to use the Simpson’s Index of Diversity to determine the level of biodiversity present in freshwater plankton ecosystems.
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Water quality conclusion
How can the health of an aquatic ecosystem be determined by the biotic and abiotic factors present in the ecosystem? How can human impact be lessened to maintain or improve the water quality rating for an aquatic ecosystem?
What students do? Students compare physical, chemical and biological factors of an aquatic ecosystem to determine water health.
What do students figure out? Students connect water health to land use and human impact on local water systems. Students create remediation plans to improve the water health of aquatic ecosystems.
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Water bioinformatics
How might we determine the organisms that impact water using biotechnology? How can we identify individual organisms in a complex mixture of DNA? What computer tools are needed to decode the source of a DNA sequence?
What students do? Students use given DNA sequences to determine the organisms in a water sample using the NCBI database.
What do students figure out? Digital databases make identification of organisms less labor intensive and more accurate.
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Teacher background
Water quality is a critical issue across the United States and globally. Over the past fifty years, the amount of nutrient input into natural water systems has been dramatically reduced from nonpoint sources such as agricultural fields. Best management practices such as reduced tillage, biofilters, and nutrient management have reduced edge of field sediment loss by 55%, nitrogen loss (surface runoff) by 42%, nitrogen loss (subsurface flow) by 31%, and phosphorus losses by 41%. Today’s farmers are producing more corn and soybeans with fewer resources by planting genetically modified crops with drought-resistant traits and maximizing infiltration rates for their soil type. With the help of programs through the USDA that seek to protect water at the source and nutrient practices such as the 4 Rs (right source, right rate, right time, and right place), the production of corn and soybeans and their impact on water quality have greatly improved.
Chemical tests are designed to give accurate readings of the current water chemical properties such as dissolved oxygen, nitrates, nitrites, phosphate, and ammonia levels. Many of these chemical properties can change quickly within an aquatic system and have immediate effects on the organisms that live there. Dissolved oxygen, for example, is the amount of gaseous oxygen (O2) dissolved in an aqueous solution and is vital for all aquatic life. It is in constant flux due to the balance between respiration and decomposition of organisms that require dissolved oxygen and photosynthetic activity and diffusion that increase it.
Biological tests are designed to indicate the overall health of a water system based upon the vertebrate and macroinvertebrate biodiversity within the water system. Organisms are good indicators of seasonal and annual water quality due to their range of tolerance for chemical and physical factors within the aquatic system. For example, mayflies and rainbow darter fish both require water with high dissolved oxygen levels and are not found within systems with low levels of DO.
Physical factors help to gauge the stream structure, flow rate, depth, turbidity, and temperature of the water. Many riparian factors may influence physical tests such as the shade cover of trees that decrease water temperature, reduce soil and nutrient erosion, and support stream integrity by maintaining stream banks. Simple changes in riparian zones can cause a stream to go into a state of chaos and rapidly change physical, chemical, and biological indicators for the worse.
Next Generation Science Standards
Science and Engineering Practices
- Constructing Explanations and Designing Solutions
Disciplinary Core Ideas
- LS1C Organization for Matter and Energy Flow in Organisms
- LS2B Cycles of Matter and Energy Transfer in Ecosystems
Cross Cutting Concept
- Energy and Matter
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