GEOL0840_S23_R6_Hydropower

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University of Pittsburgh *

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Geology

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Apr 3, 2024

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GEOL 0840: Introduction to Environmental Science Spring 2023 Recitation 6: Hydropower Names: Learning Objectives The purpose of this week’s Active Learning activity is to become more familiar with energy use and hydropower and its benefits and potential impacts on the environment.  What are the main alternative energy sources used in the United States and globally?  How do we generate energy from hydroelectric power?  What are the potential environmental impacts of hydroelectric power? This is a group (partner or groups of three) assignment. Each group can submit their assignment once on Gradescope (link on Canvas), just make sure that all your names are on the assignment. Background Hydroelectric power is a common form of renewable energy, and the power plants themselves do not create carbon dioxide emissions. However, reservoirs can lead to increases in greenhouse gas emissions from anaerobic decomposition. Brazil and Canada are the countries which rely on hydropower for electricity generation the most. Hydropower is also an important source of energy in parts of the United States, especially in the west. Figure 1:

GEOL 0840: Introduction to Environmental Science Recitation 6: Hydropower Spring 2023 Page | 2 Answer the follow questions based on the associated graphs or figures. Remember you do not need to write in complete sentences, but you should show your thought where necessary. Part 1: Energy Consumption and Electricity Generation 1. There are four main sectors that consume energy in society: residential, commercial, industrial, and transportation (see Figure 1 for data from PA). What sector(s) of energy consumption to individuals have the most control over? How? Residential and transportation as we do our everyday needs such as laundry and cooking or driving etc. 2. How has the renewable energy production for each source in the United States changed in the last 70 years (see Table 10.1/Figure 2)? Stayed the same until year 2000 that each source had some rising figures and the energy beside hydro and geothermal had rise after 2006, and the solar started rising only in 2014 Figure 2:

Spring 2023 GEOL 0840: Introduction to Environmental Science Recitation 6: Hydropower Page | 3 Part 2: Hydropower Figure 3: The figure below summarizes how conventional hydrothermal power works to generate electricity. 3. How does the flow (speed) of water in the river above and below the reservoir compared to the flow (speed) of water in the reservoir? The river above and below are very fast compared to the reservoir. 4. If water that moves faster carries more sediment, a. What do you think happens to sediments carried by a river when it reaches a reservoir? It will drop to the bottom of the reservoir b. What do you think will happen to the sediments below the dam? The workers will remove the sediments in a given time

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Spring 2023 GEOL 0840: Introduction to Environmental Science Recitation 6: Hydropower Page | 4 5. How do you think sediment changes in the river below the dam affect the number of gravel or sand bars and therefore the habitat for fish that require gravel or sand bars to lay eggs? The fish will extinct over time 6. Most of the world’s rivers have dams so they no longer flow unrestricted to the sea. What does this mean for anadromous fish species (herring, salmon, steelhead) which live in large lakes or the ocean but spawn (lay eggs) upstream in a river? It will make the fishes unable to return to river and produce offspring 7. Mosquitos lay eggs in slow moving water so in areas with malaria efforts are made to reduce standing water to limit mosquito habitat. How do you think reservoirs affect prevalence of mosquito transmitted diseases? It will largely increase mosquito population as the water is slow Figure 4: Nile River Discharge (flow) and the Aswan Dam 8. How does construction of a hydroelectric dam change the seasonal pattern of flow of water in a river? Use figure 4 above for the Nile River discharge (water flow) before and after the construction of the Aswan High Dam (pictured). It reduce the flow of water significantly in summer

Spring 2023 GEOL 0840: Introduction to Environmental Science Recitation 6: Hydropower Page | 5 9. Seasonal flooding is often used for irrigation water and brings with it fertile sediments. How might damning the Nile River affect downstream use of seasonal floods for irrigation and fertilization of farm fields? It will make it nonfunctional as all water is blocked Figure 5: In many sites with hydropower generation electricity companies use hydropeaking (increasing water flow and therefore electricity generation at times of day when more electricity is used). This leads to a diurnal pattern of water flow downstream of the dam. The figure below shows what this means for river discharge at a few sites in the western United states with different patterns of hydropeaking (red and yellow) and without hydropeaking (green). From: Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs. BioScience. 2016;66(7):561-575. doi:10.1093/biosci/biw059 Figure 6: The figure below presents a schematic of how river communities might be affected by hydropeaking. From: Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs. BioScience. 2016;66(7):561-575. doi:10.1093/biosci/biw059

Spring 2023 GEOL 0840: Introduction to Environmental Science Recitation 6: Hydropower Page | 6 10. How does hydropeaking change the level of water in the river throughout the course of the day? It will lower and higher the water level as the hydropeaking is used multiple times. 11. Many aquatic invertebrates (an important source of food for fish species) require constantly submerged, but shallow water for laying eggs. How would your answer to #10 affect these invertebrate species? These habitats would be destroyed 12. What could electricity companies do during peak insect spawning (egg laying) times in the Colorado River to reduce the impact of hydropeaking on aquatic insect and therefore fish communities? When insect have their peak spawning times do not use hyropeaking.

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