Water Resources Chapter 8 PDF

Water Resources CHAPTER 8 Core Concepts Understand some of the local Las Vegas water resources and how it is connected to Earth’s hydrologic cycle Learn how hydrologists use the water balance equation to assess water supply, describe the components of this balance, and describe this balance using w...

Water Resources CHAPTER 8 Core Concepts Understand some of the local Las Vegas water resources and how it is connected to Earth’s hydrologic cycle Learn how hydrologists use the water balance equation to assess water supply, describe the components of this balance, and describe this balance using water budget graphs Identify the difference sources of freshwater and describe how water flows in and out of Earth’s surface and subsurface Describe the limits of groundwater usage and how we (humans) have impacted this very important reservoir of water 2 Outline Local Water Resources Water on Earth Hydrologic Cycle Water Budgets and Resource Analysis Surface Water Resources Groundwater Resources Chapter 8 Review Image source: LVVWD 3 Local Water Resources 4 Where does LV Water Come From? Image source: SNWA 5 Lake Mead Spillway (1983 vs. 2022) Image sources: (L) UNLV Special Collections and (R) Yale Climate Connections 6 Lake Mead (2000 vs 2022) Image source: Earth Observatory-NASA 7 Lake Mead Historical Water Level Image source: water level data collected from Bureau of Reclamation 8 Lake Mead Intakes Three water intakes ◦ 1st pipe installed in 1971 ◦ 2nd pipe installed in 2000 ◦ 3rd pipe installed in 2015; pump station completed in 2020 Image source: SNWA 9 U.S. Drought Monitoring Image source: Monitor 10 Conservation at its Best Image source: Vegas Business Digest 11 Water on Earth 12 Is Water a Renewable Resource? Yes it is…It is constantly being replaced at a rate that is useful to humans Unfortunately, its distribution around the world is unequal ~2.4 billion people lack safe water 13 Water Reservoirs Image source: USGS 14 Hydrologic Cycle 15 The Hydrologic Cycle Endless cycle Reservoirs (e.g., oceans) and pathways (e.g., evaporation) What is it driven by? Image Source: USGS 16 Hydrologic Terminology Precipitation Evaporation & Transpiration (ET) Overland flow = surface runoff Soil moisture zone Zone of saturation Water table Infiltration Percolation Image source: Christopherson, 2015, Geosystems, 9th Edition 17 Water Budgets and Resource Analysis 18 Budgets…Yet Again!!! 19 Water Balance Equation Also known as the water budget Effective method to assess portions of water cycle as they apply to water resources Space: small to large scales; Time: minutes to years 20 What are the Components? Precipitation (P) Evapotranspiration ◦ Actual evapotranspiration (AE) ◦ Potential evapotranspiration (PE) Deficit Surplus Change in soil-moisture storage (Δ S) 21 Precipitation (P) Any form of moisture to the Earth (supply) ◦ Rain, sleet, snow, hail ◦ Irrigation water can also be added 78% falls on oceans, leaving only 22% to reach the land surface Measured with rain gauges → devices that capture precipitation and allow it to be measured by depth, weight or volume 22 Rain Gauges Image source: Christopherson, 2015, Geosystems, 9th Edition 23 Precipitation in North America Las Vegas: Annual Precipitation ~4-4.5 inches Image source: Christopherson, 2015, Geosystems, 9th Edition 24 Actual evapotranspiration (AE) The water demand Evaporation – loss of moisture from a wet surface Transpiration – loss of moisture from vegetation (stomata) Both respond to high temperatures, high winds, low moisture in the atmosphere Evaporation pan measures evaporation Lysimeter measures both evaporation and transpiration 25 Lysimeters Image source: Unknown 26 DRI – SEPHAS Lysimeters (Outside) 27 DRI – SEPHAS Lysimeters (Inside) 28 Potential evapotranspiration (PE) Potential Evapotranspiration (water demand) Amount of water that would evaporate and transpire under optimum moisture conditions Difficult to measure directly but can be estimated using mathematical models Based off of monthly mean air temperature and day length 29 PE in North America Image source: Christopherson, 2018, Geosystems, 10th Edition 30 Deficit Demand exceeds the moisture from precipitation (P), irrigation, and that stored as soil moisture Deficits result in the formation of droughts 31 Surplus Additional water beyond potential evapotranspiration demands Creates and sustains sources of surface water (runoff) and replaces lost soil and ground water 32 Change (Δ) in Storage (S) “Δ” mathematical symbol for change Differences in the ability of soil to capture and store moisture defines the type of soil Storage is defined by the balance between: ◦ + recharge ◦ – soil moisture loss 33 Types of Soil Moisture Image source: Christopherson, 2018, Geosystems, 10th Edition 34 Sample Water Budget Kingsport, Tennessee Image source: Christopherson, 2018, Geosystems, 10th Edition 35 Another Water Budget Phoenix, Arizona Image source: Christopherson, 2018, Geosystems, 10th Edition 36