Planet Water Our Planet is covered by water, an astonishing 71 percent! If the world was uniform all the way around water would cover the planet to a depth of 2.6 km, (1.6 miles). Where did all this water come from? Slide 1

Planet Water How much water is that? It would take 15.5 billion years for that volume of water to go over the Niagara Falls (Planet Water = 4.54 Billion Years old) It takes the average American 7.5 years to use up the amount of water that flows over Niagara Falls every second. That’s a lot of water, is it enough for everyone? Slide 2

Planet Water 2.5% of the water on planet water is considered fresh water. 1.7% trapped as polar ice, 0.76% fresh groundwater, and 0.1% in the surface and atmosphere. Groundwater sources are not evenly distributed around the world, and excessive groundwater pumping has negative environmental impacts. Therefore surface and atmospheric water are the most accessible and renewable resource of drinking water. Approximately 131 gallons per person per day. Slide 3

Planet Water When we turn the faucet on, water always comes out. But how does it get there and how do we know that it is safe to drink? Civil and environmental engineers design systems to move this water from surface and groundwater sources to water treatment facilities and then to our homes. It is their job to provide both quality drinking water, assuring our health and safety and a sufficient quantity of water. Slide 4

Planet Water The water cycle is the central focus of hydrology. Civil engineers that focus on water resources are required to model the flow of water and design systems to transport water from one place to another. These engineers must have an in depth knowledge of water cycle. Can you name and describe different parts that make up the water cycle? Slide 5

Planet Water How does the water cycle transform from one phase to another, are these phases connected, and why is it important to understand phase transformation processes? Environmental Engineers use the rates of reaction to design treatment systems to improve the quality of water/air, can we calculate reaction rates within the water cycle? Slide 6

Urban Water Cycle The driving force for the water cycle is the sun! How does water transform from one part of the water cycle to another? Evaporation Condensation Precipitation Infiltration Stormwater Runoff Groundwater Flow Plant Uptake Transpiration Slide 7

Evaporation Evaporation: When water changes from a liquid to a gas or vapor Transformation: heat from the sun creates energy that breaks the bonds holding water molecules together. Rate: net evaporation occurs when the rate of evaporation exceeds the rate of condensation. Rate is typically in (V)/(T), example: cm3/s, gallon/hr Example: boiling water, steam off of a lake or river Slide 8

Condensation Condensation: water vapor changes from gaseous state (vapor) to liquid phase Transformation: evaporated water vapor condenses in the atmosphere due to lower temperature resulting from less atmospheric pressure. Rate: on average the residence time for moisture in the atmosphere is 8.2 days Rate is typically in (V)/(T), example: cm3/s, gallon/hr Examples: Water droplets on outside of your drink, glasses fog when going from inside to outside in summer, cloud like trails from airplanes (contrails) Slide 9

Precipitation Precipitation: condensed water vapor that falls to Earth as rain, snow, or hail. Transformation: water molecules combine (condensation) with tiny dust that act as a nucleus to form cloud droplets. An increase in collisions occur with other droplets until the mass of the droplet creates a fall velocity that is greater than the cloud updraft speed, resulting in precipitation. Rate: When the evaporation rate is less than the condensation rate a droplet can grow into a cloud drop. Rate is typically in (L)/(T), example: cm/s, in/hr and can be calculated with a rain gauge Slide 10

Infiltration and Percolation Infiltration: movement of water into the media layer Percolation: movement of water within the media layer Transformation: when precipitation falls onto a pervious surface it may infiltrate into the media layer. Rate: The infiltration rate is dependent on intensity and duration of precipitation, vegetative cover, and the percolation rate; the percolation rate is effected by gravity, grain size, geology, depth to groundwater table, and hydraulic capacity of surrounding soil. Infiltration and percolation rates are typically calculated in (V)/(T) units, example: ml/s, gallon/hr. Activity: Does Size Matter? Slide 11

Stormwater Runoff The flow of rainwater that occurs as a result of the precipitation rate exceeding the soil infiltration and percolation rate. Stormwater runoff is also generated from roofs, roads, sidewalks and is the water you see flowing down the street when it rains. Slide 12

Groundwater Flow Water is recharged to the groundwater system by percolation of water from precipitation and then flows to the stream through the groundwater system. Slide 13

Plant Uptake Plant Uptake: the process of plants absorbing water and nutrients from roots to grow. Transformation: plants use the energy from the sun (photosynthesis) to transform inorganic nutrients into organic above ground and below ground biomass Rate: above ground biomass uptake begins in spring, peaks in mid summer, and very minimal in fall and winter months. Rate is typically in (M)/(M), example: mg/mg, g/g, lb/lb Example: How often do you need to cut the grass in the summer vs. winter? Slide 14

Transpiration Transpiration: The loss of water from the leaves of plants as a result of plant uptake from infiltrated stormwater and/or the groundwater table. Why do trees drop their leaves in the fall? Transformation: process occurs to remove heat from the plant and facilitate plant uptake. Rate: dependent on moisture content of plant vs. surrounding air (Engineering Word: concentration gradient) Rate is typically in (V)/(T), example: cm3/hr, gallons/day Example: A large oak tree can transpire 151,000 liters per year or 40,000 gallons. Could we capture this water? (110 gallons/day) Activity: Do Plants Breathe? Slide 15