Water Science and the Environment HWRS 201

Transcription

1 Water Science and the Environment HWRS 201 Dr. Mr. Ghasemian 2015

2 Office hours and contact information Office hours MWF - or by appointment Starting Harshbarger 3 Contact 621- D2L site Bring your laptops to class

3 Reading materials Articles will be posted on D2L site or given as websites 1 st assignment: Read the material at

4 Grading Exams ( 0%) Midterm ( 5%) Final (25%) Homework, Labs, and Quizzes ( 0%) Quizzes Ten minutes 5 or 6 Class participation (extra 15%)

5 Background Where does Earth s water come from? Where does it go? Where is it stored? Basic physics and chemistry of water Where does the fuel (that is, the energy) for the water cycle come from? What is water? What are its most important properties?

6 Background Where does Earth s water come from? Where does it go? Where is it stored? Basic physics and chemistry of water Where does the fuel (that is, the energy) for the water cycle come from? What is water? What are its most important properties?

7 Understanding the Hydrologic Cycle The hydrologic cycle is just another name for the water cycle. To understand the hydrologic cycle we need to study: the components of the cycle, the role that energy (mainly from the Sun) plays in the cycle and the flows among the different components of the cycle In this course we ll concentrate on the elements of the terrestrial water cycle That includes the role of human beings 8

8 Where did Earth s water come from? There are several basic hypotheses: Water came from Earth s proto-atmosphere Water came from outer space Water came from inside Earth These hypotheses are compatible Our Water Planet

9 Where did Earth s water come from? Cooling of early earth may have allowed volatile components to be held in an atmosphere of sufficient pressure for the stabilization and retention of liquid water. Water vapor may have been ejected into the atmosphere by volcanoes. Liquid water and water vapor may have gradually leaked out of rocks containing water. Comets, trans-neptunium objects, or water-rich asteroids may have brought water to Earth. Our Water Planet

10 Earth, a Perfect Place for Water Once Earth cooled enough, this water vapor condensed into liquid. Other planets are either too hot for water vapor to remain in their atmospheres or too cold for it to exist as liquid. Earth is a perfect place for water. Our Water Planet

11 The Water Cycle The water cycle is the set of processes that controls the circulation of water on Earth. Primary processes involved in the hydrologic cycle: Evaporation and transpiration Precipitation (rain, snow, sleet, ) Infiltration and groundwater flow Surface runoff HWRS 201 Water Science and the Environment 12

12 Solar energy drives the water cycle The sun is the source of most energy on earth. It s the driver of another of Earth s great cycles: the energy cycle. Evaporation is the main component of the energy cycle that affects the water cycle About 24% of the solar radiation reaching the earth is absorbed by evaporating water.

13 Elements of the water cycle The water cycle consists of reservoirs where water is stored and processes that flow water between reservoirs. Reservoirs Oceans, groundwater, lakes, rivers, marshes, the atmosphere, Antarctica, polar ice, glaciers, ordinary snowpack, soil moisture Processes (flows) Precipitation, canopy interception, snowmelt, runoff, infiltration, groundwater flow, evaporation, transpiration, sublimation, atmospheric transport, condensation in clouds and fog

14 Environmental reservoirs Oceans Groundwater Fresh Salty Soil Moisture Polar ice Other ice and snow Lakes Fresh Salty Marshes Rivers Biological water Atmospheric water

15 Human reservoirs and processes Reservoirs Surface storage (dams) Groundwater recharge Processes Agricultural irrigation Agricultural diversions Groundwater pumping Wastewater treatment Legal and management framework

16 Distribution of Earth s Water

17 Quantities of water in reservoirs The quantity of water in a reservoir is measured as a volume. On large scales volumes are frequently stated in cubic kilometers, which we write as km 3. On smaller scales it might be cubic centimeters (cm 3 ) or cubic meters (m 3 ). Remember, 1 inch = 2.54 cm So 1 cm = 0.4 inch Alternatively, at small scales we can measure volumes as liters. A liter = 1000 cm 3, which sounds like a lot, but isn t.

18 Quantities of water in individual reservoirs Reservoir Volume of water (km 3 ) % total water % fresh water Oceans 1,338,000, Groundwater Fresh 10,530, Salty 12,870, Soil Moisture Polar ice 24,023, Other ice and snow 340, Lakes Fresh 91, Salty 85, Marshes Rivers 2, Biological water 1, Atmospheric water 12, Total water 1,385,984, Total fresh water 35,029, Source: UNESCO,1978

19 Takeaway: Reservoirs Most of Earth s water (> 95%) is in the oceans. It can t be drunk directly. It s not potable. Removing the salt (desalinization) is expensive. The polar icecaps and glaciers contain most of Earth s freshwater (68.6% of all fresh water). The icecaps are pretty hard to drink. Most of the rest is in groundwater (30.1%). Some of that is brackish (mildly salty). We have to pump groundwater to get to it. The amount in rivers and lakes is really small. Using it usually requires storage behind dams, i.e., in reservoirs. They cost a lot too. Our freshwater reserves are small and precious.

20 Processes and flows Processes move water between reservoirs. For instance, precipitation moves water from the atmosphere to the land surface and the oceans. We also say water flows from the atmosphere to the land surface through the process of precipitation. This is also sometimes called an exchange. Such flows are measured as the volume of water flowing between one reservoir and another during a given time. For instance km 3 per year, liters per minute, etc. You re familiar with measuring the flow of traffic. That s the number of cars that go by a point in a given amount of time. For instance, number of cars per day.

21 Processes, Reservoirs and Traffic To continue the analogy with cars Processes are like traffic, moving water (cars) from place to place Reservoirs are like parking lots, carports, metered parking, etc. Cars stay in them for a while And cars stay in them for different amounts of time For instance, cars often stay in airport parking longer than they do in parking spaces on the street In hydrology, we call the time that water stays in a reservoir, its residence time And different reservoirs have different residence times

22 Balances of flows The net flow into most reservoirs in a year is zero! Reservoir Annual inflow Amount Annual Outflow Amount Oceans Return flow 1 Evaporation 426 Surface runoff 40 PPT 385 Total 426 Total 426 Land surface PPT 111 ET 71 Surface runoff 40 Total Atmosphere ET 71 Land PPT 111 Ocean evaporation 426 Ocean PPT 385 Total 497 Total 496 All flows measured in units of 1000 km 3 /year

23 Reservoirs and residence times

24 Residence time Since water is continually flowing through a reservoir, we re interested in how long it stays in each reservoir. This amount of time on average is the residence time. The residence time varies with the reservoir. Water stays in the ocean a lot longer than it does in the atmosphere. We can estimate the average residence time in a reservoir by comparing the flow in (or out) of the reservoir to the total amount of water the reservoir usually contains.

25 Technical note: residence time Residence time in a reservoir = Average amount of water in the reservoir Rate of flow into the reservoir For instance, Residence time in the oceans = 1,338,000,000 km 3 426, 000 km 3 /year = 3,140 years

26 Takeaway: Processes and flows Processes flow water between reservoirs Flows into and out of most reservoirs are in balance. The balances are dynamic. Water spends different amounts of time in different reservoirs. This is called residence time. Residence time in a reservoir depends on (i) the amount of water in the given reservoir (ii) the rate of flow into it.

27 Watersheds A watershed is an area of land where all of the water that drains off it goes to the same point. That point is the outlet. Watersheds are a physical feature of landscapes. They cross political boundaries. There are 2,110 watersheds in the continental US

28 Stream system Outlet Raritan Basin Council

29 Surface Water: Watersheds Every watershed consists of A stream network A topographic divide An outlet A watershed consists of surface water--lakes, streams, reservoirs, and wetlands--and all the underlying ground water. Larger watersheds contain many smaller watersheds.

30 Surface Water: Watersheds Watersheds are important because the streamflow and the water quality of a river are affected by things, humaninduced or not, happening in the land area "above" the river-outflow point

31 The Drainage Basin In hydrology the water balance and the hydrologic cycle are most relevant, for most applications, at the watershed, or drainage basin, level. 32

32 7 States, 2 Nations 15 MAF average annual flow 60 MAF of total storage (4 years of flow) Serves 30 million people, but the majority of water used for irrigation Significant environmental issues Very complicated legal & governance environment Stuff and moree

33 21 Major US Basins

34 River Systems of the US

35 The world s largest drainage basins Drainage basins can be ranked by Area Average annual discharge Length Strahler number

36 The world s longest main stems 1. Nile 6,690 km (4,147 miles) 2. Amazon 6,452 km (4,000 miles) 3. Yangtze 6,300 km (3,915 miles) 4. Mississippi-Missouri 5,970 km (3,710 miles) 5. Yenisey-Angara 5,550 km (3,441 miles) 6. Yellow River 5,464 km (3,387 miles) 7. Ob-Irtysh 5,410 km (3,354 miles) 8. Amur 4,410 km (2,734 miles) 9. Congo 4,380 km (2,715 miles) 10. Lena 4,260 km (2,641 miles)

37 The Hydrologic Cycle Recall: Earth s waters are constantly circulating. The driving forces are: Heat from the Sun The force of gravity HWRS 201 Water Science and the Environment 38

38 Dynamic balance The amount of water in each of the reservoirs of the water cycle stays fairly constant even though water is constantly flowing into and out of each reservoir. We call this kind of situation dynamic balance. Dynamic means things (water in our case) are flowing. Balance means there is no total change in the amount in the reservoir. For example, water in the ocean is dynamic It continually leaves through evaporation. It returns through precipitation, groundwater and surface runoff. But the total amount of water in the ocean is not changing It is in balance.

39 Background Where does Earth s water come from? Where does it go? Where is it stored? Basic physics and chemistry of water Where does the fuel (that is, the energy) for the water cycle come from? What is water? What are its most important properties?

40 Conservation Laws 1. Conservation of mass: mass is neither created nor destroyed. 2. Conservation of energy: energy is neither created nor destroyed (1 st law of thermodynamics) 3. Conservation of momentum: the momentum of a body remains constant unless the body is acted upon by a net force (Newton s 1 st law) 41

41 Methods of Heat Transfer Conduction: no mass movement Convection: mass moves Radiation: no mass is needed Latent Heat: transport of water Sensible Heat: raises temperature mass is needed 42

42 Conduction, Convection and Radiation 43

43 Conduction The transfer heat from one molecule to another in a substance Energy travels from hot to cold Air is a poor conductor of heat, metal is a good conductor 44

44 Convection The transfer of heat by the mass movement (flow) of a fluid (water or air) Convective circulation: warm air expands and rises then cools and sinks creating a thermal cell 45

45 Radiation Energy from the sun travels through space and the atmosphere in the form of a wave (electromagnetic waves) and is called radiation. Radiation and Temperature All objects with a temperature greater than 0 K radiate energy. As temperature of an object increases, the more total radiation is emitted by an object (Stefan-Boltzmann Law). Sun at 6000 K emits radiation, electromagnetic spectrum Shortwave radiation (high energy) from the Sun Longwave radiation (low energy) from the Earth ~288 K 46