2/12 Exam I Study Guide

Use class presentations and chapter 1,3, and from Chapter 5 sections 5.1 (all), 5.2.1 (all), 5.2.2 (all), 5.2.3 (all) [Needed formulas will be provided.]

  1. Define hydrology.—[1/19:2]
    • Hydrology focuses on the global hydrologic cycle and the processes involved in the land phase of that cycle. Hydrology describes and predicts:
      • The spatial and temporal variations of water substance in the terrestrial, oceanic, and atmospheric compartments of the global water system.
      • The movement of water on and under the earth’s surface, the physical, chemical, and biological processes accompanying that movement.
  2. Provide a schematic and briefly describe the hydrologic cycle.
  3. Define “system” and components of a system. —[1/22:2]
    • A system is any conceptually defined region of space that can receive a sequence of inputs of a conservative quantity, store some of it, and discharge outputs of that quantity. [This] region is sometimes called a control volume
    1. Apply the definition of mass balance to an arbitrary system.
    2. Show in a block diagram the system and components of the system.
  4. How does precipitation form?—[1/26:7]
    • Cooling of air to dew point temperature
    • Condensation nuclei to form droplets or ice crystals
    • Growth of droplets and ice crystals into raindrops, snow flakes, or hailstones
    • Importation of moist air to the storm area
  5. Discuss the following types of precipitation:
    1. convective precipitation,—[1/26:13],[1/26:24]
      • Generated from the rising motion occurring when the land surface heats air and leads to upward buoyancy.
      • Thermal Convection can lead to uplift of warm air masses with subsequent cloud formation and precipitation via:
      • Heating of the surface and near ground air (typically during summer)
      • Differential heating leads instability and rise of moist air
      • Condensation and freezing lead to further intensification
    2. orographic precipitation, and
      • Generated from rising motion occurring when air is forced upwards along a mountain barrier.
    3. cyclonic/frontal precipitation
      • Generated from the rising motion occurring when two air masses of different temperature meet along a front.
  6. Why is the Earth warmer than it “should” be?
  7. What is the Probably Maximum Precipitation (PMP)? What is is used for?—[2/2:12-13]
    • The theoretically greatest depth of precipitation for a given duration that is physically possible over a storm area is used for dam design.
  8. Describe two different ways to compute PMP. What is the main difference between them?—[2/2:15-16]
    • Rational Estimation Method: Uses physical limitations (zero risk implied)
    • Statistical Method: Uses statistical limitations (some risk implied)
  9. What is the Probable Maximum Storm (PMS)?—[2/2:18]
    • Spatial and temporal distribution of PMP that generates most severe runoff conditions.
  10. What is the Probable Maximum Flood (PMF)?—[2/2:18]
    • The most severe runoff condition is called Probable Maximum Flood
  11. What is a watershed?—[1/22:8]
    • A watershed (also called drainage basin, river basin, or catchment) is the area that appears on the basis of topography to contribute all the water that passes through a given cross section of a stream. A watershed is separated from other watersheds via a watershed divide
  12. What is a hurricane?—[1/26:18]
    • Tropical cyclones not associated with fronts
    • Form over ocean between 5 and 20 latitudes
    • Sea-surface temperature of at least 27 degrees
    • Fed by evaporation and driven by condensation
  13. Why [are] some gases in the atmosphere are called greenhouse gases? Elaborate.
  14. Apply the mass balance equation to a watershed.—[1/22:13-18]
    • P + Gin - (Q + ET + Gout) = ΔS
    • Over time: μP + μGin - (μQ + μET + μGout) = 0
    • μGin = 0 for a watershed, thus μRO = μQ + μGout = μP + μET
  15. What are the sources of error in regional water balance equations?—[1/26:19]
    • Model Error
      1. Groundwater Flows
      2. Storage Changes (water year)
    • Measurement Error: Accuracy of Precipitation and Streamflow Values
  16. Describe [the] types and methods of precipitation measurement.—[1/29:1]
    • Ground measurements (rain gauges, optical sensors, heat sensors)
    • Ground-based remote sensing measurements (weather radar)
    • Airborne sensors (Aircraft and satellite) (passive microwave, optical, radar)
  17. What are the main problems with rain gauge measurements?—[1/29:4-5]
    • Splash (in and out)
    • Wind eddies
    • Wetting losses
    • Evaporation
    • Mechanic and electrical malfunctioning
    • Errors associated with specific designs
    • Presence of obstruction
    • Wind effects: Problems are much worse for snow gauges
  18. What are the main differences between gauge and radar estimation of precipitation?—[1/29:2]
    • Time and space scale of measurement
      • Point versus footprint
      • Instantaneous versus storm event total
    • Measurement technique
      • Physical versus inferred estimate
      • Electromagnetic wavelength
    • Data availability
      • Continuous versus overpass time
      • Local versus regional area
  19. How and why is climate important for water resources engineering?
  20. How and why is the study of probabilities and statistics important for water resources engineering?
    • Natural processes are rarely modeled accurately as deterministic systems.
  21. How is the return period of a hydrologic variable related to the probability of its occurence?
    • TP = 1/p
  22. How can one use the Binomial Distribution to estimate the number of time a flood of return period T would occur a certain number of time within a certain period?—huh?
  23. How can one compute the probability that an event would occur at least once in N years using Binomial distribution?
    • J= 1- (1-p)N
  24. If a dam has a design life of 50 years (N=50 years), what is the probability that the 15,000 cfs flow (having a recurrence interval of 50 years), will occur, or be exceeded during the design life?
    • 63.6% = 1- (1-p)N = 1-(1-1/50)50
  25. What is the probability that this flow will occur (or be exceeded) during the 5-year construction period?
    • 9.6% = 1- (1-p)N = 1-(1-1/50)5
  26. Why [is it] most hydrologic data can not (theoretically) be normally distributed?
    • Like many natural physical parameters, most negative hydrologic values make no sense. Normal distributions always give some probability for nonsensical negative values.
  27. How can one use the frequency factor KT to estimate the return period of a given event or the magnitude of an event of a given return period?
    • Probabilities corresponding to K factors can be found from tables or a formula. The inverse of these probabilities are the associated return periods.
  28. What is [an] IDF curve? What is it used for?—[1/31:1]
    • Intensity-Duration-Frequency curves express the relationship between intensity and duration of a rainstorm. They are used to estimate the likelihood of intense rainfall.
  29. What is the procedure to develop an IDF curve?
    • Locate a vertical masonry surface. Apply your noggin to it. Repeat until done.
  30. Review all problems solved in class and homework assignments.

Discussion


Personal Tools