Hydrology Final.txt

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Hydrology Final.txt
2013-05-13 01:49:48

Hydrology Final Exam
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  1. Describe the run-off cycle:
    Much rain first intercepted by vegetation, that reaching the ground then infiltrates soil. Some intercepted water evaporates. Upon exceeding the soil's infiltration capacity, overland flow towards a watercourse occurs, some water will percolate into the water table. Some infiltrated water will flow downhill as interflow. The storm recharge to groundwater may also enter into a stream. When storm stops, things begin to dry and the water from the raised stream when into the banks and will leak out (bank storage)
  2. What are the factors affecting run-off?
    • 1. Geology > Geologic Type of soil > Permeable/impermeable (infiltration capacity lower in arid regions due to less-developed soil profiles)
    • 2. Topography > Characteristics of the watershed: steepness of the slope, shape (Narrow/long=more run-off), elevation (seasonal snow), orientation (north-facing vs. south-facing)
    • 3. Climate: Intensity of rain (usually light to moderate in a cyclonic/orographic system, in humid regions; semi/arid, convective precipitation; heavy for short periods = more runoff), vegetation (in desert, little interception); overland flow velocity higher in arid regions
    • 4. Land Use: increased runoff due to urban surfaces (impervious covers) and storm sewers
  3. What is the deal with geology affecting run-off?
    Geologic structure (folds, faults, etc) give predominant "grain" to landscape as the main determinant for the drainage pattern.
  4. How to measure run-off?
    • Overland flow:
    • Q= KiA
    • Q= Peak runoff rate (ft3/sec)
    • A= area of watershed surface
    • I = intensity of the rain
    • K= runoff coefficient
  5. How to measure stream flow:
    • River stage (water level in river channel) (nilometer)
    • Discharge (volume of water/time)
    • (River stage or discharge, volume/time = A * Velocity; or run-off in urban areas Q=KiA)
  6. Figure 8.18, West Walker River Hydrograph, representative of western US
    • draining regions in which much of the yearly precipitation is snowfall
    • Peak flow (May-June); when peaks are in spring, melting snow, if in winter, due to rain
  7. Fig. 8.19 Indiana watersheds
    Compares watersheds that are nearby peaks of streamflow at the same time but difference values because of different soils, different permeabilities, different infiltration rates. Otherwise they are the same size and subject to the general pattern of precipitation
  8. Fig. 8.20 Hydrograph from single storm
    • Discharge y axis, time x axis. period in which runoff is increasing is the rainfall. part of this runoff is from groundwater.
    • Used to know how fast the stream may rise under given storm conditions
  9. Colorado River
    • watershed is 8% of US surface, 1/5th of that of the Mississippi
    • Flow is 1% of US river flow, 1/30th of that of the Mississippi
    • Average Annual flow = 15 MAF
  10. Colorado River Compact (1922)
    • Happened to be based on the wettest 25 years in 500 yrs, so calculated MAF was 16.5
    • 7.5 MAF for Upper and Lower, 1.5 to Mexico
    • 1963 Lower basin water divided, 4.4 MAF to California
    • 1941 Colorado River Aqueduct
    • Storage capacity = 61 MAF, with Hoover Dam's Lake Mead with 1/2
    • 1.5 MAF lost to evaporation
  11. Discussion of adding dams in terms of increasing the water supply
    They don't increase total water supply, but they increase its usability by stretching out the period of use. More storage along the Colorado would probably reduce long-term supplies due to evaporative losses in the dry climate and bank storage
  12. Lake Powell, Glen Canyon Dam
    • Glen Canyon Dam took 20 years to fill due to being built in Navajo Sandstone and the banks having 25% porosity/high permeability; lost water due to evaporation/bank storage
    • Built for electricity to Phoenix, Arch concrete dam
    • 1983 Spillways opened releasing water to Hoover Dam, but flood occurred
  13. Hoover Dam
    • Arch-gravity dam, built in 1935 for flood control
    • Holds 30 MAF
  14. Grand Coulee Dam
    • Built in 1933, Concrete gravity dam, Washington state on Colombia river
    • Interfered with salmon populations and could not be built today
  15. Kingsley dam, Nebraska
    • Earthen dam, built in 1936
    • In 1972, problems caused by wind-generated waves causing erosion
    • Rip-rap (rocks) were placed along the upstream dace to protect it from erosion
    • Wave-protection regulation were then developed, dam didn’t fail
  16. Teton dam, Idaho (Earthen dam)
    Built in 1975 and failed in 1976, problems were water eroding the inside of the damn, piping (town downstream was destroyed, 11 people died, and the Bureau of reclamation changed the jobs so they didn’t have to deal with dams anymore)
  17. St. Francis dam
    Built to store water for LA, failed in 1928 for geologic reasons (built on faulty rock), an arch concrete dam
  18. Seven oaks Dam
    • Earthen dam on Santa Ana River
    • Built for flood control
    • No reservoir behind it so it will work for flood
  19. Baldwin Hills Dam
    earthen damn, failed in 1963, pumping of oil caused sinking
  20. World's Largest Drainage Basins and watersheds/streamflows:
    • Amazon, Congo (1/2 the size of watershed and 1/5 streamflow of Amazon) and Mississippi. Why #1 & 2?: because both are near equator- lots of precipitation
    • Mississippi = drainage area 1,260 x 10 mcubed miles squared-streamflow > 650,000 ftcubed/sec. Congo and Mississippi watersheds are almost the same but the stream flow in the Mississippi is less than half of the Congos.
  21. Good water quality:
    good for a particular purpose
  22. Safe water quality:
    free from contaminants and disease-causing organisms
  23. Basic parameters of water:
    Temperature, DO, pH, Turbidity, Salinity
  24. What is the deal with water temperature?
    Determines the amount of dissolved oxygen in water; higher temperature of water = lower DO content
  25. What is the deal with water DO?
    Low values may indicate eutrophication (decomposition of bacteria occurring, using up oxygen)
  26. What is the deal with water pH?
    surface water = 6.5-8.5; seawater = 7.8; distilled water = 7
  27. What is the deal with water turbidity:
    Clarity. Determined by Secchi Disk (circular disk of black and white quadrants. Lowering to a depth at in a body of water in which the pattern disappears from sight is a measure of the water turbidity)
  28. What is the deal with water hardness:
    Expressed as mg/L of CaCo3; drinking water should be <100mg/L
  29. What is the deal with water salinity:
    • Amount of TDS (total dissolved solids)
    • Seawater= 3.5% = 35 ppt = 35,000 ppm
    • Drinking water should have < 500 ppm for salinity
    • For irrigation, salinity should be <1000 ppm
    • Colorado river has high salinity by mexico→desalination plants (measured by electric conductivity)
  30. Safe Drinking Water Act:
    • 1. Primary Drinking water standards
    • a. Define amounts of substances that may have and adverse effect on health
    • 2. Secondary Drinking water standards
    • a. Define aesthetic qualities (taste, smell); “good” water quality
    • MCLG: Maximum contaminant level Goal ; non-enforceable by law