U6115: Water Monday, July 19 2004

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U6115 WaterMonday, July 19 2004
The early bird may get the worm but the second
mouse gets the cheese.
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One thing we should remember from this
summer (and the last 6)
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Today Water/Hydrology

• Intro to Hydrology
• Systems and Cycles
• Flux, Source/Sink, Residence time, Feedback
  mechanisms

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U6115 Syllabus Course Outline

• The water cycle part of the class is focused on
  basic physical principles (evaporation,
  condensation, precipitation, runoff, stream flow,
  percolation, and groundwater flow), as well as
  environmentally relevant applications based on
  case studies.
• Most specifically, students will be exposed to
  water quantity and issues from global to regional
  scales and how human and natural processes affect
  water availability in surface and groundwater
  systems.
• Note water quality issues will be mentioned but
  only briefly since they have been covered more
  extensively in the Environmental Chemistry course
  (ENVU6220)

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U6115 Syllabus Course Outline
NJ

• Class 1 (July 19) Introduction - Water for the
  world - Lab 1 Global and regional water budgets
• Class 2 (July 26) Global water issues -
  Hydrological cycle - Lab 2 Hydrological
  Forecasts and their Communication to
  Decision-Makers
• Class 3 (August 02) Dams Reservoirs - Lab 3
  Reservoirs and greenhouse gases
• Class 4 (August 09) Condensation/Precipitation
  Streamflow/Floods - Lab 4 Precipitation and
  Flood predictions A Statistical Analysis
• Class 5 (August 16) Evaporation - Droughts
  Land Use Impact on Streamflow
• Class 6 (August 18) Groundwater flow -
  Groundwater transport

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U6115 Syllabus Grading (activities)

• Water (40 of grade)
• Labs 100 (4 formal labs)
• Mostly minds-on experiments with computers. Lab
  report due

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Water for the World

• The role of water is central to most natural
  processes
• transport
• Weathering, contaminant transport
• energy balance
• transport of heat, high heat capacity
• greenhouse gas
• 80 of the atmospheric greenhouse effect is
  caused by water vapor
• life
• for most terrestrial life forms, water determines
  where they may live man is exception

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Hydrology

• literally "water science," encompasses the study
  of the occurrence and movement of water on and
  beneath the surface of the Earth
• finite though renewable resource
• finite in quantity, unlimited in supply, use rate
  is limited by 'recycling times'
• hydrologic sciences have pure and applied aspects
• how the Earth works
• scientific basis for proper management of water
  resources (or any natural resource)

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Introduction to hydrology

• use of water in 20th century has grown
  dramatically

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Inventory of water on Earth
After Berner and Berner, 1987
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Cycle Approach

• Some Definitions
• Transport and transformation processes within
  definite reservoirs Carbon, Rock, Water Cycles
• Reservoir (box, compartment M in mass units or
  moles) An amount of material defined by certain
  physical, chemical, or biological characteristics
  that can be considered homogeneous
• O2 in the atmosphere
• Carbon in living organic matter in the Ocean
• Water in the Ocean
• Flux (F) The amount of material transferred
  from one reservoir to another per unit time (M/s
  or M/s.L2)
• The rate of evaporation of water from the surface
  Ocean
• The rate of deposition of inorganic carbon
  (carbonates on marine sediments
• Source (I or Q) A flux of material into a
  reservoir
• Sink (O or S) A flux of material out of a
  reservoir

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More Definitions

• Budget A balance sheet of all sources and sinks
  of a reservoir. If sources and sinks balance each
  other and do not change with time, the reservoir
  is in steady-state (M does not change with time).
  If steady-state prevails, then a flux that is
  unknown can be estimated by its difference from
  the other fluxes.
• for a control volume this means dM/dt I'-O'
• Turnover time The ratio of the content (M) of
  the reservoir to the sum of its sinks (O) or
  sources (I). The time it will take to empty the
  reservoir if there arent any sources. It is also
  a measure of the average time an atom/molecule
  spends in the reservoir. Or
• ?0 M/O (or M/I)
• Cycle A system consisting of two or more
  connected reservoir, where a large part of the
  material (energy) is transferred through the
  system in a cyclic fashion

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The Water (Hydrologic) Cycle
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The Water Cycle (in detail)

• The volume (M) of water at the surface of the
  Earth is enormous 1.37 109 km3! (total
  reservoir) The Oceans cover 71 of the Earths
  surface (29 for the continent masses above sea
  level)

Adapted from Berner Berner (The Global Water
Cycle Prentice Hall, 1987)
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Fluxes (F in 103 km3/yr)

• Of total yearly evaporation, 84 evaporates from
  the Oceans and 16 from surface of continents.
• However, return to Earth via precipitation 75
  falls directly on the Oceans and 25 on the
  continents.
• During the year, the atmosphere transports 9 of
  Oceans evaporation to the continents!
• This water is returned via surface streams and as
  groundwater

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Errors!

• Precipitation and evaporation are difficult to
  measure precisely over the oceans. They are
  mostly estimated from models and satellite data.
• Groundwater reservoir estimates bear a inherent
  error in the fact that they are indirectly
  determined.
• Soil moisture and evapotranspiration rates depend
  on indirect measurements and average soil quality
  and global/regional respiration rates

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Concept of residence time
High probability that a certain fraction of the
atoms or molecules forming the reservoir (M) will
be of a certain age (mean age of the element when
it leaves the reservoir)
In steady state I O Residence time t V/I
V/O
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Residence Time(years months weeks)

• High probability that a certain fraction of the
  atoms or molecules forming the reservoir (M) will
  be of a certain age (mean age of the element when
  it leaves the reservoir)
• The simplified residence time ? turnover time
• The time it would take to empty a reservoir if
  the sink (O or outflow) remained constant while
  the sources were zero
• ?0 M/O (or M/I)
• M ?0O
• Residence time of water in the atmosphere
• M ? O ? ?0 ?
• M 13 103 km3
• S 297(O) 99(C) 103 km3/yr 396 103 km3/yr
• ?0 0.033 yr 12 days!
• Replacement 30 times/year

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Residence Time(years months weeks)

• High probability that a certain fraction of the
  atoms or molecules forming the reservoir (M) will
  be of a certain age (mean age of the element when
  it leaves the reservoir)
• The simplified residence time ? turnover time
• The time it would take to empty a reservoir if
  the sink (O) remained constant while the sources
  were zero
• ?0 M/O (or M/I)
• M ?0O
• Residence time of water in the ocean
• M ? S ? ?0 ?
• M 1,370,000 103 km3
• S 334 103 km3/yr (evaporation)
• ?0 M/S 4102 yrs!

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Typical residence times

• Glaciers 100s to 100,000s of years
• Oceans 3200 years
• Rivers lakes days to years
• Groundwater years to millions of years

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Continental Mass Balance

• quantitative description ? applying  the
  principle of conservation of mass
• for continents as control volume this can be
  written as
• dV/dt p - rso - et 0 (all averaged)
• on average this means p   rso et
• the water budget for all land areas of the world
  is p800mm, rs 310mm, and et 490mm
• the global runoff ration (rs/p) is 39 there are
  lots of local and regional variations.

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System Approach

• Feedback All closed and open systems respond to
  inputs and have outputs. A feedback is a specific
  output that serves as an input to the system.
• Negative Feedback (stabilizing) The systems
  response is in the opposite direction as that of
  the output. CLOUDS!

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System Approach

• Positive Feedback (destabilizing) The systems
  response is in the same direction as that of the
  output.

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System Approach

• Positive Feedback (destabilizing)
• CLOUDS!

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Surface waters
BRF
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• Watershed, catchment, drainage basin
• Catchement (drainage basin, watershed) the basic
  unit of volume (control) which is an area of land
  in which water flowing across the land surface
  drains into a particular stream and ultimately
  flows a single point or outlet.

dV/dt p - rso - et 0 on average ? p   rso
et
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• Catchment
• Our concern with precipitation and
  evapotranspiration is in knowing the rates,
  timing, and spatial distribution of these water
  fluxes between the land and the atmosphere.
• dV/dt p - rso - et 0

Texas
New York
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Measurement techniques
? precipitation ?
evapotranspiration
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Evapotranspiration
Average statewide evapotranspiration for the
conterminous United States range from about 40
of the average annual precipitation in the
Northwest and Northeast to about 100 in the
Southwest.
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Annual Precipitation - Australia
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Annual Evaporation - Australia
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Annual Evapotranspiration - Australia
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Rivers and Streams
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Measurement techniques
? flow depth (stage)
? discharge
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Colorado Riverhydrograph

• Questions
• When does discharge peak and why?
• The hydrographs were taken at different locations
  of the river, what is the difference in the
  hydrographs and why is there one?

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Colorado Riverhydrograph

• Hydrographs are variable between years
• Discharge often peaks in late winter or spring,
  snowmelt
• Reservoirs smooth out extremes

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Canada del Oro hydrograph
? extended periods with no discharge at all!
http//water.usgs.gov
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Santa Cruz River (Tucson, AZ, 1930 vs. 1964 -
1983 flood)
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Lakes and Reservoirs
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Reservoir distribution in the U.S.
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Wetlands

• Definition (U.S. Fish and Wildlife Service)
• "WETLANDS are transitional systems between
  terrestrial and aquatic systems where the water
  table is usually at or near the surface or the
  land is covered by shallow water. For purposes of
  this classification wetlands must have one or
  more of the following three attributes
• at least periodically, the land supports
  predominantly hydrophytes
• the substrate is predominantly undrained hydric
  soil and
• the substrate is saturated with water or covered
  by shallow water at some time during the growing
  season of the year."
• Hydrologic conditions Groundwater (water table
  or zone of saturation) is at the surface or
  within the soil root zone during all or part of
  the growing season.
• Hydric soils soils that are saturated, flooded,
  or ponded long enough during the growing season
  to develop oxygen-free conditions in the upper
  six inches
• Hydrophytic vegetation plants typically adapted
  to wetland and aquatic habitats plants which
  grow in water or on a substrate that is at least
  periodically deficient in oxygen due to excessive
  water content.

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Wetlands are classified into two general
categories coastal and inland. Coastal wetlands
are further classified into marine and estuarine
categories Inland wetlands are further subdivided
in riverine, lacustrine, and palustrine wetlands.
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Fens receive water from the surrounding watershed
in inflowing streams and groundwater, while bogs
receive water primarily from precipitation.
Fens, therefore, reflect the chemistry of the
geological formations through which these waters
flow.
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Benefits of Wetlands
Loss of floodplain forested wetlands and
confinement by levees have reduced the
floodwater storage capacity of the Mississippi by
80 percent increasing dramatically the potential
for flood damage. The 1993 flood proved this
prediction to be true and resulted in
immeasurable damage
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Coastal Wetlands
Tidal coastal wetlands store carbon densely,
holding on to 10 of the global stock of soil
organic carbon in only 0.1 of the Earths
surface. Despite their relatively small area (203
103 km2), tidal coastal wetlands may act as
substantial sinks for atmospheric carbon due both
to exceptional carbon burial fluxes and
negligible CH4 and N2O emissions. Because the
projected sequestration efforts in North American
croplands (0.5-2.5 Pg C) are of the same order of
magnitude as C stocks estimated to exist in the
surface meter of wetlands (4 Pg), major losses
of these ecosystems could easily offset any
improvement in preservation of SOC within managed
croplands even at its highest efficiency. In
many coastal regions (i.e. Louisiana Gulf Coast),
these wetlands are being lost are substantial
rates (50-100 km2/yr)
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Groundwater
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• Groundwater flow is controlled by
• differences in water table (hydraulic head)
• hydraulic conductivity (relation between specific
  discharge Vol/t and hydraulic gradient)
• Hydraulic conductivity depends on both the nature
  of the fluid (viscosity) and the porosity of the
  material

Hornberger et al., 1998
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Measurement techniques
? Hydraulic head, conductivity