How do humans affect watersheds and the hydrologic cycle

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How do humans affect watersheds and the
hydrologic cycle?
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Human caused disturbances

• Agriculture
• Timber harvest
• Mining
• Urbanization
• Introduction of exotic species
• Harvesting of fish and wildlife

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Landscape controls
Land use/cover and vegetation
Physiography
Climate
Gross reach morphology
Habitat Forming Processes
Solar energy and Organic input Regime

Nutrient Inputs
Sediment and Hydrologic Regime
Stream Morphology and Conditions

Habitat complexes and conditions e.g., pools,
riffles, temperature, etc.
Biodiversity
Species assemblages
Modified from Roni et al. 2002.
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Land Use and Vegetation

• The landscape control factor on which humans have
  the most influence
• Mining extent of vegetation alteration depends
  on type of mining
• Forestry tree removal and replacement over time
• Urbanization tree removal and replacement with
  grass and impervious surfaces
• Agriculture tree removal and replacement with
  pasture or crops

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Effects of vegetation removal on hydrology and
streams

• Precipitation ?

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Effects of vegetation removal on hydrology and
streams

• Precipitation ?
• Evapotranspiration ?

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Effects of vegetation removal on hydrology and
streams

• Precipitation ?
• Evapotranspiration
• Infiltration ?

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Effects of vegetation removal on hydrology and
streams

• Precipitation ?
• Evapotranspiration
• Infiltration
• Surface runoff ? Subsurface runoff ?

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Effects of vegetation removal on hydrology and
streams

• Evapotranspiration
• Infiltration
• Surface runoff Subsurface runoff
• Frequency and magnitude of
• peak flows ?

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Effects of vegetation removal on hydrology and
streams

• Evapotranspiration
• Infiltration
• Surface runoff Subsurface runoff
• Frequency, magnitude and timing of
• peak flows
• Materials transported to stream ?

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Effects of vegetation removal on hydrology and
streams

• Evapotranspiration
• Infiltration
• Surface runoff Subsurface runoff
• Frequency and magnitude of
• peak flows
• Materials transported to stream

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Aggregate Mining

• In-channel mining

In-channel and floodplain mining
Photos by M. Kondolf
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Effects of instream aggregate mining

• Continuity of sediment transport interrupted
• Produces local sediment deficit
• Can lead to increase accumulation of fines and
  blocking of sediments

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Effects of instream aggregate mining

• Incision can lower the water table
• This can lead to loss of groundwater storage
• Can affect hyporheic zone
• Reduce summer base flow

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Effects of floodplain and terrace mining

• Pumping to dewater pits
• can lower base flows in the channel and increase
  evaporation from the waste pits
• may increase saltwater intrusion near coasts
• If channel migration captures the pits,
  in-channel storage ponds will alter flow travel
  times
• Old pits may be altered to serve as off-channel
  winter habitat for salmon

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FORESTRY
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Photos by R.S. Lindsay
Agriculture
Photo by Carrie Inman
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URBANIZATION
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Forestry, agriculture and urbanization

• All of these human activities alter the watershed
• What alterations do they have in common?

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Forestry, agriculture and urbanization

• Remove trees and other vegetation
• Reduce organic matter delivery
• Build roads

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Precipitation
Natural
Developed
Rapid flow limited storage
Slow flow
Pollutant wash off
Natural cleaning
Large storage in soil, channel and valley floor
Reduced soil storage Limited infiltration
No recharge
Recharge
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Floods and Urbanization
surface runoff vs. infiltration natural land
cover vs. urban area
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TREE REMOVAL
EVAPOTRANSPIRATION
INTERCEPTION
SOIL MOISTURE
SATURATED SUBSURFACE/ SURFACE FLOW
TRAVEL TIME OF WATER TO CHANNELS FROM STORM
RUNOFF
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CHANGES TO WOOD/ORGANIC REGIME
CHANNEL ROUGHNESS AND STORAGE
WATER TRAVEL TIME THROUGH CHANNEL
FLOW PEAKS EARLIER AND HIGHER DOWNSTREAM
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Drainage Density
Channels
Roads, Ditches, Drains
Lower drainage density
P
P
Higher drainage density
Q
Q
time
time
Low peak, gradual rise and fall
Higher peak, quicker rise and fall
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Roads and Soil Modification
Compacted Soil
Soil removal/ Cut banks
Ditches, culverts, drains
Infiltration
Soil water Storage space
Subsurface flow interception
Surface runoff
Soil saturation
Drainage density and water delivery to streams
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How do we manage watershed?

• Dept of Natural Resources Regulations
• U.S. Forest Service Regulations
• Clean water act
• Endangered Species Act
• Total Maximum Daily Loads (TMDLs)

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Washington Water Types

• Type S
• Shorelines and large rivers
• Type F
• Rivers and associated wetlands, lakes, ponds,
  etc. gt 0.5 acres at seasonal low level and have
  FISH
• Type Np
• Perennial streams without fish
• Type Ns
• All other streams not included above- seasonally
  dry streams without fish

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Regulations a function of water type and forest
site class
Core No harvest or construction except for
permitted road activities Inner Zone Harvest
allowed but must meet future desired conditions
standards (140 yrs) Outer Zone Must leave 20
conifer trees per acre gt 12 inched dbh
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Lab reminders

• Float method
• if you forgot to take channel measurements at the
  upstream and downstream ends of your float reach,
  you can sum the delta areas from your velocity
  meter method to get the cross-sectional area of
  flow

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Lab reminders

• Velocity meter method
• Do NOT take the average velocity of your
  measurements and multiply by cross-sectional area
  to get discharge Q. This method involves summing
  the delta Qs to get the total Q.

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Lab Reminders

• Velocity comparisons
• Compare your float method velocity with the
  average velocity as computed dividing your
  calculate Q, discharge, (using the velocity meter
  method) by the total cross-sectional area that
  you measured across

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Project Report Concerns

• Include a section on climate in the park
• Include a section describing how your
  alternatives will affect hydrologic processes in
  the park and how that will affect aquatic ecology
  in your streams
• Include a section on processes and
  characteristics that you think should be measured
  and monitored