Hydrology

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Hydrology

• River Ecosystems and Humans

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Dimensions of river ecosystems

• Longitudinal
• Lateral
• Vertical
• Temporal

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Longitudinal Changes in Streams

• Certain characteristics of streams change
  predictably from upstream to downsteam
• Channels become wider
• Flow becomes slower, but greater in volume
• Streams become deeper

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Longitudinal Changes Reach Scale

• Longitudinal changes are also observed at shorter
  scales than the entire river length
• We call this shorter scale the reach scale
• One example of reach scale changes is the
  pool-riffle pattern found in many streams
  draining areas with medium gradient
• Riffle is an area of rapid flow over coarse
  substrate (rocks) whereas the pool is a slower
  flowing stretch with finer substrate
• Path of flow - thalweg

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Lateral Patterns

• There are also some predictable changes laterally
• The stream has a low flow channel the fastest
  flow is called the thalweg
• The stream has banks which define its frequent
  flow limit
• The stream has a floodplain which defines its
  flow limit on less frequent events, annual or
  lesser frequency

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Lateral Patterns

• Some streams and rivers will have a single
  dominant channel while others will have a network
  of interwoven channels

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Lateral Features

• As rivers increase in size they may develop a
  complex floodplain system

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Vertical dimensions

• Velocity changes with depth in stream channel
• Discharge (Q) VA

Diagram byEric G. Paterson Department of
Mechanical and Nuclear Engineering The
Pennsylvania State University
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Vertical Features

• Hyporheic (below stream) inter-actions
• Exchanges occur with groundwater just below the
  stream

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Lateral and Vertical Patterns

• In many large alluvial valleys, creatures that
  live in ground water and hyporheic water can be
  found in the subsurface water kilometers from the
  stream. In other words the stream extends well
  beyond its channel.

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Temporal dimension

• Stream flow changes
• Second by second
• Hourly
• Daily
• Monthly
• Seasonally
• Annually
• Milleniumly

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Selected Important Habitat Factors

• Substrate
• Temperature
• Oxygen levels
• Flow velocity
• Food availability
• pH
• Nutrient and sediment regimes
• Organic input and transport

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How are species distributed in space and time?
-- Environments contributing to riverine
biodiversity
Surface water
Subsurface water
Riparian system
Springs
Confined Reaches
Unconfined Reaches
Streams
Lakes
Hyporheic Zone
Ground Water
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Spatial distribution of species across a
floodplain (lateral dimension)
Species Richness
100
Eg. Fish Snails, slugs, mussels, Dragonflies,
damselflies Frogs, salamanders, toads Aquatic
plants
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River ------------------------------------------
---? Floodplain Edge
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(Ward and Tockner 2001 fig. 9.3)
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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
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Modified from Roni et al. 2002.
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Physical, chemical, and biological components
related to water quality

• Light
• Temperature
• Dissolved ions
• Suspended solids
• Nutrients and gases
• Toxics such as metals and pesticides/herbicides
• Biological features
• PPCPs (Pharmaceuticals Personal Care Products)

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Photos by R.S. Lindsay
Agriculture
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Photo by Carrie Inman
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FORESTRY
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Aggregate Mining

• In-channel mining

In-channel and floodplain mining
Photos by M. Kondolf
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URBANIZATION
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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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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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Take Home Messages

• Understand the interactions between land use/land
  cover and components of the hydrologic cycle
• Be able to describe what is typically measured in
  watersheds and why

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Hydrology Report 2-3 pages due May 25
individually Include Name, Date, Title
Introduction Methods Results and Discussion (w
tables) Conclusions Appendix (if needed for raw
calculations)
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