Watersheds and Hydrology
What’s Water Got to Do with It?
• More water moves through ecosystems than any
other material
• The materials that it carries and deposits and the
energy that it expends are major drivers in
shaping the contour of the land and the habitat
availability/suitability for organisms.
• A resource that humans cannot live without
Watersheds and Hydrology
Learning Objectives
1
Where do we find water?
2
What is the hydrologic cycle?
3
How many dimensions does a stream have?
4
How do we characterize stream water?
5
What do we want to know about stream flow?
Question 1
Where do we find water?
Global distribution of water
Global distribution of freshwater
Water Storage
Reservoir
Oceans
Ice and Permanent Snow
Groundwater
Percent (%)
of total
96.5
1.74
1.7
Percent (%)
freshwater
0
68.7
30.1
Lakes
Soil Moisture including
permafrost
Atmosphere
Streams, Rivers, Swamps
Biosphere
0.013
0.023
0.91
0.26
0.001
0.001
0.0001
0.04
0.036
0.003
Watersheds and Hydrology
1
Where do we find water?
2
What is the hydrologic cycle?
3
How many dimensions does a stream have?
4
How do we characterize stream water?
5
What do we want to know about stream flow?
Question 2
What is the hydrologic cycle?
What is the hydrologic cycle?
Precipitation
Interception
Infiltration
Evaporation
Transpiration
Runoff
Ground water
Watersheds and Hydrology
1
Where do we find water?
2
What is the hydrologic cycle?
3
How many dimensions does a stream have?
4
How do we characterize stream water?
5
What do we want to know about stream flow?
Question 3
How many dimensions does a stream
have?
Question 3
How many dimensions does a stream
have?
1.
2.
3.
Longitudinal (upstream to downstream)
Lateral (bank to bank and valley wall to valley wall)
Vertical (water surface to bed to hyporheic to
ground water)
4.
Temporal (time: seconds to millennia)
Longitudinal Changes in Streams
• Certain
characteristics of
streams change
‘predictably’ from
upstream to
downsteam
– Channels become
wider
– Channels become
deeper
– Flow becomes
slower, but greater
in volume
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 poolriffle pattern found in
many streams draining
areas with medium
gradients
Riffle is an area of rapid
flow over coarse substrate
(sediment) whereas the
pool is a slower flowing
stretch with finer substrate
Lateral Patterns
• There are also some
predictable changes
laterally
• The stream has its low
flow channel, the low
point of which is 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
Thalweg
Lateral Patterns
• Some streams
and rivers will
have a single
dominant
channel while
others have a
network of
interwoven
channels
Lateral Features
• As rivers
increase in
size they will
develop a
complex
floodplain
system
Vertical dimensions
• Velocity changes with depth in stream
channel
Diagram by:Eric G. Paterson
Department of Mechanical and Nuclear Engineering
The Pennsylvania State University
Vertical Features
• Hyporheic
(below
stream) interactions
• Exchanges
occur with
groundwater
just below the
stream
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 visible
channel.
Temporal dimension
• Stream flow changes
Second by second
Hourly
Daily
Monthly
Seasonally
Annually
Millenniumly
• Channels migrate
• Riparian areas go through disturbance and
succession
• Seasonal changes in inputs
Watersheds and Hydrology
1
Where do we find water?
2
What is the hydrologic cycle?
3
How many dimensions does a stream have?
4
How do we characterize stream water?
5
What do we want to know about stream flow?
What are the major physical, chemical,
and biological components used to
characterize water quality?
Selected Important Habitat Factors
•
•
•
•
•
•
•
•
•
•
•
Light
Substrate
Temperature
Oxygen levels
Flow velocity
Food availability
pH
Hydrologic, nutrient and sediment regimes
Organic input and transport
Toxics and other pollutants
Biological communities
Influence of temperature on growth rates
Daily Growth Rate (mg/day)
1.0
0.5
0
0
8
16
24
32
Temperature C
Modified from Benke 1993
Watersheds and Hydrology
1
Where do we find water?
2
What is the hydrologic cycle?
3
How many dimensions does a stream have?
4
How do we characterize stream water?
5
What do we want to know about stream flow?
Question 5
What do we want to know about
stream flow?
•
•
•
•
•
Magnitude - how much?
Frequency - how often?
Timing
- when?
Duration
- how long?
Rate of change – how fast?
Peak Flow (cfs) Mercer Creek
1000
800
USGS estimate of onset
of urbanization effects
1982
600
400
200
0
1956
1966
1976
1986
1996
Mean daily flow (cfs)
Juanita Creek Water Year 2010
100
90
80
70
60
50
40
30
20
10
0
Oct
1
32
May
63
94
125 156 187 218 249 280 311 342
Mean Monthly Flows
Juanita Creek Water Years 2005-2009
50
45
40
35
30
25
20
15
10
5
0
Oct-04
Oct-05
Oct-06
Oct-07
Oct-08
90
Juanita Creek Oct 13- 14, 2014
Hourly data in cubic feet per second (cfs)
80
70
60
50
40
30
20
2:00
7:12
2:24
1:36
6:48
2:00
7:12
2:24
1:36
10
0
Oct 13 midnight
Oct 12 midnight
Mean Daily Flow
Juanita Creek (cfs)
40
35
30
25
20
15
10
5
0
15 minute flows
Juanita Creek May 27-29, 2004
150
May 27
May 29
May 28
125
100
75
50
25
0
1
24
47
70
Daily mean flow as a
fraction of annual mean flow
100
Unregulated
10
1
Regulated
0.1
0.01
0.1
1
10
30 50 70
90
99
Percentage of time flow exceeded
99.9
How much water is enough?
• Depends on who or what is using the
water
• Historically managed for minimum flows
(what is the minimum flow that keeps fish
alive)
• Legal issue of water rights complicates
situation
Examples of where to locate national
data for watersheds and streams
• Watershed data
– EPA Surf your watershed
http://www.epa.gov/surf/
• Climate data (national and international)
http://www.ncdc.noaa.gov/oa/ncdc.html
• Climate data (Washington)
http://www.wrcc.dri.edu/summary/climsmwa.html
Examples of where to locate national
data for watersheds and streams
• Stream data- quantity and quality
– USGS Water Resources Data
http://water.usgs.gov/data.html
• Soils data
– http://soils.usda.gov/
• Aquatic biologic indicators
– http://www.epa.gov/bioindicators/
Take – home messages
• Flow regimes play a major role in habitat
• Land-use alters flow paths and storage
components and hence, flow regimes
• Effects vary with spatial and temporal scales
• Research on which aspects of flow are most
critical to various biotic responses are in
progress
• Don’t forget the basic processes involved