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.
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 freshwater –
Water storage bins
•
•
•
•
Atmosphere ~ 25 mm (4000 elephants)
Lithosphere ~ 12 mm
Biosphere ~ 0.1 mm
Hydrosphere
– Ice
– Lakes
– Rivers
~ 5100 mm
~ 25 mm
~
0.25 mm
Global distribution of freshwater
Water Storage
Reservoir
Oceans
Ice
Groundwater
Lakes
Soil Moisture
Atmosphere
Streams and Rivers
Biosphere
Percent
of total
97.25
2.05
0.68
0.01
0.005
0.001
0.0001
0.00004
Global distribution of freshwater –
Another way to think about global water
distribution
1 gallon
All water
3/8 cup
freshwater
2 tablespoons
surface 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 2
What is the hydrologic cycle?
What is the hydrologic cycle?
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.
4.
Longitudinal
Lateral
Vertical
Temporal
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
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
gradient like our area
Riffle is an area of rapid
flow over coarse substrate
(rocks) 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
Lateral Patterns
• Some streams
and rivers will
have a single
dominant
channel while
others will
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
channel.
How species are distributed in space and
time? -- Environments contributing to
riverine biodiversity
Surface water
Subsurface water
Riparian system
Springs
Streams
Confined
Reaches
Lakes
Hyporheic
Zone
Ground
Water
Unconfined
Reaches
Spatial distribution of species across a
floodplain (lateral dimension)
Species Richness
Species
Richness
100
Percent of maximum richness
100
50
0
0
fish
Mollusca
Odonata
Amphibia
Macrophytes
River ----------------------- Floodplain Edge
9.9 (Ward and Tockner 2001 fig. 9.3)
Temporal dimension
• Stream flow changes
Second by second
Hourly
Daily
Monthly
Seasonally
Annually
Milleniumly
Selected Important Habitat Factors
•
•
•
•
•
•
•
•
Substrate
Temperature
Oxygen levels
Flow velocity
Food availability
pH
Nutrient and sediment regimes
Organic input and transport
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 4
What are the major physical, chemical,
and biological components used to
characterize water quality?
Commonly measured substances
related to water quality
•
•
•
•
•
•
•
•
Light
Temperature
Dissolved ions
Suspended solids
Nutrients and gases
Toxics such as metals and pesticides/herbicides
Biological features
PPCPs
10.3 Effect of latitude on stream degree days
6000
4000
2000
30
40
46
Latitude in degrees N
(Modified from Vannote and Sweeney 1980)
Daily Growth Rate (mg/mg/day)
Influence of temperature on growth rates
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
600
400
200
0
1956
1966
1976
1986
1996
Annual flows (cfs) at Mercer Creek
33
31
29
27
25
23
21
19
17
15
1955
1965
1975
1985
1995
Average Monthly CFS Mercer Creek
25
20
15
10
5
0
Jan
Feb Mar Apr May Jun
Jul
Aug Sep Oct
Nov Dec
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
Mean daily flow (cfs)
Juanita Creek Water Year 2010
100
90
80
70
60
50
40
30
20
10
0
May
1
32
63
94
125 156 187 218 249 280 311 342
Mean May Discharge
Juanita Creek
12
10
8
6
4
2
0
May 04
May 05
May 06
May 07
May 08
May 09
May 10
Hourly vs 15 Minute Measurements
70
60
50
40
30
20
10
0
Juanita Creek Hourly Discharge (cfs)
70
60
50
40
30
20
10
0
Juanita Creek 15-minute Q (cfs)
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
Stream flow functions
1. Medium where aquatic organisms live
and propagate
2. Provide the forces that create and
maintain in-channel and off-channel
habitat, riparian patch communities, etc.
3. Rejuvenate floodplain soils and
vegetation and recharge groundwater
Stream flow functions
1. Medium where aquatic organisms live
and propagate
– Needs vary by species and life stage
– Focusing flow requirements on single
species can result in unintended harm to
other species
– Plays a role in stream temperature and
oxygen levels
Stream flow functions
2. Provides the forces that create and
maintain in-channel and off-channel
habitat, riparian patch communities,
etc.
– New channel formation
– Wood recruitment and distribution
– Sediment recruitment and transport
– Removal of fines
Stream flow functions
3. Rejuvenates floodplain soils and
vegetation and recharge groundwater
– Maintain connectivity with hyporheic zones
– Redistribute soil and nutrients to floodplain
forest
– Distribute seeds and prepare seed beds
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