SPARROW
­
Spatially
Referenced
Regressions
on
Watershed
Attributes
February
21,
2002
Purpose:
SPARROW
relates
in­
stream
water­
quality
measurements
to
spatially
referenced
characteristics
of
watersheds,
including
contaminant
sources
and
factors
influencing
terrestrial
and
stream
transport.
The
model
empirically
estimates
the
origin
and
fate
of
contaminants
in
streams,
and
quantifies
uncertainties
in
these
estimates
based
on
model
coefficient
error
and
unexplained
variability
in
the
observed
data.

Sample
Design:
The
SPARROW
method
uses
spatially
referenced
regressions
of
contaminant
transport
on
watershed
attributes
to
support
regional
water­
quality
assessment
goals,
including
descriptions
of
spatial
and
temporal
patterns
in
water
quality
and
identification
of
the
factors
and
processes
that
influence
those
conditions.
The
method
is
designed
to
reduce
the
problems
of
data
interpretation
caused
by
sparse
sampling,
network
bias,
and
basin
heterogeneity.
The
regression
equation
relates
measured
transport
rates
in
streams
to
spatially
referenced
descriptors
of
pollution
sources
and
land­
surface
and
stream­
channel
characteristics.
Spatial
referencing
of
landbased
and
water­
based
variables
is
accomplished
via
superposition
of
a
set
of
contiguous
landsurface
polygons
on
a
digitized
network
of
stream
reaches
that
define
surface­
water
flow
paths
for
the
region
of
interest.

Water­
quality
measurements
are
obtained
from
monitoring
stations
located
in
a
subset
of
the
stream
reaches.
Water­
quality
predictors
in
the
model
are
developed
as
a
function
of
both
reach
and
land­
surface
attributes
and
include
quantities
describing
contaminant
sources
(
point
and
nonpoint)
as
well
as
factors
associated
with
rates
of
material
transport
through
the
watershed
(
such
as
soil
permeability
and
stream
velocity).
Predictor
formulae
describe
the
transport
of
contaminant
mass
from
specific
sources
to
the
downstream
end
of
a
specific
reach.
Loss
of
contaminant
mass
occurs
during
both
overland
and
in­
stream
transport.

In
calibrating
the
model,
measured
rates
of
contaminant
transport
are
regressed
on
predicted
transport
rates
at
the
locations
of
the
monitoring
stations,
giving
rise
to
a
set
of
estimated
linear
and
nonlinear
coefficients
from
the
predictor
formulae.
Once
calibrated,
the
model
can
be
used
to
estimate
contaminant
transport
and
concentration
in
all
stream
reaches.
A
variety
of
regional
characterizations
of
water­
quality
conditions
are
then
possible
based
on
statistical
summarization
of
reach­
level
estimates.
The
application
of
bootstrap
techniques
allows
estimation
of
the
uncertainty
of
model
coefficients
and
predictions.

Watershed
Data
Used
in
Applications:
Hydrologic
cataloguing
unit
watersheds
River
reaches
of
the
conterminous
US
­
USGS
enhanced
river
reach
file
(
version
1.2
ERF1.2,
version
2.0
ERF2.0)
Stream
water
quality
measurements
(
online,
CD­
ROM)
Municipal
and
industrial
point
sources
Fertilizer
use
Livestock
nutrient
wastes
Atmospheric
deposition
Population
­
housing
and
population
census
National
Resources
Inventory
(
NRI)
of
land
use
and
natural
resource
conditions
Soil
Characteristics
­
State
Soil
Geographic
Data
(
STATSGO)
Precipitation
and
air
temperature
Results/
Applications
1.
The
National
Models
Atmospheric
Sources
of
Nitrogen
to
Major
US
Estuaries
Sources
of
Nutrients
in
the
Nations
Watersheds
Delivery
of
Nitrogen
to
the
Gulf
of
Mexico
Sparrow
Methodology
and
Predictions
by
Watershed
2.
Nutrients
in
the
Chesapeake
Bay
Watershed
Application
of
the
National
Models
A
Locally
Calibrated
Nitrogen
Model
3.
Public
Drinking
Water
Supplies
Assessing
the
Susceptibility
of
Public
Drinking
Water
Supplies
to
Contamination
4.
Total
Maximum
Daily
Loads
(
TMDLs)
a
proposed
application
Contacts:
NATIONAL
SPARROW
(
NAWQA
Nutrient
Synthesis,
Reston,
VA)
Alexander,
Richard
703­
648­
6869
(
ralex@
usgs.
gov)
Nolan,
Jacquie
703­
648­
5709
(
jnolan@
usgs.
gov)
Schwarz,
Gregory
703­
648­
5718
(
gschwarz@
usgs.
gov)
Smith,
Richard
703­
648­
6870
(
rsmith1@
usgs.
gov)

REGIONAL
SPARROW
­
Chesapeake
Bay
(
Maryland
District)
Brakebill,
John
410­
238­
4257
(
jwbrakeb@
usgs.
gov)
Preston,
Steve
410­
267­
9875
(
spreston@
usgs.
gov)

Short
Term
Followup:
Contact
appropriate
USGS
staff
to
discuss
potential
uses
of
SPARROW
for
screening
level
review
of
environmental
impacts,
and
for
use
in
thumb­
nail
environmental
assessments
for
industry
categories
where
further
investigation
is
warranted.

Long
Term
Followup:
Whether
or
not
the
model
is
useful
for
the
304(
m)
planning
process
now,
perhaps
applications
can
be
developed
that
are
tailored
to
the
planning
process.
