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NRS 522 Final Project .pdf


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Joshua Sargent
May 10, 2014
NRS 522 Final Project:
PURPOSE:
The purpose of this project was to assess the features that contribute to the surface water quality of the
water bodies contained in the Pocassett River Watershed Basin. This project specifically investigated
the potential sources of surface water contamination, as well as portraying previously surveyed water
quality assessments. The sources of contamination were primarily associated with surface runoff, or
water flowing over the ground surface after a storm event (for example: from farmland soils or
impervious road cover). Previous water quality assessments provide an essential baseline for what
water conditions may be at current conditions as well as how conditions have changed.
Understanding where these locations of runoff and how water quality conditions are changing are
important for maintaining and preserving the usefulness of the water bodies in a watershed. There are
both legal and local repercussions for decreased water quality. Legally under the Clean Water Act
Section 303d, there are state mandated limitations for pollution control and regulations for water
quality. If the uses of a water body are concluded to be impaired, it may require costly maintenance to
restore. Locally, a decrease in water quality can affect wildlife populations, recreational water use, and
limited potable water. In both cases, preventative measures are preferred to restoration.
DATA and DATA SOURCES:
The data which were acquired for the maps and mapping procedures included:
State Boundary (1989) from RIGIS
Digital Elevation Model imagery (LiDAR, 2011) from RIGIS
Watershed Boundaries (HUC, 2012) from RIGIS
Impervious Surfaces (2011) from RIGIS
Soils (SSURGO, 2014) from RIGIS
Wetlands (1988) from RIGIS
Water Discharge Locations (2014) from EPA
Roads (E911, 2013) from RIGIS
Lakes (1:5000 Lakes and Ponds, 1997) from RIGIS
Streams (1:5000 Streams, 1997) from RIGIS
Water Quality 303d (Rivers and Ponds Identity, 2006) from URI EDC
Geodetic Control Station Benchmarks (2013) from RIGIS
Geographic Names (GNIS, 2011) from RIGIS
Additional data which was collected for analysis:
Blackamore Pond Multi-Year Datasheet (2012) from URI Watershed Watch
Oak Swamp Reservoir Multi-Year Datasheet (2012) from URI Watershed Watch
Randall Pond Multi-Year Datasheet (2012) from URI Watershed Watch

Joshua Sargent
May 10, 2014
METHODS:
Initial analysis procedure included locating, downloading, and organizing the datasets into shapefiles,
rasters, and geodatabases. Once obtained, datasets which were not already in the NAD83 Rhode Island
Stateplane Feet projection were projected into it. Datasets were then clipped to the Pocassett
watershed boundary to limit the information to only those which were spatially pertinent. After the
initial steps, more specific processes were done to modify the data.
The steps for processing the digital elevation model (DEM) for the Pocassett River Watershed Basin
were as followed. First, the model below (Figure 1) was generated in ArcMap to consolidate all of the
DEM files into mosaic dataset, then into a singular raster which was clipped to the watershed boundary
(Figure 2). Finally, the generated raster product was imported into ArcScene with stream and lake data,
modified with a 15 scale elevation factor, turned to show watershed runoff from areas of higher to
lower elevation, and exported as an image (Figure 3). This DEM dataset was also processed into a
hillshade map, contour lines, and an aspect map to further understand the direction of overland water
flow in the case of a runoff event.

Figure 2

Figure 1

The steps for processing the TIN model (Figure 4) for the Pocassett
River Watershed Basin were as followed. The GNIS and geodetic
benchmark datasets were merged and modified to have a uniform
attribute denoting elevation in feet. These points were then used as
the elevations in the TIN model, as well as a hard clip of the
watershed boundary and a hard erase of the lake dataset. The hard
erase was done for the purpose of eliminating geographically
improper interpolating lakes locations in the model because a lake is
generally a flat surface. Finally, the edges were added to show the
triangles in the model and the elevations in the legend were
simplified. This TIN model was generated to provide an additional
and alternative elevation model as compared to the DEM model; the
TIN model does not cover the full extent of the watershed nor is it as
refined as well the DEM model, but they both show similar changes in
elevation in the watershed.

Figure 3

Figure 4

Joshua Sargent
May 10, 2014
The steps for processing the comparison of the impervious surfaces to stream and lake datasets in the
Pocassett River Watershed Basin were as followed. First, the impervious surface dataset was converted
from a raster to vector dataset. The areas of imperviousness were selected by attribute, dissolved into a
single polygon, and the area was calculated. Then, all of the stream lengths and lake areas were each
independently dissolved and their total length and area were calculated, respectively. These total
amounts were entered in callout boxes on the map.

Figure 5

The steps for processing the raster-calculated model (Figure 5) of
potential locations for decreased water quality in the Pocassett
River Watershed Basin were as followed. First, the EPA dataset
was reprojected into the NAD83 Rhode Island Stateplane Feet
projection. Next, a distance buffer was added to each dataset;
most were set at 300 feet, but the one for impervious surfaces
was set at 100 feet instead (due to the complexity of the
polygon); the vector version of the impervious surfaces was
reused from a previous map. Then the buffers were converted
from vector to raster and reclassed. Most of the buffers were
reclassed with the values of 1 for if the feature was present and
0 in the case of NoData. The wetland buffer was given the given
the reclass of -1 for present and 0 still in the case of NoData;
these reclass values took in consideration that the presence of
wetlands would potential improve the water quality through
natural treatment processes. The streams and lakes buffers,
which were dissolved together, were given the reclass of 0 if present and retained the NoData in the
case of NoData; this was used to extract the pertinent information currently displayed in the map.
The steps for processing the water quality assessment map (Figure 6) for the Pocassett River Watershed
Basin were as followed. The Rhode Island Integrated Water Quality Monitoring and Assessment
(IWQMA) Report is associated with categorizing water bodies by the impact pollutants have had on their
uses, where category 1 is considered as “attaining all designated uses” and category 5 is considered as
“impaired or threatened for one or more designated uses”. The RI IWQMA was created to comply with
the Clean Water Act. These categories are attributes in both the stream and lake water quality datasets.
The datasheets from URI Watershed Watch provide a more long term assessment of the water quality at
the indicated lakes and ponds. Although not readable
Figure 6
on the map, they are added as an appendix. A
graduated symbology was added to displaying the
stream order to mimic the stream size increase as the
orders increase. Stream order is a factor which plays
into water quality; larger stream orders have the
potential to have increased pollutants because they
have had more waters enter into them.

Joshua Sargent
May 10, 2014
RESULTS AND CONCLUSIONS:
From this analysis of the watershed, it is evident that there are factors contributing to decreased water
quality in the Pocassett River Watershed Basin. It is uncertain if there is a specific factor which
outweighs the rest, but rather it is the result of a combination of water interactions with impervious
surfaces, farmland soils, water discharge sites, roads, streams and lakes, and in-land wetlands. These
factors have contributed to the models in the project. Other evidence of decreased water quality is in
the multi-year datasheets of three selected bodies of water: Oak Swamp Reservoir, Randall Pond, and
Blackamore Pond.
In these datasheets, URI Watershed Watch has compiled water quality data spanning from seven to
twelve years in length. Included in these sheets are annual averages regarding: Secchi depth (visibility
from water surface downward), chlorophyll/algae levels, total phosphorus levels, and total nitrogen
levels. These elements have also been defined by three hydrological terms to characterize the
associated water body. The term “eurtrophic” refers to low water clarity, elevated nutrient levels, and,
thus, increased algae levels; this is a sign of pollution’s effect on that water body. The term
“mesotrophic” refers to moderate water clarity, nutrient levels, and algae levels; this can be normal or a
sign of shifting towards eurtropic status. The term “oligotrophic” refers to high water clarity, low
nutrient levels, and low algae levels; this is considered the most pristine conditions for a water body.
Oak Swamp Reservoir serves as an upstream, upper-elevational water body and is considered in
generally good condition. Randall Pond, as a mid-watershed water body, seems as though it has some
issues (specifically with water clarity) and is at risk of becoming more impaired. Blackamore Pond, as a
water body near the bottom of the watershed, seems to be struggling in its eurtophic status.
Errors in the data could be due to improper processing techniques. Many processes where done inbetween the starting data and the final maps, so there is the potential for a mistake in processing, but
careful protocol was enforced to prevent them from occurring. Otherwise, the data seems accurate; all
of the data used was from the reputable sources of the U.S. Environmental Protection Agency (EPA),
Rhode Island Geographical Information Systems (RIGIS) website, URI Environmental Data Center (EDC)
database, and URI Watershed Watch.
To extend the use of this information regarding making more water quality assessments of the Pocassett
River Watershed Basin, further specific data would need to be collected to make informed watershed
management decisions. From the data currently available and collected here, this project could be
important if used as baseline data for that investigation.

NRS 522: Background Maps

71°50'0"W

71°30'0"W

71°10'0"W

42°0'0"N

Oak Swamp Reservoir

41°50'0"N

Pocasset Pond

Almy Reservoir

41°40'0"N

Hughesdale Pond
Simmons Upper Reservoir

41°30'0"N

Pocasset River
Print Works Pond
Dyer Pond

Simmons Lower Reservoir

41°10'0"N

Elevation

Blackamore Pond

Value (in feet)

High : 565.201

±

0.75

1.5

3 Miles

Above Left: This map represents the digital
elevation (DEM) data for the Pocassett River
Watershed Basin. This was formed by
the mosaic of several DEM images from
RIGIS. The mosaic and clipping to the
watershed boundary was done by a model.
Lakes and streams were added to show
their relationship to the changes in elevation.

±

Maps by: Joshua Sargent
08 May 2014
Data from RIGIS and Open Street Maps

20 Miles

© OpenStreetMap (and)
contributors, CC-BY-SA

Total Stream Length: 44.92 miles
Total Impervious Surface Area:
5.55 sq miles

Total Lake Area:
0.72 sq miles

Below Right: This map represents the
general spatial relationship between
areas of impervious surface and
locations of lakes and streams. Both
datasets are from RIGIS and the
impervious surface data are from 2011.
The impervious surface raster was converted
into a vector, areas of imperviousness
selected and dissolved, and the area was
calculated. The lake and stream datasets
were also dissolved and the total stream
length and lake area were both calculated.

5 10

Above Right: This map represents the locus
location of the Pocassett River Watershed
Basin in the state of Rhode Island. Around
the map edge is a grid indicating latitude
and longitude. The base map added is a
server backdrop called Open Street Maps.

Low : 10.6197

0

0

41°20'0"N

Stone Pond Randall Pond

±

Streams
Lakes
0

0.75

1.5

Impervious

Absent

Present
3 Miles

Contour (in ft)

µ

Flat (-1)

µ

50

100
150
200
250

North (0-22.5)

Northeast (22.5-67.5)
East (67.5-112.5)

Southeast (112.5-157.5)
South (157.5-202.5)

300
350

Southwest (202.5-247.5)

400

West (247.5-292.5)

450

Northwest (292.5-337.5)

500

North (337.5-360)

550

Hillshade
Value

0 0.5 1

2 Miles

High : 254

0 0.5 1

Low : 0

2 Miles

NRS 522: Background Maps 2

Datasets included into the model:
-Roads with buffer (RIGIS, 2013)
-Impervious surfaces with buffer (RIGIS, 2011)
-Farm soils with buffer (RIGIS, 2014)
-In-land wetlands with buffer (RIGIS, 1988)
-Water discharge sites with buffer (EPA, 2013)
-Streams and Lakes (RIGIS, 1997)

µ

Streams
Lakes

Above Right: This map is a hillshade
representation of the DEM dataset
for the Pocassett River Watershed
Basin. Contour lines at 50 foot
intervals were added to further
depict the changes in elevation.
Above Left: This map represents an
aspect map of the DEM dataset for
the Pocassett River Watershed
Basin. Aspect, in terms of maps,
is the direction the slope faces.
Lakes and streams were added
for their relationship to the slopes.
Below Right: This map represents
a model of raster math to determine
the potential locations of decreased
water quality due to various factors.
The EPA dataset was reprojected
from WGS84 Web Mercator Auxiliary
Sphere to NAD83 RI Stateplane feet.
Every dataset had a 300 foot buffer
applied to it, except the impervious
surfaces which had a 100 foot buffer.

Streams

Value

Lakes
-1
0
1
2
3
4

0

0.5

1

2 Miles

Maps by: Joshua Sargent
08 May 2014
Data from RIGIS and EPA

When converted to raster from
vector, the most of datasets were
reclassed with values of 1 for present
and NoData was classified as 0.
The wetland dataset was given the
value reclass of -1 for present and
NoData was still reclassed as 0.
The streams and lakes dataset was
reclassed as 0 for present and
NoData for NoData, which served
to extract pertinent infomation.

Elevation (in ft)

508 - 571
445 - 507
381 - 444
318 - 380
254 - 317
191 - 253
127 - 190
64 - 126
0 - 63

Above Left: This map represents a TIN elevation model
of GNIS and elevation benchmark points from RIGIS.
The two point datasets were merged and edited for
uniformed attributes. The watershed boundary was
used as a hard clip and the lake dataset was used
as a hard erase. Edges were added to generate the
triangles and the legend breaks were simplified.
Above Right: This map image displays the DEM dataset
in ArcScene as a 3D representation. The orientation
was adjusted to show areas of high to low elevation.

±

0

0.5

1

2 Miles

NRS 522: Background Maps 3

Below: This map represents water quality assessments
done on the streams and lakes of the Pocassett River
Watershed Basin. The RI Intergrated Water Quality
Monitoring and Assessment Report (IWQMA) is a
catergorical methodology for classifying pollution
impact to the uses of waterbodies, where 1 is good
and 5 is considered impaired waters. URI Watershed
Watch does annual assessments of water quality in a
few of these ponds, as shown by the data sheets.
Also, stream order was denoted on the map.

Data sheets displaying water quality measurements over
the course of several years from URI Watershed Watch for:
Oak Swamp Reservoir
Randall Pond
Blackamore Pond

Oak Swamp Reservoir

Stream Order
1
2

Randall Pond

3
4

IWQMA Category
Blackamore Pond

Maps by: Joshua Sargent
09 May 2014
Data from RIGIS, EDC, and URI WW

±

3

4A
5

IWQMA Category
Category 1

0

0.75

1.5

3 Miles

Category 2
Category 3
Category 5

Blackamore Pond Multi-year Summary
2011
2011

2012

2010
2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

Annual Median (Middle) Secchi Depth Transparency

Depth (m)

0

Low water clarity - Eutrophic

1
2

Moderate water clarity - Mesotrophic

3
4

Excellent water clarity - Oligotrophic

Annual Median (Middle) Chlorophyll Level
30

Elevated algae level - Eutrophic
ppb

20

10

Moderate algae level - Mesotrophic
2012

2009

2008

2007

2005

2004

2003

2002

2001

2006

Low algae level - Oligotrophic

0

Annual Mean (Average) Total Phosphorus Level
50

Elevated nutrient level - Eutrophic

ppb

40
30
20

Moderate nutrient level - Mesotrophic

10

Low nutrient level - Oligotrophic
2010

2011

2012

2010

2011

2012

2009

2008

2007

2006

2005

Annual Mean (Average) Total Nitrogen Level

1400
1200

Elevated nutrient level - Eutrophic

1000
800
600

Moderate nutrient level - Mesotrophic

400

Low nutrient level - Oligotrophic

200

2009

2008

2007

2006

2005

2004

2003

2002

0

2001

ppb

2004

2003

2002

2001

0

Oak Swamp Reservoir Multi-year Summary
2006

2005

2004

2003

2002

2001

2000

Annual Median (Middle) Secchi Depth Transparency

Depth (m)

0

Low water clarity - Eutrophic
2

Moderate water clarity - Mesotrophic
4

Moderate algae level - Mesotrophic

2006

2005

2004

2003

2002

2001

Low algae level - Oligotrophic

2000

ppb

Annual Median (Middle) Chlorophyll Level
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0

Annual Mean (Average) Total Phosphorus Level
30

Elevated nutrient level - Eutrophic

25

ppb

20

Moderate nutrient level - Mesotrophic

15
10
5

Low nutrient level - Oligotrophic
2005

2006

2005

2006

2004

2003

2002

2001

Annual Mean (Average) Total Nitrogen Level

1400
1200
1000
800
600
400
200
0

Elevated nutrient level - Eutrophic
Moderate nutrient level - Mesotrophic

2004

2003

2002

2001

Low nutrient level - Oligotrophic
2000

ppb

2000

0


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