Phosphorus Loading in Tributary Streams of the Red Cedar Watershed
Andi Twiss; Gustavus Adolphus College
Dr. Matt Kuchta, Physics Department,University of Wisconsin-Stout
Introduction:
Phosphorus (P) is a naturally occurring labile element necessary for the health and growth of plants and animals. Due to its
easily transferable nature, phosphorus has a unique and dynamic role in biogeochemical cycles. This is especially true in
agricultural areas where P is introduced through the use of fertilizers. The dynamics of phosphorus play an important role
within the hydrology of the highly agricultural Red Cedar Watershed. The source, pattern, and impact of P was studied
during the summer of 2015 by tracking the rain fall pattern, water and sediment travel pattern response, and the source
rock that the water travels over. Observing these factors helps to answer the questions of where P sources are, how they
differ in various parts of the watershed, and what can be down to mitigate its impacts.
This study focused on 18 Mile Creek on the east side and Tiffany Creek on the west side of the watershed. These two creeks
were targeted as examples of differing average Total and Soluble Reactive Phosphorus. The question of why the P dynamics
differed was answered through a variety of tests. Tests were completed using automated ISCO samples and grab samples
collected throughout the spring and summer seasons. These samples were used in tests to determine conductivity, total
suspended solids, silica, soluble reactive phosphorus, and others which each help measure the impact, source, and pattern
of P within these two tributaries of the Red Cedar Watershed.
Figure 1:This map displays the differences in SRP readings across the
watershed and the different bedrock exposed at the surface
Figure 2: Students preparing to gage 18 Mile Creek
Figure 1:
Figure 2:
Phosphorus Type
Definition
Rock Phosphate
Original source of nearly all P fertilizer, can be mined.
Particulate
P that is bound to eroded sediment or organic matter contained in
runoff. Also called sediment-P. Particulate P is made up of particles that
do not pass through a 0.45 micron filter.
P that is readily available for plant uptake in soil solution. Has immediate
impact on algae and aquatic vegetation growth. SRP (or DP) is any P that
passes through a 0.45 micron filter and any P that is released from solids
by certain chemical extractants.
Both particulate P and dissolved P.
Soluble P
Total Phosphorus
Orthophosphate
Bioavailable P
Form of P assimilated by plants, algae, and bacteria. It is inorganic and
always in the soluble or dissolved form. H2PO4- and/or HPO4=. (Often
used interchangeably with SRP).
All soluble P in run off and estimates toward the portion of particulate P
that can come into solution and be available to aquatic algae and plants.
Organic P
Derived from plant residues and microbes within the soil and stable
compounds that have become part of the soil organic matter.
Inorganic P
Reserves in soil that include soluble fertilizers readily available to plants,
slowly soluble phosphate compounds, and Fe/Al phosphate oxides.
Figure 5:
18MC#Gage#Height,#TSS,#Rainfall#
3.5"
350"
Gage"Depth"(m)"
3"
300"
2.5"
250"
TSS"(mg/L)"
2"
200"
1.5"
150"
1"
100"
0.5"
TSS#(mg/L)#
Gage#Depth#(m)#or#Rainfall#(in/hr)#
Precip"(in/hr)"
P exists in a variety of
forms and frequently
transforms depending
on the setting it is in.
Here is a list of each
form with a brief
description. These
forms are important
when comparing
differences among east
and west watersheds in
determining which site
has more or less of
which kind of
phosphorus. Being able
to pinpoint the kind of
phosphorus works to
help pinpoint the
source and find
applicable solutions.
Figure 5: 18 Mile Creek hydrograph
depicts rain fall and resulting
stream depth and TSS response.
Figure 6: portrays the relationship
between SRP and TP in a direct
comparison between 18 Mile creek
and Tiffany Creek.
Figure 6: TP and SRP of Tiffany Creek and 18 Mile Creek
1.5
50"
1.0
0"
0"
6/17/15"0:00"
7/1/15"0:00"
7/15/15"0:00"
Date/Time#
B.A.Brown, 1988, Mudrie et. All 1987
Figure 4:
Figure 7: Total#Phosphorus#vs.#Total#Suspended#Solids#
0.5
1"
Tiffany"Creek"Samples"
0.9"
y"="0.0017x"+"0.2817"
R²"="0.66145"
Eighteen"Mile"Creek"Samples"
0.8"
0.0
TP#(mg/L)#
0.7"
TP_TICR
0.6"
y"="0.0011x"+"0.0596"
R²"="0.59452"
0.5"
0.4"
0.3"
0.2"
0.1"
0"
0"
Figure 3:
Figure 3: Pie chart predicting the 2013
sources of P in the Red Cedar Watershed
Figure 4: The picture depicts 3 batches of
automated ISCO sample of stream water.
50"
100"
150"
200"
250"
300"
350"
400"
TSS#(mg/L)#
Figure 7: shows the positive relationship between
TSS and TP of each creek.
Resources and Acknowledgements:
Austin Gentel and Jonah Sorell
Brown, B.A., 1988, Bedrock geolgoy of Wisconsin, west-central sheet: Wisconsin Geologigcal and Natural History Survey Mapp 88-7, scale 1:250,000
Mudrie et. all, 1987, Wisconsin Geological and Natural History Survey , Map 87-11a, scale 1:250,000
Sharpley, Andrew, Helen P. Jarvie, Anthony Buda, Linda May, Bryan Spears, and Peter Kleinman. "Phosphorus Legacy: Overcoming the Effects of Past Management Practices to Mitigate
Future Water Quality Impairment." Journal of Environmental Quality 42 (2014): 1308-326. Web. 29 July 2015.
Sturgul, Scott J., and Larry G. Bundy. Understanding Soil Phosphorus: An Overview of Phosphorus, Water Quality, and Agricultural Management Practices. Mar. 2004. Web.
United States of America. Wisconsin Department of Natural Resources. Tainter/Menomin Lakes TMDL. By Paul La Liberte. N.p.: n.p., 2012. Print.
TP_18MC
SRP_TICR
SRP_18MC
Conclusion:
-SRP in both creeks is less variable than TP
-Increase in Rain fall results in an increase in TSS which
results in an increase in TP.
-18 Mile Creek’s P measurements are consistently
double the EPA’s recommended TMDL.
-Rain fall and land use are not the only factor that
result in differing measurements among the east and
west watersheds, bedrock composition is an important
factor. Especially when attempting to reduce P loads.
-The form of P changes as it interacts with other
variables in the water including sediment and organic
material.
This work supported by National Science
Foundation SMA grant #135738