Danielle Braund1, Greg Phillips2, Randy Easley3, Sally Entrekin1,4 University of Central Arkansas1, GBMc & Associates2, Central Arkansas Water3, Virginia Tech4 Background Methods Results
Trang 10.01 0.1 1 10
SD-1 LC-1 WC-1 WPR-1 CC-1 TB-1 EPR-1 GC-1 EPR-2 WPR-2
Less % agriculture > More % agriculture
Total Nitrogen Annual Loads
0.01 0.1 1 10
SD-1 LC-1 WC-1 WPR-1 CC-1 TB-1 EPR-1 GC-1 EPR-2 WPR-2
Less % Agriculture > More % agriculture Total Phosphorus Annual Loads
The relationship between land use and nutrient concentrations in central Arkansas:
identifying potential nonpoint-sources of pollution in the Lake Conway – Point remove watershed.
Danielle Braund1, Greg Phillips2, Randy Easley3, Sally Entrekin1,4 University of Central Arkansas1, GBMc & Associates2, Central Arkansas Water3, Virginia Tech4
Background
Methods
Results
ACKNOWLEDGEMENTS
References
• Study Sites- Ten streams were selected in major sub-basins
in the LCPR watershed The watersheds ranged in area size
and land use composition
• Land use- National Land Cover Dataset 2011 was used to:
• area of landcover (km²)
• Nutrients- Grab samples taken at baseflow were filtered in
field and processed in at the AWRC lab for:
• Total nitrogen (TN), ammonium, nitrate-nitrite
• Total phosphorus (TP), soluble reactive phosphorus (SRP)
• Data Analysis- Nutrient concentrations and land use
composition were analyzed using multiple linear regression
models in R
USGS 104B grant #2016AR387B
University of Central Arkansas, GBMc & Associates, Arkansas Water Resource Center, Lake Conway – Point Remove Watershed Alliance
Lab and field assistance: Anastasia Mogilevski, Brian Staley, Jennifer Main, Mason Rostollan, and Rebecca Relic
• Agricultural practices and urbanization cause runoff and
subsequent nonpoint-source pollution in aquatic systems.¹
characteristics that can impact biotic communities ²
• The Lake Conway – Point Remove (LCPR) watershed in
central Arkansas has been identified as a top contributor of
nitrogen and phosphorus to the Gulf of Mexico, ranking in the
top 150 watersheds in the Mississippi River Basin (Figure 1) ³
• The sources of nonpoint-source pollution within the watershed
are currently unknown
• The LCPR watershed land use contains a mix of forested,
agricultural, and developed areas (Figure 1)
• Our objective is to identify sub-watersheds contributing
nonpoint-source pollution to the Arkansas River and to pinpoint
what anthropogenic practices are causing nutrient inputs
• Subwatersheds accumulate drainage from headwater streams,
which can account for 80% of total stream length and,
subsequently, nutrient runoff
Figure 2 Baseflow nutrient concentrations in the LCPR watershed related to percent land cover using NLCD 2011 2a Nutrients containing nitrogen (ammonium, nitrate-nitrate, and TN) increased in concentration with increases in developed land cover (R²=0.84, F 5,39 =43.99, p<0.0001) 2b Nutrients containing phosphorus (SRP and TP) tended to increase in concentrations with increases in agriculture and TN concentrations also increased with increases in agricultural land cover (R²=0.85, F 5,39 =44.12, p<0.0001)
Conclusion / Future Directions
Table 1 Land use compositions of the ten study streams in the LCPR watershed were calculated using data from the National Land Cover Dataset from 2011.
Figure 3 Annual baseflow nutrient loads for TN (a) and TP (b) per square mile of catchment within the LCPR watershed study steams 3a Total nitrogen loads were greater in Whig Creek (WC-1), Cypress Creek (CC-1), lower reach of the east fork of Point Remove Creek (EPR-2), and Galla Creek (GC-1) 3b Total phosphorus loads were greater in Whig Creek (WC-1), Cypress Creek (CC-1), Galla Creek (GC-1), and Tupelo Bayou (TB-1)
Figure 1 The LCPR watershed in central Arkansas contains a mix of forested,
agricultural, and developed areas The cities of Conway, Morrilton, and
Russellville are located within the LCPR watershed.
• Baseflow TN and TP concentrations increased with
increases in both percent development (Figure 2a) and agriculture (Figure 2b)
• Baseflow nutrient loads (TN and TP) were greater in
streams WC-1, CC-1, TB-1, and GC-1
• Urban development increases aqueous nutrients from
stormwater discharge and agriculture increases nutrients form fertilizer runoff in both row crop and pasture
• We plan to compile contemporary data collected on this
project with historic watershed data to create a watershed management plan (WMP) We also plan to included:
• Alkaline phosphatase activity which describes nutrient limitation
• Equilibrium phosphorus concentrations (EPC) which describe sorption patterns of excess phosphorus and predicts theoretical sources or sinks for phosphorus
• Storm sampling data to further expand our model compare nutrient loads with other studies to determine
if loads are elevated
• Headwater streams provide a unique opportunity to pinpoint
sources of nutrient pollution due to the smaller catchment size
• By identifying anthropogenic practices that are increasing
nonpoint-source pollution in small sub-watersheds, nutrient concentrations and the consequent accumulated annual loads from headwater streams can be reduced
1 Quantify nutrient concentrations across a one-year period
2 Calculate baseflow annual nutrient loads for the LCPR study
streams
3 Identify streams exporting greater amounts of nutrients to the
Arkansas River
4 Identify potential sources for pollution
5 Final goal to create a watershed management plan for the
LCPR watershed
Objectives
¹ Richards, C., Johnson, L B., & Host, G E (1996) Landscape-scale
influences on stream habitats and biota Canadian Journal of Fisheries and Aquatic Sciences, 53(S1), 295–311
² Vitousek, P M (1994) Beyond global warming: ecology and global change
Ecology, 75(7), 1861-1876.
³ Boesch, D F., Boynton, W R., Crowder, L B., Diaz, R J., Howarth, R W., Mee,
L D., & Scavia, D (2009) Nutrient enrichment drives Gulf of Mexico hypoxia Eos, Transactions American Geophysical Union, 90(14), 117-118.
Land use category
LCPR study streams
Figure 4 LC-1 during a storm sampling event Incorporating stormflow data will provide a more complete analysis of nutrient loads in the LCPR watershed.