Posts Tagged ‘phosphorus’

Seasonal phosphorus losses

Wednesday, May 1st, 2013

Early View Article:Spatial Considerations in Wet and Dry Periods for Phosphorus in Streams of the Fort Cobb Watershed, United States,” by Dorcas H. Franklin, Jean L. Steiner, Sara E. Duke, Daniel N. Moriasi, and Patrick J. Starks

(Abstract:) The Fort Cobb Watershed in Oklahoma has diverse biogeophysical settings and provides an opportunity to explore the association of water quality with a diverse set of landscapes during both wet (April 2007-December 2009) and dry (January 2005-March 2007) periods. The objective of this work was to identify spatial patterns in phosphorus (P) (soluble reactive P [SRP] and bioavailable P [BAP]) associated with landscape metrics for two distinct streamflow regimes. Spatial autocorrelation of P was evaluated using contiguous (side-by-side) and upstream (upstream:downstream) connectivity matrices. Biogeophysical metrics were compiled for each contributing area, and were partitioned based on association to P concentrations. Results for both SRP and BAP indicated that spatial autocorrelation was present (p < 0.05). There was more spatial autocorrelation and stream P concentrations were three to five times higher in the Wet phase than in the Dry phase (p < 0.05). Analysis with recursive partitioning resulted in higher R2 with spatial autocorrelation than without spatial autocorrelation and indicated that lateral metrics (topography, soil, geology, management) were better predictors for SRP than instream metrics. During Wet phase, lateral metrics indicative of rapid surface and subsurface water movement were associated with higher P stream concentrations. This research demonstrated that we can detect landscapes more vulnerable to P losses and/or contaminations in either drought or very wet periods.

Nutrient export

Monday, April 15th, 2013

Early View article:Modeling Nutrient Export from Coastal California Watersheds,” by Timothy H. Robinson and John M. Melack.

Nitrate and phosphate export coefficient models were developed for coastal watersheds along the Santa Barbara Channel in central California. One approach was based on measurements of nutrient fluxes in streams from specific land use classes and included a watershed response function that scaled export up or down depending on antecedent moisture conditions. The second approach for nutrient export coefficient modeling used anthropogenic nutrient loading for land use classes and atmospheric nutrient deposition to model export. In an application of the first approach to one watershed, the nitrate and phosphate models were within 20% of measured values for most storms. When applied to another year, both nitrate and phosphate models generally performed adequately with annual, storm-flow, and base-flow values within 20% of measured nutrient loadings. Less satisfactory results were found when applied to neighboring watersheds with difference percentages of land use and hydrologic conditions. Application of the second approach was less successful than the first approach.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

Background concentrations

Wednesday, August 22nd, 2012

EarlyView Article:Modeled Summer Background Concentration of Nutrients and Suspended Sediment in the Mid-Continent (USA) Great Rivers,” by Ted R. Angradi, David W. Bolgrien, Matt A. Starry, and Brian H. Hill.

The authors used regression models to predict summer background concentration of total nitrogen (N), total phosphorus (P), and total suspended solids (TSS), in the mid-continent great rivers: the Upper Mississippi, the Lower Missouri, and the Ohio. From multiple linear regressions of water quality indicators with land use and other stressor variables, they determined the concentration of the indicators when the predictor variables were all set to zero — the y-intercept. Except for total P on the Upper Mississippi River, they could predict background concentration using regression models. Their findings suggest that a total N concentration ?430 ?g l?1 for the Upper Mississippi and Lower Missouri Rivers and a total P concentration of ?65 ?g l?1 for the Lower Missouri River are worth consideration as lower bounds for nutrient criteria for these rivers.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

Uncertainty analysis of trading

Friday, December 2nd, 2011

December 2011 article (early view):Water Quality Model Uncertainty Analysis of a Point-Point Source Phosphorus Trading Program,” by Josef S. Kardos and Christopher C. Obropta.

The study identified how water quality model uncertainty affects outcomes of potential trades of total phosphorus (TP) between wastewater treatment plants. The uncertainty analysis found no evidence to suggest that the outcome of trades between wastewater treatment plants, as compared with command and control regulation, will significantly increase uncertainty in the attainment of dissolved oxygen surface water quality standards, site-specific chlorophyll a criteria, and reduction targets for diverted TP load at potential hot spots in the watershed. Each simulated trading scenario demonstrated parity with or improvement from the command and control approach at the TMDL critical locations, and low risk of hot spots elsewhere.

In addition, the study produced an efficient uncer- tainty analysis whose LHS based method could be replicated by regulators charged with administer- ing a WQT program and assessing its various risks. The method’s efficiency and practicality directly address a main obstacle that has hindered a wider practice of uncertainty analyses of water quality models.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: National Nutrient Synthesis

Tuesday, September 13th, 2011

October 2011 article (early view): “Factors Affecting Stream Nutrient Loads: A Synthesis of Regional SPARROW Model Results for the Continental United States,” by Stephen D. Preston, Richard B. Alexander, Gregory E. Schwarz, and Charles G. Crawford

Spatial Distribution of Incremental Yields of (A) Total Nitrogen and (B) Total Phosphorus Simulated by SPARROW Models of Six Major River Basins.

This overview article puts together the knowledge of the regional nutrient models. A key question in developing a SPARROW model or any other water-quality model over large watershed scales is whether the governing material transport equations should differ spatially in their functional forms and/or coefficient values to account for the effects of heterogeneity and scale.

The results confirm the dominant effects of urban and agricultural sources on stream nutrient loads nationally and regionally, but reveal considerable spatial variability in the specific types of sources that control water quality. These include regional differences in the relative importance of different types of urban (municipal and industrial point vs. diffuse urban runoff) and agriculture (crop cultivation vs. animal waste) sources, as well as the effects of atmospheric deposition, mining, and background (e.g., soil phosphorus) sources on stream nutrients. Overall, the authors found that the SPARROW model results provide a consistent set of information for identifying the major sources and environmental factors affecting nutrient fate and transport in United States watersheds at regional and subregional scales.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: Pacific Northwest

Friday, September 9th, 2011

October 2011 article (early view): “Surface-Water Nutrient Conditions and Sources in the United States Pacific Northwest,” by Daniel R. Wise and Henry M. Johnson. Part of Featured Collection on SPARROW.

Incremental phosphorus

Annual nutrient yields were higher in watersheds on the wetter, west side of the Cascade Range compared to watersheds on the drier, east side. High nutrient enrichment (relative to the U.S. Environmental Protection Agency’s recommended nutrient criteria) was estimated in watersheds throughout the region. Forest land was generally the largest source of total nitrogen stream load and geologic material was generally the largest source of total phosphorus stream load generated within the 12,039 modeled watersheds. These results reflected the prevalence of these two natural sources and the low input from other nutrient sources across the region. However, the combined input from agriculture, point sources, and developed land, rather than natural nutrient sources, was responsible for most of the nutrient load discharged from many of the largest watersheds.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: Missouri River Basin

Thursday, September 8th, 2011

October 2011 article (early view): “Nutrient Sources and Transport in the Missouri River Basin, With Emphasis on the Effects of Irrigation and Reservoirs,” by Juliane B. Brown Lori A. Sprague, and Jean A. Dupree. Part of Featured Collection on SPARROW.

Primary sources of nitrogen and phosphorus.

Agricultural inputs from fertilizer and manure were the largest nutrient sources throughout a large part of the basin, although atmospheric and urban inputs were important sources in some areas. Sediment mobilized from stream channels was a source of phosphorus in medium and larger streams. Irrigation on agricultural land was estimated to decrease the nitrogen load reaching the Mississippi River by as much as 17%, likely as a result of increased anoxia and denitrification in the soil zone. Approximately 16% of the nitrogen load and 33% of the phosphorus load that would have otherwise reached the Mississippi River was retained in reservoirs and lakes throughout the basin. Nearly half of the total attenuation occurred in the eight largest water bodies. Unlike the other major tributary basins, nearly the entire instream nutrient load leaving the outlet of the Platte and Kansas River subbasins reached the Mississippi River.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: South-Central U.S.

Wednesday, September 7th, 2011

October 2011 article (early view): “Sources and Delivery of Nutrients to the Northwestern Gulf of Mexico From Streams in the South-Central United States,” by Richard A. Rebich, Natalie A. Houston, Scott V. Mize, Daniel K. Pearson, Patricia B. Ging, and C. Evan Hornig. Part of Featured Collection on SPARROW.

Delivered total N yields

Model predictions of nutrient loads (mass per time) and yields (mass per area per time) generally were greatest in streams in the eastern part of the region and along reaches near the Texas and Louisiana shoreline. The Mississippi River and Atchafalaya River watersheds, which drain nearly two-thirds of the conterminous U.S., delivered the largest nutrient loads to the Gulf of Mexico, as expected. However, the three largest delivered TN yields were from the Trinity River/Galveston Bay, Calcasieu River, and Aransas River watersheds, while the three largest delivered TP yields were from the Calcasieu River, Mermentau River, and Trinity River/Galveston Bay watersheds. Model output indicated that the three largest sources of nitrogen from the region were atmospheric deposition (42%), commercial fertilizer (20%), and livestock manure (unconfined, 17%). The three largest sources of phosphorus were commercial fertilizer (28%), urban runoff (23%), and livestock manure (confined and unconfined, 23%).

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: Great Lakes

Tuesday, September 6th, 2011

October 2011 article (early view): “Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models,” by Dale M. Robertson and David A. Saad. Part of Featured Collection on SPARROW.

Results indicated that recent U.S. loadings to Lakes Michigan and Ontario are similar to those in the 1980s, whereas loadings to Lakes Superior, Huron, and Erie decreased. Highest loads were from tributaries with the largest watersheds, whereas highest yields were from areas with intense agriculture and large point sources of nutrients. Tributaries were ranked based on their relative loads and yields to each lake. Input from agricultural areas was a significant source of nutrients, contributing ~33-44% of the P and ~33-58% of the N, except for areas around Superior with little agriculture. Point sources were also significant, contributing ~14-44% of the P and 13-34% of the N. Watersheds around Lake Erie contributed nutrients at the highest rate (similar to intensively farmed areas in the Midwest) because they have the largest nutrient inputs and highest delivery ratio.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

SPARROW: Northeast and Mid-Atlantic

Monday, September 5th, 2011

October 2011 article (early view): “Source and Delivery of Nutrients to Receiving Waters in the Northeastern and Mid-Atlantic Regions of the United States,” by Richard B. Moore, Craig M. Johnston, Richard A. Smith, and Bryan Milstead. Part of Featured Collection on SPARROW.

The model developed to examine the source and delivery of nitrogen to the estuaries of nine large rivers along the NE US Seaboard indicated that agricultural sources contribute the largest percentage (37%) of the total nitrogen load delivered to the estuaries. Point sources account for 28% while atmospheric deposition accounts for 20%. A second SPARROW model was used to examine the sources and delivery of phosphorus to lakes and reservoirs throughout the NE US. The greatest attenuation of phosphorus occurred in lakes that were large relative to the size of their watershed.

Model results show that, within the NE US, aquatic decay of nutrients is quite limited on an annual basis and that we especially cannot rely on natural attenuation to remove nutrients within the larger rivers nor within lakes with large watersheds relative to the size of the lake.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]