Incorporating Uncertainty Into the Ranking of SPARROW Model Nutrient Yields From Mississippi/Atchafalaya River Basin Watersheds (original) (raw)
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Environments
To minimize the eutrophication pressure along the Gulf of Mexico or reduce the size of the hypoxic zone in the Gulf of Mexico, it is important to understand the underlying temporal and spatial variations and correlations in excess nutrient loads, which are strongly associated with the formation of hypoxia. This study’s objective was to reveal and visualize structures in high-dimensional datasets of nutrient yield distributions throughout the Mississippi/Atchafalaya River Basin (MARB). For this purpose, the annual mean nutrient concentrations were collected from thirty-three US Geological Survey (USGS) water stations scattered in the upper and lower MARB from 1996 to 2020. Eight surface water quality indicators were selected to make comparisons among water stations along the MARB over the past two decades. Principal component analysis (PCA) was used to comprehensively evaluate the nutrient yields across thirty-three USGS monitoring stations and identify the major contributing nutrien...
JAWRA Journal of the American Water Resources Association, 2011
SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed to estimate nutrient inputs [total nitrogen (TN) and total phosphorus (TP)] to the northwestern part of the Gulf of Mexico from streams in the South-Central United States (U.S.). This area included drainages of the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf hydrologic regions. The models were standardized to reflect nutrient sources and stream conditions during 2002. 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%).
Paper Title: A Water Quality Strategy for the Mississippi River Basin and the Gulf of Mexico
Nutrient pollution, now the leading cause of water quality impairment in the United States, has had significant impact on the nation's waterways. Excessive nutrient pollution has been linked to habitat loss, fish kills, blooms of toxic algae, and hypoxia (oxygen depleted water). The hypoxic 'dead zone' in the Gulf of Mexico is one of the most striking illustrations of what can happen when too many nutrients from inland watersheds reach coastal areas. Despite the efforts of municipal building programs, industrial wastewater requirements and agricultural programs designed to reduce sediment loads in waterways, water quality and nutrient pollution continues to be a problem. We undertook a policy analysis to assess how the agricultural community could better reduce its contribution to the 'dead zone' and also evaluate the synergistic impacts of these policies on other environmental concerns like climate change. Using a sectoral model of U.S. agriculture, we compared policies including untargeted conservation subsidies, nutrient trading, Conservation Reserve Program extension, agricultural sales of carbon and greenhouse gas credits and fertilizer reduction. This economic and environmental analysis is watershed based, primarily focusing on nitrogen in the Mississippi River basin, allowing us to assess the distribution of nitrogen reduction in streams, environmental co-benefits and impact on agricultural cash flows within the Mississippi River basin from various options. The model
A Water Quality Strategy for the Mississippi River Basin and the Gulf of Mexico
2001 Annual meeting, August 5-8, …, 2001
Nutrient pollution, now the leading cause of water quality impairment in the United States, has had significant impact on the nation's waterways. Excessive nutrient pollution has been linked to habitat loss, fish kills, blooms of toxic algae, and hypoxia (oxygen depleted water). The hypoxic 'dead zone' in the Gulf of Mexico is one of the most striking illustrations of what can happen when too many nutrients from inland watersheds reach coastal areas. Despite the efforts of municipal building programs, industrial wastewater requirements and agricultural programs designed to reduce sediment loads in waterways, water quality and nutrient pollution continues to be a problem. We undertook a policy analysis to assess how the agricultural community could better reduce its contribution to the 'dead zone' and also evaluate the synergistic impacts of these policies on other environmental concerns like climate change. Using a sectoral model of U.S. agriculture, we compared policies including untargeted conservation subsidies, nutrient trading, Conservation Reserve Program extension, agricultural sales of carbon and greenhouse gas credits and fertilizer reduction. This economic and environmental analysis is watershed based, primarily focusing on nitrogen in the Mississippi River basin, allowing us to assess the distribution of nitrogen reduction in streams, environmental co-benefits and impact on agricultural cash flows within the Mississippi River basin from various options. The model
2009
Acquisition and compilation of water quality data for a ten year time period (1996-2006) from 589 stream and river stations was conducted to support nutrient criteria development for the multi-state Red River Basin shared by Arkansas, Louisiana, New Mexico, Oklahoma and Texas, USA. Twenty-three water quality parameters were collected from five data sources (USGS, ADEQ, LDEQ, OCC, OWRB, and TCEQ) and an additional 13 parameters were acquired from at least one source. Data for the primary biological parameter of interest, chlorophyll a, was sparse and available from only two sources. Following compilation of data, medians were calculated for the ten year period and median distributions (min, 10 th , 25 th , 50 th , 75 th , 90 th percentiles and max) were presented for several different spatial scales including state specific data, HUC8 designated watersheds, and various ecoregions. Across this basin, median values for total nitrogen (TN), total phosphorus (TP), and sestonic chlorophyll-a (chl-a) ranged from <0.02 to 20.2 mg L-1 , <0.01 to 6.66 mg L-1 , and 0.10 to 26 µg L-1 , respectively. Overall, the 25 th percentiles of median TN data specific to the Red River Basin were generally similar to the USEPA recommended eco-region nutrient criteria. Whereas, median TP and chl-a data specific to the Red River Basin showed 25 th percentiles greater than the USEPA recommended criteria. The unique location of the Red River Basin in the south-central USA places it near the boundaries of several aggregate eco-regions; therefore, the development of eco-region nutrient criteria likely requires using data specific to the Red River Basin, as shown in these analyses. This study provided basin-specific distribution of medians as the first step supporting states in developing nutrient criteria to protect designated uses in the multi-jurisdictional Red River Basin and in potentially reducing nutrient export from the Red River Basin to the Gulf of Mexico.
Environments
This study investigated the annual and seasonal variations in nutrient loads (NO2− + NO3− and orthophosphate) delivered to the Gulf of Mexico from the Mississippi-Atchafalaya River Basin (MARB) and examined the water quality variations. The results indicate that (1) annually, the mean NO2− + NO3− and orthophosphate loads showed a steady increase during 1996–1999, a persistent level during 2000–2007, and a moderate increase during 2008–2016; (2) seasonally, NO2− + NO3− and orthophosphate in MARB in spring and summer were higher than those in autumn and winter. Analysis of variance (ANOVA) identified highly significant differences among seasonal loads; and (3) the median value of NO2− + NO3− in normal weather conditions were higher than that during and right after the hurricanes, while the median value of orthophosphate loads in normal weather conditions was higher than that during the hurricanes, but higher than that right after hurricanes. The two-sample t-test indicates a significa...
Scientific Investigations Report
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JAWRA Journal of the American Water Resources Association, 2014
Nitrogen (N) and phosphorus (P) loading from the Mississippi/Atchafalaya River Basin (MARB) has been linked to hypoxia in the Gulf of Mexico. With geospatial datasets for 2002, including inputs from wastewater treatment plants (WWTPs), and monitored loads throughout the MARB, SPAtially Referenced Regression On Watershed attributes (SPARROW) watershed models were constructed specifically for the MARB, which reduced simulation errors from previous models. Based on these models, N loads/yields were highest from the central part (centered over Iowa and Indiana) of the MARB (Corn Belt), and the highest P yields were scattered throughout the MARB. Spatial differences in yields from previous studies resulted from different descriptions of the dominant sources (N yields are highest with crop-oriented agriculture and P yields are highest with crop and animal agriculture and major WWTPs) and different descriptions of downstream transport. Delivered loads/yields from the MARB SPARROW models are used to rank subbasins, states, and eight-digit Hydrologic Unit Code basins (HUC8s) by N and P contributions and then rankings are compared with those from other studies. Changes in delivered yields result in an average absolute change of 1.3 (N) and 1.9 (P) places in state ranking and 41 (N) and 69 (P) places in HUC8 ranking from those made with previous national-scale SPARROW models. This information may help managers decide where efforts could have the largest effects (highest ranked areas) and thus reduce hypoxia in the Gulf of Mexico.
Scientific Investigations Report, 2013
Relation of Watershed Setting and Stream Nutrient Yields at Sites in Central and Eastern North Carolina, 1997-2008 yields. Additional environmental variables determined to further influence the stream nutrient yields included median annual percentage of point-source flow contributions to the streams, variables of land cover (percentage of forested land, agricultural land, and (or) forested land plus wetlands) in the watershed and (or) in the stream buffer, and drainage area. The regression tree models can serve as a tool for relating differences in select watershed attributes to differences in stream yields of nitrate, total N, and total P, which can provide beneficial information for improving nutrient management in streams throughout North Carolina and for reducing nutrient loads to coastal waters.