ERF1_2 -- Enhanced River Reach File 2.0

Nolan, Jacqueline V.; Brakebill, John W.; Alexander, Richard B.; Schwarz, Gregory E.

doi:10.3133/ofr0240

Cited by 36 publications

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“…Flow paths were defined by streams and reservoirs in the enhanced stream‐reach file 1 (RF1; 1:500,000 scale; Nolan et al, 2002), with incremental reach catchments delineated from 100‐m digital elevation models (Brakebill et al, 2011). Within RF1, MARB has 27,475 reaches (catchment sizes: fifth percentile, 36.5 km 2 ; median, 329 km 2 ; and 95th percentile, 51,200 km 2 ); therefore, the catchments in this model are between USGS hydrologic unit code HUC10 and HUC12 in size.…”

Section: Methodsmentioning

confidence: 99%

SPARROW Models Used to Understand Nutrient Sources in the Mississippi/Atchafalaya River Basin

Robertson

Saad

2013

J. Environ. Qual.

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Nitrogen (N) and phosphorus (P) loading from the Mississippi/ Atchafalaya River Basin (MARB) has been linked to hypoxia in the Gulf of Mexico. To describe where and from what sources those loads originate, SPAtially Referenced Regression On Watershed attributes (SPARROW) models were constructed for the MARB using geospatial datasets for 2002, including inputs from wastewater treatment plants (WWTPs), and calibration sites throughout the MARB. Previous studies found that highest N and P yields were from the north-central part of the MARB (Corn Belt). Based on the MARB SPARROW models, highest N yields were still from the Corn Belt but centered over Iowa and Indiana, and highest P yields were widely distributed throughout the center of the MARB. Similar to that found in other studies, agricultural inputs were found to be the largest N and P sources throughout most of the MARB: farm fertilizers were the largest N source, whereas farm fertilizers, manure, and urban inputs were dominant P sources. The MARB models enable individual N and P sources to be defined at scales ranging from SPARROW catchments (~50 km 2 ) to the entire area of the MARB. Inputs of P from WWTPs and urban areas were more important than found in most other studies. Information from this study will help to reduce nutrient loading from the MARB by providing managers with a description of where each of the sources of N and P are most important, thus providing a basis for prioritizing management actions and ultimately reducing the extent of Gulf hypoxia. SPARROW Models Used to Understand Nutrient Sources in the Mississippi/Atchafalaya River BasinDale M. Robertson* and David A. Saad N utrients (primarily nitrogen, N, and phosphorus, P) directly input into streams or exported from agricultural and urban areas can lead to local problems, such as the overabundance of benthic algae, phytoplankton, and macrophytes, and downstream problems, such as eutrophication of lakes, estuaries, and bays. Excess N and P exported from local drainages located throughout the entire Mississippi/Atchafalaya River Basin (MARB) have been linked to hypoxia in the Gulf of Mexico (USEPA, 2000). The Gulf of Mexico hypoxic zone (the area with bottom water having dissolved oxygen concentrations <2 mg/L) is the second-largest human-caused zone of hypoxia in the world's coastal waters (Scavia and Evans, 2012). Hypoxia in the Gulf was originally thought to be driven by excessive N loading (primarily nitrate); however, recent studies found that P limitation is also occurring in near-shore regions because the excessive N loading has dramatically altered N:P ratios (USEPA, 2007). The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force (2008) established the goal of reducing the 5-yr moving average areal extent of the Gulf of Mexico hypoxic zone to <5000 km 2 . To achieve that goal, the USEPA Science Advisory Board found that a dual strategy is needed that achieves at least a 45% reduction in both N and P loading from the MARB from the average annual 1980-1996 fluxes (USEPA, 20...

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Section: Methodsmentioning

confidence: 99%

SPARROW Models Used to Understand Nutrient Sources in the Mississippi/Atchafalaya River Basin

Robertson

Saad

2013

J. Environ. Qual.

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“…Watershed attributes were calculated using watershed boundaries from the U.S.G.S. enhanced river reach network (RF1)[ Nolan et al , 2002]. This digital stream network was initially derived from the E.P.A.…”

Section: Methodsmentioning

confidence: 99%

Dominance of organic nitrogen from headwater streams to large rivers across the conterminous United States

Scott

Harvey

Alexander

et al. 2007

Global Biogeochemical Cycles

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[1] The frequency and magnitude of hypoxic areas in coastal waterbodies are increasing across the globe, partially in response to the increase in nitrogen delivery from the landscape (Diaz, 2001;Rabalais et al., 2002). Although studies of annual total nitrogen and nitrate yields have greatly improved understanding of the contaminant sources that contribute to riverine nitrogen loads (Alexander et al., 2000;Caraco and Cole, 1999), the emphasis of these studies on annual timescales and selected nitrogen forms is not sufficient to understand the factors that control the cycling, transport, and fate of reactive nitrogen. Here we use data from 850 river stations to calculate long-term mean-annual and interannual loads of organic, ammonia, and nitrate-nitrite nitrogen suitable for spatial analysis. We find that organic nitrogen is the dominant nitrogen pool within rivers across most of the United States and is significant even in basins with high anthropogenic sources of nitrogen. Downstream organic nitrogen patterns illustrate that organic nitrogen is an abundant fraction of the nitrogen loads in all regions. Although the longitudinal patterns are not consistent across regions, these patterns are suggestive of cycling between ON and NO 3 À on seasonal timescales influenced by land use, stream morphology, and riparian connectivity with active floodplains. Future regional studies need to incorporate multinitrogen species at intraannual timescales, as well as stream characteristics beyond channel depth, to elucidate the roles of nitrogen sources and in-stream transformations on the fate and reactivity of riverine nitrogen transported to coastal seas.

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“…Further complicating factors include lag times associated with groundwater discharges (Sanford and Pope, 2013) and the travel time of water through basins (Krichner et al, 2001) and large river networks. For example, at the outflow of the Mississippi River (MISS-OUT), streamwater from different locations in the MRB can take weeks to months to reach MISS-OUT (Nolan et al, 2002), thus the relationships between antecedent flows and nitrate anomalies observed upstream in more homogenous tributaries are likely smeared as water moves downstream and mixes with water from other sources. Also, transport processes in some basins have been found to be more dependent on the permeability and storage capacity of the soil and bedrock as compared to other basins where flow-path lengths and the density of drainage networks are important influences (Hrachowitz et al, 2013).…”

Section: Methodsmentioning

confidence: 99%

Antecedent flow conditions and nitrate concentrations in the Mississippi River basin

Murphy

Hirsch

Sprague

2014

Hydrol. Earth Syst. Sci.

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Abstract.The relationship between antecedent flow conditions and nitrate concentrations was explored at eight sites in the 2.9 million square kilometers (km 2 ) Mississippi River basin, USA. Antecedent flow conditions were quantified as the ratio between the mean daily flow of the previous year and the mean daily flow from the period of record (Qratio), and the Qratio was statistically related to nitrate anomalies (the unexplained variability in nitrate concentration after filtering out season, long-term trend, and contemporaneous flow effects) at each site. Nitrate anomaly and Qratio were negatively related at three of the four major tributary sites and upstream in the Mississippi River, indicating that when mean daily streamflow during the previous year was lower than average, nitrate concentrations were higher than expected. The strength of these relationships increased when data were subdivided by contemporaneous flow conditions. Five of the eight sites had significant negative relationships (p ≤ 0.05) at high or moderately high contemporaneous flows, suggesting nitrate that accumulates in these basins during a drought is flushed during subsequent high flows. At half of the sites, when mean daily flow during the previous year was 50 percent lower than average, nitrate concentration can be from 9 to 27 percent higher than nitrate concentrations that follow a year with average mean daily flow. Conversely, nitrate concentration can be from 8 to 21 percent lower than expected when flow during the previous year was 50 percent higher than average. Previously documented for small, relatively homogenous basins, our results suggest that relationships between antecedent flows and nitrate concentrations are also observable at a regional scale. Relationships were not observed (using all contemporaneous flow data together) for basins larger than 1 million km 2 , suggesting that above this limit the overall size and diversity within these basins may necessitate the use of more complicated statistical approaches or that there may be no discernible basin-wide relationship with antecedent flow. The relationships between nitrate concentration and Qratio identified in this study serve as the basis for future studies that can better define specific hydrologic processes occurring during and after a drought (or high flow period) which influence nitrate concentration, such as the duration or magnitude of low flows, and the timing of low and high flows.

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ERF1_2 -- Enhanced River Reach File 2.0

Cited by 36 publications

References 0 publications

SPARROW Models Used to Understand Nutrient Sources in the Mississippi/Atchafalaya River Basin

SPARROW Models Used to Understand Nutrient Sources in the Mississippi/Atchafalaya River Basin

Dominance of organic nitrogen from headwater streams to large rivers across the conterminous United States

Antecedent flow conditions and nitrate concentrations in the Mississippi River basin

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