A. Coastal subnetwork

B. Mississippi–Atchafalaya 

 subnetwork

C. National Monitoring Network 

15565447 #

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322023090544500

08116650 02359170

01463500

01372058

07381600

07381590 07374000

07288955

07263620

07022000

06934500

06805500

06610000

05587455

05586100

03612500

03609750

14246900

11447650

11303500

09522000

08475000

07381495

07374525

04264331

02226160

01646580

01578310

02470500

07373420

05420500

05465500 05490500

03303280

03374100

03378500

National Stream Quality Accounting Network

National Stream Quality Accounting Network and 

National Monitoring Network Basin Boundary 

Geospatial Dataset, 2008–13

Data Series 641

U.S. Department of the Interior

U.S. Geological Survey

National Stream Quality Accounting Network 

and National Monitoring Network Basin 

Boundary Geospatial Dataset, 2008–13

By Nancy T. Baker

National Stream Quality Accounting Network

Data Series 641

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Baker, N.T., 2011, National Stream Quality Accounting Network and National Monitoring Network Basin Boundary 

Geospatial Dataset, 2008–13: U.S. Geological Survey Data Series 641, 16 p. 
iii

Contents

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Data Sources for Delineation of NASQAN and NMN Boundaries...............................................3

Delineation of the NASQAN and NMN Basin Boundary Dataset .........................................................5

Consideration of Flow Routing for Selected Basins in the Dataset ....................................................12

Summary........................................................................................................................................................16

References Cited..........................................................................................................................................16

Figures

1. Maps showing the location of A, basins included in the National Stream Quality 

Accounting Network Coastal subnetwork, B, the Mississippi-Atchafalaya 

River Basin subnetwork, and the C, the National Monitoring Network ..............................2

2. Schematic diagram showing Mississippi-Atchafalaya River Basin 

flow routing and U.S. Geological Survey stations.................................................................13

3. Maps showing the location of A, the Rio Grande Basin in the United States 

and Mexico, B, the Rio Grande Basin and subbasin boundaries, and 

C, multiple diversions from the Rio Grande into the Laguna Madre Basin 

through Arroyo Colorado...........................................................................................................14

4. Maps showing the location of A, the Colorado River in the United States, 

and B, the diversion into the All-American Canal relative to U.S. Geological 

Survey monitoring stations .......................................................................................................15

Tables

1. Numerical hydrologic unit names, number of digits in code, common names, 

hydrologic unit levels, average sizes, and approximate number of hydrologic 

units, by type, in the United States ............................................................................................3

2. Attribute item table definitions for basin boundary polygons, closed/

noncontributing polygons, and National Stream Quality Accounting Network 

and National Monitoring Network monitoring stations..........................................................6

3. National Stream Quality Accounting Network and National Monitoring Network 

monitoring stations, National Water Information System drainage areas of stations, 

calculated basin areas, and differences between National Water Information System 

drainage areas and calculated basin areas ................................................................................8
iv

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

square mile (mi2) 2.590 square kilometer (km2) 
National Stream Quality Accounting Network and 

National Monitoring Network Basin Boundary 

Geospatial Dataset, 2008–13

By Nancy T. Baker

Abstract

This report and the accompanying geospatial data were 

created to assist in analysis and interpretation of water-quality 

data provided by the U.S. Geological Survey’s National 

Stream Quality Accounting Network (NASQAN) and by 

the U.S. Coastal Waters and Tributaries National Monitoring Network (NMN), which is a cooperative monitoring 

program of Federal, regional, and State agencies. The report 

describes the methods used to develop the geospatial data, 

which was primarily derived from the National Watershed 

Boundary Dataset. The geospatial data contains polygon 

shapefiles of basin boundaries for 33 NASQAN and 5 NMN 

streamflow and water-quality monitoring stations. In addition, 30 polygon shapefiles of the closed and noncontributing 

basins contained within the NASQAN or NMN boundaries are included. Also included is a point shapefile of the 

NASQAN and NMN monitoring stations and associated basin 

and station attributes. Geospatial data for basin delineations, 

associated closed and noncontributing basins, and monitoring 

station locations are available at http://water.usgs.gov/lookup/

getspatial?ds641_nasqan_wbd12.

Introduction 

This report and the accompanying geospatial data were 

created to assist in analysis and interpretation of water-quality 

data provided by the U.S. Geological Survey’s National 

Stream Quality Accounting Network (NASQAN) and by the 

U.S. Coastal Waters and Tributaries National Monitoring 

Network (NMN), which is a cooperative monitoring program 

of Federal, regional, and State agencies. The Office of Water 

Quality of the USGS maintains three surface-water networks 

that provide stakeholders with reliable information over time 

for a fixed set of stations. Large rivers and the quality of water 

at the terminus of large watersheds entering receiving waters 

are monitored routinely at 33 stations through the NASQAN 

and at 5 stations through the NMN. Smaller rivers and streams 

are monitored at 114 stations through the National WaterQuality Assessment (NAWQA) Program “Status and Trends” 

network, and those basin boundaries will be published as part 

of a separate report (Naomi Nakagaki, U.S. Geological Survey, written commun., 2011). 

To help meet the goals of both NASQAN and NMN, 

accurate basin boundary delineations are needed for each basin 

in the network. Geospatial basin boundary data are often used 

with water-quality data for modeling, calculating loads, and 

calculating selected basin characteristics. The major objective of the NASQAN program is to report on the concentrations and loads of selected constituents delivered by major 

rivers to the coastal waters of the United States (fig. 1A) and 

selected inland subbasins in priority river basins, such as the 

Mississippi-Atchafalaya River Basin subnetwork (fig. 1B), to 

determine the sources and relative yields of constituents within 

these basins. Additional information about the NASQAN program is available at http://water.usgs.gov/nasqan/.

The goal of the NMN is to provide information about 

the health of the Nation’s oceans and coastal ecosystems and 

inland influences on coastal waters for improved resource 

management (fig. 1C). Additional information about the NMN 

program is available at http://acwi.gov/monitoring/network/. 

Purpose and Scope

Methods for delineating NASQAN and NMN basin 

boundaries and the associated geospatial data files of the 

boundaries are provided in this report. The geospatial data files 

contain 38 separate ArcGIS (Environmental Systems Resource 

Institute, 2009) polygon shapefiles of basin boundaries for 

NASQAN and NMN stations. For the 30 basins that contained 

closed and noncontributing areas (the remaining 8 basins did 

not contain these areas), an associated polygon shapefile was 

generated and is included with this data. Also included is a 

point shapefile of the NASQAN and NMN monitoring stations 

and associated basin and station attributes. Geospatial data 

for basin delineations, associated closed and noncontributing 

basins, and monitoring station locations are available at http://

water.usgs.gov/lookup/getspatial?ds641_nasqan_wbd12. This 

dataset is intended to be used with water-quality data collected 

for the 2008–13 (5-year) design component of NASQAN. 
2 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13

A. Coastal subnetwork

B, Mississippi–Atchafalaya 

 subnetwork

C. National Monitoring Network

15565447 #

Figure 1. 

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322023090544500

08116650 02359170

01463500

01372058

07381600

07381590 07374000

07288955

07263620

07022000

06934500

06805500

06610000

05587455

05586100

03612500

03609750

14246900

11447650

11303500

09522000

08475000

07381495

07374525

04264331

02226160

01646580

01578310

02470500

07373420

05420500

05465500

05490500

03303280

03374100

03378500

EXPLANATION

U.S. Geological Survey

monitoring station and 

number

#

08116650

Figure 1. Location of A, basins included in the National Stream Quality Accounting Network Coastal subnetwork, 

B, the Mississippi-Atchafalaya River Basin subnetwork, and the C, the National Monitoring Network.
Introduction 3

Data Sources for Delineation of NASQAN and 

NMN Boundaries

The primary data source for developing the NASQAN 

and NMN basin boundary delineations is the 12-digit National 

Watershed Boundary Dataset (WBD12), developed jointly by 

the USGS and the U.S. Department of Agriculture, Natural 

Resources Conservation Service (NRCS) (U.S. Department of 

Agriculture, 2009). Digital topographic maps (1:24,000 scale) 

were used to delineate boundaries near the outlet (monitoring station location) of those basins where the outlet of the 

stream did not fall directly on a WBD12 boundary line. The 

portions of basins that extended into Canada beyond WBD12 

boundaries were delineated from 1:100,000-scale Canadian 

Watershed Boundaries (Canadian Geospatial Data Infrastructure, 2009). The portion of the Rio Grande Basin that extends 

into Mexico was obtained from a Hydrologic Geodatabase for 

the Rio Grande developed by Patino and others (2004). The 

geospatial data are available online at http://www.crwr.utexas.

edu/riogrande.shtml (Patino, 2004). Information about closed 

and noncontributing subbasins was obtained from WBD12 

attribute information and Hydrologic Unit Maps (Seaber and 

others, 1987). 

The WBD12 is a geospatial dataset that defines the aerial 

extent of individual watersheds for all surface drainages at 

the Subwatershed level, at 1:24,000 scale, for the United 

States. Subwatersheds are assigned a 12-digit Hydrologic Unit 

Code (HUC) based on its location within its larger watershed 

(table 1). An explanation of HUC hierarchy is given in Federal 

Standards and Procedures for the National Watershed Boundary Dataset (U.S. Geological Survey and U.S. Department of 

Agriculture, Natural Resources Conservation Service, 2011). 

Table 1. Numerical hydrologic unit names, number of digits in code, common names, hydrologic 

unit levels, average sizes, and approximate number of hydrologic units, by type, in the United States.

[Modified from U.S. Geological Survey and U.S. Department of Agriculture, Natural Resources Conservation Service, 

2011; mi2, square miles]

Current

numerical

name

Digits in

 hydrologic

unit code

Common

name

Hydrologic 

unit

 level

Average size

(square miles)

Approximate 

number of

 hydrologic units

2 digit 2 Region 1 177,560 21

(actual)

4 digit 4 Subregion 2 16,800 222

6 digit 6 Basin 3 10,596 370

8 digit 8 Subbasin 4 700 2,270

10 digit 10 Watershed 5 227 

(40,000–250,000 acres)

20,000 

12 digit 12 Subwatershed 6 40 

(10,000–40,000 acres)

100,000 
4 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13
Delineation of the NASQAN and NMN Basin Boundary Dataset 5

Delineation of the NASQAN and 

NMN Basin Boundary Dataset 

NASQAN and NMN basins range in size from 7,000 to 

1,145,000 mi2 and were first extracted from the WBD12 based 

on the range of 8-digit HUCs contained within each basin. 

The 8-digit HUC (HUC_8) is an item in the WBD12 attribute 

table. Larger basins may encompass multiple Regions (2-digit 

HUCs). An example basin extraction may include: “HUC_8 > 

05000000 AND HUC_8 < 07000000.” This example extraction yields all Subwatersheds within the 05 (Ohio) and 06 

(Tennessee) Regions. Next, internal Subwatershed boundaries 

were eliminated using the ArcGIS Dissolve command, resulting in a single boundary for an entire basin. The shapefile 

naming convention for each basin boundary is b followed 

by the 8-digit station identification number (for example 

b01646589). Attribute table item definitions for basin boundary polygons are listed in table 2.

The location of the NASQAN or NMN monitoring 

station is considered the outlet of the basin for this dataset. 

In many cases the outlet of the basin does not fall directly 

on a 12-digit Subwatershed boundary. For those basins, the 

outlet boundary from the monitoring station to the nearest 

Subwatershed boundary was digitized in ArcGIS-ArcMap 

(Environmental Systems Resource Institute, 2009) along the 

drainage divide, which was determined from 1:24,000-scale 

USA Topographic maps served by the Environmental Services 

Resource Institute at http://server.arcgisonline.com/ArcGIS/

rest/services/USA_Topo_Maps/MapServer and provided by the 

National Geographic Society (2009). 

Noncontributing areas and closed areas are often important considerations when calculating basin characteristics and 

water-quality loads and are, therefore, provided in a companion dataset. Drainage areas that do not contribute flow toward 

the outlet of a hydrologic unit are considered noncontributing. 

If the entire Subwatershed does not contribute flow, then it 

is labeled closed in either the HUC_10_DS or HUC_12_DS 

items of the WBD12 attribute table. If noncontributing areas 

are small and dispersed within the Subwatershed, then the 

noncontributing areas are summed and an estimated total 

noncontributing area is provided in the NCONTRB_A item 

of the WBD12 attribute table. To develop the companion 

dataset to the basin boundary delineations, closed and noncontributing Subwatershed areas within each basin were first 

extracted from the WBD12. Then all Subwatersheds labeled 

closed in items HUC_10_DS or HUC_12_DS in the WBD12 

attribute table were selected, and Subwatersheds with item 

NCONTRB_A greater than zero but not labeled closed in 

HUC_10_DS or HUC_12_DS were also selected. Subwatersheds upstream of a closed system, or completely surrounded 

by closed Subwatersheds, often are not labeled closed; these 

Subwatersheds were determined by visual inspection and 

added to the appropriate polygon shapefile. Hydrologic units 

from Seaber and others (1987) also were used to identify additional Subwatersheds that should be included in the companion dataset. 

A single shapefile, containing multiple closed and noncontributing polygons, was generated for each NASQAN and 

NMN basin that contained noncontributing areas. An item 

TYPE was added to the polygon attribute table to identify 

Subwatersheds that are closed or those that have noncontributing areas. If the value in NCONTRB_A was within 98 percent 

of the calculated area of the Subwatershed polygon, then it 

was labeled closed. If the value in NCONTRB_A was less 

than 98 percent, then the polygon was labeled noncontributing. The shapefile naming convention for each basin with 

closed and noncontributing areas is n followed by the 8-digit 

station identification number (for example n01646589). Attribute table item definitions for closed/noncontributing polygons 

are listed in table 2.

A point shapefile for all of the NASQAN and NMN 

monitoring stations is provided as part of the basin boundary dataset. Site information from the USGS National Water 

Information System (NWIS) was retrieved for each station 

(table 3). The percentage difference from published NWIS 

drainage areas and drainage areas calculated for these basin 

boundary delineations is provided in the attribute tables. 

Differences between the two sources range from –0.78 to 

1.74 percent (table 3). See table 2 for attribute table item definitions for NASQAN and NMN stations.
6 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13 Table 2. Attribute item table definitions for basin boundary polygons, closed/noncontributing polygons, and National Stream Quality Accounting Network and National Monitoring Network monitoring stations.—Continued [NWIS, National Water Information System; NASQAN, National Stream Quality Accounting Network; HUC, Hydrologic Unit Code; —, not applicable; WBD12, National Water Boundary Dataset (U.S. Department of Agriculture, 2009)] Item name Item description Equation used Units of measure Source Item definitions for basin boundary polygon data files AREA Area of the basin polygon

— Square meters ArcGIS.

PERIMETER Perimeter of the basin polygon

— Meters ArcGIS.

B03303280_ Basin file identifier 

—

— (Artifact from ArcInfo polygon #ID).

B033032801 Basin file identifier 

—

— (Artifact from ArcInfo polygon -ID).

STAID Station identifier

—

— NWIS.

STANAME Station name

—

— NWIS.

SUBNETWORK NASQAN subnetwork name

—

— NASQAN.

DAMI2 Drainage area of the basin (DAMI2 = AREA/2,589,988.11) Square miles Calculated.

Item definitions for closed/noncontributing polygon data files

AREA Area of the Subwatershed polygon

— Square meters ArcGIS.

PERIMETER Perimeter of the Subwatershed polygon

— Meters ArcGIS.

STAID Station identifier

—

— NWIS.

HUC_12 12-digit Hydrologic Unit Code

—

— WBD12.

ACRES Area of the HUC_12 Subwatershed polygon

— Acres WBD12.

NCONTRB_A Noncontributing area of the 

HUC_12 Subwatershed polygon

— Acres WBD12.

NCONTRBMI2 Noncontributing area of the 

HUC_12 Subwatershed polygon

(NCONTRBMI2/640) Square miles Calculated.

HUC12MI2 Area of the Subwatershed (HUC12MI2 = AREA/2,589,988.11) Square miles Calculated.NCONPCT Percentage of the Subwatershed that is 

noncontributing 

[(NCONTRBMI2/HUC12MI2)*100] Percent Calculated.

TYPE Type of Subwatershed (closed or noncontributing) (NCONPCT >=98 = CLOSED) OR 

(NCONPCT < 98 = NONCONTRIBUTING)

— Assigned (based on NCONPCT value).
Delineation of the NASQAN and NMN Basin Boundary Dataset 

7

Table 2. Attribute item table definitions for basin boundary polygons, closed/noncontributing polygons, and National Stream Quality Accounting Network and National Monitoring Network monitoring stations.—Continued[NWIS, National Water Information System; NASQAN, National Stream Quality Accounting Network; HUC, Hydrologic Unit Code; —, not applicable; WBD12, National Water Boundary Dataset (U.S. Department of Agriculture, 2009)]

Item name Item description Equation used Units of measure Source

Item definitions for NASQAN and NMN station point data file

STAID Station identifier — — NWIS.

NWIS_STAID NWIS station identifier (includes agency code — — NWIS.

plus station number)

BASFILENAM Basin boundary file name (b followed by staid) — — Assigned (based on station id).NCFILENAM Closed/noncontributing polygons associated — — Assigned (based on station id).

with each basin polygon file name (n followed by staid)

NWIS_NAME NWIS station name — — NWIS.

SUBNETWORK NASQAN subnetwork name — — NASQAN.

LONGITUDE Station longitudinal location (NAD83) — Decimal degrees NWIS.

LATITUDE Station latitudinal location (NAD83) — Decimal degrees NWIS.

DAMI2 Drainage area of the basin (DAMI2 = AREA/2,589,988.11) Square miles Calculated from basin boundary polygon.

TOTNCON Sum of closed and noncontributing areas for — Square miles Calculated from closed/noncontributing 

the basin polygons.

NWISDAMI2 NWIS published drainage area of the basin — Square miles NWIS.NWISCONMI2 NWIS published contributing drainage area of — Square miles NWIS.

the basin

NWISNCON NWIS noncontributing drainage area of (NWISDAMI2 - NWISNCONMI2) Square miles Calculated.

the basin in square miles

NWISNASDIF Percent difference between NWIS published [(DAMI2 - NWISDAMI2)/NWISDAMI2 ] * 100 Percent difference Calculated.

drainage area and calculated area of the basin boundary
Table 3. National Stream Quality Accounting Network and National Monitoring Network monitoring stations, National Water Information System drainacalculated basin areas, and differences between National Water Information System drainage areas and calculated basin areas.—Continued [HUC, hydrologic unit code; NASQAN, National Stream Quality Accounting Network; NWIS, National Water Information System; mi2, square miles; NMN, National Monitoring Nsippi-Atchafalaya River Basin network; —, not available or not applicable] Region Station name Receiving waterbody name HUC6 HUC6 name Station identification number NASQAN subnetwork NWIS drainage area, in mi2 Calculated basin area

in mi2 (DAMI2) 

02 Mid-Atlantic Hudson River below Poughkeepsie, N.Y. New York Bay 20200 Upper Hudson 01372058 NMN 11,740 11,882 

Delaware River at Trenton, N.J. Delaware Bay 20401 Northern Delaware 01463500 NMN 6,780 6,787 Susquehanna River at Conowingo, Md. Chesapeake Bay 20503 Southern Susquehanna 01578310 Coastal 27,100 27,086 Potomac River at Chain Bridge at Washington, D.C. Chesapeake Bay 20700 Potomac 01646580 Coastal 11,570 11,570 

03 South Atlantic- Gulf Altamaha River near Everett City, Ga. Altamaha River Estuary 30701 Altamaha 02226160 Coastal 14,000 14,111 

Apalachicola River near Sumatra, Fla. Apalachicola Bay 31300 Apalachlcola 02359170 NMN 19,200 19,202 Mobile River at Mt. Vernon, Ala. Mobile Bay 31602 Mobile Bay- Tombigbee 02470500 Coastal 42,867 42,816 

04 Great Lakes St. Lawrence River at Cornwall, Ontario, near Massena, N.Y. Gulf of St. Lawrence 41503 St. Lawrence 04264331 Coastal 298,800 297,955 05 Ohio Wabash River at New Harmony, Ind. Ohio River 51201 Wabash 03378500 MARB 29,234 29,301 

White River at Hazleton, Ind. Wabash River 51202 Patoka-White 03374100 MARB 11,305 11,303 Ohio River at Cannelton Dam at Cannelton, Ind. Lower Mississippi River 51402 Lower Ohio 03303280 MARB 97,000 96,492 Ohio River at Dam 53 near Grand Chain, Ill. Lower Mississippi River 51402 Lower Ohio 03612500 MARB 203,100 203,640 
Table 3. National Stream Quality Accounting Network and National Monitoring Network monitoring stations, National Water Information System drainacalculated basin areas, and differences between National Water Information System drainage areas and calculated basin areas.—Continued[HUC, hydrologic unit code; NASQAN, National Stream Quality Accounting Network; NWIS, National Water Information System; mi2, square miles; NMN, National Monitoring sippi-Atchafalaya River Basin network; —, not available or not applicable]

Region Station name

Receiving 

waterbody 

name

HUC6 HUC6 name

Station 

identification 

number

NASQAN 

subnetwork

NWIS 

drainage 

area, 

in mi2

Calculate

basin area

in mi2

(DAMI2)

06 Tennessee07 Upper 

Mississippi

Tennessee River at 

Highway 60 near Paducah, Ky.

Mississippi River at 

Clinton, Iowa

Iowa River at 

Wapello, Iowa

Des Moines River at 

Keosauqua, Iowa

Mississippi River below 

Grafton, Ill.

Illinois River at 

Valley City, Ill.

Mississippi River at 

Thebes, Ill.

Ohio RiverGulf of MexicoUpper Mississippi RiverUpper Mississippi RiverGulf of MexicoUpper Mississippi RiverGulf of Mexico

60400708017080271000

71100

7130071401

Lower TenneseeUpper MississippiSkunk-WapsipiniconIowaDes MoinesUpper Mississippi-SaltLower IllinoisUpper MississippiMeramec

03609750054205000546550005490500055874550558610007022000

MARBMARBMARBMARBMARBMARBMARB

40,33085,60012,50014,038

171,300

26,743

713,200

40,32585,88412,50014,022

172,536

26,673

710,441
Table 3. National Stream Quality Accounting Network and National Monitoring Network monitoring stations, National Water Information System drainacalculated basin areas, and differences between National Water Information System drainage areas and calculated basin areas.—Continued [HUC, hydrologic unit code; NASQAN, National Stream Quality Accounting Network; NWIS, National Water Information System; mi2, square miles; NMN, National Monitoring Nsippi-Atchafalaya River Basin network; —, not available or not applicable] Region Station name Receiving waterbody name HUC6 HUC6 name Station identification number NASQAN subnetwork NWIS drainage area, in mi2 Calculated basin area

in mi2 (DAMI2) 

08 Lower Mississippi 10 Missouri Yazoo River below Steele Bayou near Long Lake, Miss. Mississippi River above Vicksburg at mile 438, Miss. 1Mississippi River near St. Francisville, La. 1Mississippi River at Baton Rouge, La. 1(COE) Atchafalaya River at Melville, La. 1Wax Lake Outlet at Calumet, La. 1Lower Atchafalaya River at Morgan City, La. 1Mississippi River at Belle Chasse, La. Platte River at Louisville, Nebr. Missouri River at Omaha, Nebr. Missouri River at Hermann, Mo. Lower Mississippi River Gulf of Mexico Gulf of Mexico Gulf of Mexico Atchafalaya Bay Gulf of Mexico Gulf of Mexico Mississippi River Estuary Missouri River Upper Mississippi River Upper Mississippi River 80302 80601 80701 80701 80801 80801 80801 80901 102002 102300 103002 Yazoo Lower Mississippi- Natchez Lower Mississippi- Baton Rouge Lower Mississippi- Baton Rouge Atchafalaya-Vermilion Atchafalaya-Vermilion Atchafalaya-Vermilion Southern Mississippi- New Orleans Lower Platte Missouri-Little Sioux Lower Missouri 07288955 MARB 322023090544500 NMN 07373420 MARB 07374000 MARB 07381495 Coastal 07381590 MARB 07381600 MARB 07374525 Coastal 06805500 MARB 06610000 MARB 06934500 MARB 13,355 — 1,125,300 1,129,766 93,316 —— 1,130,000 85,370 322,800 522,500 13,414 1,123,967 1,144,886 1,145,342 93,511 22,178 94,621 1,145,457 85,329 321,076 519,408 
Table 3. National Stream Quality Accounting Network and National Monitoring Network monitoring stations, National Water Information System drainacalculated basin areas, and differences between National Water Information System drainage areas and calculated basin areas.—Continued[HUC, hydrologic unit code; NASQAN, National Stream Quality Accounting Network; NWIS, National Water Information System; mi2, square miles; NMN, National Monitoring sippi-Atchafalaya River Basin network; —, not available or not applicable]

Region Station name

Receiving 

waterbody 

name

HUC6 HUC6 name

Station 

identification 

number

NASQAN 

subnetwork

NWIS 

drainage 

area, 

in mi2

Calculate

basin area

in mi2

(DAMI2)

11 ArkansasWhite-Red12 Texas-Gulf13 Rio Grande15 Lower 

Colorado

17 Pacific 

Northwest

18 California19 Alaska

Arkansas River at 

David D Terry Lock and Dam below Little Rock, Ark.

Brazos River near 

Rosharon, Tex.

1Rio Grande near 

Brownsville, Tex.

1Colorado River at NIB, 

above Morelos Dam, Ariz.

Columbia River near 

Beaver Army Terminal, Oreg.

Sacramento River at 

Freeport, Calif.

San Joaquin River near 

Vernalis, Calif.

Yukon River at 

Pilot Station, Alaska

Lower Mississippi RiverBrazos River EstuaryRio Grande EstuaryGulf of CaliforniaColumbia River EstuarySan Francisco BaySan Francisco BayNorton Sound

111102

120701130900150301170800180201180400190408

Lower ArkansasFourche La FaveSouthern BrazosSouthern Rio GrandeSouthern ColoradoSouthern ColumbiaSouthern SacramentoSan JoaquinYukon Delta

07263620

08116650

084750000952200014246900

1144765011303500

15565447

MARBNMNCoastalCoastalCoastalCoastalCoastalCoastal

158,429

45,339

176,333246,700256,900

—

13,536

321,000

157,787

45,415

3177,415

249,078258,697

23,724

13,511

318,508

1 Water-quality and streamflow at some sites are highly influenced by the diversion of water into or out of the basin. Eight sites in this dataset are known to be highly influenced b

strongly encouraged to review figures 2–4 and read the section “Considerations of Flow Routing for Selected Basins in the Dataset.”

2Includes only the area draining Bayou Teche and a small part of the Atchafalaya main stem near the Wax Lake Outlet. 3The drainage area published in U.S. Geological Survey NWIS is 176,333 mi2 and does not include the noncontributing area or the 2,564 mi2 for the Laguna Madre basin. Total ca

215,270 mi2, including 177,415 mi2 contributing, 35,291 mi2 noncontributing, and 2,564 mi2 for the Laguna Madre diversion basin.
12 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13

Consideration of Flow Routing for 

Selected Basins in the Dataset

Large basins often have complicated flow regimens that 

should be considered when using water-quality and quantity 

data associated with these basins because the data collected 

at the monitoring site may not be indicative of conditions 

throughout the basin. The Lower Mississippi River and Atchafalaya River system, the Rio Grande, and the Lower Colorado 

River all have diversions that affect not only the quantity of 

water flowing past NASQAN or NMN stations but also the 

basin area contributing to that flow. 

A portion of flow on the Lower Mississippi River is 

diverted through the Old River Outflow Channel to the 

Atchafalaya River (fig. 2). Affected stations on the Mississippi River side include 07373420 near St. Francisville, 

La., 07374000 at Baton Rouge, La., and 07374525 at Belle 

Chasse, La. Affected stations on the Atchafalaya River side 

of the diversion include 07381495 at Melville, La., 07381590 

Wax Lake at Calumet, La., and 07381600 at Morgan City, La. 

Consideration of all of these stations together can provide 

a more accurate assessment of water-quality and flow data, 

because a single station downstream of the diversion may not 

be representative of the entire basin. Users of water-quality 

data for these stations should also consider flow records for 

U.S. Geological Survey station Old River Outflow Channel 

near Knox Landing, La. (07294800), Mississippi River at 

Tarbert Landing, Miss. (07295100), and Atchafalaya River at 

Simmesport, La. (07381490). 

Basins 07381590, Wax Lake Outlet at Calumet, La., and 

07381600, Atchafalaya River at Morgan City, La., should 

be considered together, because there is no reliable way to 

determine the areal portion of the Atchafalaya River Basin that 

drains through the Wax Lake Outlet and the portion that drains 

through the main stem (fig. 2). The Atchafalaya River bifurcates below Melville, La., and some flow drains through the 

main channel to Morgan City and some drains into the Wax 

Lake Outlet into the Gulf of Mexico. The basin boundary for 

07381590, Wax Lake Outlet, includes only the area draining 

Bayou Teche and a small part of the Atchafalaya main stem 

near the Wax Lake Outlet. Users of the NASQAN water-quality data for either the Wax Lake Outlet and/or the Atchafalaya 

River at Morgan City should consider both basin boundaries 

and combined water-quality data for both stations. Because 

streamflow through the Wax Lake Outlet includes additional 

flow from the Atchafalaya River, flow and water-quality constituents may not be representative of that contributed by just 

the Wax Lake Outlet basin alone. 

Much of the flow in the Rio Grande upstream from 

the Brownsville, Tex., station (08475000) is diverted into 

the Anzalduas Canal, which flows through the Anzalduas 

Dam near Mission, Tex., and then into the Arroyo Colorado 

(fig. 3C). Almost all the water withdrawn from the Arroyo 

Colorado or the Rio Grande for irrigation and municipal 

purposes is returned to the Arroyo Colorado. The Arroyo 

Colorado drains into the Laguna Madre (WBD12 HUCs 

1211020801–1211020809), which effectively becomes an 

estuary for the Rio Grande during spring and summer irrigation seasons. Users of the NASQAN water-quality data for 

the Rio Grande near Brownsville, Tex., should consider flow 

and water-quality data for U.S. Geological Survey station 

Arroyo Colorado at Harlingen, Tex. (08470400) because it 

records much of the flow from the Rio Grande, while only a 

small portion of water from the basin flows past the Brownsville monitoring site. The Laguna Madre is included in the 

basin delineation for station 08475000. The drainage area 

for this delineation of the Rio Grande River near Brownsville is 215,270 mi2

, including 177,415 mi2 contributing 

area, 35,291 mi2 noncontributing area, and 2,564 mi2 for the 

Laguna Madre diversion basin. The drainage area published 

in U.S. Geological Survey NWIS records is 176,333 mi2

and does not include the noncontributing area or the Laguna 

Madre. When these two factors are taken into account, the 

resulting comparable drainage area is 177,415 for this delineation, or a 0.61 percent difference between the NWIS published area and the comparable drainage area for this version 

(table 2).

Much of the flow upstream of the U.S. Geological 

Survey station Colorado River at the Northern International 

Boundary (NIB), Ariz. (09522000), is diverted into the AllAmerican Canal (fig. 4). The All-American Canal diversion is 

downstream of station Colorado River above Imperial Dam, 

Arizona-California (09429490). Flow data from this station 

should be considered when assessing water-quality records 

for the NIB station because this may better represent the total 

flow from the Colorado River Basin. Routing of flow from 

Lake Powell to the Southerly International Border (SIB) with 

Mexico is described in Appendix B of Colorado River Interim 

Guidelines for Lower Basin Shortages and Coordinated 

Operations for Lake Powell and Lake Mead (U.S. Department 

of Interior, 2007).
Consideration of Flow Routing for Selected Basins in the Dataset 13

Figure 2. 

U.S. Geological Survey station type

National Stream Quality Accounting Network monitoring station and number

National Monitoring Network monitoring station and number

Streamflow and/or sampling station and number

Direction of flow

Old River Outflow Channel

Gulf of Mexico

Atchafalaya River Red River

Mississippi River

07374525

Mississippi River

at Belle Chasse, La.

07374000

Mississippi River

at Baton Rouge, La.

07373420 

Mississippi River

near St. Francisville, La.

07295100

Mississippi River at

Tarbert Landing, Miss.

07294800

Old River Outflow Channel

near Knox Landing, La.

07381490

Atchafalaya River

at Simmesport, La.

07381495

Atchafalaya River

at Melville, La.

07381590

Wax Lake Outlet, 

at Calumet, La.

07381600

Atchafalaya River 

at Morgan City, La.

Mississippi River

322023090544500

Mississippi River above

Vicksburg at mile 438, Miss.

07381600

07381490

EXPLANATION

322023090544500

Figure 2. Mississippi-Atchafalaya River Basin flow routing and U.S. Geological Survey stations (modified from 

Aulenbach and others, 2007).
14 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13

Laguna Madre Basin boundary

Rio Grande Basin boundary

National Stream Quality 

Accounting Network 

sampling site and number

08475000 

Rio Grande near 

Brownsville, Tex. 

Rio Grande

Laguna Madre

Figure 3. 

08470400 

Arroyo Colorado at 

Harlingen, Tex.

(sampled in 

1996–2000) 

A

B

C

08475000

1996–2000 National Stream

Quality Accounting Network

 sampling site 

3

EXPLANATION

SUBBASIN—(identified by the location

of the most downstream point of the

subbasin, except for closed basins)

Rio Grande at El Paso

Rio Grande at Foster Ranch

Pecos River near Langtry

Rio Grande below Amistad Dam

Rio Grande below Laredo

Rio Grande below Falcon Dam

Rio Grande near Brownsville

Closed basin

Figure 3. Location of A, the Rio Grande Basin in the United States and Mexico, B, the Rio Grande Basin and subbasin boundaries, and 

C, multiple diversions from the Rio Grande into the Laguna Madre Basin through Arroyo Colorado (modified from Lurry and others, 1998).
Consideration of Flow Routing for Selected Basins in the Dataset 15

Alamo Canal

Coachella Canal

Alamo River

All-American Canal

East Highline Canal

242 Lateral

Main Drain

Gila River

East Mai n

Canal

INTERNATIONAL BOUNDARY

West Main Canal Morelos

Dam

All-American Canal

Laguna Dam

Wellton-Mohawk Conveyance Channel

Lagunas De Enfriamiento

SAN LUIS

Northern International Boundary

Figure 4. 

UNITED STATES

MEXICO

CALIFORNIA

ARIZONA

BAJA

CALIFORNIA

SONORA

09429490

Colorado River above

Imperial Dam, Ariz.-Calif.

09522000

Colorado River at Northern

International Boundary,

above Morelos Dam, Ariz.

U.S. Geological Survey station type

National Stream Quality Accounting Network 

monitoring station and number

Colo rado River

Southern International Boundary

Colorado

River

EXPLANATION

09429490

09522000

Streamflow and/or sampling station and number

CALIFORNIA

ARIZONA

UTAH

NEW MEXICO

COLORADO

WYOMING

NEVADA

B

A

Figure 4. Location of A, the Colorado River in the United States, and B, the diversion into the AllAmerican Canal relative to U.S. Geological Survey monitoring stations (modified from International 

Boundary and Water Commission, 2010, and U.S. Department of the Interior, 2007).
16 National Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13

Summary

Geospatial basin boundary data from NASQAN and 

NMN are provided to assist in analysis and interpretation of 

water-quality data collected by the U.S. Geological Survey. 

The geospatial data contains polygon shapefiles of basin 

boundaries for 33 NASQAN and 5 NMN water-quality monitoring stations. In addition, 30 polygon shapefiles of the closed 

and noncontributing basins contained within the NASQAN 

or NMN basin boundaries and a point shapefile of monitoring 

stations and associated basin and station attributes are provided. Basin boundaries were delineated using the WBD12. 

Calculated drainage areas resulting from the delineation 

ranged from –0.78 to 1.74 percent of published NWIS drainage areas. Explanations of flow routing for the Lower Mississippi River-Atchafalaya River system, the Rio Grande, and 

the Lower Colorado River are provided to supply additional 

assistance to users of the accompanying data sets.

References Cited

Aulenbach, B.T., Buxton, H.T., Battaglin, W.A., and Coupe, 

R.H., 2007, Streamflow and nutrient fluxes of the Mississippi-Atchafalaya River Basin and subbasins for the period 

of record through 2005: U.S. Geological Survey Open-File 

Report 2007–1080, available online at http://toxics.usgs.

gov/pubs/of-2007-1080/.

Canadian Geospatial Data Infrastructure, 2009, Canadian 

watershed boundaries, Canada Land Inventory Level-I 

Digital Data: accessed December 2010 at http://geogratis.

cgdi.gc.ca.

International Boundary and Water Commission, 2010, A report 

on Colorado River salinity operations, under International 

Boundary and Water Commission Minute No. 242, January 

1, 2002 through December 31, 2009: International Boundary and Water Commission United States Section, Edward 

Drusina, P.E., United States Commissioner, accessed 

September 2011 at http://www.ibwc.state.gov/Files/Annual_

Salinity_Report_2009.pdf.

Environmental Systems Resource Institute, 2009, ArcGIS 

9.3.1: ESRI, Redlands, Calif. 

Lurry, D.L., Reutter, D.C., and Wells, F.C., 1998, Monitoring 

the water quality of the Nation’s largest rivers; Rio Grande 

NASQAN Program: U.S. Geological Survey Factsheet 

083–98, 4 p., accessed August 2011 at http://water.usgs.gov/

nasqan/docs/riogrndfact/riogrndfactsheet.html.

National Geographic Society, 2009, USA_Topo_Maps 

(MapServer): accessed May 2011 at http://server.

arcgisonline.com/ArcGIS/rest/services/USA_Topo_Maps/

MapServer.

Patino, C. 2004, Hydrologic geodatabase for the Rio Grande 

Basin: Austin, University of Texas, Center for Research in 

Water Resources, accessed August 2011 at http://www.crwr.

utexas.edu/riogrande.shtml.

Patino, C., McKinney, D.C., and Maidment, D.R., 2004, 

Development of a hydrologic geodatabase for the Rio 

Grande/Bravo Basin, in American Water Resources Association Spring Specialty Conference: Geographic Information Systems (GIS) and Water Resources III, Nashville, 

Tenn, May 17–19, 2004: Middleburg, Va., American Water 

Resources Association.

Seaber, P.R., Kapinos, F.P., and Knapp, G.L., 1987, Hydrologic unit maps: U.S. Geological Survey Water-Supply 

Paper 2294, 63 p. (Also available at http://pubs.usgs.gov/

wsp/wsp2294/.)

U.S. Department of Agriculture, 2009, National Watershed 

Boundary Dataset: Natural Resources Conservation Service, 

National Cartography and Geospatial Center, Fort Worth, 

Tex., accessed March 2011 at http://www.ncgc.nrcs.usda.

gov/products/datasets/watershed/.

U.S. Department of the Interior, 2007, Colorado River interim 

guidelines for lower basin shortages and coordinated operations for Lake Powell and Lake Mead: Bureau of Reclamation, Upper and Lower Colorado Regions, October 2007, 

Final Environmental Impact Statement, app. B, accessed 

September 2011 at http://www.usbr.gov/lc/region/programs/

strategies/FEIS/. 

U.S. Geological Survey and U.S. Department of Agriculture, 

Natural Resources Conservation Service, 2011, Federal 

standards and procedures for the National Watershed 

Boundary Dataset (WBD) (2nd ed.): U.S. Geological Survey Techniques and Methods book 11, sec. A, chap. 3, 62 p. 

Available online at http://pubs.usgs.gov/tm/tm11a3/.

Stream Quality Accounting Network and National Monitoring Network Basin Boundary Geospatial Dataset, 2008–13—Data Series 641