In cooperation with the Indiana Department of Environmental Management and the

Indiana Department of Natural Resources Division of Water

Digital Data Set of 14-Digit Hydrologic Units in Indian

Three-dimensional 

view of 

land surface

Two-dimensional topographic map 

view with drainage-basin boundaries

in red

 Digital data set of 

 basin boundaries 

hydrologic-unit c

Diagram illustrating development of hydrologic units, progressing from a three-dimensional land s

to a two-dimensional topographic map to a digital data set. 

05140201-010-

051

05140104-210-030

05140201

-010-020

05140104-

A hydrologic unit is an area of land that can contribute surface-water runoff to a designated outlet point. As 

of an initiative to create a nationally uniform hydrologic-unit data base, the U.S. Geological Survey and the 

Natural Resources Conservation Service, in cooperation with the Indiana Department of Environmental

Management and the Indiana Department of Natural Resources Division of Water, created a geographic 

information system digital data set of 14-digit hydrologic units in Indiana. The digital data set consists of arc

and polygons defining 14-digit hydrologic units in Indiana. 

Introduction

A hydrologic unit (HU) is an area

of land upstream from a specific

point on a stream that is defined by

a hydrologic boundary. The boundary

includes all of the source area

that could contribute surface-water

runoff directly or indirectly to the

designated outlet point. HU’s are

used by local, State, and Federal

agencies and by private and academic interests for natural-resource,

water-quality, and flood-damage

activities; water-data management;

and geographic information systemsbased (GIS-based) spatial analyses

(U.S. Department of Agriculture,

1992).

Before 1999, the most-detailed statewide hydrologic-unit data for Indiana

were published on a 1:500,000-

scale map of 8-digit hydrologic-unit

boundaries (U.S. Geological Survey,

1974). That map was part of a series

developed by the U.S. Geological

Survey (USGS) to provide uniform

hydrologic-unit boundaries and to

present them on nationally consistent base maps.

The 8-digit HU’s in Indiana a

identified by a unique 8-digit

hydrologic-unit code (HUC) b

on four levels of classification

(fig. 1, page 3): regions, subre

accounting units, and catalogi

units (Seaber and others, 1987

During the mid- to late-1970’

U.S. Department of Agricultu

ral Resources Conservation S

(NRCS) subdivided 8-digit H

by adding three digits to ident

fifth level of classification, 11

HU’s—watersheds.

U.S. Geological Survey

U.S. Department of the Interior
and adhering to the digitizing accuracy

standard of ±50 feet (U.S. Department

of Agriculture, 1992). All drainagebasin boundaries were plotted on paper

and overlain on the original maps to

determine the accuracy of the digitized

lines. Lines that did not meet the

digitizing accuracy standard were redigitized and replotted. This procedure

was repeated until all lines met the standard. A second person not involved

with the original digitizing followed

the same line-verification procedures

for 36 percent of the original topographic maps. Less than 3 percent of

these maps had errors, and those errors

were corrected.

Each delineated basin was attributed

with a 14-digit HUC assigned by NRCS

personnel. Drainage basins with the

same 14-digit HUC were merged to

form the final digital data set of 14-digit

HU’s. For each topographic map, the

HU boundaries and respective HUC’s

were plotted on paper and reviewed by

NRCS personnel. Errors were noted

and corrected, and new plots were produced and reviewed until no errors were

identified.

NRCS personnel assigned each 14-digit

HU a unique name based on the main

waterway within that HU. Names were

checked for accuracy by NRCS and

USGS personnel.

Digital Data Set of

14-Digit Hydrologic Units

The digital data set consists of polygons

(areas) and arcs (lines) representing

14-digit HU’s in Indiana. Each polygon

has an associated record in a

polygon-attribute table (table 

its 8-, 11-, and 14-digit HUC

of the 14-digit HU; the HU a

acres; and the noncontributin

the HU area in acres.

Each arc has an associated re

an arc-attribute table (table 2

that identifies the arc as a 2-, 

8-, 11-, or 14-digit HU boun

Indiana State line. Quality-a

data regarding the digitizatio

arc also are included in the a

table. The data set is docume

meets the Federal Geographi

Committee standards for dig

spatial data sets (Federal Ge

Data Committee, 1998).

Data Availability

This fact sheet, the digital da

and the data-set documentati

(“metadata”) are available at 

USGS Indiana District home

http://in.water.usgs.go

under the heading, “Indiana 

Publications Available on th

The HU data set for the entir

Indiana is available for down

a compressed ARC/INFO ex

(approximately 46 megabyte

spatial data transfer standard 

file (approximately 23 mega

The data set for the State also 

along accounting-unit bound

to provide smaller files for d

loading (compressed ARC/IN

approximately 0.2 to 18 meg

or SDTS files, approximately 

9 megabytes).

Table 1. User-defined polygon attributes

Attribute name Description Examp

HUC_8 8-digit hydrologic-unit code 04040001

HUC_11 11-digit hydrologic-unit code 04040001070

HUC_14 14-digit hydrologic-unit code 040400010700

HU_NAME Name of 14-digit hydrologic unit West Branch T

HU_ACRES Area of 14-digit hydrologic unit,

 in acres

15349.2

NONCONTRIB_ACRES Area of noncontributing part of

14-digit hydrologic unit, in

acres

907.4

Since that time, water-resources professionals have recognized a need for

further delineation and subdivision of

HU’s in Indiana for research, planning,

and regulatory activities. In 1992, the

NRCS developed guidelines for

mapping and digitizing a sixth level

of classification, 14-digit HU’s—

subwatersheds (U.S. Department of

Agriculture, 1992). In 1996, the USGS,

the NRCS, the Indiana Department

of Environmental Management, and

the Indiana Department of Natural

Resources Division of Water agreed

to create a digital data set of 14-digit

HU’s in Indiana.

Creation of Digital Data Set

of 14-Digit Hydrologic Units

The USGS office in Indianapolis

maintains a file of 1:24,000-scale

topographic maps with hand-drawn

drainage-basin boundaries for all

waterways in Indiana with drainage

areas greater than 5 square miles.

Many basins have been subdivided

into drainage areas smaller than

5 square miles. These topographic

maps have been used to calculate

drainage areas—an important parameter in many hydrologic analyses

(Hoggatt, 1975).

A GIS base-map coverage containing

coordinate points at every 7.5 minutes

of latitude and longitude was generated.

The coordinate points correspond to

the corner vertices of 1:24,000-scale

topographic maps for Indiana and the

immediate vicinity. For each topographic map, a root mean square error

(RMSE) was calculated on the distances

between the four corner vertices and

the corresponding coordinate points

in the base-map coverage. RMSE

values were 0.010 or less for 95 percent of the maps, indicating potential

distortions of 20 feet or less. The

remaining 5 percent of the maps had

RMSE values between 0.011 and 0.016,

indicating potential distortions of up

to 32 feet.

The hand-drawn drainage-basin boundaries were digitized into the base-map

coverage, using ARC/INFO1 software

1

The use of trade, product, or firm names is

for descriptive purposes only and does not imply

endorsement by the U.S. Government.
0 5 

0 5 10 KILO

Counties

Streams

Lake

010

040 020

08

050

060

070 0

030

060

090 070

080

110

130

140

160 150

120

040 100

020

050

010

030

010

020

030

040

050

110

100

060

070

080

090

05090203080010

030

05090203

060

040 050

070

080

110

200

130

190

180 

070

080

060

050

030

010

020

040

040 050

030

010

020

010

020 

010

0

020

030 090

010

020

010

020

040

030

050

060 070

030

010

030

Region

Subregion

EXPLANATION

HYDROLOGIC UNITS

Cataloging unit

Watershed

Subwatershed

Accounting unit

Code

OTHER SYMBOLS

030

0

1

210

030

040500

01

02

02

01

04 06

05

07

03

08 10

11

01

04

03

03

05

02

08

06

07

09

01

04

01

02

01

02

03

05

07

04

01 01

03

050902

050800

09

13

00 040500

071200

051201

040602

041000

051202

051401

051402 051201

03

Figure 1. Hydrologic units in Indiana

Regions are the largest drainage basins and

contain either the drainage area of a major

river or the combined drainage areas of

several rivers.

Subregions divide the regions and include

the area drained by a river system.

Accounting units divide or may be equivalent

to subregions.

Cataloging units divide accounting units a

represent part or all of a surface-drainage basin

a combination of drainage basins, or a distinct

hydrologic feature.

Watersheds divide cataloging units and gen

range in size from 40,000 to 250,000 acres.

Subwatersheds divide or may be equivalent to

watersheds and generally range in size from

10,000 to 40,000 acres.

EXPLANATION

HYDROLOGIC-UNIT TERMS
 Fact S

S

Potential Need

for Updates

Continuing natural processes and

human activities often change drainage patterns and therefore alter

hydrologic-unit boundaries. Such

changes would necessitate periodic

updates to maintain an accurate data

set for hydrologic calculations. Revisions of this data set ideally would

incorporate observations from and

meet the needs of public, private,

and government interests.

References Cited

Federal Geographic Data Committee,

1998, FGDC-STD-001-1998,

Content standard for digital geospatial metadata: Washington, D.C.,

Federal Geographic Data Committee, accessed September 24, 1998,

at URL http://www.fgdc.gov/

metadata/contstan.html

Hoggatt, R.E., 1975, Drainage areas

of Indiana streams: U.S. Geological

Survey, 231 p.

Seaber, P.R., Kapinos, F.P., and Knapp,

G.L., 1987, Hydrologic unit maps:

U.S. Geological Survey 

Supply Paper 2294, p. 1–

U.S. Department of Agricul

Natural Resources Cons

Service, 1992, Mapping 

digitizing watershed and 

watershed hydrologic un

boundaries: National Ins

no. 170-304, 26 p., acces

May 30, 1997, at URL h

www.nhq.nrcs.usda.gov/

ni170304.html

U.S. Geological Survey, 197

Hydrologic unit map—1

State of Indiana: U.S. Ge

Survey, 1 sheet, scale 1:5

Table 2. User-defined arc attributes

Attribute name Description Examp

QUADNAME Name of the topographic map on which the drainage-basin

boundary was determined

CABO

QUAD_PUB_DATE Publication date of the topographic map on which the drainage-basin

boundary was determined

1957

DIGITIZE_DATE Date the drainage-basin boundary was digitized 199706

RMSE Root mean square error for the transformation from the topographic

map to the digital coverage

0.009

ARC_QA_DATE Date the digitized drainage-basin boundary was checked by someone

other than the person who digitized the boundary

199802

ARC_REMARKS Relevant remarks regarding the digitized drainage-basin

boundary

Divides near O

modified p

edition of 

HU_DIV Identifies arc as a 2-, 4-, 6-, 8-, 11-, or 14-digit divide or the State line 14

For More Information

District Chief Indiana District Website

U.S. Geological Survey http://in.water.usgs.gov

5957 Lakeside Boulevard

Indianapolis, IN 46278

317-290-3333 U.S. Geological Survey Website

e-mail: dc_in@usgs.gov http://www.usgs.gov

Prepared by

Krysten M. DeBroka and David A. Cohen, U.S. Geological Survey

Robert E. Dunn and Bruce J. Nielsen, Natural Resources Conservation Service