USGS Multimedia Gallery: (Video)--Overview of the National Hydrography Dataset and The National Map

Our basic architecture for this dataset is we have a

geodatabase that consists of the National Hydrography

Dataset and the Watershed Boundary Dataset and when we

display those together it looks like this. The blue

lines you see there are the National Hydrography

Dataset; they are the streams that make up the surface

water network. Then we can see these multicolored

polygons that make up the Watershed Boundary Dataset.

We can see how these stream networks fit neatly into

these hydrologic drainage areas. So in our design of a

dataset me might want to look at more information

besides just the National Hydrography Dataset and the

Watershed Boundary Dataset. We might want to look at

information such as the National Wetlands Inventory

and the 100 year flood plain as might be found in the

“Defirmed”? dataset. These datasets can all work

together in a geodatabase. We have other types of

water information such as point source discharges,

biologic habitat, stream gages, impaired waters,

drinking water intakes, diversion structures, and

dams. Then the NHD Plus dataset that we will talk

about in a minute, a very rich dataset that contains

all kinds of additional information. We can link this

information using pointers, using these network

addresses. For example, look at a point source

discharge; where is that located? Well we know the

address on the network and we can link that to other

types of datasets, to the National Wetlands Inventory,

to the National Hydrography Dataset. All this type of

information can be related to each other using these

network addresses and explicitly identify where things

are in relation to each other. We know what is

upstream, what is downstream of each other, we know

how far away it is. We know lots of information about

the relationships of data. For example here in trying

to identify the relationship between A, B, and C, this

can easily be done simply by looking at a map. We

don’t need a GIS system to do that, we can simply look

at a map and figure this out. But in an example here

we have many thousands of points. This is too

complicated to figure out just by looking at a map. So

we really need a geographic information system and a

data structure such as we find in the National

Hydrography Dataset and the Watershed Boundary Dataset

to understand these types of relationships. So for

example we have a stream gage, this red triangle that

you see in the image. We want to know what water

diversions are upstream of that stream gage that

effect the flow of water through that stream gage. So

we can navigate upstream and identify all the stream

gages. The cyan colored circles you see there, those

are the diversions that are upstream of the stream

gage. Those black dots you see there are also

diversion but they are not upstream of the stream

gage; so using a system such as the NHD it is easy to

figure out the relationship of information to each

other. Traditionally in a GIS, we overlay information

and look at the spatial relationships. This does not

work quite as well in a hydrography system because the

way that surface water is related is through the

network not just through space. So we need these

explicit relationships that we find in the data model

to understand how things relate to each other in the

network and not just through space. So one of the

things we can do with this type of information is to

create a map such as this which shows the surface

water flow through the state of Washington. The width

of the blue lines that you see there tell us how much

water is flowing through the streams on mean annual

flow basis. This is a model that gives us a picture of

where the water is in the state of Washington flowing

through the surface water stream network. This works

by taking information such as the National Hydrography

Dataset, the Watershed Boundary Dataset, and the

National Elevation Dataset, combining this together to

create catchments. So the blue lines you see here are

the stream network and then the multi-colored polygons

you see there are catchments. It is kind of like the

Watershed Boundary Dataset but in a much more detailed

level. You can see that each individual stream segment

has its own polygon, its own drainage area. That

drainage area can then be intersected with other types

of data to get information on that drainage area such

as the precipitation in that area, the temperature,

the elevation, the slope, the land cover, how much of

the land is forest, how much is agriculture, how much

of it is urban area. You can take all this type of

information and model it to get the stream flow

information that you see in a map like this. So using

modeling techniques we can predict how much water will

be in any one of these stream segments and then

represent the amount of water using the line width to

represent that. Something else we can do is look at a

system such as this and account for the diversions of

water. So the blue lines you see there are the natural

flow that you would expect in the surface water system

of Colorado. What we have done is then accounted for

the water that is withdrawn through water diversions.

The red dots you see on this map is water that

transfers water across the Continental Divide. There

are 56 of these and 5 of them are particularly

significant. What we have done is we used the pink

lines to represent water withdrawn by these diversions

so these rivers actually have less water in them. Then

the purple lines represent rivers in which water has

been added to them. So we have taken the blue lines

and then made them wider and turned them into these

purple lines because water has been added through the

Continental Divide diversions. Just an example of some

of the things we can do to improve our understanding

of the water of the United States. How is the NHD and

WBD used? For example at the U.S. Environmental

Protection Agency (EPA), they look at pesticide risk

assessment, they look at where pesticides are applied

on the landscape. How this effects endangered species

for example of flowing downstream; looking at water

samples and looking upstream and seeing where the

pesticides are coming from. One of the things that

they do at the U.S. EPA is they look at water

discharge permits and link these to the NHD, so giving

everyone of these points an address on the network

such as we saw earlier as in the example of the stream

gage. One of the things that can also be done is time

of travel. We can look at a water contaminant entering

the system at a certain point and flowing downstream

to a drinking water intake. If there is a contaminant

in the water we can look at the breakthrough curve

that you see in the upper right-hand corner. This tell

us over a period of time, the y-axis tell us the

concentration in the water, the x-axis looks at a

point on the river and the time interval when that

contaminant plume first reaches a drinking water

intake, when peak concentration arrives and then at

the trailing edge of the plume as the contaminant

passes through, passes by the drinking water intake.

It allows emergency responders to close off the

drinking water intake until the threat has passed.

In California, for example they use the National

Hydrography Dataset to look at water rights. Where

water rights used to be something that was just

manually stored on index cards and maps we now can do

this through a GIS system using a web portal such as

WRMIS system in the state of California to allow

citizens to look at water rights in the state

of California. In Missouri what they have done is look

at fish species. They have take 316 different fish

species and indexed these or referenced these to the

NHD. So we know for example where the Ozark Minnow

live the Wedgespot Shiner the Southern Redbelly Dace

you can see these in red, it shows us which streams in

the state of Missouri these species live in.

Something else we are interested in is

looking at fish barriers. One of the issues in

California is Steelhead Trout migration to spawning

grounds and the barriers in the river systems that

prevent the Steelhead Trout from reaching the spawning

grounds. So we can look at complete fish passage

barriers, partial barriers, and potential barriers and

map those out in the river system. There is also a

system called Sparrow which allows us to look at

nutrient loads in rivers in the United States. In this

case we are looking at nitrogen loads. The red colors

are the highest concentrations of nitrogen. This

system uses an example of the National Hydrography

Dataset, an earlier version of it, and as they

modernize this system they will use the National

Hydrography Dataset for this type of modeling. Some of

the issues that we are concerned about is that we are

trying to keep up with the change in the hydrography

in the US. You can see here the stream, each color of

the stream represents a different 10 year interval of

that stream being mapped. We can see that throughout

time the stream from 1944 to 56 to 72, 81, 92, and

2006, the stream has changed many times and we need to

keep up with that change. Here is an example of the

NHD in blue. When you overlay this on a contemporary

image you can see the stream has changed course since

it was last mapped. We need to keep up with change

like this. So we have different densities, different

scales of the National Hydrography Dataset. This is

what we call the medium resolution NHD. It represents

1:100,000 scale density of streams. We also have a

1:24,000 scale representation of the NHD and many of

our customers have asked for even more detail in the

NHD and we can see this in this example of what we

call the local resolution NHD. One of the things that

is being done is to derive local resolution NHD from

Lidar data. What we have done is we have mapped the

streams from Lidar data in red then overlaid this with

24,000 scale NHD in blue and you can see that the

existing NHD in blue pretty much represents the Lidar

streams to an extent but the red lines that you see

sticking out of the blue lines are an extension of the

network; they are an additional streams that can be

gathered using the Lidar information. Canada and

Mexico are also building dataset such as the National

Hydrography Dataset and the Watershed Boundary

Dataset. This is an example of Canadian data on the

top and US data on the bottom, and for this hydrologic

unit we are combining the data from Canada and the US.

So when you take a look at data over Canada and Mexico

over the border it becomes seamless information and it

allows scientists to study the border regions without

regard to the political boundaries. We are doing the

same thing with Mexico. Here you see Mexican data on

the bottom, US data on the top side of the red line,

combining this together into one seamless hydrologic

unit. So we are adding lots of information to the NHD

to make the NHD more intelligent. The black square you

see there are the dams, the red triangles are stream

gages. Also we are looking at things like water

diversions such as this tunnel that goes under the

Continental Divide connecting the two green dots you

see there. One of the things we are concerned about

too is hydrography over urban areas. So this is

looking at Minneapolis and we can see some hydrography

represented here in the dark and lighter blue colors.

But a lot of the surface hydrography actually flows

underground through culverts and so we can take a look

at the major culverts that drain the water through the

system and add these to the NHD to get a more complete

picture of hydrography over urban areas even though

this hydrography is flowing underground through

culverts. We have the same problem over karst

topography. This is where water is flowing underground

through limestone caves and other types of caves. The

green and blue lines you see are the NHD and WBD

surface water. The red lines that you see there are

underground streams flowing through karst terrain. So

we would like to be able to add these to NHD to get a

better understanding of how the surface flow works.

One of the things that we do is we maintain the

National Hydrography Dataset through a Stewardship

process where we have a number of states who have

joined with the USGS and keep the NHD up to date. We

have 35 states that are in our Stewardship network

right now. The USGS acts as a facilitator for this

process and then the states maintain this data and

keep it up to date. And then other organizations work

through the states such as the U.S. Forest Service,

The Bureau of Land Management work through the states.

Other organizations such as the City of New York would

work through the state of New York. In Arkansas for

example the State Engineers Office or the Department

of Environmental Quality work through the state

Steward to keep the National Hydrography Dataset up to

date. Then we have a process to facilitate this where

we have experts who work in different regions of the

US to help keep the NHD up to date and to answer

questions so you can go to this web map, click on a

state and find out who to contact to maintain the NHD

and keep it up to date. So this is an overview of the

National Hydrography Dataset and the Watershed

Boundary Dataset. One of the things we are also

concerned with is how do we reach our customers and in

this trumpet shaped curve here we have on the top are

expert users and in the middle are knowledgeable users

and at the bottom are more casual users, and one of

the things we want to do with the NHD is make sure we

are addressing our full customer range and not just

providing advanced capabilities but capabilities that

will meet the needs of all users at all levels of

expertise.