WEBVTT

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perhaps you've seen maps like these on
the news

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when drought is being reported and
wondered what the different colors

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actually mean

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their categories of drought that are set
by the US Drought Monitor

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these maps have been produced every week
since 1999

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striving to accurately depict drought
severity over the entire country

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in this animation we will break down the
categories

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which includes $50,000 representing
drought watch

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in ranges from d1 to be four with t4

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being the most severe at first look

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drought seems simple enough less water
than we need are accustomed to at a

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particular place and time here

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but as we dig a little deeper it gets
more complicated

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the severity of drought is based on
factors such as

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precipitation soil moisture streamflow

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groundwater and reservoir levels
on-the-ground reports

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agricultural hell temperature water
demand

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and specific geography in some regions

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snowpack becomes a critical factor not
only to the surrounding area

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but other downstream regions as well all
elements need to be considered

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informing the drought classification

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briefly let's look at the different
classes and what they mean

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d0 indicates abnormally dry conditions

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you might expect to see the slowing of
plant growth if you're heading

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into a time drought or fields not quite
recovered if you're coming

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out more extreme conditions

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the one would indicate moderate drought
conditions you may notice lower strain

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Lake and well levels and perhaps some
damage to crops there maybe request

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curb water usage from local authorities

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D two levels indicate severe drought now
those requests to curb water

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would likely move into actual water
restrictions you could expect water

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shortages with a good chance damage
crops and pastures

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the three levels would be considered
extreme drought

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water shortages the restrictions would
be widespread in major crop and pasture

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losses would be in it

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d4 its classified as exceptional drought

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at this point you can expect depleting
reservoirs and aquifers

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water shortages what time to emergency
levels you can expect lower and the

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streams and lakes

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affecting not only agriculture but fish
and wildlife as well

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now that we haven't overview of the
categories let's add some statistics to

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further our understanding

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as you see each category has a
percentile range

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associated with it

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for example d1 drought conditions is in
the 11th to 20th percentile

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looking at it another way if we look at
a hundred years have precipitation data

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and lined up the values order from
lowest to highest

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he would then need to see a value that
fall somewhere between the 11th

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and 20th on the list and order for it to
be considered d1

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43 drought conditions or 3rd to 5th
percentile

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the value would need to fall between the
third and fifth lowest

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on record we can describe each category
this way

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by how often we would expect to see
these conditions one out of every three

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years for d0

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all the way to one out of every fifty
years for d4

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however just because a hundred year
drought is expected once in a hundred

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years

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doesn't mean you'll get that drought
every 100 years like clockwork

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it's possible to have Q hundred-year
droughts in a very short time span

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or not the C-one for over 200 years

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let's look at this example a hundred and
twenty years annual precipitation values

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from western Colorado

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as you can see p4 conditions only
occurred two to three times

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over this hundred and twenty year period
but to have them happen within about 25

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years of each other

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if droughts were to become more frequent
and more severe

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those observations would be added to the
climate record which would then change

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what we may expect

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the severity of drought can increase
over time as factors contributing to

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drought compound

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that's why the statistics are valuable
they let us know what to expect

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working at least show us how often these
events may occur

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those forecast up developing drought not
yet been perfected

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accurate depiction of current conditions
and/or trends

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along with a keen awareness and local
climate conditions can serve as an

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effective drought early warning system

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for resource managers and decision
makers

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here's something worth considering
different classes of drought mean

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different things

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in different places and the effects can
be drastically different as well

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id3 extreme drought in the nevada desert
looks very different from a d3 extreme

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drought in the middle of Kansas

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affecting tourism in one place while
agricultural and the others for instance

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it's also important to point out that
individual factors may vary greatly

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throughout our region

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which makes assigning the drought
category challenging process take upper

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Colorado River Basin as an example

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it may show snowpack at D three levels
streams ad0

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and the reservoirs and aquifers may not
be within drought range at all

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elevation because a huge disparity in
Leicester such as high snowpack in upper

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mountains

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but very dry valleys

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and in more variables such as natural
forests grasslands and human managed

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landscape

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all responding to dry out quite
differently then you start to see why

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such a balanced and integrated approach

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if needed when establishing drought
categories this is a concept called

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a convergence a evidence approach

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these maps are as detailed as reasonably
possible down to about the single county

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level

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the more quality on-the-ground reports
we receive from you

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the better the resolution of these maps
get and as you see

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the quality of these maps have been
improving over time however

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we can't yet fully depict the remarkable
local variability of precipitation

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especially from localized thunderstorms
in the end

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these quantitative values must be judged
by experts and locals in the area

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to provide a classification based on a
convergence of evidence

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taking an additional considerations such
as the time of year

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overall climbing up the area that's why
each week

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all of the information is gathered
discussed an assist

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to get in overall picture but any one
region on what drought category

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you maybe improve