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Earth - our home. 

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A rocky planet whose surface over 70% water - 

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Of that 70%, only 3% is freshwater.

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It may seem like a small number,

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but we rely on that 3% every
day for electricity,

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Farming, transportation -

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life as we know it.

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As our planet's temperatures continue
to rise, so does the frequency

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of disruptions to our aquatic ecosystems -

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algal blooms, glacial melt, mass die offs,

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pollution, drought.

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Managing and safeguarding
our water resources

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has become more important than ever.

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Thankfully, scientists have a variety
of ground-based methods at their disposal,

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such as measuring water clarity
or tracking pH levels.

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For example, assessing
how acidic or alkaline

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a body of water is can be a
good indicator of its quality.

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A sudden change in pH could point
to increased pollution or contamination.

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Data gathered through
ground-based methods

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is vital to the effort
to monitor water quality.

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But, for decades, one tool for
assessing the health of what lies

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beneath the water's surface 

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has kept watch from hundreds of miles above - 

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the Landsat program.

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The launch of Landsat 1 in 1972

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represented the advent of a revolutionary
new era of Earth observation.

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Landsat 1’s Multispectral Scanner
collected data across four spectral bands.

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Data that researchers were quick
to put to good use 

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studying vegetation cover, land use,
and you guessed it, water quality.

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In 1976, researchers from the
Environmental Protection Agency

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harnessed Landsat 1 data to analyze
chlorophyl, phosphorus, and nitrogen levels

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- important water quality indicators -  

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of 100 lakes across the United States.

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Decades later, upgrades

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to instruments across each
successive Landsat satellite

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have underscored what a powerful tool
remote sensing can be

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for global water quality monitoring

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Using satellites to keep tabs on water quality

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not only ensures the health of aquatic
 ecosystems, but can also aid

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in protecting the public health
and safety of our communities.

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Every year, bodies of water worldwide
experience algal blooms like this one

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due to both natural and human driven factors.

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Warm temperatures and excess agricultural runoff

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can create the perfect environment for algae,

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including some that are potentially
harmful to humans and wildlife alike.

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Using satellite data,

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environmental agencies can not only
detect blooms as they pop up,

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but can also issue an early
warning to the public 

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about the potential development
of these toxic algae.

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In 2017, the Utah Department of Environmental
Quality used data collected by satellites

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including Landsat, to detect an
algae bloom in Utah Lake 

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much earlier than ground observations
alone would have enabled.

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This early detection gave health
and environmental officials

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a head start in posting warnings
about the harmful algae bloom,

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preventing potential exposure
by local fishers, boaters

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and swimmers, and saving thousands of
dollars in insurance costs.

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This is the Chesapeake Bay,

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the largest estuary in the United States

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and no stranger to algal blooms.

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When it comes to the health of the bay,

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Landsat’s orbital perspective in time
provides scientists

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with a novel means of tracking
trends in watershed-wide land use.

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Agricultural runoff is a major contributor
to pollution in the Bay

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As nitrogen, phosphorus and sediment
from nearby farms

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make their way into the Chesapeake,

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depleting oxygen levels and blocking
sunlight from reaching underwater grasses.

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But the expansion of nearby urban areas
like Baltimore and Washington

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are also major contributors
of aquatic pollutants.

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As urban areas expand, so do the
amount of impervious surfaces

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like pavement and asphalt,
leading to increased stormwater runoff.

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This map of Baltimore created
using Landsat data shows the dramatic

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expansion of the city's impervious
surfaces over the course of 26 years.

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Pollutants that previously would
have been absorbed

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by the soil or vegetation
now flow into the sewer system

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and in this case, eventually
into the Chesapeake Bay.

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Data collected by satellites like Landsat
allow environmental officials to target

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areas for conservation and restoration
and to more efficiently manage resources.

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In this case, having an understanding
of urban expansion around the bay

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can aid in the development

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of unique infrastructure
that can counter stormwater runoff,

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such as bioretention systems
that filter pollutants

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and slow the flow of stormwater
into the bay.

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Assessing the quality of water bodies
like the Chesapeake is just one aspect

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of managing our water resources, fisheries
and aquaculture developments.

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a task that Landsat has played
an important hand in for years.

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Each year, over 40% of groundwater
withdrawals in the U.S.

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are used for irrigation,
watering crops across the country.

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As climate change and drought put pressure
on the nation's water

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supply, particularly in areas
across the western U.S.

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water conservationists
can turn to Landsat for data critical

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to sustainably manage water resources.

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The 30-meter resolution afforded by instruments
aboard Landsat satellites allow scientists

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to track irrigation trends over
long periods of time in striking detail.

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This map showing the irrigation
frequency of fields

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in the Republican River basin
over the course of 17 years was created

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using data from Landsats 5, 7, and 8.

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Zooming into a region
along the Colorado-Nebraska border,

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it's easy to see the amount of variability
in irrigation frequency,

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with darker colors indicating areas
watered nearly every year

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By analyzing economic data,
along with Landsat data,

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researchers believe that part of this
irrigation variability can be attributed

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to crop prices and rainfall.

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When crop prices were high,

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farmers tended to expand irrigation
to maximize profits while irrigating more

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intensely on a smaller number of fields
during times of drought.

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Yearly maps provide a clear insight
into irrigation effects and offer precise

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details on annual changes,

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guiding better farming water use decisions.

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Landslides, past and present,
have played a major role

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in providing critical data
about our planet's water resources,

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a legacy that will continue with
the next generation of Landsat satellites.

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In early 2023, NASA and
the U.S. Geological Survey

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announced the development of Landsat Next,

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a constellation of three satellites
that will help researchers and users

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to better identify sources of water pollution
and detect and quantify algal blooms,

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enabling effective management of
aquatic food industry and water quality.

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The mission's trio of satellites will have
improved spatial and temporal resolution,

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collecting a complete image of
the earth every six days,

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allowing users to see features
that were too small or happened

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too quickly for previous Landsat
satellites to detect.

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Landsat Next's advanced remote sensing
capabilities could prove useful

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in a future where climate change
and population growth

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will continue to put pressure
on our planet's water resources

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From what we eat to what we drink.

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Water is fundamental to life on Earth.

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Thankfully, Landsat view from high above
can be counted on to provide

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accurate and timely data that will help
preserve the precious waters below.