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[Roaring waterfall, sprinklers]

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[hail bouncing and rainstorm, trickling water]

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[rain pouring down, single splash of water from rock]

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Narrator: We live it every day. 

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It’s in our veins, it’s under our feet, 

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it’s in our meals, it drives our storms.

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It changes the course of history itself. [helicopter sound]

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[movie reel music] It’s that water cycle we remember from elementary school. 

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Movie reel narrator: This is the cycle of water, by which all life survives.

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Narrator: But the picture is so much more varied, 

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so much more vital, than a few arrows can represent.

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Trying to measure that complexity from both Earth and space 

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is an infinite task, but observations from NASA [music builds]

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and many worldwide partners have led to quantum leaps in our understanding.

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In the last 60 years, we’ve seen a revolutionary change,

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from relying principally on ground measurements,

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to satellite observations of rainfall, to worldide measurements

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of rain and snowfall every half hour. From space, 

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we can now monitor soil moisture every few days,

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and detect changes in aquifers deep underground.

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[sounds of rainfall] But we can't see every drop of water, everywhere, all the time.

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And water issues are incredibly localized – 

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as unique as the landscapes the water flows over.

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To fill in the gaps, see the local picture, 

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and project into the future, we use powerful computer models. 

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These models pull in an incredible amount of data

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like those daily scans of precipitation, but also rely on our understanding of the planet 

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from all those decades of ground-based hydrology and soil research.

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In every corner of the Earth, these models help people understand

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critical issues like water availability for irrigation

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drought severity, flood risk, and the likelihood 

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of crop failures and famine.

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One of the trickiest parts is understanding how we impact the water cycle, 

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with the multitudes of water use decisions we make every day, that lead to things 

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like diverting surface water, pumping from aquifers, 

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and changing our planet’s climate.

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In addition to collecting data and running sophisticated computer models, NASA funds a robust 

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set of projects to help water managers across the United States address 

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their specific water issues, from crop forecasts in the Bread Basket, 

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to snow pack in the mountains,  [crunching snow]

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to flood risk from nearby rivers. 

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NASA's water-observing fleet will expand in 2021 with a satellite that will collect data on 

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surface water height and slope, which will enable estimation of river flows. 

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With these observations we will be able to observe 

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all the major parts of the water cycle from space: 

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precipitation, evaporation, runoff, and water storage.

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Our view of Earth’s water cycle will never be perfect, 

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never be complete. But each advancement we make 

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holds the promise of helping us prepare for the future,

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avoid conflicts and mitigate disaster, feed the world, 

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and make good decisions about our most precious resource.

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[music fades]