Remember back in school when you studied how the water cycle of Earth works. The water in the oceans, lakes, rivers and streams evaporates into the air.
Clouds form and the water returns to Earth as rain or snow. The concept is quite simple, but it has become increasingly complicated. The warmer temperatures are melting glaciers, the ice shelves, and even the North Pole itself. That melting adds to the water levels in the oceans which in turn erode, and in many cases, overtake the shoreline. I remember being told in school that there is a finite amount of water available and it gets distributed unevenly throughout the planet.
Back in the “old days” many people believed in dowsing for water. They used a Y-shaped stick called a divining rod to magically find underground water sources. There were flim-flam artists who preyed on people who were desperate to find water on their property.
In more modern times we have coastal stations that monitor the shoreline and some ocean water levels. The United States Geological Survey (USGS) has more then 10,000 stream gauges all over the US.
There are also networks of sensors that monitor rainfall, soil moisture and snow depth. The most important modern advancement has been weather satellites that orbit Earth. Until recently the satellites have had a more limited ability to accurately monitor the bodies of water to determine the depth and other characteristics of the salt water oceans and fresh water lakes, rivers and streams.
Back in 2002 satellite mission called Gravity Recovery And Climate Experiment (GRACE) launched two satellites called Tom and Jerry which followed each other closely in orbit. They used measurements of the distance between them in space to measure changes in Earth’s gravity. It seems that many of these variations in gravity are caused by the movement of water. GRACE has the ability to measure total water storage across surface, groundwater and in the atmosphere. That program wrapped up in 2017, but two new GRACE satellites were launched in 2018. A team of scientists, including Jay Famiglietti, from the University of Saskatchewan, Canada were in charge of the project.
An article in Physics.org brought this subject to my attention. The February 13, 2019 article titled “Satellites reveal a new view of Earth’s water from Space” was written by Hydrologist Tamlin Pavelsky from The Conversation. The article quotes Famiglietti “[GRACE] paints a compelling picture, because it allows us to see the human fingerprint on water availability, and the climate change impact on water availability.” In Palvesky’s interview with Famiglietti it was explained that “some of his work with GRACE has shown deep losses of groundwater in northern India, the Middle East, and other places that could be vulnerable to to future water shortages.”
There are other satellites investigating measurement of the water cycle, but they apparently have some limitations. IceSAT measured the changing shape of glaciers and Ice sheets , but technical problems cut its useful life from 2003 concluding in 2009. The Tropical Rainfall Measurement Mission (TRMM) worked with low latitude precipitation, but did not work well for snow or in areas with strong thunderstorms. Passive microwave sensors have been in satellites for quite some time, but in their estimation of soil moisture they provided date only at “relatively coarse scales.”
The Global Precipitation Mission, a constellation of satellites beginning in 2014, “substantially improved on (TRMM) mentioned above. IceSAT-2 that launched in 2018 is outfitted with much better lasers than it’s predecessor IceSAT.
Quoting Pavelsky “I am part of an international team that that will launch the first project dedicated to measuring Earth’s most readily accessible water resources: rivers and lakes. The Surface Water and Ocean Topography (SWOT) mission is an active sensor that, starting in 2021, will send radar pulses down to Earth and measure how long they take to return to the satellite. Through finely tuned algorithms, SWOT will measure changes in the amount of water stored in millions of lakes and reservoirs around the world and estimate, from space, the amount of water flowing through most of the world’s major rivers.”
In the future what is needed is integrate the past and present data with computer simulations of Earth’s water cycle. The hope is to follow the trends of where water flows to and from and to monitor how much water we may be losing for various reasons and where we are gaining water, such as the oceans from the melting ice shelves.
Let me know what you would like me to talk about or explain. You can email me at: [email protected].