Project that measures water loss with satellite arrives in the country – 03/17/2024 – Environment

An ambitious project to monitor water resources – for agriculture and other purposes – will begin this year in Brazil.

OpenET-Brazil is an aspect of the original OpenET project, conducted in the USA and the result of a public-private partnership between several American agencies and research institutions, including NASA, the Department of Agriculture, the USGS (US Geological Survey) , California State University and the University of Nebraska-Lincoln, among others.

The only institution from outside the USA to participate in the project is UFRGS (Federal University of Rio Grande do Sul).

The objective of the initiative, launched on American soil in 2021, was to develop an effective method for measuring the exchange of water from the surface to the Earth’s atmosphere over vast regions, through the use of remote sensing data – mainly satellite images.

It is not easy to make this estimate accurately, due to the complexity involved in the system. It needs to take into account not only the physical effects, in which water deposited on the surface evaporates and rises as vapor into the atmosphere, but also the biological effects, with the constant transpiration of the plants that cover much of the Earth’s soil.

Hence the use of the expression “evapotranspiration” (which corresponds to the acronym ET in the name of the project) to encompass all the processes that need to be covered and measured.

“OpenET emerged in the USA especially due to the reduced water availability for irrigation of large agricultural areas, in addition to a scenario of climate change, possibly with lower water availability and greater occurrence of droughts”, says Anderson Ruhoff, researcher at the Institute of Hydraulic Research from UFRGS and leader of Brazilian participation in the initiative.

“The project was created to monitor and manage water use in agriculture, especially irrigated.”

MEASUREMENT IN STEPS

It is not easy to estimate how much water leaves the soil based on satellite images, which do not provide this information directly. The researchers had to develop a methodology to transform the raw information that comes from remote sensing into evapotranspiration estimates.

“OpenET uses mathematical models that simulate the physical processes that occur between the surface and the atmosphere, including, for example, the incidence of solar radiation, atmospheric temperature, air heating processes and water evaporation and plant transpiration,” explains Ruhoff.

“In general, these physically based mathematical models are fed by data captured by satellites, in great spatial detail – which allows the detection of agricultural crops, forest areas and deforested areas. Meteorological data are also used which, combined with data of satellites, allow us to carry out all these simulations of surface and atmosphere interaction.”

These simulations are permeated with uncertainties, which makes the challenge even greater. To mitigate them, the project follows a multi-model methodology, that is, several different models (six in total) to process data from the same region. It is something that requires a lot of computational processing, and this is where the resources provided by one of the project’s business partners, the IT giant Google, come into play.

The process allows the results of all models to be combined as a way of reducing uncertainties, producing values ​​that are closer to reality.

And how do you know that the system really works? An important milestone in this direction was a new study published by the group in January in the British journal Nature Water.

He contrasted, through complex analyses, the results collected by OpenET with local measurements made by stations in 152 different locations throughout the United States. The result?

“They demonstrate that estimates based on remote sensing data are very close to measured data, which gives the project the robustness and accuracy necessary to give credibility and confidence to the project”, says Ruhoff.

With demonstration comes practical applications. Thanks to the project, it is now possible to quantify exactly how much water is being used in agricultural areas in the western half of the US.

“This information can be used by regulatory agencies to manage the scarce resource. Likewise, producers can use this information to correlate with the agricultural productivity of their crops and maximize the use of water in irrigation, in order to produce more with less amount of water.”

This is a very important advance, considering that local measurements of evapotranspiration are extremely expensive and practically unfeasible for application over large areas.

With the use of satellite data (the main source is images from the American Landsat series), it is possible to provide coverage on a global scale. “The computational cost is still high, which is why partnerships with private institutions, such as Google, are essential to obtain evapotranspiration data over large areas”, says Ruhoff.

IMPROVEMENTS AND EXPANSION TO BRAZIL

The researchers continue working to further improve the accuracy of the estimates, either by including additional remote sensing data collected by other satellites, or by improving models of the physical processes involved.

Furthermore, the researchers decided to take a leap and bring the project outside the USA. Brazil, due to the participation of the UFRGS group, became the natural candidate for expansion.

“It’s a great moment for the country, as we will have unprecedented information for water resources management,” says Ruhoff.

The Brazilian version of the initiative, OpenET-Brasil, should begin in the coming months, expected to last five years, with the first data appearing in two. It will be financed by ANA (National Water and Basic Sanitation Agency) and will be supported by OpenET, its partner institutions, EDF (Environmental Defense Fund) and Google.

For Ruhoff, applications in Brazil can be different and more varied, going beyond the monitoring of irrigated agricultural areas and focusing on problems such as evaporation from reservoirs, which will improve resource management and water availability for the production of electrical energy, and impacts of deforestation in the distribution of water throughout the country.

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MEASURING THE WATER THAT EVAPORATES

OpenET project aims to use remote sensing to estimate how much water evaporates from each place on the planet

WHO DOES IT? The project, started in the USA, is a partnership between several American agencies and research institutions, with UFRGS (Federal University of Rio Grande do Sul)

HOW IT WORKS?

1. Satellites orbiting the Earth collect images and data that reveal surface coverage (forests, plantations, deforested areas, etc.)
2. Additional data is collected on the ground with meteorological stations, such as humidity, wind, temperature and pressure, among other parameters
3. From this raw data, the project runs computer simulations with mathematical modeling of the physical processes that occur between the surface and the atmosphere.
4. With six different models, OpenET uses the computational framework provided by big tech Google to more accurately estimate the total amount of evapotranspiration (water evaporation and plant transpiration)
5. The results produced by the combination of models are compared with data observed in the field, confirming their accuracy

MAIN APPLICATIONS FOR BRAZIL

• Expansion of irrigated agriculture by monitoring water use
• Monitoring evaporation from reservoirs to improve water management
• Measuring the impacts of deforestation on water availability