Below the Surface: Data and Groundwater
By: Chase Walz
Tags: Data, Drought, Water, Earth Observation, NASA

When the term “renewable resource” comes to mind, many think of wind, solar power, or even geothermal vents. However, one of the most important renewable resource our communities and all of life relies on is, in fact, groundwater. While these stores of water deep beneath the surface, existing in soil pore spaces and rock formation fractures, are very much “out of sight, out of mind”, groundwater physically supports our cities, quenches the thirst of our crops, and plays a vital role in Earth’s ecosystems. Unfortunately, many regions deplete this invaluable resource at rates in which it cannot be replenished — perhaps even to the point of crisis. Over-pumping of groundwater has been sinking cities, causing water contamination, and drying up wells worldwide.

Fortunately, there exists a way in which we can essentially see below ground, and monitor groundwater changes across borders. NASA’s GRACE-FO twin satellites provide the first opportunity to directly measure groundwater changes from space. By observing changes in the Earth’s gravity field, scientists can estimate changes in the amount of water stored in a region through their accompanying gravitational changes. Launched in March 2002, GRACE provides 10+ year-long data record for scientific analysis. This record, combined with data on changes in snow and surface soil moisture, can be used to calculate detailed changes in groundwater volume over a given period of time.

GRACE: Anomaly Liquid Water Equivalent Thickness (cm) for July 2011. Source: Climate Data Guide; D.Shea

As Planet OS continues to deliver streamlined access to high-quality weather, climate, and environmental data, we are excited to say that we offer this groundbreaking GRACE Tellus Dataset within our Datahub.

Planet OS Visualization: Monthly Changes in CA Groundwater Levels

GRACE Tellus provides user-friendly Level-3 data grids of monthly surface mass changes, with most geophysical corrections applied, to analyze changes in the mass of the Earth’s hydrologic, cryospheric, and oceanographic components. Through the application of GRACE Level-2 data, with additional post-processing or potential ancillary data, one is able to generate gridded, location-specific products (monthly and time-averaged) with the most up-to-date corrections. With its capabilities to visualize parts of the Earth unseen, this dataset has revolutionized investigations regarding water reservoirs over land, ice, and oceans, as well as earthquakes and crustal deformations. The applications of this data can span from informing decisions on land-use and real estate development to answering urgent questions in agriculture, regional water production, and much more.

Applying GRACE Tellus Worldwide

Using the Planet OS Datahub and the GRACE Tellus dataset, our Data Integration Engineer, Eneli Toodu created the below graphs that show the variations in groundwater levels in three different cities: Tallinn, Estonia; San Francisco, CA; and Nagpur, India.

Each of these graphs shows changes in “Water Layer Equivalent” aka changes in the mass of the thin layer of water near the Earth’s surface. On the y-axis, we see this measurement in centimeters with the accompanying years from 2002–2017 on the x-axis. Additionally, each city has its own specific regional variables and reasons for the rising and falling of the water layer equivalent.

In Tallinn, Estonia, the significant downward spike in 2002 could be connected to the synergistic relationship between high temperatures, a cyanobacterial bloom, and a significant fish die off. Whereas in San Francisco, California, the typical seasonal spikes with a greater overall decrease from 2013–2016 could be attributed to the drought that has affected the state for the past several years. In Nagpur, India on the other hand, we see typical variations due to changes in season and water demand for agricultural production.

With the GRACE Tellus dataset on Planet OS, not only are we able to create monthly spatial visualizations and linear graphs, but we can observe long-term trends across an entire country. Pictured below, Data Integration and QA engineer Andres Luhamaa created an incredible visualization showing groundwater trends from 2002–2017 across the United States. This revelatory map illustrates a clear (and potentially concerning) decrease in groundwater supplies in the Southern United States for over the past decade.

Each of these visuals tells an incredible story surrounding drought, regional water consumption, and changes in climate. As the GRACE mission took a hiatus at the end of 2017, it leaves a legacy of invaluable data and information. We are eagerly looking forward to publishing the data of the newly relaunched GRACE-FO satellite as soon as it becomes available.

The information from missions like GRACE only scratches the surface of a plethora of potential investigations and research questions regarding satellite obtained data and understanding the availability of integral resources like groundwater. We hope that with this data, users and industries can drive questions like these and advance our understanding of the climate both above and below us.