GRACE

"The Gravity Recovery and Climate Experiment (GRACE) satellite mission, in operation from March 2002 to June 2017, was the first remote sensing mission to provide temporal variations of Terrestrial Water Storage (TWS).

GRACE consisted of two identical spacecraft that flew about 220 kilometres (137 miles) apart in a polar orbit 500 kilometres (310 miles) above Earth. GRACE mapped Earth's gravity field by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. It provides scientists from all over the world with an efficient and cost-effective way to map Earth's gravity field with unprecedented accuracy. The results from this mission are yielding crucial information about the distribution and flow of mass within Earth and its surroundings.

The gravity variations studied by GRACE include: changes due to surface and deep currents in the ocean; runoff and ground water storage on land masses; exchanges between ice sheets or glaciers and the ocean; and variations of mass within Earth. Another goal of the mission is to create a better profile of Earth's atmosphere. GRACE results are making a huge contribution to the goals of NASA's Science Mission Directorate, Earth Observation System (EOS) and global climate change studies." (NASA 2014)

Sources

NASA. 2014. “GRACE.” Mission Pages. 2014. https://www.nasa.gov/mission_pages/Grace/index.html.
 

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Article

From Jakarta to Nusantara: Land subsidence and other pressing water challenges in a sinking mega city

Jakarta, “the sinking city”, is the current capital city of Indonesia. Located on the Java Sea, this coastal city is home to nearly 30 million people within the greater-Jakarta area. Jakarta has grappled with water management issues for decades, leading to several current day water-related crises. Access to a reliable, potable water supply is extremely limited as there is a significant disparity between those with piped water access and those without. Citizens without piped water access have consequently relied heavily on groundwater and have dug thousands of unregulated wells as a result. This has led to a second water crisis – the chronic overextraction of Jakarta’s underground aquifers. Land subsidence is of the utmost concern as this sinking city is placed at high flood risk from the surrounding ocean. Approximately 40% of Jakarta now lies below sea level as a result and predictive models suggest that the entire city will be underwater by 2050 (Gilmartin, 2019). Compounding these problems, the climate crisis has led to significant sea level rise as glaciers and ice caps continue to melt (Intergovernmental Panel on Climate Change, 2019; Lindsey, 2022). As the city of Jakarta continues to sink and sea levels rise, millions of citizens within Jakarta are at extremely high risk of flooding, particularly during monsoon season. Thousands of residents have already been forced to abandon their homes in search of improved conditions and higher ground (Garschagen et al., 2018).

Space technologies in the detection, monitoring and management of groundwater

Global groundwater supplies

Groundwater accounts for 30% of Earth’s freshwater resources (Shiklomanov 1993) (Figure 1) and is estimated to globally provide 36% of potable water, 42% of irrigation water, and 24% of industrial water – indicating its significant value (Global Environment Facility 2021). Groundwater affords a host of benefits, from providing better protection against drought and microbiological contamination than surface waters, to being generally low cost and accessible to many users.

От Джакарты до Нусантары: проседание грунта и другие насущные проблемы с водой в тонущем мегаполисе

Джакарта, «тонущий город», является нынешней столицей Индонезии. Расположенный на берегу Яванского моря, этот прибрежный город является домом для почти 30 миллионов человек в районе Большой Джакарты. Джакарта десятилетиями боролась с проблемами управления водными ресурсами, что привело к некоторым нынешним кризисам, связанным с водой. Доступ к надежному питьевому водоснабжению крайне ограничен, поскольку существует значительная разница между теми, кто имеет доступ к водопроводной воде, и теми, кто его не имеет. Граждане, не имеющие доступа к водопроводной воде, в значительной степени зависят от грунтовых вод и в результате вырыли тысячи нерегулируемых колодцев. Это привело ко второму водному кризису: постоянному чрезмерному извлечению водоносных горизонтов Джакарты. Проседание грунта вызывает наибольшую обеспокоенность, поскольку этот тонущий город подвергается высокому риску наводнений со стороны окружающего океана. В результате примерно 40 процентов территории Джакарты в настоящее время находится ниже уровня моря, и прогностические модели предполагают, что к 2050 году весь город окажется под водой (Gilmartin, 2019). Эти проблемы усугубляются тем, что климатический кризис привел к значительному повышению уровня моря, поскольку ледники и ледяные шапки продолжают таять (Intergovernmental Panel on Climate Change, 2019; Lindsey, 2022). В связи с тем, что город Джакарта продолжает опускаться, а уровень моря повышается, миллионы жителей Джакарты подвергаются чрезвычайно высокому риску наводнений, особенно в сезон муссонов (рис. 1). Тысячи жителей уже были вынуждены покинуть свои дома в поисках улучшенных условий и возвышенностей (Garschagen et al., 2018).

Interview with Claudia Ruz Vargas, Researcher at IGRAC

Claudia Ruz Vargas is a civil engineer, graduated from the University of Santiago, Chile, with an international master’s degree in Groundwater and Global change. Her master thesis focused on groundwater modelling for recharge and saline intrusion risk assessment under climate change scenarios, in Cape Verde. Claudia has six years of work experience as a project engineer and researcher. She is currently a researcher at the International Groundwater Resources Assessment Centre (IGRAC), where she is involved in projects of high impact on the groundwater sector. In this interview, we talked to her about her career path, and how she has contributed to an improved and more sustainable management of groundwater resources, at a regional and global levels.

Interview with Claudia Ruz Vargas, Researcher at IGRAC

Claudia Ruz Vargas is a civil engineer, graduated from the University of Santiago, Chile, with an international master’s degree in Groundwater and Global change. Her master thesis focused on groundwater modelling for recharge and saline intrusion risk assessment under climate change scenarios, in Cape Verde. Claudia has six years of work experience as a project engineer and researcher. She is currently a researcher at the International Groundwater Resources Assessment Centre (IGRAC), where she is involved in projects of high impact on the groundwater sector. In this interview, we talked to her about her career path, and how she has contributed to an improved and more sustainable management of groundwater resources, at a regional and global levels.

Capacity Building and Training Material

ARSET - Groundwater monitoring using observations from NASA’s Gravity Recovery and Climate Experiment (GRACE) missions

Overview

Groundwater makes up roughly 30% of global freshwater. It also provides drinking water for the world’s population and irrigation for close to one third of global agricultural land. Because of this level of reliance, monitoring groundwater is crucial for water resources and land management. The Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO) missions from NASA and the German Research Centre for Geosciences (GFZ) provide large-scale terrestrial water storage estimation from mid-2000 to present.

Space-based Solution

Addressed challenge(s)

Groundwater resource management using artificial intelligence and remote sensing technologies

Collaborating actors (stakeholders, professionals, young professionals or Indigenous voices)
Suggested solution

Collaborating actors

  • Department of Soil & Water Conservation Engineering, GBPUAT Pantnagar
  • Indian Institute of Technology Delhi (IIT Delhi)
  • Dr. Rajendra Prasad Central Agricultural University, Pusa
  • Central University of Jharkhand, India
  • Assam University, Silchar

 

Remote sensing can significantly aid in groundwater resource management. Further with the integration of Internet of Things (IoT), the information of groundwater storage and change in groundwater level can be shared through mobile technology to end users, policy makers and also to the government.

Here are a few key steps showing how it can be useful:

  1. Mapping and monitoring land use/land cover: Remote sensing helps identify areas of vegetation, agriculture, urbanisation and water bodies, which influence groundwater recharge and extraction.
  2. Identifying potential groundwater zones: Satellite imagery, combined with GIS, can analyse geological, hydrological and geomorphological features to locate promising groundwater zones.
  3. Monitoring groundwater levels and storage: Missions like Gravity Recovery and Climate Experiment (GRACE) measure changes in Earth's gravity field, enabling estimation of groundwater storage changes over time.
  4. Assessing drought and recharge conditions: Remote sensing provides data on precipitation, soil moisture and evapotranspiration, essential for evaluating recharge potential and drought impacts.
  5. Supporting sustainable management: Continuous remote sensing data supports long-term planning, policy-making and sustainable groundwater resource development.
  6. Integration of remote sensing with IoT: IoT modules can be developed for groundwater level; total groundwater storage; drought level etc and can be sent to end users using mobile technology.

Requirements

Data

  • GRACE & GRACE FO satellite data set
  • Central Groundwater Board, India
  • Water Resources Information System (WRIS) India
  • USGS data sets of remote sensing imagery

Software

  • QGIS
  • Visual MODFLOW flex
  • Hydrologic Engineering Center's River Analysis System (HEC-RAS)
  • MATLAB
  • R software
  • ERDAS IMAGINE

Physical

  • Workstation as servers lab for developing IoT for groundwater management

Outline steps to a solution

  • Worked on GRACE satellite data and used it in field condition to study groundwater anomalies of few cities of India (completed).
  • Developed spatio-temporal maps of Standardized Groundwater Index (SGI) (completed).
  • Water quality monitoring of water bodies using remote sensing (in progress).
  • Water spread mapping and its monitoring, of various water bodies using remote sensing and artificial intelligence (research is in progress).
  • Internet of Things (IoT) models which can link groundwater depletion/anomalies information with the end-users (in progress).

Steps to a solution

  1. Study area and data acquisition  
  • Study area has to be selected for groundwater monitoring and management.  
  • The shapefile of the study area has to be downloaded from government websites or can be ordered on request basis. Gridded GRACE products (Level-3) can be used from the Jet propulsion Laboratory (JPL), the National Aeronautics and Space Administration (NASA) to get the monthly water equivalent thickness data.
  1. Development of Standardized Groundwater Index (SGI) for understanding the severity of groundwater anomalies or draught

Standardized Groundwater Index (SGI) is a drought indicator which was developed by Bloomfield and Marchant (2013) to quantify groundwater drought. It is used for estimating groundwater level deficit at any time scale which reflects the extreme drought condition of any location. It is similar to the traditional drought index, Standardized Precipitation Index (SPI) and can be calculated on the same basis like SPI. In SGI, groundwater level data is used for measuring drought condition, instead of precipitation data which is used in SPI. Groundwater time series data obtained from ground observation can be appropriately normalized to evaluating the groundwater drought. SGI values can also be analysed by calculating groundwater deviation from the mean groundwater value (Halder et al., 2020). SGI can be given by following formula

Formula for SGI

where, K is groundwater level of the respective year; M is long term mean groundwater level of 18 years, σ is standard deviation

  1. Gravity Recovery and Climate Experiment satellite for groundwater anomalies study

GRACE was launched by NASA on March 17, 2002. It was a joint mission of NASA and German Aerospace Centre (DLR). The two twin satellites of GRACE are monitored to observe the changes in the Earth's gravity field. GRACE satellite, a first remote sensing satellite which provides an efficient and cost-effective way to map Earth’s gravity field and measure the total groundwater storage changes (TWS) with unprecedented accuracy (Yirdaw et al, 2008). GRACE studies the variation in the gravity which are caused due to effects that include: changes due to deep currents in the ocean; runoff and ground water storage on land mass; exchanges between ice sheets or glaciers and the oceans, and variations of mass within the solid Earth. The distance between the twin satellite as they orbit the Earth help in measuring changes in the Earth's gravity field for each month. From these monthly gravity field, time series of regional mass anomalies can be derived using specially designed averaging function. GRACE mission provides an opportunity to directly measure the total groundwater storage changes and with the help of gravity field data of GRACE drought conditions can also be monitored over a region. GRACE satellite has coarse resolution of 300-400 km and provides data in an interval of 30 days. The distance between the two satellite is about 200 km at a starting altitude of about 500 km. The GRACE gridded TWS products (1˚×1˚) from spherical harmonics are provided by the Centre of Research (CSR) at the University of Texas, the Jet Propulsion Laboratory (JPL) and German Research Centre for Geoscience (GFZ). The gridded products estimate the changes in mass in unit of water equivalent thickness (WET).

  1. Machine learning algorithms to model data from GRACE with observed data

Using machine learning (ML) for modelling GRACE  satellite data alongside observation datasets (e.g., in-situ hydrological measurements, meteorological data) is a powerful approach to extract spatiotemporal patterns, downscale or predict terrestrial water storage (TWS) anomalies. Machine learning algorithms like artificial neural network, random forest, support vector machines etc can be used to model satellite data with observed data.

  1. IoT for groundwater monitoring and sending information to end users

Using IoT for groundwater level monitoring is an effective way to automate the collection, transmission and dissemination of real-time groundwater data to decision-makers, farmers or the public.

Results

Today, no remote sensors can directly monitor groundwater, a combination of surface features anomalies and gravity data obtained by various satellites, allows for optimal groundwater management. Example satellites for monitoring include: GRACE and its Follow-On mission (GRACE-FO) to study groundwater fluctuations, Landsat, Moderate Resolution Imaging Spectroradiometer (MODIS) etc, groundwater management can be done using space technology.

I developed a Standardized Groundwater Index (SGI) for Bihar state of India which proved to be very important to understand the severity of groundwater problems in that region. The spatio-temporal variation of SGI using geographical information systems (see figure 1) was published in the peer reviewed Journal of the Geological Society of India (Kumar and Kumari, 2024).

Groundwater Index for Bihar state in India for different years
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