Periodic Reporting for period 2 - G3P (Global Gravity-based Groundwater Product)
Période du rapport: 2021-01-01 au 2022-12-31
Groundwater is one of the most important freshwater resources for mankind and for ecosystems. Assessing groundwater resources and developing sustainable water management plans based on this resource is a major field of activity for science, water authorities and consultancies worldwide. Due to its fundamental role in the Earth’s water and energy cycles, groundwater has been declared as an Essential Climate Variable (ECV) by GCOS, the Global Climate Observing System. However, within Copernicus there is no service yet to deliver data on this fundamental resource, nor is there any other data source worldwide that operationally provides information on changing groundwater resources in a consistent way, observation-based, and with global coverage.
This gap is filled shall be filled with G3P - the Global Gravity-based Groundwater Product. G3P (1) capitalizes from the unique capability of GRACE and GRACE-FO satellite gravimetry as the only remote sensing technology to monitor subsurface mass variations and thus groundwater storage change for large areas with global coverage, (2) incorporates and advances a wealth of products on storage compartments of the water cycle that are already part of the Copernicus portfolio and will be used for separating out the groundwater storage variations from the gravity-based total terrestrial water storage, and (3) develops a prototype cross-cutting extension of the Copernicus portfolio of an operational global groundwater service.
This gap is filled shall be filled with G3P - the Global Gravity-based Groundwater Product. G3P (1) capitalizes from the unique capability of GRACE and GRACE-FO satellite gravimetry as the only remote sensing technology to monitor subsurface mass variations and thus groundwater storage change for large areas with global coverage, (2) incorporates and advances a wealth of products on storage compartments of the water cycle that are already part of the Copernicus portfolio and will be used for separating out the groundwater storage variations from the gravity-based total terrestrial water storage, and (3) develops a prototype cross-cutting extension of the Copernicus portfolio of an operational global groundwater service.
Major activities in Work Package 1 - Management were the scientific steering of the consortium, the reporting and the organization of meetings, especially of the General Assemblies (GA). Due to Covid-19 the latter were mainly held as online meetings. Further activities included composing the Consortium’s management guidelines, the Data Management Plan (DMP), setting up of a process to establish a quality assessment system for G3P product development using the CORE-CLIMAX System Maturity Matrix (SMM, EUMETSAT (2014)), and managing the efficient preparation of any deliverable.
In Work Package 2 – satellite gravity data processing the handling of low-level (L1A) data of the GRACE-FO mission was successfully implemented. With the main focus on retrieving GRACE-D accelerometer data, we present a novel approach to recover the GRACE-D ACT1B data by incorporating non-gravitational force models and analyze its impact on monthly gravity field solutions. Level-1B to Level-2 Processing has been successfully performed for GRACE-FO at all G3P analysis centers (ACs) and are operationally computed at all ACs. The combination of the Level-2 products of the G3P ACs in the frame of the Combination Service of Time-variable Gravity Fields (COST-G) is on an operational level. Internal validation procedures have been established. User-friendly grids of the combined solutions have been produced and are available from GFZ's GravIS. The mass anomaly products are generated for a) terrestrial water storage over non-glaciated regions, b) ocean bottom pressure variations in the oceans and c) ice-mass changes in Antarctica and Greenland.
Work carried out in Work Package 3 – Quantification of storage compartments focused on adapting existing and developing additional operational Copernicus service products quantifying water storage variations in individual terrestrial water cycle compartments. All water storage compartments (WSCs) (glaciers, snow, soil moisture, surface water) were successfully brought to a status to be implemented in the G3P subtraction approach.
Work Package 4 – Groundwater product development, evaluation and service preparation (WP4) included (1) the scientific development of the subtraction process that is necessary to calculate groundwater from terrestrial water storage, (2) the evaluation and validation of the resulting data set of groundwater storage variations with in-situ data, and (3) creating the technical framework for the prototype G3P service. Activities in (1) included the test of different filters to make WP3 data compatible with GRACE observations, the evaluation of spatial correlation lengths of the different water storage data sets to find a best fitting filter width, and designing and coding the subtraction procedure for the groundwater product. For (2), a set of suitable aquifers for the evaluation of the groundwater product was selected and characterized, in-situ data was retrieved, and an extensive assessment of the groundwater product was carried out. In (3), the G3P processing chain has been set up as a basis for future operational implementation of G3P in the Copernicus Climate Change Service (C3S). The maturity of the components has been assessed and next steps towards an operational service have been defined.
Activities within Work Package 5 included G3P dissemination via publications and various other channels, exploitation and provision of a demonstrator use case by integrating G3P into a drought early warning system, the development and operation of the G3P website, and providing open access and visualizazion of G3P data via the online platforms GGMN and GravIS.
In Work Package 2 – satellite gravity data processing the handling of low-level (L1A) data of the GRACE-FO mission was successfully implemented. With the main focus on retrieving GRACE-D accelerometer data, we present a novel approach to recover the GRACE-D ACT1B data by incorporating non-gravitational force models and analyze its impact on monthly gravity field solutions. Level-1B to Level-2 Processing has been successfully performed for GRACE-FO at all G3P analysis centers (ACs) and are operationally computed at all ACs. The combination of the Level-2 products of the G3P ACs in the frame of the Combination Service of Time-variable Gravity Fields (COST-G) is on an operational level. Internal validation procedures have been established. User-friendly grids of the combined solutions have been produced and are available from GFZ's GravIS. The mass anomaly products are generated for a) terrestrial water storage over non-glaciated regions, b) ocean bottom pressure variations in the oceans and c) ice-mass changes in Antarctica and Greenland.
Work carried out in Work Package 3 – Quantification of storage compartments focused on adapting existing and developing additional operational Copernicus service products quantifying water storage variations in individual terrestrial water cycle compartments. All water storage compartments (WSCs) (glaciers, snow, soil moisture, surface water) were successfully brought to a status to be implemented in the G3P subtraction approach.
Work Package 4 – Groundwater product development, evaluation and service preparation (WP4) included (1) the scientific development of the subtraction process that is necessary to calculate groundwater from terrestrial water storage, (2) the evaluation and validation of the resulting data set of groundwater storage variations with in-situ data, and (3) creating the technical framework for the prototype G3P service. Activities in (1) included the test of different filters to make WP3 data compatible with GRACE observations, the evaluation of spatial correlation lengths of the different water storage data sets to find a best fitting filter width, and designing and coding the subtraction procedure for the groundwater product. For (2), a set of suitable aquifers for the evaluation of the groundwater product was selected and characterized, in-situ data was retrieved, and an extensive assessment of the groundwater product was carried out. In (3), the G3P processing chain has been set up as a basis for future operational implementation of G3P in the Copernicus Climate Change Service (C3S). The maturity of the components has been assessed and next steps towards an operational service have been defined.
Activities within Work Package 5 included G3P dissemination via publications and various other channels, exploitation and provision of a demonstrator use case by integrating G3P into a drought early warning system, the development and operation of the G3P website, and providing open access and visualizazion of G3P data via the online platforms GGMN and GravIS.
The prototype of a Global Gravity-based Groundwater Product (G3P) developed within the three years runtime of this European Union Project is a novel global data set of groundwater storage variations. It is unique in its approach of combining in a globally consistent way data sets of different water storage variations that are as far as possible observation-based, including (total) terrestrial water storage, snow water equivalent, root-zone soil moisture, glacier mass, and surface water storage to derive groundwater storage variations by a subtraction approach. In doing so, G3P is an unprecedented cross-cutting combination approach of the existing Copernicus portfolio, using further developed data products form different Copernicus services in combination with the so far externally running data service of IAG (International Association of Geodesy) of terrestrial water storage (TWS) variations based on satellite gravimetry. The combination approach developed here thus opens the doors for incorporating two new Essential Climate Variable (ECV) data products into Copernicus, i.e. for the ECV groundwater and for the recently defined new ECV Terrestrial Water Storage. Thus, G3P enables Copernicus to perfectly explore its given portfolio towards a new application that contributes to Copernicus staying at the forefront of climate services worldwide.
The consulting and engineering industry can largely benefit from the new groundwater product by using it in groundwater management and auditing, and restoration projects, which are increasingly required because of the aforementioned global groundwater crisis and climate change. This is a global emerging market, which, however, lacks an appropriate database to offer appropriate industry solutions for the manifold problems of groundwater use and management, including the management of hydrological extremes, in particular droughts. The proposed product can lay the foundation for large-scale, i.e. basin and aquifer wide, partly trans-boundary, water resource management plans including groundwater observation, sustainable utilization and restauration.
The consulting and engineering industry can largely benefit from the new groundwater product by using it in groundwater management and auditing, and restoration projects, which are increasingly required because of the aforementioned global groundwater crisis and climate change. This is a global emerging market, which, however, lacks an appropriate database to offer appropriate industry solutions for the manifold problems of groundwater use and management, including the management of hydrological extremes, in particular droughts. The proposed product can lay the foundation for large-scale, i.e. basin and aquifer wide, partly trans-boundary, water resource management plans including groundwater observation, sustainable utilization and restauration.