Periodic Reporting for period 2 - GEOWAT (A Global Assessment of the Limits of Groundwater Use)
Berichtszeitraum: 2023-03-01 bis 2024-08-31
Population growth and economic development have dramatically increased the demand for food and water. The resulting expansion of agriculture into areas with limited precipitation and surface water has greatly increased the reliance on groundwater irrigation. Further, urban groundwater use has risen exponentially to meet the ever-increasing population growth of mega-cities. These trends have resulted in a dramatic rise in groundwater pumping and associated high rates of aquifer depletion around the globe. The depletion of our world’s aquifers is unsustainable and will eventually impact the food security of future generations. Also, groundwater depletion results in severe environmental impacts such as land subsidence, groundwater salinisation, and damage to groundwater-dependent ecosystems. Despite decades of research on groundwater overuse, knowledge on attainable groundwater reserves and the critical time horizons of their depletion is completely lacking. In GEOWAT, I propose to take the giant leap to extractable volumes and depletion horizons by answering the obvious question that has been avoided thus far:
How much groundwater is there and how long will it last?
To this end, GEOWAT will build the first high-resolution global groundwater model supported with a 3D-mapping of the world’s aquifers. We will use these unique modelling tools, in combination with dedicated case studies, to assess, for the first time, the global volume of physically and economically extractable fresh groundwater, and determine the time to physical and economic depletion under future pumping. We will also provide the first global assessment of the effects of groundwater pumping on groundwater-dependent ecosystems and explore pathways to sustainable groundwater use. As such, GEOWAT will provide critically-needed new knowledge to address one of most pressing challenges that mankind will face: how to sustainably manage the freshwater resources needed to survive on this planet?
The key objectives of GEOWAT are:
1. Determine the physical limits of groundwater use by estimating the volume of total and fresh groundwater, estimating how much of that volume is physically extractable, and projecting the time to physical depletion of groundwater reserves under future climate and socioeconomic scenarios.
2. Determine the economic limits of groundwater use by estimating the maximum depth at which groundwater withdrawal is still profitable under current land use and future scenarios, and by finding withdrawal trajectories that are economically sustainable over time.
3. Determine the ecological limits of groundwater use by estimating how groundwater withdrawal affects groundwater-dependent ecosystems globally and valuating resulting ecosystem deterioration economically.
How much groundwater is there and how long will it last?
To this end, GEOWAT will build the first high-resolution global groundwater model supported with a 3D-mapping of the world’s aquifers. We will use these unique modelling tools, in combination with dedicated case studies, to assess, for the first time, the global volume of physically and economically extractable fresh groundwater, and determine the time to physical and economic depletion under future pumping. We will also provide the first global assessment of the effects of groundwater pumping on groundwater-dependent ecosystems and explore pathways to sustainable groundwater use. As such, GEOWAT will provide critically-needed new knowledge to address one of most pressing challenges that mankind will face: how to sustainably manage the freshwater resources needed to survive on this planet?
The key objectives of GEOWAT are:
1. Determine the physical limits of groundwater use by estimating the volume of total and fresh groundwater, estimating how much of that volume is physically extractable, and projecting the time to physical depletion of groundwater reserves under future climate and socioeconomic scenarios.
2. Determine the economic limits of groundwater use by estimating the maximum depth at which groundwater withdrawal is still profitable under current land use and future scenarios, and by finding withdrawal trajectories that are economically sustainable over time.
3. Determine the ecological limits of groundwater use by estimating how groundwater withdrawal affects groundwater-dependent ecosystems globally and valuating resulting ecosystem deterioration economically.
The work programme consists of 6 interrelated work packages. WP1 and WP2 develop a global 1 km groundwater-surface water model and a global hydrogeological schematization. With these tools past and future development of groundwater resources will be simulated and the results used to assess the global physical (WP4), economic (WP5) and ecological (WP6) limits to groundwater use. Results will be ground-truthed by in-depth studies in groundwater depletion hotspots. The final result is an integrated picture of the joint limits to groundwater use and pathways for sustainable groundwater use by integrating technical, governance and economic solutions.
Progress towards this final goal thus far (halfway ) is as follows
WP1 High-resolution global hydrological and water resources modelling (GLAM)
- A 30 arcsecond (~ 1km) spatial resolution global groundwater model (GLOBGM) has been set up using parallel technology and is now ready to be used in WP 4 physical limits.
- A 30 - arcsecond (~1km) spatial resolution global surface water model (PCR-GLOBWB) has been set up and now ready to be used in WP 4 physical limits
- An efficient parallel computing method (LUE) is currently being applied to speed up the PCR-GLOBWB calculations
WP2 Global hydrogeological schematisation (HYGS)
- A global impact analysis of sea-level rise on coastal freshwater resources has been published
- A hydrogeological database (HGdb) with bore logs, well data, groundwater level and salinity observations has been set up and curently being filled with global datasets.
- A conceptual hydrogeological model of Australia has been setup as a blueprint for a global hydrological schematization HYGS
WP3 Regional grounding
This WP is being done in synergy with the National Geographic World Water Map project
- A literature survey has been performed using a DPSIR analysis to analyze the major drivers and pressures in groundwater depletion hotspots. A publication about this is in press.
- First results have been achieved to use causal discovery to analyse the sociohydrology of hotspots
WP4 Physical limits
- A 30 arcsecond simulation with PCR-GLOBWB has been performed over the past 60 years and validated against various observation datasets with good results; a publication will be submitted soon.
WP5 Economic limits
- an agent-based micro-economic model of farmer's groundwater use called HELGA has been developed; a publication will be submitted soon.
- an analytcal model of optimal groundwater pumping including groundwater-surface water interaction has been developed and globally applied; a publication is in press.
WP6 Ecological limits
A framework has been developed to map groundwater dependent ecosystems using the global groundwater model GLOBGM; a publication will be submitted soon.
Progress towards this final goal thus far (halfway ) is as follows
WP1 High-resolution global hydrological and water resources modelling (GLAM)
- A 30 arcsecond (~ 1km) spatial resolution global groundwater model (GLOBGM) has been set up using parallel technology and is now ready to be used in WP 4 physical limits.
- A 30 - arcsecond (~1km) spatial resolution global surface water model (PCR-GLOBWB) has been set up and now ready to be used in WP 4 physical limits
- An efficient parallel computing method (LUE) is currently being applied to speed up the PCR-GLOBWB calculations
WP2 Global hydrogeological schematisation (HYGS)
- A global impact analysis of sea-level rise on coastal freshwater resources has been published
- A hydrogeological database (HGdb) with bore logs, well data, groundwater level and salinity observations has been set up and curently being filled with global datasets.
- A conceptual hydrogeological model of Australia has been setup as a blueprint for a global hydrological schematization HYGS
WP3 Regional grounding
This WP is being done in synergy with the National Geographic World Water Map project
- A literature survey has been performed using a DPSIR analysis to analyze the major drivers and pressures in groundwater depletion hotspots. A publication about this is in press.
- First results have been achieved to use causal discovery to analyse the sociohydrology of hotspots
WP4 Physical limits
- A 30 arcsecond simulation with PCR-GLOBWB has been performed over the past 60 years and validated against various observation datasets with good results; a publication will be submitted soon.
WP5 Economic limits
- an agent-based micro-economic model of farmer's groundwater use called HELGA has been developed; a publication will be submitted soon.
- an analytcal model of optimal groundwater pumping including groundwater-surface water interaction has been developed and globally applied; a publication is in press.
WP6 Ecological limits
A framework has been developed to map groundwater dependent ecosystems using the global groundwater model GLOBGM; a publication will be submitted soon.
GEOWAT is ground breaking as it will provide the first global spatially explicit estimates of extractable fresh groundwater. GEOWAT will advance the field from its current state, with over a decade of wildly varying depletion rates and no insights into time-to-depletion, to one where the physical, economic, and ecological limits of global groundwater are truly quantified in terms of available volumes, maximum pumping depths, and critical time horizons for action. Apart from that the following major scientific and technical advancements are expecteds: 1) a global hydrogeological schematisation and groundwater-surface water model at unprecedented resolution and detail (~1 km); 2) the first global spatially explicit projections of future groundwater withdrawal under socio-economic scenarios, including emerging hotspots in areas of rapid population growth such as Africa; 3) the first spatially explicit global estimates of economic depletion depths and times and assessment of economically sustainable withdrawal trajectories; and 4) the first global assessment of the impact of groundwater pumping on groundwater-dependent ecosystems.