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Hydrogeodetic – satellite and terrestrial measurements of land surface deformation and changes in gravitational acceleration – and airborne hydrogeophysical measurements are showing that they are the future for answering water resource questions at the scale of management: entire well fields, aquifers, river valleys, and regions. At the same time, low-cost IoT sensors used for doorbell cameras, temperature control and other commercial uses are creating dense sensor networks in towns and cities, which provide distributed data of the environment.  But as these sensors are increasingly applied, lack of background water data, poor understanding between the relationship between the indirect measurements of deformation, gravity changes, resistivity changes, and low-cost sensor network response all limit the broad applicability of these techniques. This indicates a need for a testbed where instruments can be tested in controlled field conditions, and where the sensed hydrological response can be modeled using a mixture of traditional modeling, and artificial intelligence (AI) or AI-enabled reduced order modeling for real-time responses.

The New Mexico Tech Playas Training Center (PTC) may have part of the answer. Located in the Playas Basin in southern New Mexico, the PTC has a unique combination of factors that make it an ideal testbed for hydrogeodetic and other hydrogeophysical techniques. It is in a classic Basin-and-Range closed basin, similar to the hydrogeology of basins across the Western U.S. It is remote, with the nearest town more than 20 miles away, limiting human-caused interference and allowing operators to precisely control hydrologic conditions. It already has a small depopulated company town that can be built from to study IoT sensor networks and peri-urban water management. It will have the capacity to transmit vast (100 GB/s) amounts of data, enabling dense sensor arrays, image transmission in real time, and remote control of both geodetic sensors and groundwater well networks. It currently has commercial low-cost IoT sensors being deployed, as well as real-time data processing and computing.  It has a friendly owner–New Mexico Tech–focused on research, with good relationships with water and air regulators, enabling the development of a groundwater research facility with the possibility of airborne sensing. And it has good neighbors interested in collaborating with New Mexico Tech, which in turn extends the possible range of research from PTC property out to the basin scale, including playa recharge research, focused recharge along streambeds, through deep vadose zones, and monitoring water in fractured bedrock terrains. Because of its location between four major water universities (New Mexico Tech, New Mexico State University, University of Texas at El Paso, and University of Arizona), several USDA ARS centers, and major military installations, it also has the promise of being a major educational and research center for a range of users.

We propose three approaches to using Playas Training Center for increasing fundamental and applied understanding of water science:

• A hydrogeophysics testbed focused on understanding  hydrogeodetic and transient electromagnetic responses to hydrologic change.
• A peri-urban laboratory to improve water management in arid-zone towns and cities, and to enable leveraging low-cost, commercial, IoT sensor networks for distributed monitoring.
• An arid-zone laboratory to develop real-time computing solutions for environmental sensing leveraging the explosion of AI-enabled techniques.

These three approaches are complementary, requiring similar background site characterization, and using the same back-bone of infrastructure that PTC provides. These approaches also dovetail with ongoing defense related contracts at PTC.Hydrogeophysics testbed

The promise of hydrogeophysics is to move hydrogeology from the point scale to the management scale. In practice, this appears as if you are just filling in the gaps between point measurements. That appearance is deceiving. The amount of property variation in the subsurface is like comparing a micrometer to a range finder–1,000s of times of difference in properties– but happening unseen and over short distances. By indirectly measuring aquifer changes via surface deformation, small changes in gravitational acceleration, and changes in electromagnetic properties, the amount of water in the subsurface can be ‘imaged’ and, more importantly, the variation in the subsurface can be measured. To do this, the relationships between geophysical measurements and …

If a hydrogeophysics testbed is developed, examples of future technologies that could be developed include

• Artificial intelligence-enabled control of well network and managed aquifer using a fusion of water level well data with geophysical data.
• Combined testing of water development, managed aquifer recharge, and novel hydrogeophysical sensing technologies.
• Testing of the capabilities of hydrogeodesy and hydrogeophysics in a fully characterized area, to both find new opportunities and to ensure realistic management practices.
• Combined aerial, land-based and well-based sensor networks for scale-free groundwater sensing.
• Development of rigorous and generalized time-dependent relationships between soil and rock properties, hydraulic properties, and their scaling, opening the door to more accurate application of these technologies across the arid West.

Is the PTC ready to become the testbed for hydrogeodetic and hydrogeophysical techniques right now? Well. No. But there is a clear path.

Phase 1. Characterization and permitting

The challenge of any subsurface testbed is heterogeneity and its connection across its boundaries. At PTC, we need to undertake

• 1:100,000 scale geologic mapping across the basin, and 1:24,000 scale geologic mapping of the quadrangles that PTC is in and neighbors.
• A basin-scale hydrogeologic study including a suite of groundwater age and environmental tracers studies, groundwater quality, and water level mapping.
• Drilling of exploratory boreholes and collection of cores from test wells, with permeability, relative permeability, elastic, consolidation and failure properties, electricomagnaetic properties, and thermal properties measured along with geologic characterization.

During the mapping phase, a base sensor network should be established. This includes high precision gravimeters, borehole strain and tiltmeters,  geodetic grade GNSS stations, three component seismometers, and permanent TEM stations. This data should be streamed, when possible, through the data backbone of PTC and archived. This data will complement the low-tech sensor networks being studied and tested under DoD contracts.

Simultaneous with the mapping and establishment of sensor networks, planning and permitting of nested piezometers, pumping wells, managed aquifer recharge facilities, and surface water monitoring should be pursued. A focus on closing the water balance between pumping and managed aquifer recharge should be taken to facilitate the permitting process.

As part of Phase 1, community and land-owner engagement should be initiated. Collaborations with BLM – who are the property owners upstream of PTC – and their leasees, of the neighboring private ranch owners, and Freeport-McMoran are vital to the long-term success of the testbed.

Phase 2. Establishment of testing network

Once regional characterization has been completed and permitting has been approved, then the establishment of the testbed can be undertaken.

The establishment of test wells with a combination of nested piezometers and boreholes for pumping. These wells should be drilled to a number of depths to understand the three dimensional patterns of the groundwater-controlling geology.
Long-term hydraulic testing of the wells to establish long-range hydrologic properties.
Deployment of airborne and terrestrial geophysical and geodetic campaigns during hydraulic testing to develop baseline data for comparison.
Establishment of surface water monitoring, including weirs, sediment sampling and monitoring and remote monitoring technologies.
During this well completion, additional measurements of samples from the wells should be undertaken. All wells should have geophysical logs collected, including gamma, sonic, neutron, MRI, image log, and …. Shallow (< 100 m) cores of the stream bed should be taken and analyzed.

Monitoring wells should be established around the boundaries of the property and, if possible, on the neighboring properties to understand the boundary conditions of the testbed.

Phase 2 is when direct collaborations and deployment of sensor networks on neighboring properties should be initiated.

Phase 3. Regional scaling and initiation of test-bed operations at PTC

As we enter Phase 3, the test bed can begin taking contracts focused on local (100s m to 1 kms) scale testing of terrestrial and airborne technologies. Customers with NSF, DOI, DOD, DOE and private funding should be sought out, and educational rates established for local partners at UofA, NMT, NMSU and UTEP.

Simultaneously, regional sensor networks, including conjunctive groundwater/surfacwater monitoring networks, GNSS and geodetic techniques, sesimic technologies and low-cost environmental sensing technologies should be established with regional partners. Key locations include upstream (mountain watershed) and downstream (playa) of PTC.

Call to Action

The National Academy, NSF, NASA and other federal agencies have identified hydrogeodetic and hydrogeophysical technologies as a vital pathway to smart water management. And scaling from wells to aquifers to basins remains one of the grand challenges of hydrology. By providing a test bed that continuously adapts and improves, and allows real-time streaming, collection and processing of data, NMT PTC is poised to fill a critical role in the future of hydrology.