2021 | Aquifer Response to Sea-level Rise

FACULTY SEED GRANT | Global Change Center

Predictability of Virginia’s Coastal Aquifer Response to Sea-level Rise and Water Consumption for Hazard Assessment 

INVESTIGATORS:

• Dr. Susanna Werth, Geosciences 
• Dr. Manoochehr Shirzaei, Geosciences
• Dr. Julie Shortridge, Biological Sciences Engineering
• Dr. Anamaria Bukvic, Geography
• Dr. Ryan Pollyea, Geosciences
• Dr. Venkataramana Sridhar, Biological Sciences Engineering

This project aims to collect new datasets, build novel models, and perform a pilot study as preparation for an NSF or NASA proposal to predict future hazards associated with depletion of coastal aquifers and sea-level rise, and inform climate change adaptation efforts and relocation plans. 

Increased demand for freshwater due to population increases and land-use change during the  past 100 years makes groundwater a vital source of potable water for nearly 20 million inhabitants of the Northern Atlantic Coastal Plain (NACP) (coasts of Maryland, Virginia, North Carolina). Increasing groundwater withdrawal rates from the NACP leads to groundwater levels declining up to 2 ft/yr. The area is also the site of the greatest rate of sea-level rise on the East coast, primarily due to a combination of isostatic glacial subsidence and subsidence due to the excessive groundwater withdrawal. In Virginia, the Hampton Road Area (HRA) experiences subsidence rates of up to ~5 mm/yr. Half of these rates are caused by aquifer compaction due to decades of pumping from the regional Potomac Aquifer, which is part of the NACP. Reduced water pressure underground manifests in land subsidence at the surface due to compaction of aquifer units. Temporal changes in deformation and groundwater decline reflect temporal changes in groundwater overdraft caused by drought-related substantial changes in surface water availability. The occurrence of droughts is expected to increase due to redistribution of rainfall depths throughout the year with more variable and less predictable precipitation patterns, and more severely in the southern NACP. The effectiveness of ongoing efforts to mitigate groundwater decline and halt  land subsidence in HRA through active management efforts could not be quantified yet.

In combination with rising sea levels, future vertical land motion due to aquifer dynamics in  coastal areas will increase relative sea-level rise and risks of nuisance and storm flooding,  exaggerate degradation of aquifers and coastal wetlands, cause habitat loss and affect freshwater availability through saltwater intrusion. In coastal Virginia, ~0.9 m sea level rise by 2100 are projected to affect ~181,000 people, and adaptation strategies impose substantially greater burden on low-income communities. Adaptation measures by one of the largest stakeholders in the region, the Department of Defense, will likely be a strong driver of communities’ response in the HRA. Thus, forecasting the impact of climate change, groundwater withdrawal, and sea-level rise on aquifers is essential for successful adaptation to global change. 

Effects of aquifer compaction can be rapid and nonlinear and they are not included in future  predictions thus far. To address this, we will formulate a 3-5-year project proposal during the  seed year that develops multi-objective models to forecast hazards due to groundwater depletion in NACP through an interdisciplinary effort integrating natural and human processes, including coupled climate, hydrology, groundwater, solid Earth, and socioeconomic systems. We will propose to build open-source modeling codes to integrate diverse remote sensing datasets of large volumes. The calibrated model will then be used to investigate socio-economic exposure and hazards due to changes in coastal aquifers under various scenarios for climate change, sea level rise, groundwater demand, and recharge efforts. Project results for predicted future subsidence rates due to groundwater withdrawals will accurately inform on need, feasibility and risks associated with relocation & adaptation efforts in the NACP area. The methods will be applicable for further US coastal aquifers.

Reference citations for project proposal description available upon request.