Numerous threats exist that could limit or harm the supply of groundwater in the Northern Atlantic Coastal Plain aquifer system. One of the more obvious threats is the increasing amount of withdrawal from the aquifers due to an increasing population. Since the turn of the twentieth century, withdrawals from the aquifer system have substantially increased, hitting record high rates of pumping during the post World War II era, from the 1940's to the 1980's (Figure 9; Masterson, et al., 2016). Approximately 27 Tgal of water has been removed from the system since 1900, but half of that total volume, 13.4 Tgal, has been withdrawn within the past 28 years. The increasing amount of water withdrawn has resulted in water level declines within multiple confined aquifers. Many are experiencing declines of up to two feet per year, but in areas like southeastern Virginia, declines have been observed to be greater than 100 feet (Masterson, et al., 2011). Total water level declines within the system equal to tens of hundreds of feet from their levels pre-1900.

The long-term effects of the excessive removal of groundwater within the last 28 years may have not occurred yet in terms of groundwater discharge and land subsidence, but studies have modeled future impacts. If the current rate of pumping stays consistent through 2043, the overall release from storage in the unconfined aquifer will decrease (Masterson, et al., 2016). There is also a concern for storage loss within the confining units. Some water is able to flow and leak through the confining units. If enough water is removed from the clay and silt sediments, compaction may occur and the storage cannot be recovered (Masterson and Pope, 2016). If the withdrawal rate continues at a steady rate or increases, the water supply for the 21 million plus people who rely on the aquifer system will be greatly limited.

High rates of water withdrawal with the addition of drought like conditions poses an even bigger threat to the aquifer system. With increasing temperatures due to climate change, droughts can become more prevalent. A prolonged drought within the NACP region that occurred from 1960 to 1967 has been of interest to many researchers who have used models to calculate the recharge from this time period with historical temperature and precipitation data (Masterson, et al., 2016). Studies found that during this 8-year period, there were 9 in/yr less recharge throughout the entire aquifer system. This reduction of recharge is approximately an order magnitude more than the total amount of withdrawal from the system in 2013. Groundwater levels during droughts are not only affected by decreased recharge, but also by increased pumping to meet needs for irrigation. The same study found that during the drought from 1960 to 1967, there would have been an estimated 110 Mgal/d increase of withdrawal of groundwater for irrigation purposes (Masterson, et al., 2016). This research shows that droughts can easily reduce the water supply within the NACP aquifer system.

A third threat to the groundwater within the NACP is saltwater intrusion. The eastern extent of the aquifer system reaches as far as 120 miles offshore, to the Continental Shelf (Charles, 2016). The seaward flow of fresh groundwater under normal conditions prevents the intrusion of saltwater (Barlow and Wild, 2002). Once water begins to be pumped out of the aquifers near the coast, saltwater can be drawn landward as well as upward towards the point of withdrawal (Figure 10). The intrusion of saltwater is a threat to groundwater because it can take up storage that was previously used for groundwater as well as increase concentrations of dissolved ions, such as chloride, making the water no longer potable.

Because the aquifer system extends across state boundaries, management of this water resource can become challenging (Masterson, et al., 2016). Multiple state and federal agencies as well as nongovernmental organizations have responsibilities managing and protecting the groundwater within the NACP, but the need for interstate aquifer management has been increasing (Masterson, et al., 2011). The U.S. Geological Survey Groundwater Resources Program has conducted research through the years to assess groundwater availability throughout the United States, focusing on principal aquifer systems (Masterson, et al., 2011). Their purpose has been to improve the nation's ability of forecasting future water availability. In 2010, the program began their research on the NACP aquifer system and concluded in 2016. Results found the depletion of groundwater varied by location. 68% of all the withdrawals from the NACP from 1900 to 2013 was from pumping in New Jersey and Long Island, but those withdrawals only accounted for 35% of the total depletion from storage (Masterson and Pope, 2016). On the other hand, 14% of the total withdrawals during the same time period occurred in Virginia and the northern portion of North Carolina, yet 46% of groundwater storage depletion occurred in these areas. These numbers are a result of the northern states within the aquifer system primarily pumping from the unconfined surficial aquifer, while the southern states are pumping deep within the confined aquifers. The differences in withdrawals and depletion rates show how management of the entire aquifer system can be complicated across state lines.

Although it would be ideal for each state to work as one cohesive group in terms of groundwater management, each state throughout the system have their own organizations and regulations. New Jersey's Department of Environmental Protection has a branch of their organization called the Division of Water Supply and Geoscience. Their purpose is to ensure that the state has an adequate water supply that is reliable, safe, and available for the future (New Jersey Department of Environmental Protection, 2017). Since 1981, New Jersey's Department of Environmental Protections has developed and revised the New Jersey Statewide Water Supply Plan. The newest plan was revised for 2017 through 2020. To better manage groundwater in New Jersey, the plan states to increase the use of aquifer storage and recovery (ASR) wells. These wells allow the injection of water from other sources into the confined aquifers to be stored during the off-peak seasons (New Jersey Department of Environmental Protection, 2017). The extra water injected could then be pumped and used during times of high needs such as droughts. ASR wells can also be used to manage saltwater intrusions. As of 2017, there were 19 ASR wells throughout the state, but the plan has been to increase their numbers within the following years.

Virginia deals with the management of groundwater differently than New Jersey. The Virginia Department of Environmental Quality has a program called Groundwater Management Areas in which groundwater withdrawal is regulated (Virginia Department of Environmental Quality, 2019). There are two Groundwater Management Areas within the state: the Eastern Virginia Groundwater Management area and the Eastern Shore Groundwater Management area. The program relies heavily on different permits and recordings for groundwater withdrawals. A permit is needed for any person or entity within one of the two areas to withdraw 300,000 gallons of groundwater or more within a month (Virginia Department of Environmental Quality, 2019). The state also has a Water Withdrawal Reporting Regulation in which those who withdraw on average 10,000 gal/d or more per month must report their withdrawal information annually. The Department of Environmental Quality has also focused on identifying the largest groundwater users and negotiating possible reductions of withdrawal. In 2017, they identified 14 of the top users and issued them new 10-year permits that reduced their permitted withdrawal volumes by 52%.

The other four states within the NACP region have their own management and allocations for groundwater as well. With each state having different methods, it is easy to assume that disputes over water use occur regularly from state to state due to competing demands of local domestic, industrial, agricultural, and environmental purposes. Luckily, water rights within the 6 states are all relatively similar by following a variation of the Riparian Doctrine, which helps mitigate transboundary issues. Under this doctrine, owners of land bordering or adjacent to a water body have the authority to use it (Fetter, 2001). While Virginia simply follows the Riparian Doctrine, Maryland and Delaware follow the same doctrine but with regulations (Ridenbaugh Press, 2020). New Jersey, New York, and North Carolina follow a mix between the Riparian Doctrine and the Prior Appropriation Rights. Landowners who were the first to own the land have the rights to use the water within the property according to the Prior Appropriation Rights (Fetter, 2001). With Virginia only following the Riparian Doctrine and North Carolina using some of the Prior Appropriation Rights, disputes between the bordering states have prevailed concerning water bodies near or at the border (Ridenbaugh Press, 2020).