Providing alternative sources of fresh water can take the pressure off valuable aquifers
When a stretch of road suddenly collapses into a sinkhole, it’s likely to make the national news. When land sinks slowly, a process known as ground subsidence, it usually happens gradually and with less fanfare but with potentially devastating effects in the long run.
Science can shed light on slowing ground subsidence problems while there is still time to take action. For example, a recent University of Houston study informed suburban Houstonians that many of their neighborhoods are sinking significantly. While the granularity of the study may be uncommon, subsidence itself isn’t. It’s a widespread problem across the nation and the globe.
Ground Subsidence Hot Spots
In the United States, 80% of ground subsidence is caused by overextraction of groundwater. According to a National Groundwater Association publication, more than 123,000 km2 of land and waterways in over 50 areas of the conterminous U.S. — an area greater than that of Pennsylvania — have been directly impacted.
In California’s Central Valley, where a great deal of groundwater is pumped to irrigate one of the most productive growing regions in the nation, the U.S. Geological Survey (USGS) estimates that the ground has subsided 28 feet.
Where such subsidence occurs, subterranean formations can collapse, leaving aquifers unable to store as much water. A great deal of the damage is irreversible.
Subsidence also threatens the real estate sector. In Florida, subsidence has caused hundreds of millions of dollars in damage, with Fort Lauderdale and Miami at risk. New Orleans has suffered subsidence, compounding flooding risk from hurricanes already made more severe by climate change.
Solutions for Groundwater Depletion and Subsidence
Solutions to groundwater depletion and subsidence include a variety of measures, such as:
- Reduction of groundwater pumping
- Water conservation
- Supplementation of groundwater with alternate sources such as surface water
- Wastewater reuse and desalination, which take pressure off of freshwater sources
Groundwater regulations and initiatives can be highly effective, making cities more resilient and more attractive to private investment.
The recent study of Houston’s suburbs, for instance, showed a remarkable difference between suburban areas and areas within the Houston city limits. While the suburban areas showed high subsidence rates, areas within Houston proper had negligible subsidence rates as a result of Subsidence District regulations, which have been in place for decades.
Anything that reduces the amount of groundwater pumped is a step in the right direction to stop ground subsidence. Conservation may mean measures to prevent domestic overuse of water, including low-flow fixtures or limits on lawn irrigation, but another important focus is supplementing groundwater with other sources.
Wastewater reuse can allow municipalities and industries to stop wasting precious drinking water on uses that can be served by nonpotable recycled water, including toilet-flushing, landscape irrigation, equipment washing, industrial processes, and more. With a high standard of treatment, wastewater can even be reused to recharge groundwater as part of a managed aquifer recharge initiative.
Seawater desalination in coastal areas can also supplement water supplies. While generally more costly than wastewater reuse, advances in reverse osmosis desalination have increased its cost-efficiency. Meanwhile, water scarcity and increasing demand from development and rising populations have increased the value of fresh water. Where fresh water comes at a premium, new generation reverse osmosis desalination may now be economically viable where it was not before.
Seven Seas Water Group, a global water and wastewater treatment company, can help meet suburban groundwater conservation goals. Contact our water experts to learn how our Water-as-a-Service® performance-based financing can remove the obstacles to the water you need.
Image Credit: U.S. Geological Survey/flickr