The Hawthorn Aquifer System is a key part of Florida’s groundwater resources, particularly in Southwest Florida including Lee County and Cape Coral. It is part of the larger Intermediate Aquifer System and the Upper Floridan Aquifer System.
What is the Hawthorn Aquifer?
- Geology and Structure: The Hawthorn Group consists of Miocene-age sediments (limestones, dolomites, sands, clays, and marls). It is divided into:
- Mid-Hawthorn (or Upper Hawthorn) Aquifer: A confined freshwater aquifer, typically 100–200 feet deep (around 125 feet in Cape Coral areas). It has variable productivity and is used for private wells.
- Lower Hawthorn Aquifer: Deeper (roughly 400–800+ feet), more brackish/saline (chlorides often 500–2,000 mg/L). Widely used for public supply via reverse osmosis (RO) treatment. It is part of the Upper Floridan Aquifer and has higher transmissivity in places.
- Recharge: Primarily from rainfall infiltration, but slow (historical 13–15 feet/year recharge reduced to ~4 feet in some areas due to development, drainage, and climate factors). It is semi-confined with variable permeability due to karst features, fractures, and heterogeneity.
- Water Quality: Mid-Hawthorn is generally fresher; Lower Hawthorn is brackish, requiring treatment. Risks include increasing salinity from upconing, saltwater intrusion, or vertical conduits (natural or manmade, e.g., old wells).
Who and Where Relies on It
- Primary Users in Cape Coral / Lee County:
- Northeast Cape Coral: ~14,000 residences (est. 34,000 people) rely on private wells in the Mid-Hawthorn for both drinking water and irrigation. This area has faced severe restrictions.
- Unincorporated Lee County portions, especially northern areas.
- City of Cape Coral Public Supply: Uses the Lower Hawthorn extensively for its Reverse Osmosis plants (Southwest and North facilities), supplying much of the city’s potable water. Capacity expansions target future growth.
- Other Southwest Florida: Cities like Fort Myers (historical use), North Collier, and surrounding areas tap the Lower Hawthorn for brackish supply and RO treatment.
Cape Coral’s public system is mostly separate from the stressed Mid-Hawthorn private wells, but overall growth pressures the system.
Concerns Around Overuse
The Mid-Hawthorn in Northeast Cape Coral has been critically stressed:
- Record Low Water Levels: Dropped to historic lows (e.g., -93+ feet NAVD in 2025), triggering South Florida Water Management District (SFWMD) water shortage orders (Modified Phase IV in 2025, later eased to Phase II by May 2026).
- Impacts:
- Mandatory irrigation restrictions (initially 1 day/week; potential full bans).
- Risk of permanent aquifer compaction/damage, reducing future yield.
- Saltwater intrusion/upconing risks, degrading quality.
- Higher pumping costs and well failures.
- Causes:
- Rapid development and population growth (high demand in northern Cape Coral).
- Over-pumping by private wells.
- Reduced recharge (drought, drainage, climate factors).
- Competition from other users in Lee/Collier/Charlotte counties.
City/State Responses: Transition ~2,000+ homes to city water (the UEP project is costly for residents), joint action plans, conservation, and exploring alternatives. Long-term concerns include sustainability for build-out and broader Floridan system pressures (saltwater intrusion, over-extraction statewide).
Sources include SFWMD, City of Cape Coral, USGS, and local news. Data as of mid-2026; check sfwmd.gov or capecoral.gov for latest monitoring.