Explanation of Indicator
Florida’s coastal counties depend on their water resources for drinking water, agriculture, industry, and to support the many diverse natural systems found there. Unfortunately, nearly all human activities may adversely affect ground water quality and qua ntity in some way. In addition, the state is expected to grow at a rate of three percent annually, with most of the growth concentrated in coastal areas where the water resources are already being threatened by over-consumption, contamination, and saltwa ter intrusion.
Public supply refers to water supplied by a publicly or privately-owned water system for public distribution. The Florida Department of Environmental Protection (DEP) considers any water system that serves more than 25 people or has 15 year-round service connections a public water supplier.
Increases in water withdrawals for public supply purposes is a direct indicator of increasing demand on water resources. If withdrawals exceed water recharge, the potential for saltwater intrusion and low flows in surface water bodies will increase. Low flow in surface water bodies may have significant impacts on the surrounding communities. For example, competition for dissolved oxygen and habitat will increase for the marine plants and animals as the water level drops. Depending on the depth and rat e of flow in a waterbody, the water temperature may shift, impacting the ability of water to hold dissolved oxygen. As a result the waterbody community may lose species less tolerant of environmental changes. Additionally, species that can readily adapt to environmental changes may displace other species.
Data Characteristics
SOURCE
The Water Resources Division of the United States Geological Survey (USGS) is the lead office for this information. The USGS publishes a report, Water Withdrawals, Use, and Trends in Florida, every five years which contains these data. It is prepared in
cooperation with the Florida Department of Environmental Protection and the water management districts. The publication is prepared by Richard L. Marella, who can be contacted at the USGS, 227 North Bronough Street, Suite 3015, Tallahassee, Florida 3230
1, or at (904) 942-9500, extension 3004.
ACQUISITION
This information can be obtained in a hard copy format from the Water Resources Division of the USGS. There are no costs associated with obtaining this information.
COLLECTION
The data are collected statewide throughout the year by both DEP and the water management districts, and the USGS compiles the information about every five years for the publication referenced above. Some of the public supply water use values have been a
djusted or modified from previously published data. Most of the modifications were a result of eliminating the previous double counting of water withdrawals for several utilities in some counties or adding utilities that were missed in the original inven
tory.
Data Limitations
The USGS does collect data annually for public supply water withdrawals; however, the data are published only every fifth year. When data are displayed for every fifth year, anomalies may exist for a given year, which could lead to an incorrect interpret
ation. If a given year has above or below normal precipitation (extremely wet or dry), or has an event like a hurricane, the water use value will most likely be skewed for that year
Data Analysis
Public supply fresh water net use in 1965 was 574.9 million gallons per day (mgd). Public supply fresh water net use has followed an increasing trend, and in 1990 it was 1,522.4 million gallons per day. The total fresh water withdrawals have increased as
well. Since 1965 the amount of water used by the coastal counties (net use) has exceeded the amount of water withdrawn by these counties, and the coastal counties have had to import drinking water from other counties in order to meet demand. The percen
tage of the public water supply that is imported from other counties is shown in the table below, next to net use in brackets. From 1965 to 1975 the percentage of public supply water being imported into the coastal counties declined. However, after 1975
, the percent of the public supply water that was imported began to increase. If use of this resource continues to increase water shortages and salt water intrusion will likely result.
Year Ground Surface Total Net Use* (MGD) Water (MGD) Water (MGD) Withdrawal [Percent Imported] (MGD) 1965 495.79 64.80 560.59 574.92 [2.5%] 1970 582.86 225.88 808.74 825.28 [2.0%] 1975 767.00 155.20 922.20 926.80 [0.5%] 1980 992.10 173.80 1165.90 1186.30 [1.7%] 1985 1159.20 189.10 1348.30 1375.90 [2.0%] 1990 1274.70 213.80 1488.50 1522.40 [2.2%] *Net Use = Total Withdrawal + Imported Water - Exported Water.