Chassahowitzka Main Spring (photo by R. Means). 

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... through the two passages rather than through the fracture leading to the main vent (Jones et al., 1997). Weeki Wachee Spring discharges from the bottom of a conical depression with gentle side slopes. The spring pool measures 165 ft (50.3 m) east to west and 210 ft (64 m) north to south. Spring depth is 45 ft (13.7 m) over the vent in the center of the pool. Bare limestone is located near the vent, but none is exposed around the pool edges. The water is clear and light greenish blue, and a boil is visible in the center of the pool. Thick, filamentous algae cover the majority of the spring bottom, and there are some native aquatic grasses in the spring pool. The spring is rich with fresh and salt water fishes and aquatic turtles. The Weeki Wachee River flows westward approximately 5 miles (8 km) into the Gulf of Mexico. The river flows through low-lying, densely forested swamp. The nearest high ground east of the spring is rolling sand hills terrain and gently rises to 15 ft (4.6 m) above the water level. All uplands and land adjacent to spring are developed. Twin Dees (aka Little Spring) is approximately 3000 ft (914 m) southwest of Weeki Wachee Main (Fig. 15). Discharge varies from zero to second magnitude at Twin Dees. Discharge is significantly lower than Weeki Wachee Main, however this relatively small spring is fed by a large conduit system with rooms that exceed 100 ft (30 m) in diameter. Divers have mapped an extensive conduit system at Twin Dees (Fig. 16). Cave maps suggest that the geometry of the system has been influenced by both fracture sets and bedding. Divers describe the main vent at Weeki Wachee as a narrow vertical fracture which opens into a large room at a depth of approximately 150-205 ft (46-62 m) bls (Sinclair, 1978; Jones et al., 1997). Two passages exiting the room were identified, but their trends were not indicated. Divers report that more water appears to be exiting the room through the two passages rather than through the fracture leading to the main vent (Jones et al., 1997).The maximum extent of the conduits have not been explored as they continue to depths beyond 300 ft (91 m) bls. Two vents exist at Twin Dees, but one vent, according to cave divers, has been plugged for some time. Freshwater discharges from Twin Dees, but cave divers have identified the influx of brackish water at various locations in the conduit system (Champion and Starks, 2001). The region surrounding Weeki Wachee Springs can be characterized as a karst terrain with internal drainage. Additional evidence for the abundance of cavities occurs at a former irrigation well which tapped into the ceiling of a conduit at approximately 270 ft (82 m) bls (Well WW-F) Fig. 2. However, not much is known concerning the degree of connection among these karst features. Anecdotal evidence suggests that a high degree of connection may exist among south-southeast trending conduits and Weeki Wachee Main. On or around March 19, 1976, Weeki Wachee Main became cloudy allegedly due to collapse of a conduit below Crescent Lake, which is approximately 1.6 miles southeast of the vent. Additional episodes of cloudiness have not been documented, nor has a cessation of flow occurred since the 1930's. Based on diver accounts, Twin Dees has periodically ceased to flow during periods of drought. Weeki Wachee Main is topographically lower that Twin Dees. It has long been suspected that Weeki Wachee Main and Twin Dees are hydraulically connected. Geochemically, the discharge is very similar from the two vents. Natural tracer studies are currently in progress to evaluate response times for the springs. Future quantitative tracer studies are planned. It is hoped that the quantitative tracer studies will reveal travel times and the degree of connection among the vents. Weeki Wachee Spring is extensively developed into a tourist attraction that features underwater mermaid shows with a submerged observation area. It was recently purchased from private ownership by the Southwest Florida Water Management District (SWFWMD). The District leases the land to a private firm for the continuation of the mermaid shows. Shops and facilities are located all around the spring. Chassahowitzka Springs form the headwaters of the Chassahowitzka River, which flows westerly to the Gulf of Mexico approximately 6 miles (9.7 km) though low coastal hardwood hammock and marsh. Chassahowitzka Springs are located 5.8 miles southwest of Homosassa Springs on the Chassahowitzka River. Rosenau et al. (1977) report as many as five springs flow into the upper part of the river and many more springs are known to exist in the lower portion. Average discharge from Chassahowitzka Springs is 138.5 ft 3 /s with a maximum recorded discharge of 197.0 ft 3 /s on May 18, 1966 and a minimum recorded discharge of 31.8 ft 3 /s on July 8, 1964. The entire river is tidally influenced. Chassahowitzka Main Spring is 360 ft (110 m) northeast of the boat ramp and is in the middle of the run (Fig. 17). This spring is at the head of a large pool that measures 147 ft (44.8 m) north to south and 135 ft (41.1 m) east to west. The depth measured over the vent in 13.5 ft (4.1 m). The spring has a sand bottom. No limestone was exposed. Water is clear and greenish. The spring run from Chassahowitzka Number 1 Spring flows into the Chassahowitzka Main spring pool from the east. There is a boat ramp with facilities on the southwest side of the pool. Aquatic vegetation is common including exotic aquatic vegetation and algae. A boil is visible at low tide. The spring is surrounded by lowland hardwood swamp forest with mixed hardwoods, cypress, and palm. Chassahowitzka Number 1 is at the end of a spring run that flows into the Chassahowitzka River from the north approximately 250 ft upstream from the boat ramp (Fig. 18). This spring issues from a small cavern in the bedrock limestone. The spring pool measures 69 ft (21 m) north to south and 81 ft (24.7 m) east to west. There are two closely spaces openings though which the small tannic stream flows into the northeast side of the spring pool. There is a thin layer of algae covering most of the bottom of the spring pool. The surrounding land is low lying and heavily forested with hardwoods and palm. The spring flows southwest approximately 350 ft (106.7 m) into the Chassahowitzka Main Spring pool. There are several other spring vents along the spring run about half way to the Chassahowitzka Main spring pool. Chassahowitzka Springs and River are used for fishing, swimming, snorkeling, and pleasure boating. Manatees frequent the springs and river year round, but are especially common in the winter. The Homosassa Springs Group is located in west-central Citrus County at Lat. 28° 47’ 56.65" N., Long. 82° 35’ 18.70" W (Fig. 19). The springs are at the head of the Homosassa River and contribute significantly to the discharge of the river. Most spring discharge at Homosassa is tidally influenced and water quality is slightly brackish. The largest spring is located at the Homosassa Springs State Wildlife Park, which like the Rainbow Springs State Park, was once a private tourist attraction, with the head spring area remaining developed as a botanical garden. The main spring pool, into which all three vents issue, is also developed as a manatee sanctuary and education facility, and a large viewing structure remains in the center of the spring pool, known as the Fishbowl. The main spring pool contains several spring vents, the largest being the opening to a fairly restricted cave-conduit system underneath the spring. Water quality samples are collected from three sampling tubes positioned at different depths in separate conduits to monitor discreet discharge points in the cave system. Discharge from Homosassa Main averages about 104 cfs, or about 66 mgd. The Halls River is a major spring-fed tributary to the Homosassa River downstream of the head springs. A small head spring exists north of Homosassa, but much of the discharge appears to be dispersed across the shallow, sandy stream bottom. Spring flow is difficult to determine from discreet vents, but an approximate composite discharge for the tributary varies between 130 and 190 cfs. Several smaller springs also occur upstream of the main spring and state park, on the Southeast Fork of the Homosassa River. The springs are typically located on private residential lots and are generally not accessible, although property owners have cooperated in allowing data collection at the springs for many years. The head springs on the Southeast Fork are not brackish, although the combined discharge is somewhat less than Homosassa Main Spring. The main spring pool and adjacent lands are within Homosassa Springs Wildlife State Park. The area is developed into an interpretive center for manatee and Florida wildlife education. There is a floating observation deck in the spring pool with a submerged aquatic observation room. Injured and rehabilitating manatees are captive in the spring pool for year round observation. Swimming is not ...