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The Hillsborough River begins in southwest Pasco County in the Green Swamp. From the Green Swamp, the river begins as an overflow from the Withlacoochee River, north of US Highway 98. Its headwaters begin as a slow moving sheet flow that percolates through a heavily vegetated riverine forest that has no discernable channel. Approximately a quarter of a mile south of its beginning point, a channel emerges and becomes more defined as a channelized riverine system (SWFWMD). The Hillsborough picks up a little steam with the influence of Crystal Springs which discharges millions of gallons of water per day.
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