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=== Upper basin ===
The St. Johns River is separated into three basins and two associated watersheds managed by the [[St. Johns River Water Management District]]. Because the river flows in a northerly direction, the upper basin is located in the headwaters of the river at its southernmost point.<ref name="bigpicture">[{{cite web|url=https://www.sjrwmd.com/static/waterways/Story-of-the-SJR.pdf "|title=Fact Sheet: A Story of the St. Johns River: The Big Picture"] {{Webarchive|archive-url=https://web.archive.org/web/20211013171812/https://www.sjrwmd.com/static/waterways/Story-of-the-SJR.pdf |archive-date=October 13, 2021 }}, |publisher=St. Johns River Water Management District (|date=May 3, 2007). |url-status=dead}}</ref><ref name=north group=note>The St. Johns is frequently cited as being a rare north-flowing river in North America (Benke & Chusing, p. 100; Randazzo, p. 12), though most rivers in Canada and in parts of the United States drain north (Verdin, K. L. (March 19, 2010). [http://proceedings.esri.com/library/userconf/proc97/proc97/to350/pap311/p311.htm "A System for Topologically Coding Global Drainage Basins and Stream Networks"] {{webarchive|url=https://web.archive.org/web/20100116085805/http://proceedings.esri.com/library/userconf/proc97/proc97/to350/pap311/p311.htm |date=January 16, 2010 }}, ESRI; Gonzalez, M. A. (2003). [http://www.state.nd.us/ndgs/NEWSLETTER/NLS03/pdf/Divide.pdf "Continental Divides in North Dakota and North America"] {{Webarchive|url=https://web.archive.org/web/20061024005601/http://www.state.nd.us/ndgs/Newsletter/NLS03/pdf/Divide.pdf |date=October 24, 2006 }}, ''North Dakota Geological Survey Newsletter'' '''30''' (1), pp. 1–7; {{cite web|last1=Kamiar|first1=M.|date=April 27, 2013|title=Due North: The St. John's River is One of Many|url=http://www.metrojacksonville.com/article/2013-apr-due-north-the-st-johns-river-is-one-of-many|website=Metro Jacksonville|access-date=November 8, 2015|archive-date=November 17, 2015|archive-url=https://web.archive.org/web/20151117063256/http://www.metrojacksonville.com/article/2013-apr-due-north-the-st-johns-river-is-one-of-many|url-status=live}}).</ref> Indian River County is where the river begins as a network of marshes, at a point west of [[Vero Beach, Florida|Vero Beach]] aptly named the St. Johns Marsh in central Florida. The St. Johns River is a [[blackwater river|blackwater stream]], meaning that it is fed primarily by swamps and marshes lying beneath it; water seeps through the sandy soil and collects in a slight valley.<ref>Whitney, p. 216.</ref> The upper basin measures approximately {{convert|2000|sqmi|km2}}; the St. Johns transforms into a navigable waterway in [[Brevard County, Florida|Brevard County]]. The river touches on the borders of [[Osceola County, Florida|Osceola]] and [[Orange County, Florida|Orange Counties]], and flows through the southeast tip of [[Seminole County, Florida|Seminole County]], transitioning into its middle basin a dozen miles (19 km) or so north of [[Titusville, Florida|Titusville]].<ref name="bigpicture"/>
The upper basin of the St. Johns was significantly lowered in the 1920s with the establishment of the Melbourne Tillman drainage project. This drained the St. Johns' headwaters eastward to the Indian River through canals dug across the Ten-Mile Ridge near [[Palm Bay, Florida|Palm Bay]]. As of 2015, these past diversions are being partially reversed through the first phase of the Canal 1 Rediversion project.<ref name=Floridaswater2015>{{cite web|title=District, partners celebrate restoration of historic water flows|url=http://webapub.sjrwmd.com/agws10/news_release/ViewNews.aspx?nrd=nr15-120|website=Floridaswater.com|publisher=St. Johns River Water Management District|archive-url=https://web.archive.org/web/20160109223519/http://webapub.sjrwmd.com/agws10/news_release/ViewNews.aspx?nrd=nr15-120|archive-date=January 9, 2016|location=Palatka|date=November 13, 2015|quote=For decades, Canal 1 in Palm Bay shunted storm water east to the lagoon, but recent upgrades in pumps now send up to 39 percent of the average annual storm water to Sawgrass Lake where it is naturally filtered before flowing to the St. Johns River.}}</ref>
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