Editing Springfield, Illinois (section)

===Topography===
The city is at an elevation of {{convert|558|ft}} [[above sea level]].<ref name="gnis"/> According to the 2010 census, Springfield has a total area of {{convert|65.764|sqmi|sqkm|2}}, of which {{convert|59.48|sqmi|sqkm|2}} (or 90.44%) is land and {{convert|6.284|sqmi|sqkm|2}} (or 9.56%) is water.<ref name="census-g001">{{cite web |url=http://factfinder.census.gov/bkmk/table/1.0/en/DEC/10_SF1/G001/1600000US1772000 |title=G001 – Geographic Identifiers – 2010 Census Summary File 1 |access-date=December 27, 2015 |publisher=[[United States Census Bureau]] |archive-url=https://archive.today/20200213050438/http://factfinder.census.gov/bkmk/table/1.0/en/DEC/10_SF1/G001/1600000US1772000 |archive-date=February 13, 2020 |url-status=dead }}</ref> The city is located in the Lower [[Illinois River]] Basin, in a large area known as Till Plain. Sangamon County, and the city of Springfield, are in the Springfield Plain subsection of Till Plain. The Plain is underlain by glacial [[till]] that was deposited by a large continental ice sheet that repeatedly covered the area during the [[Illinoian (stage)|Illinoian Stage]].<ref name="WillmanOthers1970">Willman, H.B., and J.C. Frye, 1970, ''Pleistocene Stratigraphy of Illinois.'' Bulletin no. 94, Illinois State Geological Survey, Champaign, Illinois.</ref><ref name="McKay2007">McKay, E.D., 2007, ''Six Rivers, Five Glaciers, and an Outburst Flood: the Considerable Legacy of the Illinois River.'' Proceedings of the 2007 Governor's Conference on the Management of the Illinois River System: Our continuing Commitment, 11th Biennial Conference, Oct. 2–4, 2007, 11 p.</ref>

The majority of the Lower Illinois [[River basin|River Basin]] is flat, with relief extending no more than {{convert|20|ft}} in most areas, including the Springfield subsection of the plain. The differences in topography are based on the age of drift. The Springfield and Galesburg Plain subsections represent the oldest drift, Illinoian, while Wisconsinian drift resulted in [[Moraine|end moraines]] on the Bloomington Ridged Plain subsection of Till Plain.<ref name=usgs>{{cite web |last=Warner |first=Kelly L. |url=http://il.water.usgs.gov/proj/lirb/pubs/esr/Environ03.html |title=Lower Illinois River Basin – Physiography – Water-Quality Assessment of the Lower Illinois River Basin: Environmental Setting, USGS Water Resources of Illinois |publisher=Il.water.usgs.gov/ |work=United States Geological Survey |page=3 |access-date=April 6, 2007 |archive-url=https://web.archive.org/web/20060924210559/http://il.water.usgs.gov/proj/lirb/pubs/esr/Environ03.html |archive-date=September 24, 2006 |url-status=dead }}</ref>

[[Lake Springfield]] is a {{convert|4200|acre|adj=on}} human-made reservoir owned by [[City Water, Light & Power]],<ref name=lake/> the largest municipally owned utility in Illinois.<ref name=about>[http://www.cwlp.com/about_cwlp/about.htm About CWLP] {{webarchive |url=https://web.archive.org/web/20070203205738/http://www.cwlp.com/about_cwlp/about.htm |date=February 3, 2007 }}, City Water, Light & Power, City of Springfield. Retrieved February 20, 2007.</ref> It was built and filled in 1935 by damming [[Lick Creek (Sangamon River tributary)|Lick Creek]], a tributary of the [[Sangamon River]] which flows past Springfield's northern outskirts.<ref name=levels>[http://www.cwlp.com/Lake_Springfield/Lake_Levels/lake_water_levels.htm Lake Water Levels] {{webarchive |url=https://web.archive.org/web/20070203235333/http://www.cwlp.com/lake_springfield/lake_levels/lake_water_levels.htm |date=February 3, 2007 }}, City Water, Light & Power, City of Springfield. Retrieved February 24, 2007.</ref> The lake is used primarily as a source for drinking water for the city of Springfield, also providing cooling water for the condensers at the power plant on the lake. It attracts approximately 600,000&nbsp;visitors annually and its {{convert|57|mi|0}} of shoreline is home to over 700&nbsp;lakeside residences and eight public parks.<ref name=lake>[http://www.cwlp.com/lake_springfield/lake.htm Lake Springfield] {{webarchive |url=https://web.archive.org/web/20000824162327/http://www.cwlp.com/Lake_Springfield/lake.htm |date=August 24, 2000 }}, City Water, Light & Power, City of Springfield. Retrieved February 20, 2007.</ref>

The term "full pool" describes the lake at {{convert|560|ft|m}} above sea level and indicates the level at which the lake begins to flow over the dam's [[spillway]], if no gates are opened.<ref name=levels/> Normal lake levels are generally somewhere below full pool, depending upon the season. During the drought from 1953 to 1955, lake levels dropped to their historical low, {{convert|547.44|ft|2}} [[Sea level#AMSL|AMSL]].<ref name=levels/> The highest recorded lake levels were in December 1982, when the lake crested at {{convert|564|ft|0}}.<ref name=levels/>