What is a watershed?
A watershed is an area of land that all surface water under it or on it drains to the same location. Within the United States, there are over 2,000 defined watersheds of varying shapes and sizes. Based on data on the EPA website, there are 54 watersheds located within the state of Florida. The area within a watershed acts as a funnel to channel water to a central location.
Catchment factors
So, what exactly plays in to how much and how quickly water reaches an area like Newnan's Lake and why how would that be impacted in times of drought or heavy rainfall? Catchment factors are: topography, shape, size, soil type, and land use (paved or roofed areas). Catchment topography and shape determine the time taken for rain to reach the basin with areas of more significant elevation change and more round watershed areas having water reach the basin faster; while catchment size, soil type, and development determine the amount of water to reach the basin.
Newnan's Lake
Newnan's Lake is a shallow basin located in Alachua County, FL. The average depth of the lake is just under 5 feet and the maximum depth is only 12 feet. The surface of the lake averages about 7,200 acres, however this varies significantly depending on rainfall. The Newnan's Lake watershed covers an area of about 119 square miles.
As recently as 2000, severe drought conditions dropped the surface area of the lake significantly and allowed for the discovery of more than Native American 100 canoes, some dating back more than 5,000 years. With easing of those drought conditions, the site where they were discovered is again underwater. The vast majority (>85%) of the Newnan's Lake watershed is forest and wetlands. A large drainage area north of the lake supplies the majority of the water inflow (via Hatchett Creek and Little Hatchett Creek with Bee Tree Creek and Lake Forest Creek providing additional inflow) and the major outflow source is Prairie Creek to the south. In the 1960s, a weir was constructed to increase water levels in the lake, however this was later removed to allow a more natural fluctuation in levels.
Topography
The area surrounding Newnan's Lake is relatively flat. The entire watershed ranges from an elevation of around 75 feet up to a maximum elevation just over 150 feet.
Shape
The shape of the Newnan's Lake watershed is relatively round.
Soil Type
The soil under Newnan's Lake is a fairly impermeable clay. The soil in the area is mostly hydric or partially hydric, meaning that they are either seasonally or permanently saturated. There are nearly 30 different soil types identified within the watershed according to the water management district report.
Land Use
About 85% of the watershed is forest and wetland, although there are areas of heavy industrial use and the Gainesville airport within the watershed.
To claim credit for this earthcache, please email the answers to the following questions to the owner through their profile page. Do not post your answers in your log, even if encrypted. If an email is not received or answers are posted in your log, your log will be deleted
1) At GZ, you should be near a bench. How far is it from the bench to the water's edge?
2) What factors would make the distance from the bench to the water change from season to season and from year to year?
3) Using the map of the watershed above, which inflow creek do you think provides the highest levels of pollution to Newnan's Lake?
4) What impact do you think it would have on the lake if there was a lower percentage of hydric soils in the watershed area?
5) While not required, please feel free to post any pictures of your time at the park.
References:
http://water.epa.gov/type/watersheds/whatis.cfm
http://alachuacounty.us/Depts/EPD/Documents/WaterResources/Newnans%20Lake.pdf
http://www.dep.state.fl.us/water/tmdl/docs/tmdls/final/gp1/newnans_lake_nut_tmdl.pdf
http://www.sjrwmd.com/landmanagementplans/pdfs/2013_Newnans_Lake_CA.pdf