Authorized by the Flood Control Act of 1938, Mosquito Creek Lake is one of 16 flood control projects in the Pittsburgh District. The project provides flood protection for the Mahoning River Valley as well as the Beaver and upper Ohio Rivers. Since its completion in 1944, Mosquito Creek Lake has prevented flood damages estimated to be in excess of $415 million. Mosquito has the capability to store the equivalent run-off of 29 inches of precipitation from its 97 square mile drainage area. When compared to the savings which have resulted, the construction cost of just over $4 million appears small. Mosquito Creek Lake also stores water and releases it downstream during dry periods to improve water quality and quantity for domestic and industrial use, recreation, esthetics and aquatic life. A feature unique to Mosquito Creek Lake is its use of an uncontrolled natural spillway. The natural spillway is located at the upper end of the lake in a low-lying reach of the Mosquito Creek – Grand River Divide. The elevation of the spillway at the point of divide is such that if an impoundment of flood waters should fill the lake, to an elevation of 904 feet above sea level, the southerly outflow of the lake would be reversed. The outflow would then be discharged through the natural spillway into a tributary of the Grand River which flows north into Lake Erie.
Mosquito Creek Lake Dam is known as a Rolled-Earth Dam. Earth-fill dams, also called earthen, rolled-earth or simply earth dams, are constructed as a simple embankment of well compacted earth. A homogeneous rolled-earth dam is entirely constructed of one type of material but may contain a drain layer to collect seep water. A zoned-earth dam has distinct parts or zones of dissimilar material, typically a locally plentiful shell with a watertight clay core. Modern zoned-earth embankments employ filter and drain zones to collect and remove seep water and preserve the integrity of the downstream shell zone. An outdated method of zoned earth dam construction utilized a hydraulic fill to produce a watertight core. Rolled-earth dams may also employ a watertight facing or core in the manner of a rock-fill dam. An interesting type of temporary earth dam occasionally used in high latitudes is the frozen-core dam, in which a coolant is circulated through pipes inside the dam to maintain a watertight region of permafrost within it. Because earthen dams can be constructed from materials found on-site or nearby, they can be very cost-effective in regions where the cost of producing or bringing in concrete would be prohibitive.
During extended periods of increased precipitation the US Army Corps. of Engineers maintenance workers must inspect the dam daily to ensure that their are no issues with the dam's structural integrity. This is accomplished by checking the the readings on five pressure gauges located inside the heart of the dam as well as checking the water levels in two dozen piezometers located on the earthen portions of the dam.
Most people underestimate the effect that a dam of this scale can have on the land and environment around it. Take a moment to familiarize yourself with some of the terms commonly used when discussing Hydrology and understand what hydrology is.
The definition of hydrology is the branch of science or geology that studies the Earth's water. The study of how the major bodies of water have shifted, expanded and changed land masses is an example of hydrology.
Hydrology is the study of the distribution and movement of water. The dam spillway regulates the lake's level (stage) by allowing the discharge (flow) to vary throughout the seasonal changes in the watershed. This prevents erosion of the area along the streams and the lake's shore.
Hydrological Terms:
Headwater - The upstream portion of a watershed.
Reservoir (pool) level - The elevation of the water in a reservoir at a given time, measured in feet above sea level.
Top of gates - The maximum controlled elevation at a project, typically the top of a spillway gate in a closed position or crest elevation of an uncontrolled outlet structure.
Spillway - A channel or passageway around or over a dam through which water is released, or "spilled," past the dam. Spillways at some dams are controlled with gates. At others, water flows over the top of the spillway automatically when the reservoir level gets to a certain elevation. A spillway is a safety valve for a dam; it can be used to discharge rainfall and runoff from major storms as necessary to maintain the reservoir below a predetermined maximum level.
CFS - Cubic feet per second, typically used as a measure of flow in a stream. A cubic foot is equivalent to about 7.5 gallons. A measure of 1,000 cfs is equal to about 7,500 gallons of water per second
Tailwater - The part of a river downstream from a dam, where the flow and quality of the water are substantially affected by the dam's discharge.
Now that you understand some of the basic terms of hydrology, you should have a firm understanding of the basics needed to make good observations at the posted coordinates.
Once you arrive at the posted coordinates, you’ll want to take a moment to notice what’s around you. As you venture down the stairs, you’ll see the dam and a fenced/concrete area to the left. This fenced concrete area is the spillway to the dam. Just below the spillway and further to the right, you’ll notice a more natural creek area (and most likely a few people fishing).
This natural area below the dam and the spillway is the area most impacted by the change in flow caused by the dam. For example, take a moment to imagine what the area you’re standing in would look like if the dam were not in place. Would the water level be higher or lower than it is now? Would the creek be wider or narrower? Why? The spillway has had a profound impact on the makeup of the creekbed as well. The decrease in water flow due to the reservoir leads to water losing the sediments it carries, to the bottom of the reservoir. This decreases the water storing potential of the reservoir and also decreases the silt and nutrients from being carried downstream, makes soil downstream less fertile, which harms the plants and animals that live and grow there, since the reduced fertility will reduce the number of plants and trees that can grow downstream and so, cause the number of animal habitat to drop, decreasing the biodiversity of the area. Because of the drop in the number of trees that can grow and hold soil together, the soil is more prone to erosion, meaning the structure of the soil is lost, making it less and less suitable for human or animal habitation.
Habitat loss is the biggest cause of extinction. Freshwater habitats are thought to be the habitats face the highest loss of biodiversity. Building a dam in a river causes great changes within the river and leads to great changes in the river systems, leading to habitat loss. The structure of the dam itself acts as a barrier preventing fish populations from migrating along the river. The formation of a large still body of water in place of a small rapidly moving body of water changes the dynamics of the water system, which makes it less suitable for the original species to survive, which may lead to extinction. The temperature and chemical composition of water in the reservoir is also different from that of the flowing river. The reduced water flowing downstream causes the water downstream to be more saline, making it less suitable for certain fish nurseries and also enables predators to reach them. The water running off from the catchment areas upstream carry with them sediments and nutrients. Human activity upstream can increase the nutrient level in the reservoir with may lead to eutrophication, which eventually leads to the loss of most species in the reservoir. For example, river dolphins of the Yangtze were lead to extinction after the Three Gorges Dam was built; the variety of fishes dolphins in the Mekong region are also at risk or extinction. The Glines Canyon Dams in the Elwha River in Washington, USA, has been responsible for almost wiping out the entire steelhead trout and salmon population. This loss of fish populations can also lead to loss of economy from fisheries.
This EarthCache deals with an aspect of Earth Science that teaches geocachers about how the area has been influenced by processes that have shaped the landscape of this site (hydrology). Hopefully, you will learn some of the terms pertaining to hydrology and be able to relate them to this dam/lake.
The requirement to log this cache is that you email the cache owner (DO NOT POST) the answers to the questions below.
Please reference the GC code of this geocache in your email so I know which cache you have found. (GC61FEW) ** Failure to do so will result in your log being deleted**
Requirements:
1. Describe the processes put in place along the spillway to prevent additional land erosion.
2. Observe the area below the spillway and provide one example of a change caused by the spillway hydrology.
3. Describe what you think the area would be like if the dam were not in place (use landmarks and examples from the landscape around you).
4. Please post a picture of yourself with the spillway in the background along with your log. (REQUIRED)
History:
In 1930's, plans were drawn up to dam the Mosquito Creek under the Federal Flood Control Act to alleviate floods on the Mahoning, Beaver and Ohio rivers. The dam would also provide domestic water supply for the city of Warren and pollution abatement as a result of the industrialized steel production along the Mahoning River. Completed in April 1944, the dam's capacity held 34 billion gallons of water covering 7,850 acres of land. In 1946. the U.S. Army Corps of Engineers entered into an agreement with the Ohio Department of Natural Resources to manage the recreation on the lake.
Natural Features:
Before Ohio was settled, the banks of Mosquito Creek were hidden by a vast forest that covered most of the state. Little remains of the ancient forest that stood for nearly 10,000 years. In the Mosquito Lake area, regrowth has occurred and the nice stands of beech-maple woodlands can be enjoyed. In pioneer times, the beech-maple belt was very extensive and stretched from Mansfield to Pennsylvania. The reason is that this area has more cloudy days, cooler summer temperatures and more winter snow cover as compared to the rest of Ohio.
The park's woodlands support colonies of spring beauties, anemones, Dutchman's breeches, purple cresses and other spring wildflowers. Goldenrod and asters will bloom in the fall in the park's open areas. Many wildlife species find the park's varied habitats suitable. Red fox, woodchuck, muskrat, beaver, fox squirrel, raccoon, rabbit and white-tailed deer are common. Recently, river otters were reintroduced in nearby favorable locations. Several otter families have been sighted.
Many birds live in or migrate through the area including robins, warblers, swallows and sparrows. The yellow-bellied sapsucker and hairy woodpecker are uncommon in other parts of Ohio but abundant in this part of the state. Numerous species of waterfowl and shorebirds take advantage of the park's many wetlands during spring and fall migrations. Canada geese, herons, tundra swans, great egrets and a variety of ducks can be observed. Large predatory birds including several species of hawks and the magnificent bald and golden eagles have been spotted here.
CAUTION: Water levels in this area may change rapidly due to the nature of the dam. Never put yourself in harms way when seeking this cache. All logging requirements of this earthcache can be safely completed without entering the water or any restricted area of the dam or its facilities. Please remain outside the fenced areas, and remain off of concrete structures.
History and other information borrowed from:
http://www.lrp.usace.army.mil/Portals/72/docs/Recreation/Mosquito2010.pdf
http://parks.ohiodnr.gov/mosquitolake#history
http://www.lrp.usace.army.mil/Portals/72/docs/Recreation/MosquitoLakeStats.pdf
http://waterdata.usgs.gov/nwis/inventory/?site_no=03095500&agency_cd=USGS
http://water.usgs.gov/wsc/glossary.html
http://12.000.scripts.mit.edu/mission2017/dams-and-reservoirs/