Lake Needwood is a

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

in Derwood,

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

, United States. Located east of Rockville, in the eastern part of Montgomery County, it is situated on Rock Creek. The lake was created by damming Rock Creek in 1965 with the goal of providing

flood control Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...

and reducing

soil erosion Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...

. Lake Needwood also protects the

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

of the creek by functioning as a

retention basin A retention basin, sometimes called a wet pond, wet detention basin, or stormwater management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater r ...

to trap

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

from storm-water

runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock market ...

. The lake is part o
Rock Creek Regional Park
Visitors can rent pedal boats, rowboats, and

canoes A canoe is a lightweight narrow water vessel, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel and using a single-bladed paddle. In British English, the term ...

, and a flat-bottom

pontoon boat A pleasure boat with two lengthwise pontoons A pontoon boat is a flattish boat that relies on floats to remain buoyant. These pontoons (also called ''tubes'') contain much reserve buoyancy and allow designers to create large deck plans fitted wi ...

, the Needwood Queen, is available for rides. Also, the

picnic A picnic is a meal taken outdoors ( ''al fresco'') as part of an excursion, especially in scenic surroundings, such as a park, lakeside, or other place affording an interesting view, or else in conjunction with a public event such as preceding ...

areas surrounding the lake are popular locations for various events. Other park features include a visitors center and snack bar, hiking and biking trails,

playground A playground, playpark, or play area is a place designed to provide an environment for children that facilitates play, typically outdoors. While a playground is usually designed for children, some are designed for other age groups, or people ...

s, an

archery Archery is the sport, practice, or skill of using a bow to shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting and combat. In m ...

range and Needwood Golf Course. About one mile (1.6 km) southeast is Lake Needwood's sister lake, Lake Frank. Th
Rock Creek Trail
begins at Lake Needwood and can be followed along the course of Rock Creek, ending at the

Potomac River The Potomac River () drains the Mid-Atlantic United States, flowing from the Potomac Highlands into Chesapeake Bay. It is long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map. Retrieved Augus ...

Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...

Lake Needwood Dam

Lake Needwood is a Rock Creek impoundment formed by an earthen embankment, the Lake Needwood Dam. It is made of a high earthen dam built on a fractured rock foundation formed at the junction of the Boulder Gneiss and Upper Pelitic Schist geological formations. In addition to the Lake Needwood's principal spillway outlet, it has a wide emergency spillway originating between the Westside and the Rock Creek Trails. The dam was designed by the Natural Resources Conservation Service. The construction of the Lake Needwood Dam was complete in 1965. The dam is owned by the Maryland-National Capital Park and Planning Commission. At the time of construction, only the right portion of the dam bottom was treated with grout, likely predisposing the structure to generate a concentrated seepage of water from the left abutment during the 2006 Mid-Atlantic United States Flood. In 2007–2008, the earthen dam underwent a $3 million repair project to install a grout curtain below the Lake Needwood Dam to decrease seepage through its rock foundation and to upgrade the outlet control tower.

Habitat

Lake waters are inhabited by

largemouth bass The largemouth bass (''Micropterus salmoides'') is a carnivorous freshwater gamefish in the Centrarchidae ( sunfish) family, a species of black bass native to the eastern and central United States, southeastern Canada and northern Mexico, but ...

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

bluegill The bluegill (''Lepomis macrochirus''), sometimes referred to as "bream", "brim", "sunny", or "copper nose" as is common in Texas, is a species of North American freshwater fish, native to and commonly found in streams, rivers, lakes, ponds and ...

crappie Crappies () are two species of North American freshwater fish of the genus ''Pomoxis'' in the family Centrarchidae (sunfishes). Both species of crappies are popular game fish among recreational anglers. Etymology The genus name ''Pomoxis'' ...

, and

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...

. With a license,

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...

is permitted. Lake Needwood serves as a temporary stop for many North American migratory birds. However, the shoreline vegetation and soil integrity have been affected by non-migratory

Canada geese The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...

prompting efforts to control their population.

Mid-Atlantic United States flood of 2006

FEMA - 25162 - Photograph by Aaron Skolnik taken on 06-28-2006 in Maryland

There have been several evacuations of downstream residents during periods of heavy rain, due to concerns about the structural integrity of the

earthen dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...

constructed in 1965. The latest evacuation, of approximately 2,400 people, was on June 28, 2006. Communities just south of the lake were evacuated and were housed in temporary shelters at nearby high schools until the lake's level dropped. The evacuees lived in 500

apartment An apartment (American English), or flat (British English, Indian English, South African English), is a self-contained housing unit (a type of residential real estate) that occupies part of a building, generally on a single story. There are ma ...

s at the Rock Creek Terrace complex on Veirs Mill Road in Rockville and in 700

single family home A stand-alone house (also called a single-detached dwelling, detached residence or detached house) is a free-standing residential building. It is sometimes referred to as a single-family home, as opposed to a multi-family residential dwelling ...

s in that area. Officials stated that the lake was above its normal level during the flood, and many

road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...

s in the surrounding area had been closed down for fear of

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

ing. As the flood subsided, evacuees returned home on June 29, 2006. Montgomery County

Homeland Security Homeland security is an American national security term for "the national effort to ensure a homeland that is safe, secure, and resilient against terrorism and other hazards where American interests, aspirations, and ways of life can thrive" to ...

director Gordon Aoyagi and County

Chief Administrative Officer A chief administrative officer (CAO) is a top-tier executive who supervises the daily operations of an organization and is ultimately responsible for its performance. Government and non-profit A CAO is responsible for administrative management of ...

Bruce Romer estimated that if the dam had broken, areas south of the lake could have flooded up to .

2010–2011 dredging project

Until 1990, the county government regularly conducted

dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...

projects of the lake to remove accumulated sediment. Dredging was then deferred for budgetary reasons. In 2008, the County started preparations to dredge sediment from the lake during 2010-2011. The dredging project aimed to improve water quality, as well as boating and fishing conditions. In October 2010, the water level was lowered by about six feet to allow more time for the sediment to dry out for dredging. The shallower north end of the lake was deepened from 1–4 feet deep to 12–18 feet deep. The lake was reopened in summer 2012.

Water quality

In 2010, lake waters tested positive for

microcystin Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria, commonly known as blue-green algae. Over 250 different microcystins have been discovered so far, of which microcystin-LR is the most common. Che ...

, a

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...

produced by

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

that can cause

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

damage. The toxin was also reported in the water in 2012–2017 and in 2020. Approximately 50 bright yellow signs are posted along trails around the lake advising patrons to keep pets away from the water. Cyanobacteria develop in the lake due to an overabundance of nutrients (nitrogen and phosphorus) in the water. In residential areas, the nutrients are generated by excessive

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

use and associated

urban runoff Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precipit ...

, which cause

harmful algal bloom A harmful algal bloom (HAB) (or excessive algae growth) is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes ...

s (HABs) in water bodies. Higher water temperature and low circulation are contributing factors.

References