Arroyo de en Medio
Encyclopedia
Arroyo de en Medio is a 2.5 miles (4 km) coastal stream
in western San Mateo County, California
. Arroyo de en Medio rises on the western slopes of Montara Mountain
and discharges to the Pacific Ocean
at Half Moon Bay
at the location of the unincorporated community of Miramar
at Miramar Beach
. The watershed of Arroyo de en Medio consists of relatively permeable sandy soils capable of significant recharge to its aquifers, which supply considerable potable water
to the local area. Arroyo is Spanish for creek; de en Medio means literally "of in between" but a closer more functional translation may be in the middle.
overlies heavily fractured granitic
based bedrock
aquifer
s. This upper pocket groundwater complex feeds down-basin alluvial fan deposits on the coastal plain
. These alluvial fans exhibit some characteristics of a confined aquifer, but also respond to recharge from precipitation
.
s in a marsh
y setting.
The streambed at the mouth is essentially covered by water dependent plant species. These include willow
(Salix sp.), sedge
(Carex
sp.), stream monkey flower (Mimulus sp.) and red alder
(Alnus oregona). These and other riparian plants form the food resource of many fauna
l species, either directly or indirectly. Many orb web weaving spiders at the mouth indicates the abundance of insects utilized as prey by certain vertebrate
s such as salamander
s, tree frog
s, lizard
s, and many resident and migratory birds. The site is also utilized for avafaunal nesting and breeding. In the 1989 survey by Earth Metrics, no sightings of the endangered San Francisco garter snake
were made, although this snake was observed at nearby Denniston Creek
. The mouth reach is classified as a riparian corridor under the strict meaning defined by the San Mateo County Local Coastal Plan
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
in western San Mateo County, California
San Mateo County, California
San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and...
. Arroyo de en Medio rises on the western slopes of Montara Mountain
Montara Mountain
Montara Mountain, positioned between the unincorporated community of Montara, California to the southwest and the city of Pacifica, California to the north, forms the northern spur of the Santa Cruz Mountains, a narrow mountain range running the length of the San Francisco Peninsula that separates...
and discharges to the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
at Half Moon Bay
Half Moon Bay
Half Moon Bay is a city in San Mateo County, CaliforniaHalf Moon Bay may also refer to:- Geographic features :* Half Moon Bay , a bay on the San Mateo County Coast of California...
at the location of the unincorporated community of Miramar
Miramar
Miramar is a place name of Spanish origin. It means "sea-view" or "sea sight" from mira and mar .-Places:Asia*Miramar, Panaji, GoaEurope*Miramar, a hamlet in the commune of Théoule-sur-Mer, France...
at Miramar Beach
Miramar Beach, California
Miramar Beach is a sandy beach in western San Mateo County, California. Miramar Beach is one of the numerous beaches on Half Moon Bay, a Pacific Ocean embayment noted for its surfing and extensive visitation...
. The watershed of Arroyo de en Medio consists of relatively permeable sandy soils capable of significant recharge to its aquifers, which supply considerable potable water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
to the local area. Arroyo is Spanish for creek; de en Medio means literally "of in between" but a closer more functional translation may be in the middle.
Groundwater
In the headwaters area, coarse grained decomposed graniteDecomposed granite
Decomposed granite, also known as DG, is granitic rock that has weathered to the point that it readily fractures into smaller pieces or chunks of weak rock. Further weathering produces rock that easily crumbles into mixtures of gravel, sand, and silt-sized particles with some clay...
overlies heavily fractured granitic
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
based bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s. This upper pocket groundwater complex feeds down-basin alluvial fan deposits on the coastal plain
Coastal plain
A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in eastern South America. The southwestern coastal plain of North America is notable for its species diversity...
. These alluvial fans exhibit some characteristics of a confined aquifer, but also respond to recharge from precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
.
Mouth
At the mouth of Arroyo de en Medio, the stream cuts through a flat marine terrace plain of alluvium, forming steep sided banks of approximately 40 degrees with respect to the channel floor; the channel floor is about eight meters deep relative to the bank tops. Even at the mouth, Arroyo de en Medio is considered intermittent, since the flow typically ceases in the summer months. However, there is some summer standing water in the channel near the mouth, the result of street runoff from summer irrigation and car washing. The stream mouth is clear of canopy vegetation but densely filled with sedgeCyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
s in a marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
y setting.
The streambed at the mouth is essentially covered by water dependent plant species. These include willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
(Salix sp.), sedge
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
(Carex
Carex
Carex is a genus of plants in the family Cyperaceae, commonly known as sedges. Other members of the Cyperaceae family are also called sedges, however those of genus Carex may be called "true" sedges, and it is the most species-rich genus in the family. The study of Carex is known as...
sp.), stream monkey flower (Mimulus sp.) and red alder
Red Alder
Alnus rubra, the Red alder, is a deciduous broadleaf tree native to western North America.-Description:It is the largest species of alder in North America and one of the largest in the world, reaching heights of 20–35 m. The official tallest red alder stands 32 meters tall in Clatsop County, Oregon...
(Alnus oregona). These and other riparian plants form the food resource of many fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
l species, either directly or indirectly. Many orb web weaving spiders at the mouth indicates the abundance of insects utilized as prey by certain vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s such as salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s, tree frog
Tree frog
Hylidae is a wide-ranging family of frogs commonly referred to as "tree frogs and their allies". However, the hylids include a diversity of frog species, many of which do not live in trees, but are terrestrial or semi-aquatic.-Characteristics:...
s, lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s, and many resident and migratory birds. The site is also utilized for avafaunal nesting and breeding. In the 1989 survey by Earth Metrics, no sightings of the endangered San Francisco garter snake
San Francisco garter snake
The San Francisco Garter Snake is a slender multi-colored colubrid snake. Designated as an endangered species since the year 1967, it is endemic to California and resides only in San Mateo County, California, and the extreme northern part of coastal Santa Cruz County, California...
were made, although this snake was observed at nearby Denniston Creek
Denniston Creek
Denniston Creek is a coastal stream in western San Mateo County, California. Denniston Creek rises on the western slopes of Montara Mountain and discharges to the Pacific Ocean at Pillar Point Harbor somewhat north of El Granada Beach...
. The mouth reach is classified as a riparian corridor under the strict meaning defined by the San Mateo County Local Coastal Plan
See also
- Denniston CreekDenniston CreekDenniston Creek is a coastal stream in western San Mateo County, California. Denniston Creek rises on the western slopes of Montara Mountain and discharges to the Pacific Ocean at Pillar Point Harbor somewhat north of El Granada Beach...
- List of watercourses in the San Francisco Bay Area
- Naples CreekNaples CreekNaples Creek is a stream in San Mateo County, California, USA that rises on the western slopes of the Santa Cruz Mountains and discharges to the Pacific Ocean. The specific point of discharge is onto Naples Beach, a unit of the Half Moon Bay State Beach...