Lopez Lake is a reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 near the city of Arroyo Grande

Arroyo Grande, California

Arroyo Grande is a city in San Luis Obispo County, California, United States. The population was 17,252 at the 2010 census.-Geography:Arroyo Grande is a small coastal town with historic, suburban, and rural elements located at...

 in San Luis Obispo County, California

San Luis Obispo County, California

San Luis Obispo County is a county located along the Pacific Ocean in the Central Coast of the U.S. state of California, between Los Angeles and the San Francisco Bay Area. As of the 2010 census its population was 269,637, up from 246,681 at the 2000 census...

. The lake is formed by Lopez Dam on Arroyo Grande Creek, 9 mi (14.5 km) upstream from 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...

. The creek

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...

 drains about 60 sq mi (155.4 km²) above the dam and 90 sq mi (233.1 km²) below. The dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 was built in 1969 and is operated by the San Luis Obispo County Flood Control and Water Conservation District. The earth-fill dam was retrofitted to protect against earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s between 2001 and 2003. The lake's capacity is 49200 acre.ft.

Lopez Lake provides drinking 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...

 for Arroyo Grande, Grover Beach, Pismo Beach, Oceano and Avila Beach. It also provides groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 recharge, water for irrigation

Irrigation

Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

 and flood control

Flood control

In communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...

. Unlike most municipal water supplies, human contact with the water is permitted. Sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

, wind surfing, water skiing

Water skiing

thumb|right|A slalom skier making a turn on a slalom waterski.Waterskiing is a sport where an individual is pulled behind a boat or a cable ski installation on a body of water, skimming the surface.-History:...

, swimming, fishing

Fishing

Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....

 and camping

Camping

Camping is an outdoor recreational activity. The participants leave urban areas, their home region, or civilization and enjoy nature while spending one or several nights outdoors, usually at a campsite. Camping may involve the use of a tent, caravan, motorhome, cabin, a primitive structure, or no...

 are popular activities. There is also a waterslide next to the lake. To prevent contamination of the drinking water, water from the lake is piped 3 mi (4.8 km) to a terminal reservoir, where it remains to allow particles to settle out and pathogen

Pathogen

A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s to die off. The water then goes through flocculation

Flocculation

Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually...

, filtration

Filtration

Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...

 and chlorination

Chlorination

Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...

at the Lopez Water Treatment Plant.

The recreation area consists of 4200 acre (1,699.7 ha) of open space, trails and camping areas. A network of equestrian, bike and hiking trails criss-cross the park which is primarily oak woodland and coastal sage scrub. The area is frequented by black bears, mountain lions, mule deer and a number of other small mammals.

Several special events are held at the park yearly such as the Lopez Lake Trout Derby held in May, the California Polytechnic University Triathlon and the Scott Tinley Dirty Adventures Triathlon.