Misplaced Pages

#188811

32-518: Lake Hodges has a total capacity of 30,251 acre-feet of water. Water level elevation in the lake is maintained at a maximum of 280 feet (85 m) above sea level, 35 feet (11 m) lower than the dam's maximum of 315 feet (96 m) spillway to ensure safe operations. The lake level can fluctuate significantly, depending upon the amount of runoff received from the San Dieguito River drainage basin. Interstate 15 crosses Lake Hodges via

64-402: A fuse plug . If present, the fuse plug is designed to wash out in case of a large flood, greater than the discharge capacity of the spillway gates. Although many months may be needed for construction crews to restore the fuse plug and channel after such an operation, the total damage and cost to repair is less than if the main water-retaining structures had been overtopped. The fuse plug concept

96-443: A baffle of concrete blocks but usually have a "flip lip" and/or dissipator basin, which creates a hydraulic jump , protecting the toe of the dam from erosion. Stepped channels and spillways have been used for over 3,000 years. Despite being superseded by more modern engineering techniques such as hydraulic jumps in the mid twentieth century, since around 1985 interest in stepped spillways and chutes has been renewed, partly due to

128-463: A few dams lack overflow spillways and rely entirely on bottom outlets. The two main types of spillways are controlled and uncontrolled. A controlled spillway has mechanical structures or gates to regulate the rate of flow. This design allows nearly the full height of the dam to be used for water storage year-round, and flood waters can be released as required by opening one or more gates. An uncontrolled spillway, in contrast, does not have gates; when

160-565: A plunge pool, or two ski jumps can direct their water discharges to collide with one another. Third, a stilling basin at the terminus of a spillway serves to further dissipate energy and prevent erosion. They are usually filled with a relatively shallow depth of water and sometimes lined with concrete. A number of velocity-reducing components can be incorporated into their design to include chute blocks, baffle blocks, wing walls, surface boils, or end sills. Spillway gates may operate suddenly without warning, under remote control. Trespassers within

192-419: A spillway to regulate downstream flow—by releasing water in a controlled manner before the reservoir is full, operators can prevent an unacceptably large release later. Other uses of the term "spillway" include bypasses of dams and outlets of channels used during high water, and outlet channels carved through natural dams such as moraines . Water normally flows over a spillway only during flood periods, when

224-499: Is a structure used to provide the controlled release of water downstream from a dam or levee , typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels . Spillways ensure that water does not damage parts of the structure not designed to convey water. Spillways can include floodgates and fuse plugs to regulate water flow and reservoir level. Such features enable

256-460: Is designed like an inverted bell , where water can enter around the entire perimeter. These uncontrolled spillways are also called morning glory (after the flower ), or glory hole spillways. In areas where the surface of the reservoir may freeze, this type of spillway is normally fitted with ice-breaking arrangements to prevent the spillway from becoming ice-bound. Some bell-mouth spillways are gate-controlled. The highest morning glory spillway in

288-443: Is set by dam safety guidelines, based on the size of the structure and the potential loss of human life or property downstream. The United States Army Corps of Engineers bases their requirements on the probable maximum flood (PMF) and the probable maximum precipitation (PMP). The PMP is the largest precipitation thought to be physically possible in the upstream watershed. Dams of lower hazard may be allowed to have an IDF less than

320-469: Is significantly out of their reach. The city has a volunteer program, managed by Kayaking For The Birds , which maintains all of the lake's shoreline areas, keeping it free of discarded fishing line and other angling supplies, as well as all other litter which could pose a threat to birds and wildlife. It is home to the Lake Hodges Colony of Argentine ants. Spillway A spillway

352-604: Is used where building a spillway with the required capacity would be costly. A chute spillway is a common and basic design that transfers excess water from behind the dam down a smooth decline into the river below. These are usually designed following an ogee curve . Most often, they are lined on the bottom and sides with concrete to protect the dam and topography. They may have a controlling device and some are thinner and multiply-lined if space and funding are tight. In addition, they are not always intended to dissipate energy like stepped spillways. Chute spillways can be ingrained with

SECTION 10

#1732791841189

384-662: The Lake Hodges Bridge . Approximately 1,000 feet (300 m) west of the I-15 freeway bridge is a bicycle/pedestrian bridge which opened on May 15, 2009, and is the longest stressed ribbon bridge in the world. Lake Hodges Dam is a multiple-arch dam that sits on the San Dieguito River. It was commissioned by the Volcan Water Company and designed by John S. Eastwood . It was completed in 1918 (106 years ago)  ( 1918 ) , and later purchased by

416-463: The PMF. As water passes over a spillway and down the chute, potential energy converts into increasing kinetic energy . Failure to dissipate the water's energy can lead to scouring and erosion at the dam's toe (base). This can cause spillway damage and undermine the dam's stability. To put this energy in perspective, the spillways at Tarbela Dam could, at full capacity, produce 40,000 MW; about 10 times

448-430: The ability to store 20,000 acre-feet (25,000,000 m) of water at Hodges Reservoir for emergency use. This system is also used to provide electrical power to the grid during high demand times of the day. Water is pumped from Lake Hodges to Olivenhain at night when demand (and rates) for electricity is low. It is then flowed back down through generators during peak demand times. In 2019 a hypolimnetic aeration system

480-407: The capacity of its power plant. The energy can be dissipated by addressing one or more parts of a spillway's design. First, on the spillway surface itself by a series of steps along the spillway (see stepped spillway ). Second, at the base of a spillway, a flip bucket can create a hydraulic jump and deflect water upwards. A ski jump can direct water horizontally and eventually down into

512-508: The city expects to complete construction of a new dam to replace this one. The reservoir has to be kept at a low elevation of 280 feet due to safety concerns, which means that the city can't access the water. Lake Hodges is a popular location for hiking, birding, fishing, kayaking, windsurfing, photography, and picnicking. It is surrounded by the hiking trails of the San Dieguito River Park and those trails are connected to

544-873: The city of San Diego. Water from the Lake Hodges Reservoir services the customers of the Santa Fe Irrigation District and the San Dieguito Water District. The dam is 131 ft tall and 729 ft wide. In 2005, the San Diego County Water Authority , in conjunction with the City of San Diego , began work on a pipeline to connect Hodges Reservoir with Olivenhain Reservoir . The project was completed in 2012. The connection provides

576-414: The difference in height between the intake and the outlet to create the pressure difference required to remove excess water. Siphons require priming to remove air in the bend for them to function, and most siphon spillways are designed to use water to automatically prime the siphon. One such design is the volute siphon, which employs volutes or fins on a funnel to form water into a vortex that draws air out of

608-423: The flood is sometimes expressed as a return period . A 100-year recurrence interval is the flood magnitude expected to be exceeded on the average of once in 100 years. This parameter may be expressed as an exceedance frequency with a 1% chance of being exceeded in any given year. The volume of water expected during the design flood is obtained by hydrologic calculations of the upstream watershed. The return period

640-496: The lake is home to nesting pairs of the least Bell's vireo , an endangered species. Two other threatened bird species, the California gnatcatcher and the coastal cactus wren , can be found in the areas around the lake. When water levels are up, and remain consistent, it is possible to observe the courtship and parenting behaviors of the western grebe as well as Clark's grebe . Both species can be seen seasonally nesting at

672-455: The maximum level of the lake 20 feet below the spillway. Due to its advanced age, Lake Hodges had been closed to the public so the dam could undergo repair work. The water level was lowered in May 2022, when routine maintenance revealed cracks and defects, which turned the dam repairs into a yearlong process. On June 2, 2023, the dam, lake, and recreation area opened to the public again. Around 2034,

SECTION 20

#1732791841189

704-404: The park's 65 miles of trails . The Audubon Society has proclaimed Lake Hodges and vicinity to be a Globally Important Bird Area . The ability to see almost 200 bird species attracts many birders as well as amateur and professional photographers. Fishing is allowed 9 months of the year and near record sized Largemouth Bass have been caught in the lake. The riparian habitat surrounding

736-428: The reservoir has reached its capacity and water continues entering faster than it can be released. In contrast, an intake tower is a structure used to control water release on a routine basis for purposes such as water supply and hydroelectricity generation. A spillway is located at the top of the reservoir pool. Dams may also have bottom outlets with valves or gates which may be operated to release flood flow, and

768-411: The reservoir is controlled by the mechanical gates. In this case, the dam is not designed to function with water flowing over the top if it, either due to the materials used for its construction or conditions directly downstream. If inflow to the reservoir exceeds the gate's capacity, an artificial channel called an auxiliary or emergency spillway will convey water. Often, that is intentionally blocked by

800-459: The river downstream. One parameter of spillway design is the largest flood it is designed to handle. The structures must safely withstand the appropriate spillway design flood (SDF), sometimes called the inflow design flood (IDF). The magnitude of the SDF may be set by dam safety guidelines, based on the size of the structure and the potential loss of human life or property downstream. The magnitude of

832-404: The shallow eastern end of the lake. However, the lake's pumping system can raise or lower the water level by quite a few inches every day; these fluctuations can potentially cause the raft-like, floating grebe nests to float to shore, run aground, and be at risk of predation by carnivorous animals. In the event that a nest is beached, it will be subsequently abandoned by the parents, especially if it

864-414: The spillway are at high risk of drowning. Spillways are usually fenced and equipped with locked gates to prevent casual trespassing within the structure. Warning signs, sirens, and other measures may be in place to warn users of the downstream area of sudden release of water. Operating protocols may require "cracking" a gate to release a small amount of water to warn persons downstream. The sudden closure of

896-424: The system. The priming happens automatically when the water level rises above the inlets. The ogee crest over-tops a dam, a side channel wraps around the topography of a dam, and a labyrinth uses a zig-zag design to increase the sill length for a thinner design and increased discharge. A drop inlet resembles an intake for a hydroelectric power plant, and transfers water from behind the dam directly through tunnels to

928-474: The use of new construction materials (e.g. roller-compacted concrete , gabions ) and design techniques (e.g. embankment overtopping protection). The steps produce considerable energy dissipation along the chute and reduce the size of the required downstream energy dissipation basin. Research is still active on the topic, with newer developments on embankment dam overflow protection systems, converging spillways and small weir design. A bell-mouth spillway

960-474: The water rises above the lip or crest of the spillway, it begins to be released from the reservoir. The rate of discharge is controlled only by the height of water above the reservoir's spillway. The fraction of storage volume in the reservoir above the spillway crest can only be used for the temporary storage of floodwater; it cannot be used as water supply storage because it sits higher than the dam can retain it. In an intermediate type, normal level regulation of

992-695: The world is at Hungry Horse Dam in Montana, U.S., and is controlled by a 64-by-12-foot (19.5 by 3.7 m) ring gate. The bell-mouth spillway in Covão dos Conchos reservoir in Portugal is constructed to look like a natural formation. The largest bell-mouth spillway is in Geehi Dam , in New South Wales, Australia, measuring 105 ft (32 m) in diameter at the lake's surface. A siphon uses

Lake Hodges - Misplaced Pages Continue

1024-400: Was installed at the site of the former Reservoir keeper's house with a Speece cone installed at the bottom of the lake between that location and Alva canyon. Following the 2017 Oroville Dam crisis , the state of California conducted spillway inspections on all dams in the state. Hodges Dam did not pass inspection and, as a result, San Diego Public Utilities Department was ordered to keep

#188811