**James J. Lenihan Dam**
**Definition:**
James J. Lenihan Dam is an earthfill dam located in Santa Clara County, California, primarily constructed for flood control and water conservation purposes. It impounds the Los Gatos Creek to form Lexington Reservoir, serving as a critical water resource and recreational area for the region.
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# James J. Lenihan Dam
## Overview
James J. Lenihan Dam is a significant infrastructure project situated in the Santa Cruz Mountains of Santa Clara County, California. The dam impounds Los Gatos Creek, creating the Lexington Reservoir, which plays a vital role in regional water management, flood control, and recreation. Named after James J. Lenihan, a prominent local figure in water resource management, the dam is operated by the Santa Clara Valley Water District (SCVWD).
Constructed in the mid-20th century, the dam has contributed to the development and sustainability of the Santa Clara Valley by providing a reliable water supply, mitigating flood risks, and supporting local ecosystems. Its location within a mountainous terrain and proximity to urban areas underscores its importance in balancing environmental conservation with human needs.
## History
### Planning and Construction
The need for a dam on Los Gatos Creek was identified in the early 20th century as the Santa Clara Valley experienced rapid population growth and agricultural expansion. Flooding events and water shortages highlighted the necessity for a controlled water storage and flood mitigation system.
Planning for the dam began in the 1950s, with the Santa Clara Valley Water District spearheading the project. The design focused on an earthfill dam structure, chosen for its adaptability to the local geology and cost-effectiveness. Construction commenced in the late 1950s and was completed in 1956, marking a significant milestone in regional water infrastructure.
### Naming
Originally referred to as Lexington Dam, the structure was renamed James J. Lenihan Dam in honor of James J. Lenihan, a former director of the Santa Clara Valley Water District. Lenihan was recognized for his dedication to water resource management and his contributions to the development of the district’s water systems.
## Structural Characteristics
### Design and Dimensions
James J. Lenihan Dam is an earthfill dam, a type of embankment dam constructed primarily from compacted earth materials. This design is well-suited to the local topography and seismic considerations of the region.
– **Height:** Approximately 208 feet (63 meters)
– **Length:** Approximately 1,000 feet (305 meters)
– **Crest Width:** Varies, typically around 20 to 30 feet (6 to 9 meters)
– **Volume:** The dam contains millions of cubic yards of earthfill material.
The dam features a spillway designed to safely pass floodwaters downstream without damaging the structure. The spillway is an uncontrolled concrete chute located on one side of the dam.
### Reservoir Capacity
The dam impounds Lexington Reservoir, which has a total storage capacity of approximately 21,430 acre-feet (26.4 million cubic meters). The reservoir’s surface area covers roughly 450 acres (182 hectares) at full pool.
The reservoir serves multiple functions, including water supply storage, flood control, and recreational activities such as fishing, boating, and hiking.
## Hydrology and Watershed
### Los Gatos Creek
Los Gatos Creek is the primary inflow source for Lexington Reservoir. Originating in the Santa Cruz Mountains, the creek drains a watershed area of approximately 36 square miles (93 square kilometers). The creek’s flow is highly seasonal, with peak flows occurring during winter storms and reduced flows in the dry summer months.
The dam regulates the flow of Los Gatos Creek downstream, reducing flood risks in the urbanized areas of Los Gatos and Campbell, and ensuring a more consistent water supply during dry periods.
### Watershed Management
The Santa Clara Valley Water District manages the watershed to maintain water quality and ecological health. Efforts include monitoring sedimentation rates, controlling invasive species, and implementing erosion control measures to preserve the reservoir’s capacity and water quality.
## Operations and Management
### Flood Control
One of the primary functions of James J. Lenihan Dam is flood control. The dam captures and stores runoff from winter storms, releasing water in a controlled manner to prevent downstream flooding. The spillway and outlet works are designed to handle significant flood events, protecting communities along Los Gatos Creek.
### Water Supply
The reservoir provides a supplemental water supply for the Santa Clara Valley, particularly during dry seasons. Water stored in Lexington Reservoir is released downstream to recharge groundwater basins and support municipal and agricultural water demands.
### Environmental Considerations
The dam’s operation balances water resource needs with environmental protection. The Santa Clara Valley Water District implements flow release schedules to maintain aquatic habitats downstream, supporting native fish species and riparian ecosystems.
## Recreation and Public Use
Lexington Reservoir, formed by James J. Lenihan Dam, is a popular recreational destination. The surrounding area offers opportunities for:
– **Fishing:** The reservoir is stocked with various fish species, including trout and bass.
– **Boating:** Non-motorized boating such as kayaking and canoeing is permitted.
– **Hiking and Biking:** Trails around the reservoir provide scenic views and access to natural habitats.
– **Picnicking and Wildlife Viewing:** Designated areas support family outings and birdwatching.
The Santa Clara County Parks Department manages the recreational facilities, ensuring public safety and environmental stewardship.
## Environmental Impact
### Ecological Effects
The construction of the dam altered the natural flow regime of Los Gatos Creek, impacting native fish migration and riparian habitats. However, mitigation measures, including fish passage improvements and habitat restoration projects, have been implemented to reduce these effects.
### Sedimentation
Sediment accumulation in Lexington Reservoir reduces its storage capacity over time. The Santa Clara Valley Water District conducts periodic sediment surveys and employs sediment management strategies to prolong the reservoir’s operational life.
### Water Quality
Water quality in the reservoir is monitored regularly to detect pollutants and maintain standards suitable for aquatic life and recreational use. Efforts to control nutrient loading and prevent algal blooms are ongoing.
## Seismic Considerations
Located in a seismically active region, James J. Lenihan Dam was designed and constructed with earthquake resilience in mind. The earthfill structure provides inherent flexibility, and the dam is subject to regular inspections and seismic evaluations to ensure safety.
## Future Developments and Challenges
### Infrastructure Upgrades
As infrastructure ages, the Santa Clara Valley Water District plans periodic maintenance and upgrades to the dam’s facilities, including spillway improvements and instrumentation enhancements for better monitoring.
### Climate Change Impacts
Changing precipitation patterns and increased frequency of extreme weather events pose challenges for dam operations. Adaptive management strategies are being developed to address potential impacts on water supply reliability and flood control effectiveness.
### Community Engagement
Ongoing public outreach and education programs aim to increase community awareness of the dam’s role and promote responsible recreational use of Lexington Reservoir.
## See Also
– Santa Clara Valley Water District
– Lexington Reservoir
– Los Gatos Creek
– Flood control dams in California
– Earthfill dams
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**Meta Description:**
James J. Lenihan Dam is an earthfill dam in Santa Clara County, California, creating Lexington Reservoir for flood control, water supply, and recreation. Operated by the Santa Clara Valley Water District, it plays a vital role in regional water management and environmental stewardship.