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Position Statement of the Jasper Ridge Committee as Regards Removal
or Modification of Searsville Dam 
FROM: Jasper Ridge Committee-Professors Harold Mooney (chair) and Paul Ehrlich, Assistant Professor David Ackerly, Charles Knight (graduate student), and Philippe Cohen (Administrative Director).
Over the past several years, Stanford University has addressed a host of issues associated with San Francisquito Creek watershed management. The future of Searsville Lake and Dam, especially as it concerns potential modification or maintenance of existing conditions, has become a significant focus of the University, local and regional jurisdictions, and stakeholders within the watershed. The statement below clarifies the priorities and concerns of the Jasper Ridge Committee with respect to the future of Searsville Lake and Dam. The Committee wishes to make clear at the outset that we view the range of management options for Searsville Dam in terms of both their potential impacts to habitats in the Preserve and their potential to yield important research and educational opportunities. Currently, there are a number of options under consideration, including:
With this in mind and given the current state of knowledge, the option of altering Searsville Dam for other uses, such as flood damage mitigation, would have such obvious and debilitating impacts on the Preserve without any discernible benefits for the Preserve or its program activities, that it is viewed as an unacceptable management option. Specifically, the rapid rise and fall of lake water levels associated with flood control efforts would result in significant disruption and impact to Preserve habitats without any habitat enhancements that would benefit the Preserve and its mission. Important wetland, riparian, open water, and oak woodland habitat could be lost. Activities associated with dam modification would also take a heavy toll on infrastructure and potentially disrupt research and educational activities. To varying degrees the other management options present a broad range of potential costs and benefits to the Preserve. Currently, there is little information to suggest that lowering the dam provides any potential benefits to the Preserve that could mitigate the identifiable costs both in terms of the heavy toll on infrastructure and in lost or disrupted habitat. Specifically, wetland habitat could be lost and increased vulnerability to exotic species invasions could further undermine the integrity of Preserve habitats. Without further information to indicate otherwise, we see little potential benefit to the Preserve in lowering the dam. The best that dam lowering provides is the hope of maintaining current habitat extent and diversity. While dam removal presents many of the same costs as lowering the dam, it does hold the potential for significantly enhancing riparian habitat and restoring steelhead trout runs through the Preserve and to the upper watershed. So unlike lowering the dam, removing Searsville Dam could potentially provide a net gain to the Preserve. Whether considering lowering or removing the dam, we want to caution that potential impacts from either option are significant enough that careful study is needed to determine the real extent and nature of the impacts in order to avoid severely undermining the integrity of Preserve habitats and its research and educational mission. Therefore, whatever management options are considered for Searsville Dam, the Committee urges Stanford to include the following objectives and conditions: 1) The removal, alteration, or even long-term maintenance of Searsville Dam presents a unique opportunity for research on the ecological, hydrological, and technological criteria and consequences of dam aging and removal. The dam is located within a biological preserve with an extensive background of ecological research, and the protection of the watershed and surrounding communities provides an ideal setting for long-term research on ecosystem effects of dam removal or alternative management strategies. Therefore, any dam removal or management proposal must be accompanied by a commitment to implement and support long-term research on the consequences for biodiversity and ecosystem function. Such research represents both an opportunity and a responsibility for the University in its commitment to advance and disseminate knowledge on issues of national and global importance. 2) Baseline surveys must be integral before, during, and after any dam removal or alteration effort. Such surveys should include, but not be limited to current lake bathymetry, upstream and downstream streamflow and sediment flux, groundwater head distribution, and changes in size, location, and composition of associated habitats. Monitoring of these and other conditions should continue during and following any changes in the dam. 3) An adaptive management approach should be adopted for any plan for dam removal or modification to protect native biodiversity and ongoing research and educational program activities. 4) Any sediment removal requiring dewatering before transport include de-watering on lands outside the boundaries of Jasper Ridge Biological Preserve due to the associated loss of land that would be dedicated to such an effort. Such activities often create conditions that increase the presence and spread of invasive exotic species. 5) Dam removal or alteration feasibility studies should answer the following questions:
Finally, the Committee recognizes that until long-term plans and commitments have been developed for Searsville Lake and Dam, interim strategies will be needed to address upstream flooding concerns. While the committee understands the need for interim actions, these must not depend upon or include repeated disturbances and significant intrusions into wetland habitat. Such activity increases the likelihood of exacerbating exotic species invasions and other potential problems such as Sudden Oak Death to nearby oak and other tree populations. While the management challenges presented by Searsville Lake and Dam also present a unique assemblage of opportunities that could be of national or global significance, these are likely to be most effectively provided if the Preserve's integrity is maintained. Mosquito Abatement
Mosquito Report for Jasper Ridge Biological Preserve - December 2006The San Mateo County Mosquito Abatement District works with Stanford University and the staff of the Jasper Ridge Biological Preserve (JRBP) to control mosquitoes arising from the cattail marshes surrounding Searsville Lake. This report is a summary of the work done at this site and its results to date. Click here to download the report (PDF format) Mosquito Abatement at JRBP The San Mateo County Mosquito Abatement District (SMCMAD) has treated the Preserve's wetlands south and west of Searsville Lake with a bacterial agent that attacks mosquito larvae, Bacillus thuringiensis subspecies israelensis, for at least a couple of decades. However, due to the density of vegetation, especially in the tules and cattails, the District is unable to access some areas they consider to be potential mosquito threats to nearby residents. With the increased concern about West Nile virus, SMCMAD used a helicopter to spray about 25 acres of wetlands in the Preserve with another bacterial agent, Bacillus sphaericus in September of 2003, and again in July, August, and September of 2004. Mosquito larvae ingest the bacteria, which produce a toxin that disrupts the gut in the larvae by binding receptor cells present in insects that are not found in mammals. The product is typically marketed under the trademark name of VectoLex and is generally effective for up to 4 weeks. To date, most of the information indicates that this larvicide and Bacillus thuringiensis subspecies israelensis, have little or no significant environmental impacts. The District intends a more aggressive monitoring and management regime in 2004 than has been the case historically at Jasper Ridge Biological Preserve that includes more frequent spraying and increasing the area to include all of Searsville Lake. The Preserve not only bears the costs associated with the aerial spraying, but also makes an effort to keep nearby residents informed about upcoming spraying activity. San Mateo County is using "sentinel" chicken flocks as an early detection mechanism for West Nile virus and Jasper Ridge Biological Preserve's flock of 10 chickens is part of the early warning network. Technicians from the San Mateo County Mosquito Abatement District take blood samples from the chickens every two weeks to test for the presence of West Nile virus and other mosquito-borne diseases. SMCMAD posts monthly updates on West Nile virus and the sentinel chicken monitoring system in their entomology reports located at http://www.smcmad.org/news1.htm. For further information on West Nile virus: |
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