Incorporating Climate Change into the San Lorenzo Watershed Management Plan
In 2008, the Board of the San Lorenzo Water District approved a climate change resolution that commits the District to reducing greenhouse gas emissions and considering the impacts of climate change in all planning documents. The 2009 Master Water Supply and Management Plans discuss how climate change will impact local water resources. Climate change is expected to cause drier and shorter wet seasons regionally, making both water conservation and efficiency priority issues for water managers.
In April 2008, the San Lorenzo Water District (SLWD), in collaboration with nearby water districts, sponsored a local forum titled “Tools for Addressing Climate Change and Local Water Resources.” The forum addressed three key questions:
- What are the potential impacts of climate change on local water resources?
- How can local water managers plan for these impacts?
- How can local water agencies reduce their carbon footprint?
After the forum concluded, the SLWD Board of Directors approved a climate change resolution mandating that all future documents and plans properly address the impacts, mitigation opportunities, and adaptation strategies to climate change.
To assess the vulnerability of the SLWD to future climate change, the District first turned to global climate models to ascertain predicted regional changes. The climate models presented a drier and shorter wet season with a 3-10°F increase in annual temperatures by 2100. These findings indicate that the total amount of water available statewide will decrease, water demand will increase, and the timing of water availability will be altered. To design a water management plan capable of addressing climate change, the SLWD reanalyzed historical hydrological conditions and water production records dating to 1984 over which time period the SLWD incurred two droughts. This analysis was then extrapolated to 2030 to infer the potential effects of climate change on water resources, assuming that future climate variability reflected historical norms. By 2030, without any supplemental water resources, the Southern Service area of the SLWD may not have enough water to fulfill water resource demands. However, it is expected that the Northern Service will be more resilient to climate impacts; therefore, if the Northern and Southern Service areas could be connected (an “Intertie”), some future problems could be averted.
To help the SLWD in decision-making and to prepare for changes in water resources, two scenarios are presented:
- Use supplemental waters only when needed to supply the Northern Service which would then secondarily supply the Southern Service.
- Routinely access supplemental waters to recharge groundwater supplies even when water demands are being met.
Ultimately, scenario 2 is recommended because it allows the SLWD to access and utilize supplemental waters to recharge groundwater reservoirs and will lessen the likelihood that the SLWD is in direct competition with other water districts during periods of drought.
Outcomes and Conclusions
The SLWD is funded primarily from water service fees from its customers. Reports are written by internal staff and external contractors. For more details, please review the San Lorenzo Water District Water Supply Master Plan.
Project File (s)
Feifel, K. (2009). Incorporating Climate Change into the San Lorenzo Watershed Management Plan [Case study on a project of the San Lorenzo Valley Water District]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: http://www.cakex.org/case-studies/incorporating-climate-change-san-lore… (Last updated December 2009)