Climate Ready: Napa County, Departments of Planning and Public Works and Flood Control and Water Conservation District
 Napa tributaries that flood |
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Napa County Responsibilities and Jurisdictions
The Napa County departments engaged in Climate Ready North Bay included Planning (Building and Environmental Services), Public Works (Natural Resources Program) and Napa County Flood Control and Water Conservation District. These departments are engaged in long-term resource management planning, as well as permitting of new residential, commercial, and vineyard developments. The scope of the Planning department includes general plan implementation, agricultural erosion control plans, watershed planning, and development permit review. The Flood Control and Water Conservation District was also engaged based on its role in management of the watershed as a whole, with restoration and maintenance obligations on specific stream reaches and the main stem of the Napa River. The District is charged with flood protection planning and complying with state and federal requirements, including compliance with storm-water permitting requirements. While these agencies have countywide jurisdiction, this initiative is focused on the Napa Valley (which is equivalent to the Napa River watershed). However, the GIS database provided covers for the entire County, such that subsequent explorations could be conducted at the full County scale or for sub-regions.
Napa County Climate-related Concerns and Management Priorities
Napa County presented the most diverse array of management concerns and priorities of all the Climate Ready North Bay partners. As the County is embarking on a groundwater management plan, there are concerns about groundwater sustainability in general and relationships between granting vineyard permits and impacts on groundwater supplies. For example, there is a new requirement for vineyard permits to show that new wells can supply the project without impacting neighboring streams or properties. Because of this, it will be important to understand potential increases in demand. With multiple reservoirs located throughout the eastern hills of the valley [Napa Valley reservoirs are primarily managed by managed by the cities rather than the County, except for Rector Reservoir which is managed by the State of California], there is concern about both local water surface supplies and the sustainability of imported water, which provides 40% of the County’s supply.
For watershed management purposes, Napa County had an interest in climate impacts on forest resources in terms of species of conservation concern. With a large stream and river restoration program underway, the County has questions specifically about the riparian zone, including impacts of climate change on riparian hydrology and appropriate plants for installation as part of restoration. The Flood Control and Water Conservation District’s Watershed Operation staff’s field experience is already showing that planting more drought-tolerant pioneer species is proving a more successful strategy than planting “classically” riparian species alone. With a strong emphasis on fisheries conservation, the County is also interested in understanding the potential hydrologic impacts on fish-bearing streams. The District’s flood control responsibilities lead them to have concerns about the likelihood of increased frequency or intensity of flooding events. It was also raised that the sanitation district is doing an independent sea level rise analysis that would complement this analysis of inland climate impacts.
Napa County’s management concerns are grouped into three resource areas: 1) Water Resources (including surface and groundwater supply, fisheries, and flooding); 2) Agricultural Sustainability; and 3) Native Vegetation Response and Fire Risks.
Management Concerns for Future Analysis
In the process of identifying management concerns and questions, a number of key questions amenable to analysis given the scope of this project were identified and are presented by resource areas below. Additional management questions were identified that the team determined were beyond the scope of this study, and therefore not addressed here. However we share them here as they can provide a starting point for subsequent climate adaptation work.
- What are the implications of climate change for site-specific riparian vegetation and restoration projects?
- What are the best tools to assess the localized impacts of groundwater withdrawal from a particular well?
- What will be the impact of climate change on the determination of suitable growing regions in the Napa Valley?
- What are the implications of more variable hydrology on site-specific flood infrastructure requirements?
- What are the impacts of climate change likely to be on the watersheds outside the Napa Valley from which Napa imports water?
Vulnerability Assessment Results
Key Vulnerability Assessment Findings for the North Bay Region
- Rising temperatures across the region will generate unprecedented warm conditions for both summer and winter seasons
- Rainfall is likely to be more variable in the future in term of both low and high annual extreme
- The North Bay region is becoming more arid (subject to drier soil conditions) due to rising temperatures
- Runoff may be increasingly flashy, with rates of groundwater recharge relatively less variable over time
- Protecting available recharge areas will be critical to water supply sustainability
- Water demand for agriculture may increase on the order of 10%
- Fire frequencies are projected to increase on the order of 20%, requiring additional readiness planning and more aggressive fuels management
- Vegetation may be in transition, meriting additional monitoring and consideration of a more drought-tolerant planting palette for restoration
See Climate Ready North Bay: Region-wide Findings and Applications for more about the vulnerability assessment findings for the Northbay Region.
Key Management Questions by Resource Area
The following management questions are addressed in the CRNB Napa Valley Technical Memo:
Water Resources
Management Question: How is climate change projected to impact the variability of regional annual rainfall relative to the historic record?
Management Question: How does rainfall variability translate to variability in Napa Valley watershed-wide water availability and potential delivery to reservoirs?
Management Question: What are the potential impacts of climate change on the flow regime of the Napa River?
Management Question: How will climate change potentially impact the hydrology of high value main stem reaches and tributaries for fish?
Management Question: How will climate change potentially impact the seasonality of the Napa Valley’s water cycle?
Agricultural Sustainability
Management Question: How will the agricultural lands of the Napa Valley be potentially impacted by climate change in terms of irrigation demand?
Native Vegetation Response and Fire Risks
Management Question: What will be the impact of climate change on important upland vegetation types, and can you identify potentially stable vegetation communities for conservation planning?
Management Question: What will be the impact of climate change on the potential fire frequencies in the Napa Valley?
Potential Climate Ready Napa Valley Watershed Data Applications
- Use of localized climate temperature and rainfall data to inform the County's current Climate Action Plan.
- Presentations to raise public awareness regarding the benefits of greenhouse gas
reduction (mitigation) and the need to plan for adaptation. - Use of hydrologic data to inform partner agencies’ long-term planning for surface water supply including the cities of Napa and Saint Helena.
- Use of recharge maps to inform the groundwater management plan underway, as well as planning required by the new Sustainable Groundwater Management Act, in particular, to identify high recharge zones.
- Integration of potential vegetation transition risks and fire hazards into long-term natural resource management plans and fire mitigation planning.
- Use of hydrologic assessments to evaluate potential high value resource streams and riparian zones at risk, as well as development of strategies to build adaptation into maintenance and restoration planning.
Management Concerns for Future Analysis
In the process of identifying management concerns and questions, a number of key questions amenable to analysis given the scope of this project were identified and are presented by resource areas below. Additional management questions were identified that the team determined were beyond the scope of this study, and therefore not addressed here. However we share them here as they can provide a starting point for subsequent climate adaptation work.
- What are the implications of climate change for site-specific riparian vegetation and restoration projects?
- What are the best tools to assess the localized impacts of groundwater withdrawal from a particular well?
- What will be the impact of climate change on the determination of suitable growing regions in the Napa Valley?
- What are the implications of more variable hydrology on site-specific flood infrastructure requirements?
- What are the impacts of climate change likely to be on the watersheds outside the Napa Valley from which Napa imports water?
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