What is the significance of climate change on water resources in the Truckee-Carson River System?
Climate change poses critical challenges to water management in river systems dependent on snow for water supply (Dettinger, Udall, & Georgakakos, 2015; Hatchett et al., 2017; McCabe, Wolock, & Valentin, 2018; Mote, Li, Lettenmaier, Xiao, & Engel, 2018). In the Truckee-Carson River System, in the western United States, the majority of water supply originates as snowpack from the Sierra Nevada and flows northeastward (Figure 1). Snowmelt runoff generates a majority of surface water supply for diverse downstream municipal, industrial, agricultural and environmental water-use communities in the Great Basin of northwestern Nevada. Snowpack also recharges groundwater that is relied upon as a supplemental water supply, particularly during drought years.
Warming temperatures alter both the accumulation and melt of snow-derived water resources, leading to shifts in timing of water supply and challenging water-management institutions that are based on historical snowmelt records (Barnhart et al., 2016; Li et al., 2017; Milly et al., 2008). To assess these challenges, a collaborative research approach becomes useful to harness local knowledge to identify the salient climate change impacts and local water-management challenges, and examine the effectiveness of potential adaptation strategies (Sterle & Singletary, 2017).
How is local knowledge used to inform research activities?
A collaborative modeling research program in the Truckee-Carson River System convenes an interdisciplinary research team, including hydrologists and climatologists, with a core group of local stakeholders representing the diverse water-use interests from headwaters to river system terminus (Singletary & Sterle, 2017, 2018). Iterative interactions ensure that research and modeling activities incorporate local stakeholder perspectives and information needs.
Figure 2 illustrates the idealized collaborative modeling process for using local knowledge in applied climate science research. An assessment of climate resiliency begins with conversations with local stakeholders to identify climatic conditions and impacts of greatest concern. These narratives are then translated into climate scenarios that are used to model changes to water availability and subsequent consequences under existing and alternative water-management practices.
Conditions may focus on extreme events, such as prolonged drought (Dettinger et al., 2017); specific climate changes, such as warming temperature or increased precipitation variability; or overall changes as depicted in multiple projections of future climate. Regardless, the climate scenarios focus on plausible storylines that reflect the climate change risks that are of greatest concern to local stakeholders.
Impacts of climate scenarios and management alternatives are simulated using hydrologic and operations models tailored to the river system (for additional details on these models, see Sterle et al., 2017). Modeling results are then visualized in terms of performance metrics that serve as indicators of important impacts (e.g., river flows or reservoir stage at a particular location and time of year) and presented back to stakeholders in a workshop setting to identify alternative water management strategies capable of alleviating the simulated impact.
What climate scenarios were developed for the Truckee-Carson River System, and what research questions can be addressed?
Table 1 summarizes the four sets of climate scenarios developed as part of the Water for the Seasons research program using local stakeholder input (Albano, 2019). These scenarios include:
- Extended Drought + Mid-Century Warming,
- Late Century Warming Scenarios,
- Low- and High-Frequency Precipitation Variability, and
- Range of Climate Projections for Lake Tahoe.
The degree of warming aligned with projected changes in temperature under two greenhouse gas scenarios, and include 2.5 degrees Celsius (4.5 degrees Fahrenheit) by mid-century (2050) and 4.3 degrees Celsius (7.7 degrees Fahrenheit) by late-century (2080) (IPCC, 2014). The data for each of these scenarios will be freely available through the Consortium of Universities for the Advancement of Hydrologic Science at https://www.hydroshare.org/.
Through simulation of these scenarios, researchers and stakeholders are working together to address the following research questions:
- How are the timing and availability of water supplies affected under each climate scenario at key locations in the system?
- To what extent does earlier capture and storage of water in surface reservoirs help to meet water users’ needs under conditions of earlier snowmelt and streamflow timing?
- To what extent does managed aquifer recharge enhance water storage and supplies, and what are the implications of this strategy for diverse water uses?
- How do agricultural water demands change under warmer conditions, and how effective are agricultural efficiency measures at lessening impacts to ground and surface water supplies?
Preliminary results indicate periods of greater-than-historical precipitation variability and warming temperatures introduce challenges to water management, necessitating identification of viable adaptation strategies for the river system.
Collaboratively reviewing modeling results provides an opportunity for stakeholders to gain insights into the potential effectiveness of alternative management strategies. At the same time, researchers are able to further refine their efforts based on additional stakeholder input. The research reported in this fact sheet demonstrates how collaborative modeling provides information useful for stakeholders’ climate adaptation planning.
Acknowledgements
The authors acknowledge Truckee-Carson River System stakeholders and researchers who contribute to the Water for the Seasons research program. Thanks to Christina Clack and Ron Oden for graphic design support. For additional details on stakeholders’ perspectives and information needs, see Singletary & Sterle (2017), Sterle et al. (2019, 2020), and Sterle & Singletary (2017). For additional details on climate stress test scenarios, see Albano (2019).
For the complete fact sheet with figure and graphs use the link below.