2020-2040 Water Resource Plan - Q&As

A: Yes, multiple models were used and applied in this Water Resource Plan. 

Regarding the impact of drought and climate change:  TMWA evaluated a range of scenarios that included historic droughts (including the worst droughts on record), climate change models, and future greenhouse gas emission projections.  Precision Water Resources Engineering was also retained by TMWA to provide third-party verification regarding how climate factors may impact future conditions of the Truckee River system.

Regarding the impact of population growth on water demand:  To estimate future water demand in the Truckee Meadows, the following data sources were used: Washoe County population, historical water services in TMWA’s service area, and historical water use data. TMWA’s population projection used in this report is based on a logistical growth curve, assuming that current trends and conditions continue.

With these conditions and projections, multiple drought and climate scenarios were simulated to the year 2098 to evaluate the resiliency and sustainability of TMWA’s water resources.  Using this information, the results show that TMWA’s water supply is extremely resilient at least 50 years into the future, even under extreme climate change scenarios where more severe droughts are projected to occur.

Of related note:  New residential development served by TMWA is required to dedicate water rights to not only meet a project’s estimated water demand, but also includes an additional 11% safety factor of additional water rights which are dedicated to TMWA for drought storage.

To explore this topic more:  Details about models used and outcomes of all simulations are provided in Chapter 3 of the draft plan.

For more information see the 2020-204 Water Resource Plan, pgs. 34-40.

A: TMWA’s plans consider a 20-year horizon to be consistent with the Truckee Meadows Regional Planning Agency’s Regional Plan, which considers land use and growth projections over a 20-year time frame.  Furthermore, 20 years is a reasonable timeframe to plan, design and construct capital improvements and solutions, many of which can take years to implement.  TMWA uses the Water Resource Plan in conjunction with its Water Facility Plan, which addresses necessary infrastructure improvements over a 20-year timeframe as well.  Both the Water Facility Plan and the Water Resource Plan are updated every 5 years. TMWA’s Funding Plans are updated annually.

With every update, the Water Resource Plan accounts for change that could impact TMWA’s approach to resource management (e.g. population shifts, availability of convertible water rights, changes in available sources of supply, regulatory issues, etc).

For more information see the 2020-204 Water Resorce Plan (Plan Goals and Objectives & Scope), pg. 10.

A: No. Truckee River reservoir storage capacity is not likely to increase, although the Truckee River Operating Agreement allows TMWA to greatly expand the amount of upstream water stored during prolonged drought periods.  Additionally, TMWA continues to pursue other innovative ways to increase and diversify its water resources.  In Chapter 5 of the draft Water Resource Plan (see PDF), future water resource projects are identified, which include adding additional groundwater capacity, aquifer storage and recovery projects, utilizing creek resources in more efficient ways, investigating new reclaimed water treatment technologies, and other options.

For More Information See:

A: Recharging treated surface water into aquifers, which typically occurs during winter months when customer demands are low, has water quality requirements that are permitted and monitored by the Nevada Department of Environmental Protection.  In adherence to these requirements, water recharged into aquifers cannot negatively impact groundwater quality.  In some areas with higher levels of naturally occurring minerals, such as Arsenic, groundwater quality is improved through TMWA’s aquifer storage and recovery program.

For More Information see the 2020-2040 Water Resource Plan (ASR), pgs. 21-22

A: The water conveyed in irrigation ditches continues to play a role in aquifer recharge, specifically in southwest Reno and Spanish Springs.  The irrigation ditches are managed and operated by private irrigation companies.  Exceptions to this are the hydroelectric ditches and flumes supplying TMWA’s three run of the river hydroelectric plants (see Chapter 6) and the Highland Ditch, which supplies the Chalk Bluff Water Treatment Plant.  Decisions about the future of these ditches would be under the purview of the individual irrigation companies and the local government jurisdictions where the ditches are located.  TMWA has no authority on decisions made regarding the private irrigation ditches in the Truckee Meadows.

Currently, TMWA has no plans to take over any additional irrigation ditches in the region.

A: TMWA has three hydroelectric plants on the Truckee River that are over 100 years old but remain important to our energy portfolio. From a lost-revenue perspective, the Washoe Hydroelectric Plant is the lowest grossing energy producer of TMWA’s three plants.  Replacement construction costs are estimated to be around $3 million to repair the Washoe flume, which had been budgeted in TMWA’s Capital Improvement Plan and now is set at a higher priority.  We anticipate approximately $500,000 in lost hydrogeneration revenue before the flume is fully operational again.

Meanwhile, the Verdi and Fleish Hydroelectric Power Plants are fully operational and continue to help offset TMWA’s power costs.  Last year, the two plants generated $2.3 million in revenue.  Also, a new hydroelectric facility at the Chalk Bluff Water Treatment Plant has been recently approved by the TMWA Board of Directors. The new hydroelectric facility will not require new dams or diversions on the Truckee River.

For More Information see the 2020-2040 Water Resource Plan (ASR), pg. 78

A: The Truckee River Fund, established by TMWA in 2005, has been very active in funding forest management and bank stabilization efforts, particularly on the California side of the watershed where the river is more susceptible to landslides during thunderstorm events.  When these events happen, advanced water quality monitoring systems can identify upstream mudflows, and if substantial, TMWA can opt to shut off treatment-plant intake channels to allow the impacted water to flow by.

For More Information see the 2020-2040 Water Resource Plan (Truckee River Fund & Wildfires), pg. 74

A: Data used in this Water Resource Plan was based on the most current customer demand, after the removal of flat-rate billing and reflects a customer base that is 99% metered.

We believe community conservation of 10% is very realistic:  When TMWA requested 10% conservation during the 2015 drought year, our customers conserved 15-18%.  Based on this outcome, we believe achieving 10% water conservation from our customers is reasonable.  Additionally, since 2015, we are observing that more customers are using highly efficient, drip-style irrigation. Also, most new development lots are smaller with bigger buildings, further reducing water demand for landscaping needs.

For More Information see the 2020-2040 Water Resource Plan (Increased Conservation During Drought), pg. 54

A: While commercial usage is down due to office and other business closures, commercial billing only accounts for approximately 10% of TMWA’s total revenue. For our residential customers, usage is up due to a dry spring and the fact that the pandemic has many people spending more time at home.  TMWA fiscal year projected revenues are within 0.5% of what had been estimated before the pandemic.  Of note:  Customers who have not been able to pay their bill due to the economic shutdown have continued to receive service.  TMWA will work with customers who need to delay their bill payments during this health crisis.

A: TMWA planned an extensive public outreach process. The draft plan was scheduled to be presented to the Board in March 2020. Due to the COVID-19 pandemic, the release was delayed until June 2020. The original outreach process included approximately 20 public presentations, including to all relevant Reno Neighborhood Advisory Boards and Sparks and Washoe County Citizen Advisory Boards. TMWA amended its outreach process to include four public webinars (via Zoom and Facebook Live) and presentations to agencies, including WRWC, NNWPC, and the TMWA SAC. The plan update was advertised on TMWA’s social media pages and website (smartaboutwater.com and tmwa.com/wrp2020) and an email was sent out to TMWA’s customer list, which includes over 115,000 email addresses.

  • “Conserving water” – Chapter 4 explains TMWA’s conservation policies.
  • “Maintaining adequate flows in the Truckee River” – In an average year, TMWA uses approximately 3% of river flows from the Truckee River. Required rates of flow at the CA/NV state line were set in place many years ago by various court decrees and are still administered by the Federal Water Master under the terms of the new Truckee River Operating Agreement (TROA). In any given year, TROA helps to improve flows in the Truckee River for both habitat and recreation.
  • “TMWA’s role in providing water for habitats” – TMWA does not provide water for habitats directly. TROA does, however, increase the amount of water stored upstream for the purposes of improving fisheries and instream flows. This water which is generally used to improve habitat for fisheries in the lower river and Pyramid Lake is managed by the Pyramid Lake Paiute Tribe (PLPT). The state of California also can store water for the purposes of improving habitat under TROA. TMWA works with both parties to help shift releases to improve habitat for fisheries and recreation whenever possible.

A: The plan explains WC3 on pg. 43. The projected Washoe County water use over the next 20 years can be supported by the sustainable water resources identified in WRWC’s Comprehensive Regional Water Management Plan. TMWA’s Water Resource Plan helps guide the development of the Comprehensive Regional Water Management Plan.

A: TROA requires that for each acre-foot of demand, applicants dedicating Truckee River water rights to meet their project’s water demand must dedicate 0.11 acre-feet of additional water rights.  These additional water rights are used, to the extent physically and legally feasible, by TMWA to establish credit water under TROA in upstream reservoirs. These additional rights are committed when they are dedicated to TMWA and are used for upstream storage.  As stated on pg. 42 of the plan, TMWA does not re-commit these additional rights for future growth and that is expressly prohibited by Section 4.B.3 of TROA.

A: This plan differs from previous plans in the following ways:

  • Focuses less on TMWA history, and more on future planning with an analysis of demand and supply through 2098 with climate change scenarios.
  • Provides a look at the benefits and challenges of potential future resources to further increase the diversity of TMWA’s water supply portfolio.
  • Includes a clear description of TMWA’s commitment to protecting the watershed and environment through its involvement in community programs and initiatives.
  • Includes a recommended actions chapter that builds on the previous plan.
  • Includes more engaging content for plan readers to help inform the general public about TMWA’s water resource management strategies.

There are not major policy changes in this plan that will impact the way TMWA manages water resources during the next five years. The plan results show that the water supply is resilient over the next 20 years and beyond, regardless of the hydrologic scenario. As presented in Ch. 7, TMWA will continue to implement many of its existing programs and policies. Additionally, TMWA will continue to analyze demand projections, climate change models, and future water resource options to ensure that the water supply is reliable into the future. If major policy changes are needed based on TMWA’s continued analyses, those policy changes will be reviewed and adopted by the TMWA Board and included in the next version of the WRP.

A: Many projects are still conceptual or being investigated at this time. TMWA does not need additional resources in the immediate future, but TMWA is constantly assessing the feasibility of additional water resources. For example, other creek resources, such as Thomas Creek and Galena Creek, are still in the investigatory stages, therefore no project scope or cost estimates have been developed. Similarly, the OneWater Nevada advanced purified water feasibility study is just that, a feasibility study.  If proven technically feasible, it may be several years before a project scope is fully developed.

A: TMWA, along with the team of climate scientists that TMWA worked closely with, felt that it was also important to include these historic droughts (the worst on record) as a comparison with future climate change conditions. TMWA presented the data in a way that went from the best-case scenario (historic droughts) to the worst-case scenario (RCP 8.5). The presentation of the data in this order did not reflect the relative likelihood of these events occurring. The summary on pg. 40 does not suggest that the historic scenario results are expected.

A: TMWA is not suggesting that emissions will decrease or that the climate change scenarios are unlikely. TMWA tested the dependability of the Truckee River system 80 years into the future using the best science available. The most recent climate change scenarios available today (endorsed by the Intergovernmental Panel on Climate Change (IPCC)) were used to evaluate the regional water supply under both moderate (RCP 4.5) and very high (RCP 8.5) emissions scenario. These emission trajectory scenarios were evaluated well beyond the typical 20-year timeframe of the plan, to determine how the water supply would fare under climate change. The system proved to be extremely resilient for at least 50 years into the future under all scenarios evaluated, including the RCP 8.5 scenario. TMWA will continue to monitor current climate change science and will update the plan in five years with new models and projections. Ch. 3 acknowledges that climate change is occurring, that runoff will likely occur earlier, and precipitation may shift to more rain instead of snow. TMWA is currently working with many federal partners to model and adjust upstream reservoir storage operations to help adapt to future climate change.

A: Demand increases are due to projected regional growth in the future. The projected demands 50+ years out, as modeled in the climate scenarios, are extremely difficult to accurately project. TMWA conservatively estimates projected increases in water demand to prepare for potential future conditions. However, as shown in Figure 3-9, TMWA’s annual water production is essentially equal to what is was in the year 2000, after adding over 36,000 new customers, an increase of approximately 30%. This speaks to TMWA’s efforts regarding water conservation and increased water use efficiency.

A: TMWA’s conservation plan relies heavily on actions such as water restrictions and enforcement mechanisms, educational programs, funding of landscape retrofit projects and a broad multi-media communication campaign (demand side management practices). These actions have helped thousands of customers conserve water. Moreover, TMWA’s Meter Retrofit Fund has installed meters on nearly all flat-rate services, giving those customers information on monthly consumption, allowing them to better track their water usage behaviors. These actions have a direct impact on water efficiency, and this effect can be measured via the approximately 30% decline in per-capita water usage since TMWA’s inception. So, while TMWA’s customer base has grown by about 30% over the past 18 years, its water production has remained relatively stable over time.

A: TMWA continually monitors the efforts and research conducted on source water supplies by Tahoe Environmental Research Center, Desert Research Institute, National Oceanic and Atmospheric Administration, and other agencies.

TMWA is also paying attention to ongoing research regarding microplastics in drinking water. There is little research on whether small microplastics make it through conventional water treatment processes, and testing is still difficult. The World Health Organization says “… drinking-water treatment systems—where they exist and are optimized—are considered highly effective in removing particles of similar characteristics and sizes as microplastics. Drinking-water treatment has proven effective in removing far more particles of smaller size and at far higher concentrations than those of microplastics. Conventional treatment, when optimized to produce treated water of low turbidity, can remove particles smaller than a micrometer.”

A: Standard conservation is defined as programs TMWA engages in every year. Enhanced conservation is defined as increasing implementation of existing programs (increasing water restrictions, increasing drought awareness media campaign, increasing staffing of the Water Watcher Program. See Table 4-2 on pg. 55 for more detail on standard and enhanced conservation programs and restrictions. TMWA can also implement additional enhanced conservation, such as requesting additional water usage cutbacks (as done in 2015).  The Drought Contingency Plan (DCP) more explicitly explains TMWA’s conservation programs and implementation (see page 48 of the plan or go to http://www.tmwa.com/dcp).

A: The goal of the WRP is to look at overall water supply and demand for the entire system. Area specific water use and future infrastructure improvements are included in TMWA’s Water Facility Plan, which was also recently updated. The executive summary of that plan is located here: https://tmwa.com/wp-content/uploads/2019/11/2035-WFP-5-1-19.pdf.

A: In every previous Water Resource Plan, when comparing actual water usage to the projected use, actual usage has never exceeded the projected amounts. Therefore, TMWA’s water demand projections are considered the upper limit of the consumption range. Due to this estimation bias, TMWA considers its projection to be conservative and therefore doesn’t include lower demand curves in its analysis. The thought process is that any lower demand scenario is manageable if the upper limit is predicted to be manageable. When building the demand estimation curve, TMWA aggregates average usage from its various customer classes. For an in-depth discussion on this demand process, please refer to Ch. 4 of the 2016-2035 Water Resource Plan (https://tmwa.com/wp-content/uploads/docs/your_water/2035WRP/__2035_WRP_VolumeII_chptr_1-6_Final.pdf).

A: Data suggests that we can expect a more variable and even volatile hydrology in the Truckee River system under both the RCP 4.5 and the RCP 8.5 scenarios. This means that the region will not only experience more severe droughts, but it will also experience more severe flooding in the future under continued climate change. The form, timing and volume of precipitation is expected to continue to change over the years, leading to more severe, prolonged droughts and more, significant wintertime flooding events. The Lake Tahoe hydrograph you refer to depicts the projected future median annual elevation under the most extreme hydrological year out of each of the 9 models in the ensemble run under each RCP, which in the case of those years were very wet, contributing to the high elevations.

A: As indicated on pg. 78, TMWA can offset up to 90% of the power it uses to provide drinking water to its customers on an annual basis through hydroelectric generation. Prior to the merger with Washoe County and STMGID in 2015, TMWA was able to produce more renewable energy than it consumed in some years. TMWA is currently coordinating with a solar project in Honey Lake Valley and investigating the possibility of using renewable energy to power the Fish Springs Ranch project.

A: TMWA has no plans to retire its hydroelectric plants which produce cost-effective renewable energy. These plants have been operating reliably on the river for over 100 years, and the bypass flows now in place and recognized under TROA have been evaluated by the USFW, NDOW, PLPT and others as being more than adequate to protect fish and the habitat that supports them.

A: The plan provides a link to the Truckee River Fund website (truckeeriverfund.org) where all projects funded over the past five years and previously are listed and described.