I heard the Truckee fire district is planning a summer ban on outdoor wood-burning fires. Why such extreme measures, what would be allowed under this ban, and how would it be enforced?
On March 19, the Truckee Fire Protection District Board passed a ban (Ordinance 03-2019) on wood-burning outdoor fires, like backyard campfires and charcoal barbecues, during fire season, which usually runs from June to November and is determined by Cal Fire. Campgrounds, gas barbecues, and gas fire pits would be exempt. The fire district will respond to all 911 reports of a campfire during the fire ban period.
The constant fire danger we are experiencing is at an all-time high due to excess dry fuels and changes in the climate, including a significant long-term drought and strong fire-season winds throughout California. Nine of the most destructive wildfires in California have occurred in just the last five years with 39,056 structures destroyed and 166 fatalities. Cal Fire has rated Truckee a “Very High Fire Severity Zone.”
Most wildland fires are caused by humans, and escaped campfires are the leading cause. Truckee Fire District personnel responded to 39 wildfires last year, 13 of which were campfires. Charcoal and campfires that are not thoroughly extinguished can escape their ring the following day when the winds pick up, leading to wildfire. A recent opinion poll showed that over 75 percent of people in Truckee favored the ban. The district is taking this action to reduce the possibility of a wildfire in the Truckee area.
~ Bill Seline, Truckee Fire Protection District Fire Chief
With such a healthy snowpack this year, why did flows out of Lake Tahoe not increase earlier, and why not let out more? A large amount of rain could easily lead to flooding with current lake levels.
There are specific criteria that must be met before water can be released from Lake Tahoe in amounts that would exceed downstream legal targets. That criteria includes the current elevation, and the forecasted runoff, in other words, how much water is forecasted to come into the lake versus how much room there is remaining in the lake. When we reach the point at which those criteria are satisfied, we commence “spill” releases from the lake. When Lake Tahoe is spilling, a very complicated process is used to determine the total volume, flow level, and duration of releases that are needed. The releases must be managed to allow flow reductions if the forecast is too high, so the lake can still be filled, and flow increases if the forecast is too low, so the upper limit is not exceeded.
The runoff forecasts can be inaccurate due to differences in many factors such as snowpack and soil moisture, varying weather conditions, and rate of snow melt. There are many unknowns, or more accurately, uncertainties, when it comes to the volume that will run off and flow into Lake Tahoe. To help balance the operations, tools were developed in conjunction with the California-Nevada River Forecast Center (CNRFC). One example is, the CNRFC provides 68 [predictions] of possible inflow patterns based on the climatology from the years 1950 to 2017. Those predictions are developed by taking the current conditions, for example, today’s soil moisture and snowpack, and applying the weather from historic years.
After many more steps of processing, we can then use the results to provide a forecast of certain events, for example, the probability of exceeding the [lake’s] upper limit, or the probability of not filling. These forecasts are continually updated as we move through the water year, with the goal of having releases, over a period of time, that allow flexibility to adjust up or down to varying conditions, but still meet objectives.
We are legally required to store water in Lake Tahoe when it is available, that includes filling if possible. In doing so, we need to avoid exceeding the upper limit of 6,229.10 feet, “in so far as practicable.” Exceeding the upper limit is not always practicable, or possible, to avoid. There is always a chance that an inaccurate inflow forecast, or a rain event could cause the lake to rise above 6,229.10 feet. If that were to happen, we would be required to evacuate the water in excess of the upper limit as quickly as possible.
This is a very brief and condensed example of one tool of many, used to manage the Lake Tahoe elevation and releases during high water years. The tools and methodology used for forecasting inflows and managing the lake levels have evolved significantly over the 93 years that the water master’s office has been operating the lake and will continue to evolve as new tools and methods are developed.
~ Chad Blanchard, U.S. District Court Water Master