WEATHER WATCH: Let the spring thaw begin. No rain in the forecast for the next two weeks and the nighttime lows in the mountains will start inching above freezing. This means that waterways will be on the rise, icy cold, and dangerous. It is especially important to keep a safe distance from all forks of the Kaweah River. The rocks along the shoreline are water-polished and slippery and, take careful note: drownings occur in all high-water years.
It’s difficult to predict the precise effects of climate change but what is for certain is that the weather will be full of surprises and extreme events will become more frequent. The April showers in Kaweah Country have been well-timed, especially in light of the fact that up until mid-
February water-wise, California looked like it would suffer another year of extreme drought.
But now after recurring storms for the past six weeks, dire straits no longer look so dire. The majority of California’s reservoirs remain full due in large part to a healthy carry-over from last season. The central San Joaquin Valley and Three Rivers remain clearly on the edge of the more extreme events, and that’s not such a bad place to be.
At Lake Kaweah, where annually late-season runoff is critical to fill the reservoir to its capacity (185,000 acre feet), the current storage is not decidedly different from each of the water years since the basin was enlarged in 2004. As of April 19, the storage was 134,115 acre feet; the mean inflow is 866 cubic feet per second; outflow is 18 cfs.
Read between those stats and it’s apparent the lake level will continue to rise. Though Lake Kaweah storage for late April has remained fairly constant, there are some obvious trends beginning to emerge in the last 10 years.
Every other precipitation year since 2009, when averaged together, has been characterized by drought. Rainfall is occurring later in the season when it’s warmer, which translates to less snowpack, and where it is extant after April 1 it’s at the higher elevations.
The March 2018 rainfall of 8.59 inches is a local record for that month in the last 10 years and is more than double the next highest year (3.75 inches in 2012). The lowest March in the past 10 years was .29 in 2015, one of the most extreme drought years.
The April 1 snowpack in the Kaweah drainage checked in at 42 percent of normal. That’s remarkable considering the March 1 numbers in the Kaweah drainage averaged 7 percent of the norm.
Current rainfall to date for the Three Rivers environs is almost right on 13 inches.
March 2018 will go down in weather annals in some measure as miraculous because it was a period of mitigation and helped California dodge yet another bullet of ever-looming drought.
Not to be outdone by March, some impressive storms have also occurred in April 2018. A warm storm on Saturday, April 7, caused the Middle Fork of the Kaweah River to rise rapidly to 12,000 cfs. Then, a storm on Monday, April 16, brought much colder air that dropped snow levels to almost 3,000 feet elevation.
In the midst of a trend where precipitation events come later in the season, the Southern Sierra might expect more frequent warm rain events and less runoff from snowpack.