![]() Products on this page are considered experimental. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, etc., for these figures.Ĭontribution from Dr. The fraction of years that at least reached that threshold is the probability estimate. To arrive at the probabilities shown, the precipitation totals for the remaining months of the water year were tabulated in the long-term historical record (WY1948-2017 in these figures) and the number of years in which that precipitation total equaled or exceeded the amount still needed to reach normal were counted. Thus the odds of reaching normal by the end of the water year are just the odds of precipitation during the remaining of the year equaling or exceeding that remaining amount. How the probabilities above were estimated:Īt the end of a given month, if we know how much precipitation has fallen to date (in the water year), the amount of precipitation that will be required to close out the water year (on Sept 30) with a water-year total equal to the long-term normal is just that normal amount minus the amount received to date. The bottom plots show the probability of reaching 100% (and other exceedances) of normal two year precipitation by the end of the next water year (combining the current and next water years). The top plots show the probability of reaching 100% (and other exceedances) of normal two year precipitation by the end of the current water year (combining the current and previous water years). The plots below combine the current water year with either the previous or the next water year. The above methodology can be applied to time periods spanning multiple water years. ![]() Odds of Two Water Years Reaching Various Fractions of Normal Precipitation Totals It also shows the present precipitation level and its percentile within the historical data for the day of the water year.Below uses the same methodology above, but is calculated for various fractions (including 100%) of water year total precipitation.īelow flips the analysis and shows what water year total precipitation percentage has a 50% (and other exceedances) chance of being equaled or exceeded this year. You can see the current water year plotted on this to show how it compares to historical values. The second graph shows the percentiles of precipitation over the course of the historical water year, spreading out like a cone from the start of the water year (October 1). The second graph shows the percentiles of precipitation over the course of the historical water year, spreading out like a cone from the start of the water year (October 1). The top graph is a histogram of water year precipitation totals on the specified date (in blue) as well as the precipitation total for the current water year in red. The top graph is a histogram of water year precipitation totals on the specified date (in blue) as well as the precipitation total for the current water year in red. The visualization consists of two primary graphs both of which show the range of historical values for precipitation. Data from the CDEC website appears to be updated at around 8:30am PST each day. These stations are tracked because they provide important information about the state’s water supply (most of which originates from the Sierra Nevada Mountains). There are three sets of stations that are tracked in the data and these plots: Other California water-related visualizations include reservoir levels in the state as well. I used data for California rainfall totals from the California Department of Water Resources. This year has been a relatively dry year and wanted to visualize how this year compares with historical levels for this time of year. It’s winter in California and that means the rainy season (snowy in the mountains). How do current California rainfall and precipitation totals compare with Historical Averages?Ĭheck out the California reservoir dashboard.
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