Why This Viral Map Isnt The Best Indicator Of California Drought

"All the drought monitor did was subtract one category," Jones said. "All they did was pull back their D4 [exceptional drought]. That’s definitely not saying the drought is over. The US Drought monitor attempts to summarize many different things on one map for everyone and when you try to be the one answer for everyone that is difficult. It really doesn’t reflect the water supply circumstances in California and it doesn’t distinguish between different types of water users."

Jones explained that the city and county of San Francisco, which pulls water from Hetch Hetchy reservoir in the Sierra Nevada, has different water needs than cattle ranchers dependent on non-irrigated grazing. Cattle ranchers benefit immediately from December rains that turn the hills green, creating an immediate food source for their livestock. While California's largest reservoirs have seen rises in capacity due to the December precipitation, water storage generally remains below average after the past two consecutive dry winters. 

This week’s Hot Topic focuses on California. In the past month, all D4 and nearly all D3 disappeared from the state. On Dec. 14, 28.27% of the state was D4, and 80.28 percent was D3. But it isn’t over yet -- 99% of the state is still in D2. pic.twitter.com/os81aEkqxk

— Drought Center (@DroughtCenter) January 13, 2022

The Drought Monitor is a joint effort of the National Oceanic Atmospheric Administration, the U.S. Department of Agriculture and the National Drought Mitigation Center at the University of Nebraska-Lincoln. The weekly map isn't a forecast, but rather a reflection of the precipitation from the past week.

While the map takes precipitation totals into account, it indexes a wide array of indicators, including groundwater storage, river levels, soil moisture, satellite-based assessments of vegetation health and more. 

The map is a mechanism to measure a drought that's mainly applied to agriculture, and the U.S. Department of Agriculture uses it for the basis of decisions about agricultural financial assistance, Jones said. 

"It was developed by folks in an area where hydrological conditions are very different from those in California," Jones said. "Nebraska doesn’t have major water projects that move water from one place to another."

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The map classifies four levels of drought with color codes, from "D1 moderate drought" (pale orange) to "D4 exceptional drought" (maroon). White indicates no drought conditions and yellow "abnormally dry" but still no drought conditions.

"Exceptional drought" disappeared from the California map this week and also, "extreme drought" nearly disappeared. Despite these changes, 99% of the state remains within a level of drought. Statewide precipitation is above normal this season, but the state has a significant water deficit to make up.  

Jones said that the state of the water supply in California won't be clear until the end of the wet season.

"An important point to make from a water management perspective is that we’re only midway through January," Jones said. "We've gone through about six weeks of our wettest period and we won't know until end of March what our complete water year is like. Northern California did well with the December storms but Southern California, not so much. We are one state so we have to think about Southern California as well. With La Niña conditions in place it’s likely Southern California will be dry this year and this is in fact the NOAA outlook."

 Long-range forecast models from NOAA for January through March suggest that Southern California is more likely to be dry than wet, while Central and Northern California have equal chances of being wet, dry or normal. As of Friday, there was no significant chance of rain in Northern California over the next week. 

"At this point, we’re still ahead of average for statewide precipitation because of those December storms," said Jones. "Actually Northern California and the Bay Area did very well. But the longer we go without precipitation, the closer our 'above average' will get to 'average.' Maybe by the end of this month, we might be close to average if we don’t get more precipitation."

Source : https://www.sfgate.com/california-drought/article/Drought-Monitor-map-California-16774215.php

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Why this viral map isnt the best indicator of California drought

Source:SFGate

Why this viral map isnt the best indicator of California drought