Conference highlights deficiency of models for drought situations

IRVINE, Calif. (CN) — As the drought in California and across much of the western United States enters another summer season, several experts participated in a conference hosted by the California Department of Water Resources and the Water Education Foundation on Thursday to discuss issues of how modeling precipitation can impact decisions made by policymakers.

One of the main takeaways of the conference was that the current modeling programs are not effective as they should be in helping water districts, state water agencies and federal departments in planning water distributions.

Jeanine Jones, interstate resources manager for the California Department of Water Resources, said modeling by the National Weather Service is more focused on short-term forecasts, weather events that impact health and safety and lack the precision to conduct long term forecasts called season-to-season modeling.

“NOAA (National Oceanic and Atmospheric Administration) and the National Weather Service are more focused on the issues impacting the eastern United States such as hurricanes and do not allocate a lot of money for long term modeling for the western United States,” said Jones.

With not much money, there are few scientists who study long-term modeling and projections, especially from season-to-season forecasts which will increasingly drive decisions made by state and federal agencies on how they allocate water.

“The seasonal outlooks created by NOAA are not usable by for water management,” said Jones. “They change over a short period of time.”

She gave the example of the 2016 water year in which NOAA initially forecast that California, Nevada, Arizona would have an average year of precipitation. In actuality the water year in California was another dry one.

“We need a minimum of $15 million per year over the next 10 years so that we can improve the long-term modeling and make it where it is more useful,” said Jones.

Mike Anderson, state climatologist for the California Department of Water Resources, said the changes in weather variability have impacted the models that are in use today. He said this is driving models to diverge from each other and make it more difficult to predict what a typical wet season will be.

“In the first part of the 20^th century there was little variability around the mean between temperature and precipitation,” said Anderson. “In the latter part of the 20^th century you begin to see more data points at the extreme from the mean, not too many. In the 21^st century, there are more points further from the mean which make it difficult to accurately model going forward with so many points away from the mean.”

With the change in rain and snowfall, and when they are occurring, Anderson stated that forecasters and modelers need to take into account not only when the precipitation occurs but the time between the events. He said last season the temperature between events, along with an extended dry period, led to the ground to dry out, which can impact moisture reaching streams and reservoirs when it does actually rain or snow.

Jones pointed out that with many universities, state and federal government running season-to-season forecasting models that they can diverge and provide conflicting data to water managers. She told the conference she is hopeful that additional money will be allocated to help researchers create more accurate long-range climate models and make them where they can be used by water managers who might need to make a decision in February or March about water allocation.

With droughts occurring more frequently in California since the beginning of the 21^st century, all the participants in the conference highlighted the need to further refine data, model, and predictions so that they are useful to state and federal governments as the drought conditions look set to continue.

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