California Microclimates Pose Complex Drought Challenges in Some Communities
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Connecting state and local government leaders
But a new tool can calculate localized risk on a smaller scale.
VALLEJO, Calif. — Most of Solano County’s top 10 million-dollar commodity crops are water hogs. In a normal year the rainy season months spanning October through April provide enough water to grow such highly valued crops like walnuts and alfalfa. But with California now in its fifth year of drought conditions, this “new normal” has farmers, as well as city, county and state government in this Northern California region northeast of San Francisco, on high alert as they plan emergency and drought mitigation strategies to manage a very uncertain future.
Complicating matters is the patchwork of microclimates in Northern California, a phenomenon that makes growing grapes so favorable. This climate condition, however, creates havoc for such traditional measurements as the Palmer Drought Severity Index, widely used by climatologists to assess long-term drought analysis by comparing climate divisions that theoretically have the same climate.
But thanks to the development of a new drought calculator created by a team of former Vanderbilt University graduate students, it is now possible to assess drought risk on a smaller scale.
The problem with using climate divisions according to John Jacobi, a member of the team and now a catastrophic management group analytics consultant for Chicago-based CNA Insurance, “is that they miss the differences within the division. One town might be experiencing much more severe drought than a town a few miles away due to local climate effects, different soil types, or any number of factors. Our tool allows the Palmer Drought Indices to be calculated at any scale in an easy to use tool.”
Jacobi said that making the calculations transparent and on a more refined scale offers a wide range of benefits to a broad range of users, all of whom have a stake in creating as accurate drought risk assessments as possible.
“Farmers would be interested in this information because it might show that their portion of the climate division is experiencing a much more severe drought than surrounding areas. With this information, individual farmers could make more informed planting or irrigation decisions.” It is this same kind of localized values that farmers need, said Deb Perrone, another team member and currently a postdoctoral fellow at Stanford University, when they are applying for disaster relief funds.
“Drought is an especially vulnerable time for groundwater managers and users. One of the key principles of California’s new groundwater legislation is to provide local agencies with the tools that they need to manage groundwater sustainably,” Perrone added, referring to the Sustainable Groundwater Management Act. “Our tool can characterize drought conditions at a local scale, making it particularly appealing for the new Groundwater Sustainability Agencies.”
The chain of stakeholders who assess and manage drought risk is a long one, Jacobi said. It extends past farmers, city managers, water managers and relief agencies to crop insurance companies and agricultural options/future traders. “Another benefit of our tool is that it allows this full range of stakeholders the ability to measure and visualize drought at any scale that impacts them," Perrone said.
Presently Jacobi and Perrone’s drought calculator is being used by academics around the world. The Sri Lankan government is also using the tool to monitor their drought conditions, and Jacobi is consulting with a Canadian crop insurance company interested in using the tool.
The likelihood of an intense El Niño system gifting the West Coast this rainy season with much-needed precipitation continues to be high. But with nature offering no guarantee, there are a growing number of stakeholders who would jump at the prospect of finding a crystal ball that can predict the length and severity of the present drought.
Predicting the future is one feature, Jacobi said, that their new calculator does not possess.
“Our tool can’t predict where droughts will occur or how bad they will be. It’s a purely retrospective tool that requires at least 10 years of historic data to get reasonable results," he said. "It only calculates drought severity on a monthly basis. If the user is interested in daily or weekly values, our tool can’t do that. Luckily, all the code is available so users can modify the tool to meet their needs.”
The tool is available for download from the Water Resources Research website. Farmers, or anyone who uses this tool, need four pieces of information—the latitude of the location where drought is being measured, monthly rainfall amounts, monthly temperature amounts, and a measure of how much water the soil is capable of holding. The National Weather Service and the National Oceanic and Atmospheric Administration provide all this information for free online.
Patricia Kutza is a Vallejo, California-based business and technology writer.
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