California has seen so much rain over the past few weeks that farm fields are flooded and normally dry creek and drainage ditches have become a torrent of water racing toward the ocean. The majority of the state is still in a severe dry spell.
Why can't more rain be collected and stored for the long dry spring and summer when it's needed?
I am a hydrogeologist at the University of California at Santa Cruz and I am interested in what can be done to collect the storm water. There are two primary sources of large-scale water storage that could be used to make up for the lack of water in the area.
When California gets storms like the atmospheric rivers that hit in December and January, water managers around the state probably shake their heads and wonder why they can't hold on to more of that water. It's a complex issue.
California has big dams that can hold a lot of water but they are usually located in the mountains. Water has to be released to be ready for the next storm once they reach capacity. A lot of the water goes out to the ocean.
One of the reasons storm water isn't automatically collected for use on a large scale is because the first run off from roads is often contaminated. Flooding can cause sewage to overflow. That water needs to be treated.
We could use the captured water on golf courses if we wanted to. You can't put the water in the same pipes as drinking water so you have to distribute it with separate pipes and pumps.
It is possible to put it in the ground to help replenish the water supply.
In many areas, managed recharging has been used for a long time. The techniques have gained more attention recently as well as the dry weather. The state estimates that if all of the proposed projects were built, an additional 500,000 acres of water a year would be saved.
The state Department of Water Resources is discussing a method called Flood-MAR. During big flows in rivers, water managers could potentially divert some of that flow onto large parts of the landscape. Flooding the land in the winter and then farming in the summer is the idea.
If we can find people who are willing to inundate their land, Flood-MAR will be a success. Not every part of the landscape is capable of taking that water.
A lot of the 1,000 acres on the ranch might be flooded for a while. Some crops will be okay if the water soaks in quickly, but other crops could be hurt. Creating habitat that encourages pests is a concern.
Most of the big river flows are in the northern part of the state, and many of the areas with the worst water quality are in central and southern California. Transport and distribution of excess water can be complex and costly.
In the Pajaro Valley, an important agricultural region at the edge of Monterey Bay, regional colleagues and I are working on a different type of project where there is a lot of storm water.
The idea is to suck off some of the water and put it in basins where the water can trickle into the ground. It could be on agricultural land or open space. We look for coarse soils that make it easier to get water out of the ground. Careful site selection is important because much of the landscape is covered or underlain by fine soils.
Landowners in the Pajaro Valley can get a rebate on the fee they pay for water use through a program.
When you add in all the capital costs for construction and hauling away some soil, the costs are competitive with finding alternative supplies of water, and it's cheaper than water recycling.
It will take many methods and several wet years to make up for the low precipitation. One storm doesn't do it and even one wet year doesn't do it
It can take years for basins to be recharged. We could be in trouble again if this is the last rainstorm.
The Conversation is a news site that shares ideas from academic experts. It was written by Andrew Fisher. There are a lot of free newsletters on The Conversation.
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