Agriculture

Researchers show off groundwater recharge near Modesto

Modesto storm water fills Nick Blom’s almond orchard Tuesday morning, Jan. 19, 2016. The release of water was for an Almond Board research project on whether storm runoff can be captured in key spots and seep into the aquifer during wet winters.
Modesto storm water fills Nick Blom’s almond orchard Tuesday morning, Jan. 19, 2016. The release of water was for an Almond Board research project on whether storm runoff can be captured in key spots and seep into the aquifer during wet winters. jlee@modbee.com

A farmer on Tuesday spread canal water across an almond orchard southwest of Modesto. He wasn’t irrigating the trees – the rain took care of that. He was recharging groundwater.

The almond industry and its partners are researching whether excess water in wet years such as this one could boost aquifers that might be stressed during drought. In Tuesday’s demonstration for the media, the water came from city storm drains via a Modesto Irrigation District canal that usually is idle in winter.

The farmer was Nick Blom, an MID board member. The crowd at the Paradise Road site included University of California, Davis, researchers who are monitoring the water movement and possible damage to the trees.

“If we recharge that and make everything a lot better, it’s just a plus for everybody,” Blom said. “And if through their research we find out that it’s not hurting my trees, all the better.”

The Almond Board of California, based in Modesto, launched the study with Sustainable Conservation, a San Francisco group that works with businesses on environmental projects. It also involves a farm near Livingston and another in Fresno County. All have soil and underlying rock that favor downward movement of water.

Parts of the San Joaquin Valley are dealing with reduced groundwater because of pumping by farms and cities, coupled with a drought that has reduced the rain and snowmelt that naturally recharge the aquifers. Merced County is a hotspot for a related problem – subsidence of land after the water beneath it is removed.

This is a story about capturing the rain when it’s raining. Get it while you can.

Kat Kerlin, UC Davis

Farmers have argued that flood irrigation during the growing season, which might look wasteful to some people, has helped with recharge. But many of them now use drip lines and microsprinklers, which keep water near the plant roots.

Recharge also has been done right after a growing season in years when water districts have extra river supplies. The project described Tuesday involves doing it in winter, when the dormant trees are preparing for next month’s bloom and yet another crop.

Davis hydrologist Helen Dahlke said the Blom orchard got 6 vertical inches of recharge water Tuesday, part of 24 inches planned for the winter.

It was a strange sight – releasing water onto soil already muddy from this week’s rain – but the researchers say it could be just what the drought-prone state needs. Blom said the city storm runoff otherwise goes into the Tuolumne River.

Scientists are using high-tech equipment to track the water’s movement down to the aquifer, which Blom said is about 45 feet deep in that area, better than much of the Valley.

Researchers will check whether pesticides, fertilizers and other possible pollutants travel along with the water, said Kenneth Shackel, a plant scientist at Davis. They also will monitor the health of the trees and see if the extra water affects the size of the almond crop.

The demonstration drew a media horde – newspaper, television and farm press – that got a good soaking but also a look at a possible tool for future water management.

“This is a story about capturing the rain when it’s raining,” said Kat Kerlin, part of the Davis media relations staff. “Get it while you can.”

John Holland: 209-578-2385

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