By Vicky Boyd
Recent heavy rains have been bitter sweet for San Joaquin County agriculture, helping reduce impacts of the 5-year-old drought but also causing localized flooding.
They also serve as a stark reminder of the state's need for more storage, said Joe Valente, an orchard and vineyard manager and San Joaquin Farm Bureau board member.
"Seeing all of this water, it's kind of a crime that a lot of it isn't being saved in a reservoir," he said. After two large storms in mid-January, Valente saw levees on the Mokelumne River and Dry Creek wash out, flooding about 1,000 acres of winegrape vineyards and young almond orchards near Thornton on the Sacramento-San Joaquin County border.
He blamed a couple of factors for the high water. The Mokelumne River is considered a controlled waterway regulated by Camanche Dam. When flows were increased to 5,000 cubic feet per second from 1,500 cfs to increase reservoir storage space, the river overflowed its banks.
The flow increases coincided with king tides in the Delta, which backed up water in the Mokelumne, aggravating the problem.
Valente said he doesn't know when floodwaters would begin to recede. The East Bay Municipal District has water rights on the Mokelumne and as long as the district calls for higher flows, high water in adjacent fields will continue.
Dry Creek is different since it is an uncontrolled waterway. Torrential rains filled the creek. eventually topping the banks. In fields adjoining the creek, Valente said he was beginning to see flooding recede a few days after the storms.
When the flooding began, his initial concerns were about his workers. But once they were safe, Valente turned to the vineyards, some of which were under more than 5 feet of water, and almond orchards planted last summer. Because the grapevines are dormant, the plants should be able to withstand some short-lived flooding with minimal damage. Since he's fairly new to almonds, Valente said he's unsure what the high water will do to the young trees. "We do have experience with cherries and apples, and typically with fruit trees, they don't like to have wet feet,"" he said.
The same can be said for alfalfa, said Michelle Leinfelder-Miles, a University of California Cooperative Extension farm adviser for the Delta, including San Joaquin County.
"Standing water isn't good for most things," she said. "Plant roots need air like humans need air. When you have anaerobic conditions, you're eliminating air in the root zone."
Once standing water has receded from alfalfa fields, Leinfelder-Miles recommended growers assess fields by pulling up plants and examining roots.
"If they're pretty squishy, discolored and maybe smell or have an odor, that's an indication that there's disease or infection,"" she said.
Depending on the stand health and spring weather, flood damage may not be immediately apparent, so Leinfelder-Miles suggested continuing to monitor fields throughout the summer.
To help affected producers, Extension has published online information on flooding and water-logged alfalfa fields at http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22996.
Encouraging water outlook
But recent heavy rains in the foothills and heavy snowpack in the Sierra should bode well for San Joaquin County water users this coming season.
As of midnight, Jan. 19, New Melones Reservoir held 895,653 acre-feet of water, or 64 percent of historic average for the date. At the same time in 2016, the reservoir held only 351,566 acre-feet. An acre-foot, about 326,000 gallons, can meet the annual water needs of one to two four-member families. New Melones capacity is about 2.4 million acre-feet.
Oakdale Irrigation District and the South San Joaquin Irrigation District together have senior water rights to the first 600,000 acre-feet in the reservoir.
"Reservoir storage is on the way up, and we feel good about the trend lines we're seeing now," said Steve Knell, OID general manager. "Obviously in the long term, we want good water management in all of our reservoirs so we can meet our future needs."
Reviewing past inflow since 1982-1983, when the reservoir started to fill after construction, he said current inflow to date of 493,000 acre-feet makes it the wettest on the books. The previous record of 435,000 acre-feet was set in 1983.
The Bureau of Reclamation owns junior water rights to a portion of New Melones storage that in recent years have gone toward meeting fish flow requirements in the Delta. Flows are calculated based on the year's hydrology, which currently point to above-normal precipitation.
"As the winter gets wetter, more water is shipped out of the dam," Knell said. "That's why New Melones is in such bad shape. That's what their argument is all about -- they have the perception that more water is better for the fish."
Based on the current water situation, he said growers will likely see full allotments this season, adding February snowpack survey results will give a bitter indication of summer water supplies. A daily report issued Jan. 20 by the California Department of Water Resources showed snowpack water content in the central Sierra Nevada to be 159 percent of average for the date.
"For us, we'd like the reservoir to fill up,"" Knell said. "The more it fills up, the more security we have." Much-needed relief
For Lodi area grape grower Dave Simpson, the recent storms have signaled some much-needed drought relief. "I'm just dealing with saturated ground, which isn't a bad thing – it's really a good thing after the drought,"" said Simpson, a SJFB board member and chairman of the SJFB water advisory committee. But he pointed to the southern part of the county and New Melones Reservoir as continued cause for concern. Compared to other reservoirs in the state, New Melones has not seen the same recovery because it had been drained precariously low the past few years to meet Delta fishery flows.
For the North San Joaquin Water Conservation District, where Simpson also serves as a board member, the rains could mean surface water deliveries this year – something that hasn't occurred in several years.
In addition, the Tracy Lake Groundwater Recharge Project, built near Acampo by the conservation district, is completely full just from runoff without pumping from the Mokelumne River.
Nevertheless, Simpson said the picture isn't all rosy when it comes to the area's groundwater.
"I'm hoping this year we will maybe see groundwater elevations go up," he said, adding that historically they've dropped about 1 foot per year because of continued overdraft.
Mary Hildebrand, who farms in the south Delta, said she noticed river levels have risen significantly since the mid-January storms. But they haven't come out of the banks yet.
"So we're just keeping a close eye on it," she said. After the initial storms, releases from Don Pedro Reservoir were increased, accounting for much of the rise. Subsequent but smaller releases from Friant Dam added to river flows.
"But we haven't reached monitor stage on the Lower San Joaquin (River) in the South Delta," Hildebrand said. The last time the South Delta saw high water was in 2011 at about the same time of year. "But it didn't come out of its banks until late March, and then we had some flooding but it was pretty minor," she said. "So I think it's entirely possible that we have that happen – something of low magnitude."
At the beginning of the storms, the Office of Emergency Services distributed sandbags, and Hildebrand said she hadn't had to use them yet.
"I don't think we're going to have to need these supplies now, but we have a few months to go."
The higher river flows should help flush out salinity in the Delta, although the heavy rains haven't been as beneficial to leaching salinity in soils, she said. With current saturated soils, additional rain simply runs off without helping push salinity deeper into the soil profile below the root zone.