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Flooding orchards with winter runoff to recharge groundwater is research subject
modesto orchard
Water is diverted from a Modesto Irrigation District in the winter of 2016 as part of a study of using storm runoff to flood orchards and recharge water tables

The next “big thing” in California water development may not be soaring 300-foot high dams.

Instead, it may be intentionally diverting winter storm runoff to flood almond orchards northeast of Ripon and vineyards near Manteca and similar permanent cropland throughout the San Joaquin Valley.

Proactive recharging of groundwater using California’s immense acreage of permanent crops such as almond orchards and grape vineyards could emerge as a pivotal and critical component of a plan to meet water demands as well as address hydrology patterns expected to be modified by climate change.

It is the premise of a study the state Department of Water Resources is launching of the Stanislaus River basin in concert with the South San Joaquin Irrigation District and Oakdale Irrigation District.

The study will look at the hydrology and explore various soil types. The goal is to determine the degree of soil permeability throughout the basin and the potential for diverting runoff.

The irrigation districts are the perfect study subject. That’s because they already have conveyance systems in place that draws from the Stanislaus River which drains the 1,195 square mile basin.

And they also have distribution systems in place that could move excess storm runoff diverted from the Stanislaus River. That means instead of heading out into the Pacific Ocean, the excessive runoff could be directed to orchards and vineyards most suitable for recharging groundwater.

Unlike building off-stream reservoirs such as San Luis Reservoir to divert excess storm runoff for later use, ground recharging reduces the loss of water to evaporation. It also “stores” water where it is needed.

Not only would it be a tool to secure groundwater stability but it could conceivably start restoring groundwater back toward previous levels that could be drawn down on periods of drought.

The study is not being down in vacuum.

The University of California is conducting multiple-year studies on the impact of long-term flooding of orchards when trees and vineyards are dormant.

There are a lot of “ifs” and “variables” that need to be addressed.

First and foremost, is the amount of long-term damage — if any — such a practice may have on roots of trees and vines.

Preliminary research is promising. Vines appear to be more resilient while  also

California is grappling with more than just the drought, overdevelopment in water-starved basins, and uneven distribution of available water supplies.

Experts say climate change in Northern California may more than likely increase winter rains at lower elevations and reduce the snowpack in the higher elevations.

The state’s dams and water conveyance systems are based primarily on capturing the Sierra and Cascades snowpack runoffs to meet roughly percent of California’s water need.

As such current dams may be end up being in the wrong place to capture the bulk of winter precipitation going forward.

SSJID General Manager Peter Reitkerk  said initial meetings regarding how data will be collected have been conducted with the Department of Water Resources.

Reitkerk said such a study is keeping with the commitment the district has made since its inception in 1909 to be stewards of the Stanislaus River basin as well as maximize the use of water whether it is for irrigation or urban use or to generate power.

The general manager stressed the district is not making a commitment one way or another.

If the study shows there is an effective way to recharge orchards in such a manner and a corresponding UC Davis research can address growers concerns about how roots when they are dormant will fare with such recharging, winter recharging could be a future option for the district to pursue.

The district delivers irrigation water to 50,000 acres, down about 2,000 acres over the past 20 years or so due to urbanization mainly in the Manteca area.

Of that acreage 66 percent of the land is planted in almonds. There is also a healthy amount of grape vineyards as well.


To contact Dennis Wyatt, email