Eastern San Joaquin groundwater draft plan reaches milestone

An important but not widelypublicized local planning process reached a milestone with the July release of the draft Groundwater Sustainability

Plan for the Eastern San Joaquin Subbasin. This is the public’s first chance to see how groundwater in this region may be managed for the next 20 years.

Californians rely on groundwater more than we usually realize. In a drought, up to 40% of the water used by cities and agriculture comes from underground, not from rivers we can see. About half of Lodi’s water supply is groundwater. All the water delivered to Lodi residents was groundwater until 2012, when the Lodi Surface Water Treatment Plant became operational and the City was able to take advantage of an agreement with Woodbridge Irrigation District (WID) for Mokelumne River water to which WID holds rights. (The East Bay Municipal Utility District — EBMUD — is the other major holder of Lower Mokelumne River water rights.)

Groundwater is not inexhaustible. Particularly in arid agricultural regions south of us with little or no surface water supplies, groundwater pumping increases and wells must be deepened when surface water transfers decrease, as they do in years when there is less water for all users, including fish, to share. In the southern Central Valley, groundwater overdraft in response to drought conditions has actually caused the land to drop, or subside, damaging the canals built to deliver water from Delta watersheds.

In the Eastern San Joaquin Subbasin, which underlies much of San Joaquin County, there is plenty of groundwater deep underground, and the land is not subsiding. But getting that water out would be prohibitively expensive. Meanwhile, groundwater at more accessible levels, from which agricultural, municipal, and domestic wells draw water, has been in decline for decades in some parts of the subbasin. It is for that reason that the Department of Water Resources has classified the Eastern San Joaquin Subbasin as critically overdrafted.

Under the Sustainable Groundwater Management Act (SGMA), which was passed by the California Legislature in 2014, critically overdrafted subbasins have until Jan. 31, 2020 to submit a plan to manage their groundwater in such a way that by 2040, no more water is being drawn out annually than is being replenished.

If groundwater overdraft is a problem, why does the law give subbasins 20 years to fix it? To begin with, our water has never been centrally managed. It has been managed by a variety of cities and irrigation districts with a variety of surface water rights, sometimes in competition with each other. In the Eastern San Joaquin Subbasin, 15 agencies have declared themselves to be Groundwater Sustainability Agencies (GSAs) for

purposes of managing groundwater, and it is taking time for them to create a framework for cooperation. To achieve a common sustainability goal, they have formed the Eastern San Joaquin Groundwater Authority.

California has a complicated system of surface water rights, but groundwater in California has never been carefully measured, monitored, or regulated. The unseen subsurface terrain where groundwater lies is not a tidy layer cake, and water moves around it in ways that are not well understood. It is going to take time for the Groundwater Authority to accumulate the information needed to fairly and sustainably manage this invisible public resource while also protecting water quality and the health of surface rivers and streams and the ecosystems that rely on them.

To bring a groundwater subbasin into balance, water managers can manage demand and/or manage supply. Managing demand by limiting groundwater pumping would have devastating economic consequences, particularly for the agriculture on which this region relies. Planners think that won’t be necessary in this subbasin. The plan is for GSAs to develop projects involving conservation, recycling, in-basin transfers of surface water, or recharge. Direct recharge puts water underground; in-lieu recharge involves using available surface water instead of groundwater for irrigation, allowing groundwater levels to recover.

The City of Lodi has proposed two projects using surface water or recycling instead of groundwater: an expansion of the surface water facility and delivery pipeline, and an expansion of the White Slough Water Pollution Control Facility. The North San Joaquin Water Conservation District immediately to the east of Lodi is already working on delivering Mokelumne River water to irrigators through a modernized pipeline system. Altogether, GSAs in this subbasin are planning eight supply projects and proposing nine potential projects.

Implementing the Groundwater Sustainability Plan will cost money, but the Groundwater Authority and the agencies in this subbasin have a strong incentive to make the plan successful. If they can’t, the law provides for the State of California to manage the subbasin.

With seven chapters plus appendixes, the draft of the complete Groundwater Sustainability Plan is 331 pages long. Fortunately, the Executive Summary — including a complete list of proposed projects — is a manageable 12 pages. The documents are available online at

the website of the Eastern San Joaquin Groundwater Authority. Comments on the draft are due to

by Aug. 25, 2019.