California relies heavily on groundwater for its water supply, particularly during drought.  Climate change is increasing drought intensity, making groundwater―with its immense potential for low-cost storage―an ever more important water source. Sustainable groundwater management will be vital to adapting to a warmer future and should be a top policy priority for the next administration.

In non-drought years, groundwater supplies approximately one-third of urban and agricultural water use in California, but its share rises during droughts, when snow and surface water are scarce. In severe drought years, it provides more than half of urban and agricultural water use.

A recent report by the PPIC Water Policy Center and a large team of experts highlighted the impacts of climate change on water supply and ecosystem management during drought. As winter precipitation shifts from snow to rain in a warming climate, a key issue will be adapting the management of the state’s water storage system. A more volatile climate and changes in precipitation could shift the use of large multipurpose reservoirs from water storage to protection against flood risk, thus reducing the water available from reservoirs in some years―and making groundwater storage even more important.

In some regions, including the San Joaquin Valley, groundwater overdraft—taking more water out of aquifers than is put back—has been going on for decades. This has increased the cost of groundwater pumping, dried up wells in many rural areas, and caused land to sink, damaging infrastructure.

But the greatest long-term impact of unsustainable groundwater use is the loss of stored water that can be economically pumped during dry periods. This makes the state increasingly vulnerable to drought in a changing climate.

The 2014 Sustainable Groundwater Management Act (SGMA) requires water users and other stakeholders to self-organize into groundwater sustainability agencies (GSAs) and prepare and implement plans to achieve sustainability in the next 20 years. Done well, these efforts will restore the capacity of the state’s groundwater basins to supply water during drought.

GSAs have begun the hard work of developing their sustainability plans—due in January 2020 for critically overdrafted basins and two years later for the rest. The Department of Water Resources is providing technical and planning assistance, and the State Water Board―which has ultimate authority over these plans―is offering policy and legal guidance where it can.

Making SGMA a success will require additional action in the following four areas:

Advance planning. At the top of the list is expanding state and regional support for groundwater sustainability plans. Factoring in the predicted effects of climate change and developing robust water accounting and regional strategies for managing scarcity will be key.
Modernizing the water grid. A major priority for helping groundwater basins achieve sustainability is to upgrade and modernize the state’s water “grid”―the network of reservoirs, canals, rivers, and groundwater basins that store and convey water. Improving the grid’s capacity to move surface water into groundwater storage during wet periods is essential.
Updating water allocation rules. For the improved grid capacity to function well, the state will need to make it easier to recharge, trade, and bank groundwater.
Finding the money. Finding the money for groundwater sustainability programs will be crucial. The best solutions focus on expanding funding from local water bills and taxes—which currently fund roughly 85% of water management expenditures—and using state general obligation bonds to fund projects with clearly defined public benefits.

Achieving sustainable groundwater management is one of the most important things California can do to prepare for a warming climate. Getting there will require a suite of actions―including some reforms beyond those called for under SGMA. Better planning, modernizing the grid, streamlining water allocation, and finding program funding can help us manage this critical water supply.

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