California needs better accounting of groundwater

California’s prolonged drought has driven home the need to improve our balance sheet for water – determining how much there is, who has claims to it and what is actually being used.

Our research, released last week, has identified major gaps in the collection, management and use of water information. Compared to 11 other western states, Australia and Spain – places that also struggle with water scarcity – California has significant room for improvement.

One of the biggest challenges is accounting for groundwater, which supplies about one-third of agricultural and urban water use in normal years, but up to 60 percent during droughts.

The good news is the work has begun. Under a landmark 2014 law, California requires groundwater basins to be managed sustainably. The bad news is that achieving comprehensive accounting systems for groundwater will be a heavy lift. Water pumped from most wells is not consistently measured, monitored or reported.

The new law puts the reins in the hands of local officials, which harnesses local knowledge and creativity, but also risks creating chaos leading to costly litigation.

Farmers, irrigation districts and urban water utilities will have to work together to recharge more water into basins and pump less out. The state can make this task easier.

California can have a common system of water accounting standards, based on units and frequency of measurement, so local agencies can manage and share information. Australia, which pioneered water accounting standards, does this especially well.

The state can also develop standards for computer models that are needed to estimate how much groundwater each basin holds and how much water moves within and across basins. Many local agencies have incentives to use customized models, but that invites conflict. At a minimum, California needs to require that model assumptions, methods and results are electronically documented, publicly available and easily replicated. Even better, we could follow the lead of Texas and invest in models that serve as a standard for determining pumping limits and settling disputes.

California should clarify groundwater claims. The law authorizes local groundwater agencies to limit individual pumping. Defining and capping pumping rights would increase incentives to invest in groundwater recharge and facilitate trading within basins, a key way to lower the costs of limiting pumping.

The state must account for groundwater use and recharge. The new law has spurred widespread interest in using available surface water to recharge aquifers. Establishing transparent estimates of volumes recharged, and crediting land owners who implement such practices, can defray costs.

Across California, local water managers and users are beginning the hard work of bringing groundwater resources into balance. The administration and Legislature should bolster this process by establishing accounting standards and supporting adoption at the local level.

This story was originally published July 23, 2016 at 10:18 AM with the headline "California needs better accounting of groundwater."