HASHIMOTO: TID's groundwater management based on sound principles

August 17, 2013 

— An Aug. 4 article in The Modesto Bee attempted to explain Turlock Irrigation District's role within the region's groundwater basin.

In a good-faith effort to inform the public, TID cooperated with The Bee and provided information as requested, and continues to do so. Unfortunately, the rationale supporting TID's long-standing groundwater practices was represented in an incomplete manner in the article.

The clarifying statements below are meant to fill in some of the missing pieces that did not make the published version of the article.

• Groundwater planning is key. TID is a leader in regional groundwater stewardship, planning, monitoring and interagency coordination. TID operates under a groundwater management plan that was created in conjunction with the Turlock Groundwater Basin Association, of which TID is a founding member.

The plan helps answer many questions about TID's practices, as well as paint a realistic picture of groundwater concerns facing the region. Interested parties should visit www.tid.com/ groundwater to learn more.

• Groundwater is pumped by design. TID uses groundwater in conjunction with surface water from the Tuolumne River to provide irrigation water to farmers. Surface water is used by TID customers to irrigate crops. Some of the water percolates into the ground and recharges groundwater. This has been managed successfully by TID for 90 years.

Planned recharge in wet years, combined with strategic pumping in dry years, known as conjunctive use, is a standard water management practice employed throughout California, and is encouraged by state water managers. From 1991-2011, an average of 14 percent of irrigation water came from groundwater supply. In dry years like this, that percentage is approximately 17 percent.

• TID is a good steward of groundwater. By way of conjunctive use, TID puts more water into the groundwater basin than it takes out. Within the Turlock Groundwater Basin, which stretches beyond TID's irrigation boundaries, surface water imported from the Tuolumne River for irrigation is the main source of groundwater recharge.

Our most recent report indicates that from 1991-2011, imported surface water resulted in an average net gain of approximately 117,000 acre-feet annually to the groundwater basin. That's a net increase (after taking TID pumping out) of more than 38 billion gallons per year to the groundwater system. This practice benefits all groundwater users, including those who receive water from cities or other small community water systems, those who irrigate and those who use private wells large or small.

• TID has no authority to regulate groundwater use. Part of our mission is to provide a reliable supply of surface water to irrigators. While we monitor our pumping and adjust accordingly, TID cannot control when, where, or in what amounts others pump groundwater.

However, we strive to provide reliable and affordable surface water to TID customers so there is less of a need to pump groundwater.

The Turlock Groundwater Basin extends far beyond Turlock and well beyond TID's irrigation boundaries. The basin is relied upon by agriculture, municipalities, industries and private domestic water users alike.

Despite TID's efforts to recharge the basin through conjunctive use programs, groundwater levels continue to decline in some areas of the basin. Without TID's conjunctive use stewardship and proactive resource management, groundwater in the region would likely already be depleted and even the deepest of wells would have already run dry.

Hashimoto is general manager of the Turlock Irrigation District.

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