Disagreeing with Dallas-Fort Worth-area water officials, the Texas Water Development Board decided on Wednesday that a years-long conflict over a yet-to-be-built reservoir in the region’s 50-year water plan is serious enough that it should be resolved.

The water-planning agency voted unanimously to deem a disagreement between two contiguous water-planning regions in North and Northeast Texas an “interregional conflict,” setting into motion a third-party mediation that must begin by Oct. 5.

WIMBERLEY — On a recent weeknight, nearly 200 Hays County residents packed into the Wimberley Community Center for what some described as a celebration.

Six months earlier, three times as many had stormed the place demanding state legislation they hoped would thwart a major water development project that could cannibalize their own supplies.

A bill passed — barely — days before the end of this year’s legislative session, resurrected after a rare about face by the House parliamentarian. Enacted weeks later, state Rep. Jason Isaac’s House Bill 3405 expanded the jurisdiction of the Barton Springs/Edwards Aquifer Conservation District to encompass a previously unregulated Trinity Aquifer well field in western Hays County owned by Houston-based Electro Purification.