A rebate program that will make already discounted rain barrels even less expensive for area residents will be available through the end of this year, the San Diego County Water Authority announced Monday. The 50-gallon barrels will be available at the Solana Center for $90, discounted from $149, according to the water authority. Until Dec. 31, purchasers can also get a $75 rebate through the SoCalWaterSmart program. The offer will be reduced to $35 on Jan. 1, according to the agency. “Water stored in rain barrels can gradually be released into landscapes between rains,” said Joni German, water resources specialist for the water authority.