Local farmers are fighting against a plan to sharply reduce their special water rate discount, contending it could wipe out much of the county’s already-shrinking agriculture industry. The cash-strapped County Water Authority says it must roll back the longtime rate discount it now gives to roughly 1,000 local farmers because of dropping demand and changes to the authority’s business model. Farmers say the rate hike proposal is shortsighted because it would accelerate the demise of many farms, stripping the water authority of existing customers at a time when it needs more customers — not less. Losing hundreds of local farms would also hurt ordinary San Diegans, the farmers say, by replacing local fruits and vegetables with imported produce that would be more expensive and less fresh. … While the discount varies from local water agency to water agency, it is typically in the neighborhood of 25%.