Below Prado Dam, the Santa Ana River crosses into Orange County, and cuts between the Santa Ana Mountains and Chino Hills via the narrow Santa Ana Canyon. The river roughly bisects the county as it flows southwest towards the ocean. In Anaheim, the entire flow of the river (except during wet seasons) is diverted into spreading grounds for groundwater recharge of the north Orange County aquifer, providing about half of the county's municipal water supply. Downstream of there, the river is mostly confined to a concrete channel, serving only for flood control and urban runoff drainage, and is usually dry or a small trickle. At Orange it receives Santiago Creek from the east before entering Santa Ana. After crossing under Interstate 5 it passes through the River View Golf Course, one of its few non-concreted sections within Orange County, and then becomes a concrete channel again through most of Santa Ana and Fountain Valley to a point below the 405 Freeway, where the river bed becomes natural (though the banks remain concrete). The mouth of the river is located in a small tidal lagoon between Huntington Beach and Newport Beach, at the northern end of Santa Ana River County Beach.