ðə ɹˈɛzɚvwˌɑːɹ ɪz fˈɔːɹmd baɪ ɐn ˈɜːθfɪl dˈæm əkɹˌɑːs ðə kˈænɪən ʌv ˈoʊsoʊ kɹˈiːk, wˌɪtʃ ɪz pˈɑːɹt ʌvðə tɹæbjˈuːkoʊ kɹˈiːk ænd sˌæn hwˈɑːn kɹˈiːk dɹˈeɪnɪdʒ bˈeɪsən.
The reservoir is formed by an earthfill dam across the canyon of Oso Creek, which is part of the Trabuco Creek and San Juan Creek drainage basin.