The CZU Lightning Complex Fire’s threat to water quality in Santa Cruz came into sharper focus Tuesday as a Cal Fire emergency watershed response team neared completion of a damage study.

The most pressing risk is debris that could clog the San Lorenzo River near River Street and Highway 1 where water enters the city’s system, said Santa Cruz Water Director Rosemary Menard. The San Lorenzo River is the city’s largest water source. It represents about 45% of the water supply.