The powerful storms that have pounded California for the past two weeks have disrupted life statewide, leaving at least 19 dead, causing widespread flooding and closing or destroying iconic piers from Ocean Beach to Capitola. The precipitation has also done some good. Wednesday, the Sierra Nevada snowpack — which provides about 30 percent of the state’s water supply — was 226 percent of normal, the highest in at least 20 years. With two more storms looming, the snowpack is expected to keep growing ahead of an important April 1 measurement date for forecasters when it tends to peak.