They changed the law in 2009. You can collect rainwater with these restrictions:
- Harvesting takes place on residential property
- The owner of the property has a legal entitlement to a well
- No water is provided in the area by a water district or a municipality
- The roof is the only location collecting rainwater
- The collected rainwater is put to uses explicitly permitted in the well permit
IMHO any laws making rain water collection illegal are ridiculous, but such things happen in a society that tries to assign ownership rights to everything imaginable.