Nothing in this part shall be construed to do any of the following:
(a) Alter or impair any existing rights.
(b) Change existing water rights law.
(c) Authorize a landscape contractor to engage in or perform activities that require a license pursuant to the Professional Engineers Act (Chapter 7 (commencing with Section 6700) of Division 3 of the Business and Professions Code).
(d) Impair the authority of the California Building Standards Commission to adopt and implement building standards for rainwater capture systems pursuant to existing law.
(e) Affect use of rainwater on agricultural lands.
(f) Impair the authority of a water supplier pursuant to Subchapter 1 of Chapter 5 of Division 1 of Title 17 of the California Code of Regulations.