The following acts shall constitute offense against the purity of the water supply: swimming, fishing, and boating in Cle Elum Lake; dumping raw sewage into any lake, river, spring, stream, creek or tributary constituting the source of supply of water of the city, or camping on the shores of the streams, lakes, etc. No dwelling shall be constructed or maintained on the watershed, unless the dwelling is provided with a sanitary toilet so designed and so kept that the contents of the toilet cannot drain on the surface of the ground or reach the water through the ground.