Whenever, under the provisions of the laws of this state, any intercommunity water or natural gas supply association obtains or has obtained any money or credits by means of the issue of its bonds or other evidences of indebtedness for the purpose of the purchase, construction or extension or repair of any particular system, it shall be unlawful to divert, use or expend any of the money or credits in the purchase, construction or extension or repair of any other system or for any purpose other than that for which the money or credits were or shall be obtained.