This act shall not operate or be so construed as to impair, diminish, control or divest any existing or vested water rights acquired under the laws of the state of Idaho or the United States, nor to interfere with the diversion of water from lakes under existing or vested water rights or water right permits for irrigation, domestic, commercial or other uses as recognized and provided for by Idaho water laws nor shall permit be required from a water user or his agent to clean, maintain or repair any existing diversion structure or works provided the board is notified of the work proposed to be done and the work is done as nearly as possible in a manner conforming to rules and regulations of the board for work done under permit nor shall this act be construed to impair existing encroachments in aid of navigation or any right heretofore granted an applicant by the director of the Idaho department of water resources or the director of the department of lands, nor shall this act be construed to impair existing nonnavigational encroachments not extending beyond the natural or ordinary high water mark if they have been in existence at least five (5) years prior to the effective date of this act nor any other existing nonnavigational encroachment unless action to abate the same by legal proceedings be instituted by the board within three (3) years of the effective date of this act. If abatement proceedings be instituted by the board, the court shall hear such evidence as would be pertinent upon an original application and shall consider also the length of time the encroachment has existed and its general acceptance.