Includes the following as an option of providing evidence of an adequate water supply when applying for a building permit: A water well report for a groundwater withdrawal exempt from permitting that is not prohibited by an applicable water resources management rule.

Authorizes a county or city to: (1) Impose conditions on building permits requiring connection to certain existing public water systems; and

(2) In providing for the protection of the quantity of groundwater used for public water supplies, rely on or refer to applicable water resources management rules.

Authorizes certain local governments, in approving a subdivision, dedication, or short subdivision, to rely on or refer to applicable water resources management rules to determine if appropriate provisions have been made for potable water supplies.

Requires a permit to make beneficial use of public waters to be conditioned to mitigate impacts to fish or aquatic resources.

Directs the department of ecology to: (1) In areas where it has adopted a rule setting minimum flows or levels, establish a program, under certain circumstances, to mitigate the cumulative impacts of withdrawals for domestic uses that are exempt from permitting; and

(2) Upon written request by a county legislative authority, allow certain counties to administer the watershed-based exempt well mitigation program for that area.