Iowa Code § 481A.14
It shall be unlawful for any person, firm, or corporation to place, erect, or cause to be placed or erected, any dam or other device or contrivance in such manner as to hinder or obstruct the free passage of fish up, down, or through such waters, except as otherwise provided in this chapter. Dams for manufacturing or other lawful purposes may be erected across the waters of the state. No permanent dam or obstruction across such waters shall be erected or maintained which is not provided with a fishway, except by written approval of the director, nor shall any pumping station or plant except sand pumping and dredging machines, in or connected with such waters be constructed or operated except by written approval of the director, which is not provided with screens to prevent fish from entering the pumping station or plant. Such fishways and screens shall be constructed and used according to the plans and specifications prepared and furnished by the director. Any dam, obstruction, or pumping plant which is not so constructed is a public nuisance and may be abated accordingly.
Iowa Code § 481A.14
86 Acts, ch 1245, §1855
Nuisances in general, chapter 657