The refunding bonds issued by the drainage district pursuant to this part shall be legal investments for all trust funds and for the funds of all insurance companies, banks, both commercial and savings, and trust companies, and for the State school funds, and whenever any moneys or funds may by law now or hereafter enacted be invested in bonds of cities, cities and counties, counties or school districts, in the State, such moneys or funds may be invested in the bonds of the drainage district.