Drainage districts were first authorized by the Texas legislature in 1905; modifying laws followed in 1907, 1909, 1911, and 1945. The Canales Act of 1918 is also applicable. Drainage districts, which may be established upon a two-thirds vote of qualified resident property-tax payers in the proposed districts, are organized for the construction of canals, drains, ditches, and levees. The governing board is composed of three commissioners selected by the county commissioners' court for four-year terms, although under certain conditions they may be elected. A civil engineer is appointed by the board. The board has the authority to examine levees, railroad culverts, ditches, and other drainage structures on land in or out of the district and can acquire right-of-ways for the purpose of surveying or drawing plans. The engineer makes a map of the district. The board can call for construction bids and awards contracts to the lowest bidders. Districts availing themselves of the Canales Act have no limitation on taxation or indebtedness; under the drainage acts indebtedness is limited to one-fourth of the assessed valuation of real property. Districts organized under the 1917 conservation amendment may use either the benefits or the ad valorem basis for taxation; other districts use ad valorem only. The county treasurer serves as the treasurer of the district, and the county tax assessor and collector handles the taxes, although county commissioners can appoint an assessor-collector specifically for the district through election approval. Many drainage districts are found along the Gulf Coast and in the irrigated sections of the state. In 1992, forty-six were registered with the Texas Water Commission. See also WATER LAW.