Approximately 230 feet below this area lies the Ogallala Aquifer, an underground water basin beneath portions of eight states. Its water volume varies with rainfall and with use by domestic, livestock, municipal, and irrigation wells. The headwaters of the three tributaries of the Republican River—the North Fork, South Fork, and Arikaree—originate in Colorado north and west of Burlington and are hydrologically connected to the Ogallala Aquifer. The land area that feeds the river is the Republican River Basin. After leaving Colorado, the Republican River flows through portions of Nebraska and into Kansas, where it joins the Smoky Hill River at Milford Reservoir near Junction City to form the Kansas River. In the late 1800s and early 1900s, floods were common on the plains. On May 31, 1935, a thunderstorm over eastern Colorado dropped up to 14 inches of rain, and as the waters gathered, a devastating flood developed in which 105 residents drowned and losses of homes, livestock, and crops were overwhelming. On December 31, 1942, commissioners from Colorado, Nebraska, and Kansas signed the federally approved Republican River Compact to obtain federal funds for reservoirs and flood protection and to agree on sharing water in the basin. Commissioners from the three states still meet annually to administer the compact and manage Republican River water. To comply with the compact, Colorado, Nebraska, and Kansas have made significant changes to reduce water use and lessen depletion of the Ogallala Aquifer. In 2004, the Colorado legislature created the Republican River Water Conservation District, or RRWCD, to assure local involvement in the state's compliance efforts.