True. Water extraction from the Colorado River has indeed changed the water supply to northern Mexico. The Colorado River is a significant water source for several states in the United States and northern Mexico. Over the years, due to water diversion and extraction for various purposes such as agriculture, industry, and municipal use, the water flow in the Colorado River has been significantly altered. This has resulted in reduced water availability and changes in water supply patterns for regions in northern Mexico that rely on the Colorado River for their water needs.