It’s been 20 years since the largest water agencies in Southern California agreed on a historic deal: San Diego would buy water from Imperial Valley farmers. More importantly, though, the deal outlined exactly how much water these agencies could claim from the Colorado River and reduced the amount of water California took from the river.   It quantified the water (why it’s called the Quantification Settlement Agreement) and put a price on water rights for the first time. … Voice of San Diego and CalMatters will be gathering top water officials from Southern California, Nevada and Arizona to discuss the past (the historic 2003 settlement) and the future (the needed deal for the Colorado River) at 2023 Politifest, Oct. 7 at University of San Diego.