Found on TheWaterChannel: a great, informative video from the Colorado Water Institute about the South Platte River and its alluvial aquifer. The video gives a very good overview about the prior appropriation system of water rights, especially as it applies to groundwater and Colorado.
A very good source for learning about the physical aspects of the South Platte alluvium is the Groundwater Atlas of Colorado by the Colorado Geological Survey.
A good source of information about groundwater administration in Colorado is the Colorado Division of Water Resources.
As the birthplace of several major rivers, Colorado has a long history of water legislation, regulation and collaboration to address the appointment of our water supplies. Here is a Brief Timeline of Groundwater Management in the South Platte Basin.
"I'd rather be upstream with a shovel and a ditch than downstream with a decree." - Unknown, said about the prior appropriation system