The aquifers
175,512 permits draw on one of the four named Denver Basin aquifers, which have their own legal regime and their own depths.
| Aquifer | Permits | Share |
|---|---|---|
| All Unnamed Aquifers | 465,783 | 77.6% |
| Not stated | 19,134 | 3.2% |
| Dawson | 14,024 | 2.3% |
| Denver | 13,929 | 2.3% |
| Alluvial | 13,890 | 2.3% |
| Ogallala | 11,241 | 1.9% |
| Arapahoe | 9,456 | 1.6% |
| Laramie Fox Hills | 7,796 | 1.3% |
| Upper Dawson | 6,943 | 1.2% |
| Quaternary Alluvium | 5,403 | 0.9% |
| Lower Dawson | 4,944 | 0.8% |
| Unconfined San Luis Vall | 3,975 | 0.7% |
| Unconfined San Luis Valley Aquifer | 3,520 | 0.6% |
| Laramie-fox Hills | 2,605 | 0.4% |
| Confined San Luis Valley | 2,551 | 0.4% |
| Upper Arapahoe | 2,224 | 0.4% |
| Lower Arapahoe | 2,084 | 0.3% |
| Dakota | 1,758 | 0.3% |
| Confined San Luis Valley Aquifer | 1,683 | 0.3% |
What each one is
All Unnamed Aquifers
the Division’s catch-all, and by far the largest group. It means the permit is not tied to one of the named Denver Basin formations.
Not stated
an aquifer the Division records under this name.
Dawson
the shallowest of the four named Denver Basin aquifers.
Denver
a named Denver Basin aquifer, below the Dawson.
Alluvial
shallow water in river gravels — easy to reach and closely tied to the surface stream, which is why it is regulated differently.
Ogallala
the great High Plains aquifer, under Colorado’s eastern counties.
Arapahoe
a named Denver Basin aquifer, deeper again.
Laramie Fox Hills
an aquifer the Division records under this name.
Upper Dawson
an aquifer the Division records under this name.
Quaternary Alluvium
an aquifer the Division records under this name.
Lower Dawson
an aquifer the Division records under this name.
Unconfined San Luis Vall
an aquifer the Division records under this name.
Unconfined San Luis Valley Aquifer
an aquifer the Division records under this name.
Laramie-fox Hills
the deepest of the four named Denver Basin aquifers.
Confined San Luis Valley
an aquifer the Division records under this name.
Upper Arapahoe
an aquifer the Division records under this name.
Lower Arapahoe
an aquifer the Division records under this name.
Dakota
an aquifer the Division records under this name.
Confined San Luis Valley Aquifer
an aquifer the Division records under this name.
Which aquifer a well draws on is not administrative detail: it decides how deep the hole has to be, and it decides which rules apply. Depth and yield, county by county.