This GIS mapping project created a 1:50,000 map of alluvial deposits along streams and rivers throughout Colorado — deposits with the potential for forming alluvial aquifers in direct hydraulic connection with surface water. Augmented by lidar and the use of NAIP 10-meter elevation data and limited strictly to alluvium (excluding aeolian, glacial drift, and landslide deposits), the GIS dataset is a major improvement on prior work mapped at 1:250,000. Free ZIP download. ON-010-02D
QUICK LINKS TO:
ON-010 — Colorado Groundwater Atlas — This web-based report, including many graphics and tables, explores the most current state of Colorado’s groundwater.
Direct to the GIS map: ON-010D Colorado Groundwater Atlas (Map) – v20210304 — The statewide alluvial aquifer layer is found in the “Layer List” under “Statewide” then “Colorado Alluvial Aquifer”.
Excerpt from map metadata:
Alluvial deposits can be complex because of a long history of periods of deposition alternating with periods of incision. As a result, younger alluvial deposits tend to be lower in the landscape where they are hydraulically connected to modern stream. These deposits typically are those of Holocene, Late and Middle Pleistocene in age. Older alluvial deposits tend to be higher in the landscape where they often sit on bedrock-cored terraces and are less likely to be hydraulically connected to modern streams. The intent of this effort was to include only those deposits directly connected to modern streams. Differentiation of the two types of deposit is not always obvious using lidar, DEM, and aerial photography. Published geologic maps provided information to guide delineation that could then be extrapolated over large areas. Alluvial fans from tributaries extend out into trunk river valleys and their deposits can merge with the alluvium of the main river. Because of implied hydraulic connection alluvial fan deposits in the main valleys were included with the alluvium.