Environmental geology lecture outline
- Nebraska's geohydrology
For purposes of simplicity we will consider
3 different groundwater provinces, each with differing geologic
and aquifer characteristics:
below are units listed from youngest (most recent) to oldest:
- alluvium: e.g.
along Platte, Missouri, Elkhorn rivers. Shallow, high quality
aquifers, with quick recharge, but greater contamination potential.
- loess: wind
blown silt deposits, fine-grained so relatively impereable, has
- glacial outwash:
well sorted sands and gravels, discontinuous in distribution,
usually thin so not a good aquifer, potentially important as
- tills: poorly
sorted deposits and hence impermeable, thicker to N and E, discontinuous
in Omaha area,
- Dakota sandstones:
good high porosity sandstones, thin to the E and locally absent
in Omaha area, high TDS.
- Pennsylvanian age limestones and shales: generally impermeable, except where have fracture
porosity, widespread, generally subsurface.
Sand Hills and the underlying Ogallala
- geologic nature of Sand Hills
- lakes, marshes and subirrigated meadows,
groundwater fed rivers
- major recharge mechanism for underlying Ogallala
paleo-channel deposits (old alluvium, unrelated to present river
- Ogallala Group and aquifer, High Plains Aquifer
Tertiary strata in western Nebraska
- decrease in volcanic ash component with stratigraphic
ascent, and corresponding decrease in permeability.
- basal White River Group Chadron conglomerate.
- local sandstone channels as exceptions.
- fracture aquifers in the Brule Fm..
Links for advanced exploration of the topic:
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