Examples of aquifers - Physical Geology lecture notes
There are many types and examples of aquifers of which two are particularly relevant to Nebraskan's . Omaha gets more than half its water from the Platte River alluvial aquifer, and the city of Lincoln also taps into this aquifer. In addition, the High Plains Aquifer, that covers a good bit of Nebraska and is crucial to the state's agricultural productivity. is widely known. The USGS and other governmental agencies monitor the quality of the water - and one report from the USGS can be found here - http://ne.water.usgs.gov/projects/mud.html .
Above is photograph of the Niobrara River valley wall in the Fort Niobrara area. The blue arrows point to a water seep horizon. The Rosebud Formation sediments below are rich in volcanic ash and clays and so are relatively impermeable. Overlying them are sands and gravels of the Ogalalla Group which hosts the major unconfined aquifer in Nebraska, the High Plains aquifer, also informally known as the Ogallala aquifer. This aquifer extends all the way down into Texas. Thus, here the water seep represents a perched aquifer intersecting the landscape. Note that in this case the Niobrara River is partly groundwater fed as some of the seeps reach water level.
Map showing extent and thickness of the High Plains aquifer. Image source: USGS - http://ne.water.usgs.gov/ogw/hpwlms/hpfs97.html .
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