This image represents a three dimensional view of the Au Sable River valley, looking from the east down onto the basin. Mio Dam Pond is the blue lake nearest us.  The river snakes through the valley, and drains into the Alcona Dam Pond on the far side of the image.  The upper left side of the picture (approximately) is north.  Relief is shown in shading; shades of pink to red represent the rate of groundwater delivery.  Rate of groundwater delivery is a function of gradient and hydraulic conductivity, which is related to soil porosity--in other words, in areas with high hydraulic slope and porous soils (such as the Au Sable) one would expect considerable volumes of groundwater to reach the stream.  The image was created in ArcView 3D Analyst using the Michigan Rivers Inventory (MRI) groundwater input cover layer overlaying the elevational coverage of the state of Michigan.  20x actual elevation.

Groundwater driven streams are thermally stable, maintaining cool temperatures during summer months, which is particularly important for thermally intolerant species such as trout.  In addition, groundwater fed streams show slow response to precipitation events, maintaining a fairly stable discharge.  Runoff driven streams show a "flashy" response to storm events, with peak discharges far above mean discharge.  Between storm events, runoff driven streams are dominated by low flows.


A two dimensional graphical representation of rate of groundwater delivery to the stream (based on the Darcy Equation, which estimates groundwater flow based on hydraulic conductivity of the soils, head pressure, cross sectional area, and gradient.) Again, the darker pink/red areas are areas which have greater rates of groundwater delivery.


End Medium Till 
Lacustrine Clay and Silt 
Ice Contact/Outwash 
End Coarse Till 
Glacial Outwash 
End Fine Till


Surficial geology of the catchment after Farrand's quaternary geology maps. The main branch of the Au Sable between Mio Dam and Alcona Dam flows exclusively through glacial outwash, with tributaries originating in lacustrine deposits, ice contact/outwash, fine till, medium till, and coarse till.  The coarse material in the Au Sable basin is very porous, so water infiltration into the soil is high.  Porosity and infiltration are factors which drive the groundwater system.

Soil types in the basin

Inland waters 
Wet sandy/organic 
Wet clayey/loamy 
Au Sable River, tributaries, and impoundments


Single Family Residential/Duplex 
Air Transportation 
Outdoor Recreation Development 
Shrub Rangeland 
Aspen/Birch Dominated Hardwood Forest 
Upland Pine Coniferous Forest 
Forested Wetland--Mixed Forest 
Au Sable River, associated tributaries, lakes, and impoundments 
Basin Boundary
Predominant land uses in the area.  Landuse can dramatically affect the function of a stream.  Because the Au Sable basin is dominated by forested areas, soils are well drained (not compacted), pollution, nutrient, and sediment inputs are minimal, and impervious surfaces in the floodplain are virtually non-existant.