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Justin Mackey, Bay Creek Watershed

Bay Creek Watershed: What to know!

  • The Bay Creek Watershed is located in Pike county Illinois.  
  • The catchment lies in-between the Mississippi River to the west and the Illinois River to the east.
  • The Bay Creek is a tributary to the Illinois River.


  • Total surface area of 39.4 Square Miles
  • Low degree of urbanization
  • Row crop farming is the primary land use
  • The terrain is moderately hilly and the watershed drains to the south east.
  • The soils are not well drained, mostly poorly sorted glacial till. and classified as group C.    For more information on soil classification follow this link:   Hydrologic Soil Group Classification

Watershed Balance: Where does it go?
 Inflow  (inches)                                  (Averaged totals)     Outflow (inches) (Averaged totals)
 precipitation= 36.84 Stream Flow= 10.21
   Evapotranspiration= 26.96
   Lake evaporation, Groundwater runn off and infiltration= Negligible 
 Total Input= 36.84 Total Output= 36.84*
* Statistical variations are due to annual anomalies in derived averages.  Raw data can be found at this link: 
Stream Data and Precip.xls
Rainfall and Runoff relationships:

  • Plotting precipitation versus discharge in the watershed doesn't provide a strong correlation between the two.
  • The evapotranspiration rates have a stronger positive correlation with the increase in precipitation as displayed by the graph.
 The negligible correlation between the run off and precipitation is likely the result of the low degree of urbanization.  This also explains the strong correlation between the increase in rate of precipitation and increased evapotranspiration depths. 
  • Comparing the hydrograph of Bay Creek directly after a rainfall event and the corresponding hyetograph of rainfall amounts shows a direct response between the two.  
~ 2% of the runoff calculated in the Bay Creek watershed reaches the stream as runoff.  It is assumed the remaining volume of water is lost through evapotranspiration.
    The large evapotranspiration rate is largely due to the low degree of urbanization, moderately hilly terrain, and lack of channelization.  

Olimette Torchecul,
Mar 15, 2012, 2:39 PM