LAR 512 – Fall 2002

 

PROBLEM #15 – MAPPING GROUNDWATER DISCHARGE

& RECHARGE AREAS

 

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This problem involves the mapping of groundwater discharge & recharge areas on a map of the Falling Creek Watershed near Drewrys Bluff, Virginia.  The watershed is located in a rapidly urbanizing portion of Chesterfield County and south of Richmond.  The watershed drains a portion of the eastern piedmont upland immediately west of the fall zone to the coastal plain.  The watershed is upstream of the USGS gauging station located at Latitude 37o 27’ 40” and Longitude 77o 28’ 00”.  The drainage area is 54 square miles. 

 

  1. Using the methodology in Heath (1994) “Ground-Water Recharge in North Carolina, pages 12 - 14, map those areas in the watershed that represent “recharge areas” and map those areas in the watershed that represent “discharge areas”.

 

  1. If you assume that the average groundwater discharge rate is 0.265-cfs/sq.mi., what is the groundwater discharge rate for the entire watershed?  __________ cfs  What is the volume of groundwater discharge for the entire watershed over an average year?  ____________________ cf

 

  1. If you assume that this suburban watershed is currently 17.5-percent undisturbed forested, 10.0-percent slightly disturbed woodlands, 12.5-percent former farmland, 22.5- percent disturbed and revegetated lawns, 10-percent highly disturbed lawns, and 27.5-percent impervious surfaces, then using Heath’s methodology on page 32 – 33 and Table 2, calculate a revised average groundwater discharge rate? __________ cfs/sq.mi.  Calculate a revised average groundwater discharge for the entire watershed?  __________ cfs  Calculate a revised volume of groundwater discharge for the entire watershed over an average year?  ____________________ cf