MILLIGAN CREEK - ATTEMPTING TO RECONCILE DISCHARGE WITH BASIN SIZE IN A KARST SETTING

Milligan Creek is part of the Davis Spring drainage basin; a 192 sq km karst basin in Greenbrier County, southeastern West Virginia. Milligan Creek is underlain by the 300+ meter sequence of the Greenbrier Limestone of the Mississippian period. Regional dip in the basin is gently to the northwest. The basin is dissected by a series of north-south faults and folds where dip can locally increase to near vertical. Previous studies indicate that faults act as a barrier to conduit development (though not necessarily to flow movement).The downstream exit of the Davis Spring basin is Davis Spring, a 20m wide spring which issues from a hillside breakdown collapse approximately 300m away from the Greenbrier River. Discharge at Davis Spring fluctuates between 10 cfs and over 1000 cfs. Storm response is very flashy. Milligan Creek is the main surface stream along the western portion of the drainage basin. Milligan Creek receives much of its water from upland clastic sources. Milligan Creek sinks and rises repeatedly along favorable limestone beds.

Ten months of datalogger recording were done in the Milligan Creek sub-basin. These discharge data were compared to the collected precipitation data and the discharge data at Davis Spring. When a short-term water budget was constructed, it was determined almost 80% of the precipitation in the Milligan Creek basin was being taken up as ET. Regional ET rates are in the 55% range. Possible reasons for the unusually high ET rate include recent changes in land use, incorrect basin boundaries, water lost permanently underground or problems with a short term study. Of the possible reasons, the most likely are changes in land use and water lost underground.