Investigation of seepage flow path(s) in the right embankment of Sheshpeer Dam, the Zagros Region, Iran

Abstract

Gar and Bare Anticlines are located in the Zagros mountain range, southern Iran. The cores of the anticlines are comprised of the calcareous Sarvak formation sandwiched between two impermeable marly formations, namely Pabdeh-Gurpi at the top and Kazhdomi at the bottom. Sheshpeer spring with an average discharge rate of 3.2 m$^{3}$ s$^{-1}$ emerges from the Gar Anticline, forming the Sheshpeer River. To the west, the Sheshpeer River is delimited by the Albian aged calcareous Sarvak formation, while the Santonian-Oligocene impermeable deposits of the marly Pabdeh-Gurpi formation constitute the eastern limit. Sheshpeer Dam is currently under study and under construction. Parts of the Sheshpeer riverbed lie directly on the Sarvak formation and its water seeps into the adjacent karst aquifer at a rate of approximately 340–650 l s$^{-1}$ which will increase undoubtedly after reservoir impoundment. In addition, two tracing tests, for determination of underground seepage flow path(s) were accomplished. However, no dye tracer was detected in any source of ground water located downstream of the reservoir. Interestingly, water levels of the studied boreholes have dropped during drilling operations indicating the existence of a deep karst aquifer in the region. Finally, the seepage flow direction was investigated and assumed to be most likely parallel to Gar Anticline which strikes toward the adjacent Bare Anticline based on the dye tracing, borehole permeability, water table profiles, water budget, hydrochemistry of water resources and due to the presence of extensive crushed zones on the southern flank of the Gar Anticline.