the uncertainties in hydrogeological study in karstic dam site

Leakage from dam reservoirs has been reported in different karst regions of the world. In most cases tremendous additional grout curtains have been constructed to stop or minimize leakage. The practical solution of leakage is extremely complex and costly. The estimation of leakage is mainly erroneous due to uncertainties in the non-homogenous nature of a karst formation, the method of study, the limited investigation due to time and cost limitations, measurement error, and type of flow model. The qualitative uncertainties in geological features, borehole study, isopotential mapping and dye tracing are discussed based on the direct experiences of the authors with several dams in Iran. The leakage uncertainty was calculated for the diffuse and conduit flow models for two strategies of with or without any grout curtains under the combined effect of input uncertainties such as permeability, hydraulic gradient, conduit cross section and friction factor in one of the dam sites of Iran, The results reveal that there are significant uncertainties in conduit flow systems. A big diameter conduit can convey significant amounts of water under high reservoir pressure heads. The uncertainty may be decreased if a detailed study is carried out on the stratigraphical and tectonic settings, karst hydrogeology, geomorphology, speleogenesis, and by performing several dye tracings outside the proposed grout curtain area.

کلیدواژه ها:

Karst ، Uncertainty ، Leakage ، Dye tracer ، Zagros zone