We discuss the reconstruction of neutrino flavor neutrino at a distant source in the very high en- ergy regime. This reconstruction procedure is relevant to the confirmation of detecting cosmogenic neutrinos, for example. To facilitate such a reconst
ruction, it is imperative to achieve effective flavor discriminations in terrestrial neutrino telescopes. We note that, for energies beyond few tens of PeV, a tau-lepton behaves like a track similar to a muon. Hence, while it is rather challenging to separate { u}{mu} from { u}{tau} in this case, one can expect to isolate { u}e from the rest by a distinctive shower signature. We present the result of flavor ratio reconstruction given the anticipated accuracies of flavor measurement in neutrino telescopes and current uncertainties of neutrino mixing parame- ters. It is shown that the further separation between { u}{mu} and { u}{tau} events does not improve the flavor reconstruction due to the approximate { u}{mu} - { u}{tau} symmetry.
We present the reconstruction of neutrino flavor ratios at astrophysical sources. For distinguishing the pion source and the muon-damped source to the 3$sigma$ level, the neutrino flux ratios, $Requivphi( u_mu)/(phi( u_e)+phi( u_tau))$ and $Sequivphi
( u_e)/phi( u_tau)$, need to be measured in accuracies better than 10%.
