Temporal sequential analyses of the hydrological observational data in the Tarim Ba-sin over the last forty years revealed an annual increase of 2 × 107m3 in the water quantities at thethree headstreams of the upper courses and an annual decrease of 3 × 107m3 in the water flowfrom Alaer, which is on the upper main stream. A prediction of the trends indicates that there canbe severe situations under which intermittent water interceptions occur. By means of approximateestimations on vegetative water consumption through phreatic evaporation combined with a quotaassessment, the ecological water demands required to maintain the ecological environment in themainstream area over the three different targeted years of 2005, 2010 and 2030 are defined asstanding at 31.86× 108m3, 36.27× 108m3 and 41.04× 108m3 respectively. Ecological fragility in-dexes are established on the basis of the selection of environmental sensitivity factors. Rationalevaluations give proof that the lower reaches of the mainstream have already turned into zoneswhere their ecological environments are gravely damaged. Multi-objective optimization should beconducted and protective schemes be framed within the threshold limits of the bearing capacitiesof water resources and the environment.