|Other Abstract||Because of global climate change and its significant impact on regional climate and water resources, Stream-flow components and precipitation vapor sources were studied in typical mountain regions of the Tarim River basin (TRB), northwest arid area of China. We analyzed on the streamflow components using a model of isotope hydrograph separation and computed the contributions of different water sources to streamflow throughout the year. We evaluated the sensitivity of the Aksu River to climate change based on the meteorological and hydrological data during the past 50 years. Using the backward trajectory model, we also identified the precipitation vapor sources and its contribution to streamflow.
(1) The isotope values of precipitation, river water, and groundwater in the mountain areas of the TRB show a larger range. Water isotopic composition varies significantly in time and space within the basin. Precipitation δ18O and δ2H show a typical trend with high values in summer and lower values in winter, indicating the temperature control the precipitation isotopic composition. River water δ18O and δ2H in the mountain is higher than that in the plain area, and is also higher in September 2011 than in May 2012. The chemical characteristic of precipitation, river water, and groundwater also shows significant differences in time and space within the basin.
(2) Water vapor is mainly transported to TRB by the westerlies. The Caspian Sea and the Balkhash Lake are the main sources of water vapor. Water vapor from the Arctic Ocean also influences the TRB in winter. Water vapor from the Arabian Sea and Indian Ocean can influence the southwest area of the TRB. Water vapor from the interior of the basin is important during melting season. Based on the deuterium excess parameter, we caculated the recycled fraction of precipition , our results showed the recycled fractions at Xiehela, Shaliguilanke, Jiangka, and Huangshuigou are 15.7%, 22%, 18.1%, and 19%, respectively.
(3) Results show that the contribution of glacial and snow melt-water to stream flow varies from 7.1% to 39.4%, and the contribution of precipitation varied from 12.56% to 47.4% in the rivers of TRB. Groundwater contributions in most rivers are more than 50%. This indicates that groundwater is the major recharge source of the Tarim River. Groundwater had a larger proportion in May than in September in all the rivers except for the Aksu River. While the Kaidu and Tiznafu Rivers have a relatively stable runoff composition in different seasons, the runoff composition of in the Aksu and Weigan Rivers varies seasonally.
(4) The variation ranges of the runoff from groundwater, glacier meltwater, snow meltwater, and precipitation in the Aksu River are 46%–54%, 31%–36%, 5%–8.8%, and 10%, respectively. Results from isotope hydrograph separation analysis showed that groundwater made the greatest proportional contribution to the streamflow of the Kumalak River throughout the summer and autumn of 2012. The streamflow compositions in Toxkan River are similar as in the Kumalak River. Snow meltwater and precipitation had greater proportional contribution to the streamflow in the Kumalak River. The recharge from the glacier melt water in the Toxkan River is much greater than that in the Kumalak River, especially in summer.
(5) Based on isotope hydrograph separation, melt-water, groundwater, and rainfall contribute 17%, 41%, and 42% of the annual stream flow, respectively, in Tizinafu River.
(6) Based on isotope hydrograph separation, melt-water, groundwater, and rainfall contribute 29.5%, 56%, and 14.5% of the annual stream flow in Huangshuigou River, respectively.
(7) We examined climate change in the last 50 years using meteorological data from 1957 to 2010. Results indicated that temperature and precipitation in the entire basin exhibited significant increase trends. The climate change in the TRB showed a significant spatial difference. Based on the results of isotope hydrograph separation, we found the streamflow of the Tizinafu Rive is more sensitive to precipitation change. The streamflow of the Aksu River and Kaidu River is more sensitive to temperature change.|