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Hydrological processes of lakes in the Tibetan Plateau are an important indicator of climate change. Due to the high elevation, inaccessibility and limited availability of historical observations, water budget evaluation of typical lake basins has been inadequate. In this study, stable isotopes are used to trace the multiple water sources contributing to two adjacent lakes on the north slope of the Himalayas, Gongmo-tso and Drem-tso. The two lakes have nearly the same elevation, lake area and climatic condition. However, the isotopic composition of the two lakes presents significant differences. Qualitative observations attribute the differences to hydrological discrepancies: Gongmo-tso is a through-flow lake, whereas Drem-tso is a terminal lake. Quantitative analyses, including water and isotope mass balance modelling, clarify the fluxes and isotopic compositions among the various hydrological elements. The isotopic composition of input water, calculated as the summation of rainfall and upstream runoff, is estimated using the local meteoric water line (LMWL) combined with the time series of lake water isotope values. The isotopic composition of evaporation is calculated with a linear resistance model using local meteorological data. The results show that Drem-tso is a closed lake in a hydrological steady state with relatively more enriched lake water isotope values resulting mainly from evaporation. In contrast, through-flow accounts for more than 88% of the water input into Gongmo-tso. The large amount of upstream runoff with lower isotopic composition and enrichment due to evaporation are the major contributions to the observed lake water isotope values. Isotopic modelling of the two neighbouring lakes is effective for isotopic and hydrological research in this region with limited in situ observations. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Studies have been devoted to the transport and accumulation of persistent organic pollutants (POPs) in mountain environments. The Himalayas have the widest altitude gradient of any mountain range, but few studies examining the environmental behavior of POPs have been performed in the Himalayas. In this study, air, soil, and leaf samples were collected along a transect on the southern slope of the Himalayas, Nepal (altitude: 135-5100 m). Local emission occurred in the lowlands, and POPs were transported by uplift along the slope. During the atmospheric transport, the HCB proportion increased from the lowlands (20%) to high elevation (>50%), whereas the proportions of DDTs decreased. The largest residue of soil POPs appeared at an altitude of approximately 2500 m, and may be related to absorption by vegetation and precipitation. The net deposition tendencies at the air--soil surface indicated that the Himalayas may be a 'sink' for DDTs and PCBs. [ABSTRACT FROM AUTHOR]

δ18O measurements based on systematic sampling and isotopic modeling have been adopted to study the controls of stable isotopes in lakewater in two lake basins (lakes Yamdrok-tso and Puma Yumtso) at two different elevations on the southern Tibetan Plateau. Temporally, d18O values in precipitation and lake water display a seasonal fluctuation in both lakes. Spatially, δ18O values in the two lake basins increase by 10%from the termini of glaciers to the lake shores, by ~1% from the lake shores to the lake center and by 0.4% from the water surface to depth in these lakes. The clear annual δ18O variations indicate that lake water mixes sufficiently in a short time. Model results show that glacial meltwater and surface lake-water temperature are not the dominant factors in the balance process of stable isotopes in lake water. Equilibrium d18O values decrease by 0.8%for Yamdrok-tso lake and 0.6% for Puma Yum-tso lake when glacial meltwater contributions to these lakes shrink by 60%. δ18O ratios increase rapidly during the initial stages and take a longer time to approach the equilibrium value. [ABSTRACT FROM AUTHOR]

Stable isotope variability and fractionation associated with transformation of precipitation/accumulation to firn to glacial river water is critical in a variety of climatic, hydrological and paleoenvironmental studies. This paper documents the modification of stable isotopes in water from precipitation to glacier runoff in an alpine catchment located in the central Tibetan Plateau. Isotopic changes are observed by sampling firnpack profiles, glacier surface snow/ice, meltwater on the glacier surface and catchment river water at different times during a melt season. Results show the isotopic fractionation effects associated with glacier melt processes. The slope of the δD-δ18O regression line and the deuterium excess values decreased from the initial precipitation to the melt-impacted firnpack (slope from 9.3 to 8.5 and average d-excess from 13.4‰ to 7.4‰). The slope of the δD-δ18O line further decreased to 7.6 for the glacier runoff water. The glacier surface snow/ice from different locations, which produces the main runoff, had the same δD-δ18O line slope but lower deuterium excess (by 3.9‰) compared to values observed in the firnpack profile during the melt season. The δD-δ18O regression line for the river water exhibited a lower slope compared to the surface snow/ice samples, although they were closely located on the δD-δ18O plot. Isotope values for the river and glacier surface meltwater showed little scatter around the δD-δ18O regression line, although the samples were from different glaciers and were collected on different days. Results indicate a high consistency of isotopic fractionation in the δD-δ18O relationships, as well as a general consistency and temporal covariation of meltwater isotope values at the catchment scale. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fully physics-based, process-level, distributed fluid flow and reactive transport hydrological models are rarely used in practice until recent years. These models are useful tools to help understand the fundamental physical, chemical, and biological processes that take place in nature. In this study, sensitivity analyses based on a mountain area river basin modelling study are performed to investigate the effect of river channel geometric characteristics on downstream water flow. Numerical experiments show that reduction in the river channel geometric measurement interval may not significantly affect the downstream water stage simulation as long as measurement accuracy at special nodes is guaranteed. The special upstream nodes include but are not limited to 1) nodes located close to the observation station, 2) nodes near the borders of different land covers with considerable riverbed roughness changes, 3) nodes at entering points of tributaries causing discharge jump and 4) nodes with a narrow cross-section width that may control the flow conditions. This information provides guidelines for field investigation to efficiently obtain necessary geometric data for physics-based hydrological modelling. It is especially useful in alpine areas such as the Tibetan Plateau where field investigation capability is limited under severe topography and climate condition. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article focuses on a study on the rapid growth of Linggo Co, a glacier-fed lake in the central Tibetan Plateau, resulting from glacier mass loss. It is said that the negative mass balance of glaciers and ice caps play a role in the expansion of inland lakes yet such impact is difficult to assess as not all meltwater from glaciers does not go into lakes. Findings show that the lake expanded by a total of 20.26 square kilometers (km²) or 21.34% from 1974 to 2010. Results indicate that the growth of the lake is being caused by the increased influx of meltwater from glaciers between 1974 and 2000.

The article looks at the Third Pole Environment (TPE) Program that promotes the study of the mechanisms behind environmental changes in the Third Pole region of Tibet. It reveals that the Third Pole region, an area that covers 5,000 square kilometers between the Pamir and Hindu Kush in the west to the Hengduan Mountains in the east, is an ideal location for researching possible strategies for adapting to climate change due to its high altitude and the presence of permafrost and glaciers.

Abstract: Event-based rain and snow samples were collected from May 2009 to April 2010 at Madoi in the eastern Tibetan Plateau, and the stable isotopic compositions (δ18O and δD) of these samples were analyzed. The local meteoric water lines (LMWLs) based on individual samples and monthly weighted means were δD = 8.37δ18O + 11.86 (R 2 = 0.97, n = 175) and δD = 8.80δ18O + 20.16 (R 2 = 0.98, n = 11), respectively. Although fluctuations of the isotopic compositions in precipitation throughout the year were high, monthly amount-weighted means revealed seasonal signals. According to the monthly averaged data, the δ18O values decreased distinctly from June to July, indicating that summer monsoon circulation can significantly influence precipitation in this region. The high d-excess values from May to June and from October to November were probably the result of local moisture recycling. Apart from moisture sources, the δ18O and d-excess values in precipitation were also affected by subcloud evaporation/sublimation, which could be inferred from their relationships with different temperature and relative humidity ranges. The results of this study augment the understanding of the water cycle in the eastern Tibetan Plateau. [Copyright &y& Elsevier]