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Precipitation plays an important role in global water cycle, and the stable hydrogen and oxygen isotopes of precipitation provide useful information in hydrological processes. To evaluate the controlling factors on stable isotopes of precipitation in the northwesternmost Tibetan Plateau (NWTP), the spatial-temporal variation of δ18O and δ2H in precipitation was investigated based on 120 event-based precipitation samples collected from 3 stations (Jiangka, Shaman and Xihexiu) during 2011–2014 and 45 monthly average precipitation data of Hetian station (GNIP) and 23 individual precipitation events of Shiquanhe station during 2001. The values of δ18O and δ2H in precipitation are more positive in the summer (June to July) and negative in the winter (November to March). The seasonal d-excess pattern observed in the NWTP is remarkably different from that in adjacent regions. The local meteoric water line (LMWL) was calculated as δ2H = 8.22 δ18O + 12.41 (R2 = 0.98, n = 194) based on the event-based samples. Temperature and altitude effects show significant influence on the precipitation δ18O in the study area. Sub-cloud evaporation and recycling moisture also are important controlling factors during the precipitation process. The sub-cloud evaporation decreased d-excess between 1.7% and 45.8%, and the d-excess decreased linearly with increasing sub-cloud evaporation at about 1.15‰ per 1% change of sub-cloud evaporation. The recycled moisture has an important influence on the precipitation on the Xihexiu, Shaman and Jiangka stations. The result of this study is helpful to the understanding of regional water cycling and optimal water resource management during water shortages.

Soil erosion is a critical environmental problem of the Chinese Loess Plateau (CLP). The effects of vegetation cover on soil erosion reduction under different rainfall types are not well understood especially in the eastern Chinese Loess Plateau (ECLP). In this study, we monitored runoff and sediment yield at the Fengjiagou water and soil conservation station with five types of vegetation cover (arbor trees (ARC), shrubs (SHC), arable (ABC), natural vegetation (NVC), and artificial grass (APC)) and three slope gradients (10°, 15°, and 20°) in the ECLP. Based on long-term monitoring data, five rainfall types were classified by the maximum 30 min rainfall intensity (I30). We also quantitatively revealed the interactive effects of different types precipitation, vegetation cover and slope gradients on regional soil erosion. The results showed that (1) The RII (13 times) and RIII (eight times) type are the most threatening erosive rainfall in this region. (2) The ARC and SHC type were most beneficial for soil and water conservation in the ECLP; The APC and ABC are not conductive to the prevention of regional soil erosion. (3) Runoff and sediment yields increased with the slope gradient. The farmland is vulnerable to soil erosion when the slope gradient exceeds 10°. The results of this study can improve the understanding of regional soil erosion processes on the ECLP and provide useful information for managing regional water and land resources.

Runoff generation and dynamics is an important issue in watershed and water resource management. Taking the Aksu River as a typical inland river, the spatial and temporal variations of δ18O and δD of the river water and its sources component pattern were investigated from May 2012 to May 2013. The results showed the following three main findings. Firstly, we analysed the runoff generation and mechanism over a longer time-scale in two tributaries of the Aksu River. Secondly, 46–54% of the runoff in the Aksu River was derived from groundwater, 31–36% from glacier meltwater, 5–8.8% from snow meltwater and 10% from precipitation. The third major finding was the significant inconsistency of the climate change impact on water resources. Specifically, our results showed that the Toxkan River is recharged by more glacier meltwater (36%), and responds to sensitive temperature changes. Autumn runoff is more sensitive to changes of precipitation and temperature.Editor Z.W. Kundzewicz Associate editor Not ass...

By using 233 isotope samples, we investigated the spatial and temporal variations of δ(18)O and δ(2)H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ(18)O and δ(2)H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ(18)O and δ(2)H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary.

Runoff generation and its dynamics are fundamental to hydrology and very crucial to water resource management. Based on isotope hydrograph method, we explored and compared the runoff generation mechanism of two typical inland rivers in the Tianshan Mountains (i.e., Urumqi River on the north slope and Huangshuigou River on the south slope), based on a year-long frequently monitored weather, flow and isotope data. Results show the following: (1) In both rivers, precipitation, river water and groundwater exhibit noticeable spatial and temporal variations in stable δ18O and δD compositions in the Urumqi River and Huangshuigou River, and there is an increasing trend of δ18O in the river water during snowmelt period; (2) isotope hydrograph separation shows that generally groundwater is the major recharging source (over 50 % of streamflow), followed by glacier melt, snowmelt and precipitation in these two rivers, and Urumqi River has a larger contribution from glacier melt than Huangshuigou River; (3) these two rivers have similar contribution components in all seasons except spring in which Huangshuigou River has similar contributions from groundwater (55.6 %) and snowmelt (44.4 %) whereas Urumqi River has a larger contribution from groundwater (72.7 %) than snowmelt (27.3); (4) the Urumqi River is more sensitive to the temperature change than the Huangshuigou River, which might cause flooding that resulted from glacier melt in the Urumqi River.