Characteristics Of Runoff And Its Response To Climate Change At Thealpineaera Of Urumqi River In The Tianshan Mountains

With the global warming intensification, river runoffs have significantspatiotemporal variations, which directly influence the rational allocation,development and utilization about water resources along the basin, as well as physical,chemical and biological processes of river ecosystems. Runoff is an important part ofthe hydrological processes, and researching runoff changes for the understanding ofthe trend of regional surface water resources, rational development and utilization ofwater resources has an important practical significance. Based on the runoff andmeteorological data nearly50years from the Urumqi River Basin mountain, thisstudy had a detailed analysis. The results were showed as follows.(1) The runoff on the whole showed a rising trend at mountain outlet of theUrumqi River in the past50years, but runoff occurred mutation from the late1980sto the early1990s. Different oscillation periods were displayed very clearly in themountain outlet runoff. Significant periodic variations with periods of a25-year, a8-year and a5-year appeared in the mountain outlet runoff, and annual runoffcoefficient of variation was0.15. Mountain outlet runoff in the number of days ofextreme runoff presented a downward trend from1992to2004. The maximum ofmountain outlet runoff appeared in July, accounting for29.1%of the entire year ones,the minimum in February. From the season terms, The runoff in spring, summer,autumn and winter, respectively accounted for10.7%,54.8%,15.5%,5.0%of theannual total, more than half concentrating in the summer, but the ones in winter atleast. The runoff of Glacier No.1had an increasing trend with the tendency rate of33405m~3/a, the minimum appearing in1976, the maximum with309×104m~3in2010,while the change trend at Zongkong station was almost stable, especiallyinconspicuously in recent years, which had the obvious mutation in1993. Themonthly runoff at Glacier No.1and Zongkong station increased from May, reached amaximum and then began to decline in July. From the annual runoff ratio, the runoffof Glacier No.1and Zongkong station in July respectively accounted for42%and39%of the ones in entire year.(2) The temperature and precipitation overall presented an ascending in Urumqimountain. The linear trend rate of temperature is0.023℃/a, extremely low temperature value with-6.7℃in1984, then rising acceleratedly. The linear trend rateof precipitation is2.15mm/a, extremely low precipitation value in1980s when theprecipitation changes happened mutation, the precipitation decreasing before1980s,afterwards increasing apparently. Using temperature gradient changes with altitude,the average elevation gradient is-0.49℃/100m in Urumqi River basin.(3) For the correlation between the temperature and precipitation and mountainoutlet runoff, the latter correlation was better. The runoff coefficient was0.58atmountain outlet of the Urumqi River. Based on grey Relevancyindicates, correlationcoefficient between the runoff and precipitation was more than that between therunoff and temperature, which demonstrated that the precipitation was moresignificant impact on the Urumqi River. The results were consistent with the ones ofthe correlation analysis. The runoff of Glacier No.1presented an increasing trendoverall, showing negatively correlated with glacier mass balance, and was greatlyinfluenced by the temperature. The runoff at Zongkong station with temperature andprecipitation was on the rise, increased before1996, slowly decldine afterwards. Therelationship between runoff and precipitation and temperature at Zongkong stationwas not simply cumulative. Under the context of the temperature and precipitationincrease, the runoff at Zongkong station was no significant increase in recent years.(4) Without considering the influence of human factors, the mountain outletrunoff showed a sustainable growth trend in the future in Urumqi River basin. Themountain outletflow of Urumqi River will fluctuate around2.9×10~8m~3,3.0×10~8m~3,2.9×10~8m~3,3.1×10~8m~3,3.0×10~8m~3,2.9×10~8m~3,2.4×10~8m~3,2.8×10~8m~3,2.7×10~8m~3,3.0×10~8m~3in the next decade (2008to2017) by gray topology predictionmodel.