The Impact Of Climate Change On Runoff In Northwest Arid Region Of China Using VIC Model And SDSM

In northwestern China, continental river basins located deep in the Eurasia hinterland,away from the ocean, are the driest areas in China. These basins have scarce precipitation,which cause water shortage and fragile ecological environment. They are facing more andmore problems caused by water shortage. Most rivers here are very sensitive to climatechanges, such as temperature and precipitation. And the water resources system has veryweak bear ability to climate change. The future global climate change could increase watersupply pressure in part of the basins. And affect the sustainable development in water scarcityareas directly.Combining hydrological models with General Circulation Model to analyze differentmeteorological elements, and using climate change scenarios to assess the change rule ofrunoff and the influence of meteorological factors on runoff, can provide some reference forthe prediction of future trends and river basin water resources planning, managementdecision-making.In this paper, take the typical arid basin in northwest China, shiyang river basin, as theresearch object. We used the method of singular spectrum analysis analyzed history changecharacteristics of temperature, precipitation and runoff series in upstream region of shiyangriver basin in recent50years. We applied and verified VIC model in the same region. Thenwe used different future climate scenarios to assess the runoff response to climate change.Main conclusions are as follows.(1) By the analysis of time series of temperature, precipitation and runoff in the shiyangriver basin, the rusults showed that in50years, temperatures had a rising trend the fourseasons, most significant in winters; precipitation significantly increased in summers andsprings; runoff had a relatively clear decreasing trend in summers. Volumes of precipitationand runoff mainly concentrated in May to September, accounted for81.8%of annualprecipitation and75.4%of mean annual runoff respectively. Monthly precipitation had stableinterannual variation in wet period while monthly runoff changed astatically; same month dryseason the interannual variability of precipitation is unstable, Monthly precipitation had unstable interannual variation in dry period while monthly runoff changed stably. Then weused Kendall rank test method with a confidence level of0.05. The temperature of shiyangriver basin had an obviously rising trend; the annual precipitation unobvious rised and annualrunoff was unobvious decreased.(2) Through singular spectrum analysis about the time series of temperature,precipitation and runoff in the shiyang river basin, we got the oscillation periods of eachelements in recent50years. Temperature sequence exists mainly in12,6and109months(about9years) three kind of oscillation cycle, rainfall sequence exists mainly in12,6,4,156months (13years), runoff sequence exists mainly in12,6,41and65months oscillationperiod. Compared the results with previous research, the singular spectrum analysis methodhas a good applicability and rationality in trend analysis on time series and medium-termcycle judgement, but has certain disadvantages in long period judgement.(3) After VIC model applied in research area, the results showed that VIC model hascertain adaptability in upstream region of shiyang river basin. The runoff simulation resultswere consistent with the observation data on general process, the efficiency coefficient was0.76and0.69in calibration period and verification period respectively; correlation coefficientwas0.96and0.89respectively. This means the model can describe the hydrological cycle inshiyang river basin. But the simulation results in dry periods were significantly greater thanthe observation data and the relative errors of simulation results were obvious.(4) We analyzed the runoff responses to the future climate change using statisticaldownscaling model in two scenarios. The results showed that climate change will cause thechange of runoff. Annual precipitation reduce7.6%and15.2%respectively in the2020s and2050s under A2scenario, reduced8.7%and13.1%respectively under B2scenario. Averagehighest temperature were1.3and1.3℃higher than the status quo in2020s under A2andB2scenarios, rise by1.3and2.5℃respectively under the two scenarios in2050s. Averageminimum temperature only rise by0.1℃or so. Runoff had reduction in2020s and2050sunder A2and B2scenarios and appearedobvious dry seasons in2050s. Runoff decreased by13.2%and8.3%under A2and B2scenarios respectively in2050s, and had bigger reductionunder B2scenario. At the same time, same as the temperature and precipitation, runoffchanges differently in years.