Snowmelt Runoff Characteristics And Its Influence Factors In Songhuajiang River

About 60% of land area is covered by the seasonal snow in the world.The snow cover area in China is up to 900 × 104 km2, and the area which is capable of forming the snowmelt runoff are mainly distributed in the stable snow area covered by snow more than two months reaches 420× 104km2, mainly including the northeastern, northern and eastern Inner Mongolia, northern Xinjiang and western Qinghai-Tibet Plateau area, and these areas are also greatly influenced by freeze-thaw action. Songhua River basin is a "Rain-Fed Agricultural Areas", and the spring drought is prone to occurred in this watershed at the end of spring and the beginning of summer, thus giving rise to a "Decade of nine spring" climate characteristics.The formation and occurrence of the Spring drought mainly depends on the spring rainfall, snowmelt and soil freezing water,and it is more likely to trigger the water deficit of Spring crop, regardless of the insufficient spring precipitation or the lack of snow or soil freezing water. The Songhua River Valley is located in the high latitude region,where is full of severe winter, frozen river and snow cover.The specific spring freshet of the cold region will be formed in April for the dramatic increase compare with January, February and March after the increasing of spring temperature. April-May, coincided with the spring planting season, the small amount of rainfall, the Mongolia high voltage and the dry air are the factors of the spring drought on husbandry production. Therefore, the practical problems of the agricultural production about how to increase the snowmelt runoff, make up the river in dry season, alleviate the disparities on water using in spring ploughing season between Upstream and downstream, are urgent to be solved.Based on full analysis of the main factors of snowmelt runoff production, this study selected the Songhua River Basin as research sites, combing various research methods(Moving average method, non-parametric Mann-Kendall test, the estimated sen slope method, Correlation analysis), to study the distribution characteristics of the snowmelt runoff generation basic conditions including snowfall and snow cover in the Songhua River Basin. On this basis, analyze snowmelt runoff distribution characteristics through the water content observation data during the spring thawing period in Songhua River basin, and then clear the correlativity among snow flow, snowmelt runoff occurrence and development, and the snowfall, landforms, land utilization and climates through the relation analysis between distribution characteristics and the mainly factors of snowmelt runoff occurrence and development, to lay a theoretical foundation for snowmelt runoff regulation and utilization of the Songhua River Basin. Analyze the temperature, radiation, snowfall and the change trend, range ability, the special varying regulation of the runoff, and spring snowmelt runoff characteristics and its influence factors from 1956 to 2010 in the Songhua River Basin. The main conclusions are as follows:The average radiation change can be divided into four stages, 1956-1980 radiation tended to be steady, 1981-1985 average radiation sagged rapidly, 1986-1997, radiation showed a rising trend, After 1988, the annual radiation change tended to be steady slightly down. The radiation station Heihe, Changchun, Harbin, Jiamusi radiation decrease, respectively: 0.007KJ/ m2? yr、0.011KJ/ m2? yr、0.008KJ/ m2? yr、0.004KJ/ m2? yr,the Fuyu radiation station radiation appear small increase showed a small amplitude increase, 0.004KJ/ m2? yr. The multi-year average radiation of the Songhua River Basin tributaries is significantly greater than the mainstream,shows the tend that decreased from southwest to southeast,and increased from the main stream of songhua river middle reaches and northeast to northwest.The average temperature change can be divided into four stages, from 1956 to 2011 in the Songhua River Basin. 1956-1962 for a rapid increase, and then the temperature was slowly decreased in 1963-1972, 1973-1987 temperature showed small amplitude fluctuations rise, after 1988, the average annual temperature change got into the fast rising phase. The temperature changes during the spring thaw can be roughly divided into three stages. 1956-1963 rapidly increased in temperature, 1964-1972 average temperature tended to reduce, 1973-1988 temperature showed amplitude fluctuations rise, after 1988, the temperature began to rise rapidly. The variation tendency between spring thaw and annual mean temperature was approximately the same; amplitude is respectively 0.036℃/yr and 0.047 ℃/yr.In the Songhua River Basin, the average temperature ranged roughly to increase from southeast to central section, and then decrease in northwest.The snowfall has obvious phasic changes from 1956 to 2011 in the Songhua River Basin, 1956-1963 annual snowfall sharply decreased, 1964-1989 annual snowfall slowly increaaed, in which 1974-1978 annual snowfall had a small amplitude decreasing trend, 1990-1999 snowfall showed a downward trend, 2000-2011 snowfall showed an upward trend, especially after 2008, a substantial rise in snowfall was up to 0.15mm/ yr。In the Songhua River Basin, the biggest snowfall lay in northern Greater Khingan forest region and the lower reaches of the Songhua River, the least snowfall lay in Midwest, the middle reaches was placed in the center.The runoff mean from 1956 to 2010 in the Songhua River was 19.94-724.26×108m3/yr, the runoff mean in spring thaw period was between 1.26×108m3/yr and 119.97×108m3/yr, the secific performance was Jia Musi > Harbin> Kumotun> Chenming> Lanxi >Nianzishan, and the runoff variation in the following stations were of high consistency, Kumotun, Chenming, Lanxi, Harbin, Jia Musi.1956-1979 showed a fluctuating down, 1980-1988 annual runoff increased rapidly, 1989-2010 annual runoff showed a fluctuant trend of decline.The average annual runoff and the spring thaw period runoff of six hydrologic stations in the Songhua River Basin showed a decreasing trend.The runoff variations of Harbin and Jia Musi were respectively 4.01×108m3/yr and 6.67×108m3/yr,and those in Spring thaw period were respectively 0.5×108m3/yr and 0.7×108m3/yr.