Precipitation, Streamflow And Sediment Transport Changes And Its Response To Human Activities In Songhua Basin

The Songhua River is located in the north of black soil zone in Northeast China, which is the world's only remaining one of the three major black soil zones, and the Songhua River plays an important role in the national economy. In recent years, by human excessive reclamation of land and unreasonable farming, soil erosion is becoming a constraint factor in sustainable use of arable land and food production in Northeast China. In this paper, the Songhua River as the research object, based on the precipitation, streamflow, sediment transport series data, using modern mathematical statistical test methods and wavelet method, analysis of precipitation, streamflow and sediment transport variatation and its response to human activities. The main conclusions are as follows:1. Analyzed the precipitation spatial variability.In Songhua River, the average annual precipitation from 1959~2008 varied generally 400~700mm, and it declined from southeast to northwest, in which there was the least precipitation of downstream of Nen jiang. Annual precipitation coefficient of variation was small in Songhua basin, and it changes between 0.20 and 0.26 in most areas, so precipitation was stable in this basin. The west of the line Zhalantun-Jiangqiao-Tongyu weather station coefficient of variation was greater than 0.26, so the west of line of annual precipitation change was more larger than other areas.2.Analyzed the temporal variation of the streamflow.The average streamflow depth of hydrological stations selected in Songhua River was between 49.4 mm and 221.6mm, and the extreme ratio was between 4.6 and 55.1, and the coefficient of variation between 0.34 and 0.88, in which the annual variation of Taonan station was the largest. Analyzed streamflow trends of hydrological stations selected with Mann-Kendall in Songhua Basin, and the results showed that the streamflow decreased from different years, in which the streamflow of Dalai, Harbin, Jiamusi hydrological station decreased significantly, and the downward trend of Lanxi station reached a significant level. There were two abrupt change points in Dalai, Harbin, Lanxi, Jiamusi, and all occurred in the 1960's and 1990's. Streamflow stage characteristics of the basin was obvious, and the inflection point's positions in stage characteristics were tributaries earlier than main stream, and upstream earlier than downstream. Except Lanxi, the primary cycles of streamflow of other hydrological stations consistent.There was bimodal variation of streamflow of hydrological stations selected in a calendar year in Songhua Basin. The streamflow in August was about the most, while the streamflow in February was the least. By Mann-Kendall, monthly and yearly streamflow showed decreasing trend in Songhua Basin. The streamflow in a calendar year was uneven, the uneveness of tributaries > main stream, and the Nenjiang Basin > Songhua Basin > Second Songhua Basin. The streamflow of Kumotun, Ayanqian, Fuyu, Changjiangtun were prone to drought in the early spring, while The streamflow of Jiangqiao, Taonan, Dalai, Harbin, Lanxi, Jiamusi were prone to drought in the late spring.3. Analyzed the temporal variation of the sediment transport.The maximum of sediment transport of Jiangqiao and Harbin was in 1998(respective 1.24×10~7t, 1.17×10~7t), and the maximum of sediment of Jiamusi was in 1994(3.97×107t), while the minimum of three hydrological stations was in 1979 (respective 0.27×106t,1.52×10~6t,2.11×10~6t). The smallest variation of sediment transport was Harbin, followed by Jiamusi, and the largest variation was Jiangqiao. Jiangqiao and Jiamusi showed an increasing trend in the sediment transport, but the increasing trend was not significant. The sediment transport of Harbin were significantly decreased, and there were two abrupt change points in 1978 and 1994. The anomaly cumulative curves of Harbin and Jiamusi in sediment transport had good consistency.4. Precipitation, streamflow and sediment transport change and its response to human activities in Songhua Basin.Taken harbin station for example, Precipitation, streamflow and sediment transport change and its response to human activities form 1955 to 2005 in Songhua Basin were analyzed. precipitation, streamflow and sediment transport had significant approximate periodicity and multi-time scale features. At the 7a scale, changes of precipitation, streamflow and sediment transport had the synchronization from 1950's to 1960's; in 1970's, due to massive population move, as well as to address the irrational development of food problems led to three curve disorder; after 1980's, the implementation of comprehensive measures made three curves re-converge. At 17a and 26a scales, because of water diversion project, the construction of reservoirs and other human activities, there was not always synchronization between the three curves. Wet and dry years and singular points were closely to the time scale.