Spatiotemporal variability of climate and streamflow in the Songhua River Basin, northeast China

Abstract

Summary The Songhua River Basin (SRB) is located in the high latitude region of China’s far northeast and is sensitive to global warming. This study utilized long-term meteorological and river discharge records in the SRB to assess spatiotemporal variability and trends in temperature, precipitation, and discharge. Daily precipitation and temperature data were collected from 37 meteorological stations across the SRB for the period from January 1960 to December 2009. Monthly discharges from 33 major river gauge stations in three sub-basins of the SRB were gathered for the same period. The modified Mann–Kendall tests, flow duration curves and correlation statistics were performed to identify the long-term trend and interrelation of the hydrometeorological variables. The results showed that temperature in the SRB has steadily increased in the past five decades, while precipitation fluctuated greatly among the years and the decades with a declining trend since 1980s. The largest change in temperature was found in the last two decades, with a decadal increase of about 1 °C. Concurrently, a declining trend in annual discharge from the SRB was found after 1990, while intra-annual variation of discharge increased. Overall, annual discharge at most gauge stations across the SRB showed a downward trend in the past five decades, with a significantly decreasing trend in the Lower Songhua River. Seasonally, the declining trend in discharge was prevalent in spring and discharge mainly declined in the lower Nenjiang River and the Lower Songhua River throughout most of a year. The flow duration analysis showed a decrease in high flow (Q5), but an increase in low flow (Q95) after 1990 at most mainstream stations of the SRB. However, both the lowest and highest monthly discharge displayed a declining trend during 1960–2009. Because precipitation in this river basin is concentrated during the summer and fall months, annual discharge was closely and positively correlated with precipitation amount occurred during these two seasons.