Analysis of spatial and temporal evolution of hydrological and meteorological elements in Nenjiang River basin, China

This study examined hydrological and meteorological changes in China’s Nenjiang River Basin. Taking account of the physical processes in hydrology and meteorology revealed by the hydrological elements, we selected typical periods and sites for analysis on temperature (1951–2004), precipitation, and runoff data (1955–2005). Through some methods including improved cumulative curve method, the Sen slope estimation method, Mann-Kendall non-parametric test analysis, the Pettitt mutation point test and Spearman rank correlation test, and the spatiotemporal characteristics of hydrological and meteorological elements were evaluated. An innovative concept of the “centroid of precipitation” was proposed to analyze the spatial evolution tendency of precipitation. The results are concluded as follows: (1) the temperature began to show a rising trend during the 1960s and 1970s in Nenjiang River Basin in the twentieth century. The temperature had risen significantly by the 1990s. Furthermore, the temperature increased significantly at the coldest place and in the coldest month. (2) There was no significant trend change in the annual precipitation in the Nenjiang River Basin. However, monthly precipitation before the flood season (April) and after the flood season (October) exhibited a significant upward trend. The centroid of precipitation was concentrated in a compact spatial distribution in the main flood season but was dispersed relatively in the other months. (3) River runoff showed a downward trend year by year and exhibited a mutation in 1979. The spatial variation in runoff showed that the fluctuation of downstream runoff was greater than that in the upper reaches of the basin and that the runoff from the upstream to the downstream reaches gradually decreased. According to the M-K mutation point test, the Pettitt mutation point test, and the improved cumulative curve method, a mutation in annual runoff sequence occurred in 1979. These findings will be helpful for understanding evolution of hydrological changes and will be supportive for local water managers to deal with changing climate.