The Runoff Declining Process and Water Quality in Songhuajiang River Catchment, China under Global Climatic Change

Abstract

The runoff in Songhuajiang River catchment has experienced a decreasing trend during the second half of the 20th century. Serially complete daily rainfall data of 42 rainfall stations from 1959 to 2002 and daily runoff data of five meteorological stations from 1953 to 2005 were obtained. The Mann-Kendall trend test and the sequential version of Mann-Kendall test were employed in this study to test the monthly and annual trends for both rainfall and runoff, to determine the start point of abrupt runoff declining, and to identify the main driving factors of runoff decline. The results showed an insignificant increasing trend in rainfall but a significant decreasing trend in runoff in the catchment. For the five meteorological stations, abrupt runoff decline occurred during 1957-1963 and the middle 1990s. Through Mann-Kendall comparisons for the area-rainfall and runoff for the two decreasing periods, human activity, rather than climatic change, is identified as the main driving factor of runoff decline. Analysis of land use/cover shows that farmland is most related with runoff decline among all the land use/cover change in Nenjiang catchment. From 1986 to 1995, the area of farmland increased rapidly from 6.99 to 7.61 million hm 2 . Hydraulic engineering has a significant influence on the runoff decline in the second Songhuajiang catchment. Many largescale reservoirs and hydropower stations have been built in the upstream of the Second Songhuajiang and lead to the runoff decline. Nenjiang and the Second Songhuajiang are the two sources of mainstream of Songhuajiang. Decreased runoff in these two subcatchments then results in runoff decrease in mainstream of Songhuajiang catchment. It is, therefore, concluded that high percent agricultural land and hydraulic engineering are the most probable driving factors of runoff decline in Songhuajiang River catchment, China.

Separating the Impacts of Climate Variation and Human Activities on Runoff in the Songhua River Basin, Northeast China

“…However, the specific changing characteristics were found to be various among the five sub river basins and different sub periods in our study. Apart from the decreasing trend in streamflow of the SRB reported by other researchers [27,42], our study identified a change-point of the year of 1974 for runoff. The results showed that the average runoff during the last 35 years declined in all sub river basins of the SRB when compared with that of the previous 15 years before 1974.…”

“…In the past half century, climate in the SRB has become warmer and drier [6] and a large area of wetlands has degraded while farmland has been increasing rapidly within the river basin [26]. At the same time large-scale river engineering projects (primarily, construction of dams and ditches) were completed in the basin to meet the increased water use demand for agriculture, industry, and public [27]. A recent study [6] found a decreasing trend of discharge in all major tributaries of the SRB over the past half century.…”

Methodologies and Management Framework for Restoration of Wetland Hydrologic Connectivity: A Synthesis

“…Climate change is one of the main reasons for large‐scale shrinkage, fragmentation, and salinization of wetlands, especially in arid regions (Fay et al 2016; Zhang et al 2019). To reveal the pattern of climate change, a large number of researchers reconstructed historical temperature regimes for a series of different environmental types, different resolutions, different regions, and different starting and ending times (Mu et al 2012; Mitsch et al 2013; Zhang et al 2019). These results confirm the occurrence of climate change for the historic period.…”

Assessing Impacts of Climate Change and Human Activities on Streamflow and Sediment Discharge in the Ganjiang River Basin (1964–2013)

“…The non-parametric Mann-Kendall statistical test has been widely used for trend detection in the time series of hydro-climatic data [29]. For a group of hydrological time series variables, X i (i = 1, 2, 3, ......, n), the Mann-Kendall test statistic S is calculated by:…”