The 24th IAHR-APD Congress (24th IAHR-APD Congress)

265 / 2024-02-28 16:54:05

Spatio-temporal variation of riverine flow and sediment of the upper Ganjiang River based on multi-site long-term time series data

humid climate region,riverine flow discharge and sediment load,annual distribution patterns,inter-annual variations,spatial patterns

The climate change and human activities have significantly altered riverine flow discharge and sediment load. Exploring the changing patterns of  riverine flow discharge and sediment load under the dual impact of climate change and strong human activities at different spatial and temporal scales is an important prerequisite for scientific and precise river basin management. Based on daily flow and sediment data at 7 hydrological stations in the upper Ganjiang River from 1964 to 2020, as well as corresponding rainfall data, a comprehensive analysis has been carried out on the basic characteristics, annual distribution patterns, inter-annual variations and spatial patterns of riverine flow and sediment discharge  in the upper reaches of the Ganjiang River. The results indicate that:  (1) The runoff depth in the upper reaches of the Ganjiang River ranges from 769.37 to 957.88 mm, the runoff coefficient ranges from 0.48 to 0.58, the average sediment concentration and maximum sediment concentration are between 0.14 to 0.34 kg/m³ and 1.45 to 3.33 kg/m³, respectively, and the sediment transport modulus ranges from 116.25 to 295.63 t/km². The sediment concentration and modulus are highest in Pingjiang.  (2) The flood season is the main period of runoff and sediment transport, with the most concentrated period being April to June, of which the riverine sediment load is more evident than that of the riverine flow discharge. (3) The minimum riverine flow shows a significant change trend. The rivers in the western and northwestern subbasins show a significant increasing trend, with an increase of more than 32.0%, while the rivers in the eastern and southern subbasins show a significant decreasing trend, with a decrease of more than 24.5%. Riverine sediment concentration contents and sediment loads show significant change trends. The riverine sediment transport parameters of Lianjiang River show a significant increasing trend, with an increase of more than 210.3%, while other tributaries show a decreasing trend, with the decrease up to 67.2%. (4) Based on the temporal variation characteristics of riverine flow discharge and sediment load, the 7 tributaries of the upper reaches of the Ganjiang River can be grouped into 4 types as follows: less flow and high sediment concentration contents with  significant decrease in baseflow and increase in sediment load, less flow with significant decrease in both baseflow and sediment load; more flow and low  sediment concentration contents with significant decrease in both baseflow and  sediment load; and more flow with significant decrease in both baseflow and  sediment load. The study would deepen the understanding of the change patterns of riverine flow discharge and sediment load in the humid region under the dual impact of climate change and strong human activities, which provides scientific evidence for local governments to precisely manage riverine flow and sediment issues in large basin.