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【Objective】 The Fuhe River Basin is an important food production region in Northwestern China. It is increasingly affected by droughts. This paper analyses the occurrence of droughts and their key determinants in this region. 【Method】 The analysis was based on modelling. We simulated the changes in monthly soil water content from 1962 to 2019 using the SWAT model. The resulting data were then used to calculate the standardized soil moisture index. The characteristics of agricultural droughts were analyzed using the theory of runs, and the key determinants of the droughts were analyzed using the geographical detector. 【Result】 ① The coefficient of determination (R2) and the Nash efficiency coefficient (ENS) between the modelled and measured results in the calibration are both higher than 0.80; the coefficient of determination between the predicted soil moisture content and the measured soil moisture content is 0.52. ② The duration of droughts in different regions in the basin varied from 3.60 to 4.31 months, and the drought intensity ranged from 4.91 to 5.61, both varying spatially, higher in the North and South and lower in the center. ③ The influence of temperature, solar radiation, and wind speed on spatial variation in the droughts, characterized by the q-value, exceeds 0.30. Other environmental factors are nonlinearly interacted in their influence on the droughts. 【Conclusion】 The standardized soil moisture index can quantitatively characterize droughts in the Fuhe River Basin. Droughts in the basin vary spatially, with temperature, solar radiation and wind speed being the main contributing factors.

【Objective】 Located in Jiangxi province, Poyang Lake is the largest freshwater lake in China. It has five tributaries, and this paper analyzes the change in water and sediment flows at their confluences with the lake. 【Method】 The study was based on runoffs and sediments measured from hydrological stations in the five tributaries. Temporal evolutions of water flow and sediment transport were analyzed using the sliding correlation coefficient method, double cumulative curve method, and copula function. We also calculated the probability of occurrence of flooding and droughts during different periods in the basin. 【Result】 The analysis showed an overall increase in total runoff in all five tributaries, with the most significant increase observed in the Xiu River. In contrast, the total sediment flow exhibited a significant decrease, except the Rao River which showed a significant increase in sediment flow. Abrupt changes in water-sediment relationship were identified for all tributaries, except the Fuhe River. Following the abrupt changes, the Xinjiang River experienced a maximum increase in runoff (15.9%), whereas Ganjiang River had a maximum decrease (67.3%). Compared with the 1956—1971 period, the runoff in the Raohe River in the 2004—2018 period increased by 100.3%. Asynchrony between high and low levels of water and sediments in the five tributaries was less probable compared to synchronous high and low levels, with the highest probability observed for the same level of high and low levels. 【Conclusion】 Extreme precipitation, soil and water conservation projects, reservoir construction, and sand mining in the tributaries and lake are the factors that have significantly influenced water and sediment changes in the basin.

The shaft tubular pump device is widely used in various water diversion projects because of its ultra-low head and large flow characteristics. Due to the tip clearance between the blade and the shroud, it is easy to cause hydraulic mechanical performance changes, induced vibration, and noise, which seriously affects the safe and stable operation of the pump. Steady and unsteady three-dimensional flow field numerical simulations of a shaft tubular pump device were carried out using computational fluid dynamics to investigate the impeller flow properties of the device under various flow conditions, including the tip clearance leakage flow (TCLF) and change rule of pressure pulsation. The TCLF, vortex morphology evolution, and pressure pulsation properties of the impeller tip clearance were analyzed. The results show that with an increase in the flow rate, the influence of the tip clearance size on the tip clearance flow decreases, the TCLF decreases, and the axial velocity of the water flow at the tip clearance increases. When the flow rate increases, the swirling strength of the tip leakage vortex decreases, and the distance between the tip leakage vortex and the suction surface of the blade increases. With the increase in flow rate, the pressure pulsation amplitude at the tip clearance increases first and then decreases. The focus of this study is to analyze the variation of tip clearance flow field and pressure pulsation under multiple working conditions, aiming to provide some help for improving the performance of the pump device and ensuring its safe operation. [ABSTRACT FROM AUTHOR]