The Poyang Lake Basin has been suffering from severe water problems such as floods and droughts. This has led to great adverse impacts on local ecosystems and water resource utilization. It is therefore important to understand stream flow changes and their driving factors. In this paper, the dynamics of stream flow and precipitation in the Poyang Lake Basin between 1961 and 2012 were evaluated with the Mann–Kendall test, Theil–Sen approaches, Pettitt test, and Pearson’s correlation. Stream flow was measured at the outlets of five major tributaries of Poyang Lake, while precipitation was recorded by fourteen meteorological stations located within the Poyang Lake Basin. Results showed that annual stream flow of all tributaries and the precipitation over the study area had insignificant (P > 0.1) temporal trends and change points, while significant trends and shifts were found in monthly scale. Stream flow concentration indices (SCI) at Waizhou, Meigang, and Wanjiabu stations showed significant (P < 0.05) decreasing trends with change points emerging in 1984 at Waizhou and 1978 at Wanjiabu, while there was no significant temporal trend and change point detected for the precipitation concentration indices (PCI). Correlation analysis indicated that area-average stream flow was closely related to area-average precipitation, but area-average SCI was insignificantly correlated with area-average PCI after change point (1984). El Niño/Southern Oscillation (ENSO) had greater impacts on stream flow than other climate indices, and La Niña events played a more important role in stream flow changes than EI Niño. Human activities, particularly in terms of reservoir constructions, largely altered the intra-annual distribution of stream flow but its effects on the amount of stream flow were relatively low. Results of this study provided a useful reference to regional water resource management and the prevention of flood and drought disasters.

Abrupt runoff reduction in the Wei River Basin (WRB) has attracted extensive attention owing to climate change and human activities. Nevertheless, previous studies have inadequately assessed the respective contributions of climate variability and human activities to runoff change on different spatial scales. Using Mann–Kendall and Pettitt’s methods, this study identified long-term (1970–2018) changes in hydro-meteorological variables. Furthermore, the Budyko-based method was used to quantify the influence of climate change and human activities on runoff change at different spatial scales of the WRB, including the whole WRB, three sub-basins, and sixteen catchments. The results show that a significant decrease trend was identified in runoff at different spatial scales within the WRB. Runoff in almost all catchments showed a significant downward trend. Temperature, potential evapotranspiration, and the parameter n showed significant increases, whereas no significant trend in precipitation was observed. The change in runoff was mainly concentrated in the mid-1990s and early 2000s. Anthropogenic activities produced a larger impact on runoff decrease in the WRB (62.8%), three sub-basins (53.9% to 65.8%), and most catchments (–47.0% to 147.3%) than climate change. Dramatic catchment characteristic changes caused by large-scale human activities were the predominant reason of runoff reduction in the WRB. Our findings provide a comprehensive understanding of the dominate factors causing runoff change and contribute to water resource management and ecosystem health conservation in the WRB.

Evapotranspiration is a key process between the atmospheric hydrological cycle and the energy cycle, which has a great significance in understanding climate change and the rational use of water resources, especially for the Weihe River basin (WRB) (a basin in China experiencing a shortage of water resources). We investigated the spatial-temporal change of actual evapotranspiration (ET_a) based on the daily meteorological variables of 22 meteorological stations and the annual streamflow of three hydrological stations from 1970 to 2018 in the WRB. The contributions of key meteorological variables to ET_a changes and the sensitivity coefficient are also quantified. The temporal trends of ET_a showed an increasing trend from 1970 to 2018, and the spatial distribution of ET_a increased from northwest to southeast in the WRB. Increasing trends were detected in the multi-year average, spring, and winter, but only a few stations passed the significance test. Summer and autumn showed a decreasing trend, but this trend was not significant. Solar radiation is the most sensitive meteorological variable, followed by vapor pressure, wind speed, and mean temperature. Vapor pressure contributes the most to ET_a changes, followed by solar radiation. In general, vapor pressure (relative humidity) is the dominant meteorological factor affecting ET_a in the WRB. In addition to meteorological factors, the ET_a is also affected by combined and complicated factors caused by precipitation and human activities. As an important part of the hydrological cycle, ET_a has important research significance for water resources management, economy, agriculture, and ecology and results of this study may be helpful to further clarify the climate change and human activities impacts on the basin hydrological cycle.