The analysis of drought propagation has garnered mounting attention in the changing global environment. The current studies tend to focus on the propagation characteristics from meteorological to hydrological drought in rivers. Lakes, despite being a key component of watershed ecosystems, have received little attention to their response to meteorological and hydrological droughts. To this end, here, we investigated the characteristics of propagation from meteorological to hydrological drought for a lake in a changing environment. To determine the drought propagation time from meteorological to hydrological drought, we analyzed correlations between the standardized precipitation index (SPI), standardized runoff index (SRI), and standardized water level index (SWI). Lake Baiyangdian in China served as the case study. The results showed that meteorological droughts occur at high frequency but are short in duration, indicating that not every meteorological drought will necessarily lead to a hydrological drought. By contrast, lake hydrological droughts have low frequency and long duration and feature more severe consequences. Comparing drought characteristics before and after a changing environment, we found a reduced frequency of the SPI, SRI, and SWI, yet their duration was prolonged. For the SWI especially, these results were even more pronounced, which suggests the changing environment enabled further intensification of the lake hydrological drought. In addition, more time was needed for a meteorological drought to transition into a lake hydrological drought after a changing environment.

Water level variability and temporal change are critical for shaping the structure of aquatic vegetation. Much research has examined the response of aquatic vegetation to hydrological metrics. However, the hydrological sequence is a fundamental driver of aquatic ecosystem structure and function. Given the aleatory uncertainty of future water levels under an unstable climate, how aquatic vegetation responds to changing dynamics in hydrological processes, especially shifting water level sequences, remains insufficiently explored. In this paper, we establish an evaluation framework to study the response of vegetation diversity to variation in water level sequences during a drought event. To do this, the uncertainty and variability of water level processes are both considered. Altering water level processes was achieved using two types of scenarios in order to explore the effects of differing water level sequences (i.e., changing the order of high vs. low water levels) on the probability distribution of four indexes of aquatic plant diversity (e.g., Margalef’s, Simpson’s, Shannon’s, and Pielou’s evenness index). Our results show that altering the order of water level state can lead to differences in the diversity of aquatic vegetation, with a pronounced impact on vegetation complexity. This suggests that the specific sequence of water level events is critical for shaping aquatic vegetation structure. In addition, we found that a uniform distribution of water level state is beneficial for enhancing a species’ dominance in aquatic vegetation. Our findings provide guidance for improving the future development of freshwater ecosystem protection and lake management.

In the past few decades, the water resources in the Tang–Bai River Basin showed a declining trend, due to the human–driven alteration of surface water and groundwater management. There are potential risks to the sustainable utilization of future water resources in response to agricultural, industrial, and domestic water supply. In this work, we used the water allocation and regulation model based on SWAT (SWAT–WARM model) to quantify the characteristics of water resources response under human activities in this basin. The multi–source water supply module was modified to improve the applicability of the SWAT–WARM model in this basin. We validated our simulations against observed runoff, water consumption, and supply. The main results were as follows: (a) We used the percent bias, the correlation coefficient, and the Nash–Sutcliffe efficiency coefficient to measure the model validity and found that the modified model did not show obvious advantages in runoff simulations, whereas it reproduced water consumption and supply better than the original model. The modified model had more advantages in reflecting the process of water resources transformation and utilization in the basin driven by strong human activities. (b) By comparing the variation of watershed water circulation fluxes under natural and human disturbance conditions in the Tang–Bai River Basin from 1995 to 2016, we found that human activities increased evapotranspiration by 6.8% and surface runoff increased by 10.0%, while groundwater resources decreased by 0.23 million m3/yr. (c) There was water shortage in the basin at different flow frequencies, among which agricultural water shortage accounted for the largest proportion, >70%. The basin should further strengthen agricultural and industrial water saving, reduce water consumption fundamentally, and ensure the sustainable development of economy and society.

Safety, progress, and investment risks are correlated during the construction period of large-scale water transfer projects. However, previous studies have only considered individual risk factors, overlooking the potential systemic risk posed to safety, progress, and investment, as well as any underlying common cause failures. Since traditional risk analysis methods are ill-suited to addressing common cause failure, this paper’s objective was to establish a comprehensive evaluation index framework and to identify the basic events of common cause failure. To do that, we developed a risk analysis method that models common cause failure based on a Bayesian network for assessing that systemic risk. The Henan Section of the Yangtze-to-Huaihe River Water Diversion Project in China was then used as a case study. The results show that a variety of common cause failure events, such as epidemic disease, design alteration, lagged approval process, heavy rain in the flood season, renewal material and failing equipment, construction accidents, and external interference, can significantly impact the safety, progress, and investment systemic risk. Design alteration poses the greatest risk, with renewal material and failing equipment exerting the strongest influence among all common cause failure events. It is also possible to elucidate the predominant causal chains; specifically, the contributing influence of each basic failure event to the systemic risk can be clarified by adjusting their respective initial state. The failure of renewal material and failing equipment was found to significantly increase the safety risk. This study effectively simulated the complex causal relationships and uncertainties of pertinent risk factors, thereby enhancing our understanding of the systemic risk associated with safety, progress, and investment in large-scale water transfer projects.

To protect the river ecosystem and sustain ecological flow regime, it’s vital to consider environmental flow management in reservoir operation. Many researches try to use more detailed environmental flow management strategies to improve ecological flow regime. However, ecological flow regime not only is influenced by environmental flow management strategy, but also by three kinds of parameters, including reservoir capacity, reservoir inflow and water supply yield. The aim of this paper is to illustrate how ecological flow regime is affected by different reservoir capacities, reservoir inflows and water supply yields and to find a proper reservoir capacity, reservoir inflow or water supply yield under which the optimal ecological flow regime is the best and could not be improved. In this paper, an environmental flow management strategy, which is Four-period release approach (FP), is developed. Besides, social benefit and ecosystem needs are satisfied simultaneously. The results show that changing reservoir capacity, reservoir inflow or water supply yield could improve ecological flow regime.