Identifying the spatiotemporal change of the groundwater table to precipitation at the river basin scale can be important for regional water resource management. In this study, we proposed a method that combines singular value decomposition and cross-wavelet approaches to analyze the relationship between groundwater level dynamics and precipitation. The method was applied to the Naoli River Basin, Northeast China. Moreover, the method of continuous wavelet using fast Fourier transform was also used to reveal clearly the relationship between groundwater level and heavy precipitation. The results showed that the major mode of relationship between groundwater and precipitation was divided into four patterns in the study area. In general, the lag time is 27.4 (standard deviation: ±8.1) days in pattern 1, 107.5 (standard deviation: ±13.2) days in pattern 2, 139.9 (standard deviation: ±11.2) days in pattern 3, and 173.4 (standard deviation: ±20.3) days in pattern 4, respectively. In addition, the response of groundwater level dynamics is very sensitive to heavy precipitation in all patterns. Therefore, enhancing the utilization of heavy rainfall and flood resources is an effective way to increase groundwater recharge in this basin.

Assessing the fairness of water resource allocation and structural water shortage risks is an urgent problem that needs to be solved for the optimal allocation of water resources. In this study, we established a new multi-objective optimization model of water resources based on structural water shortage risks and fairness. We propose an improved NSGA-III based on the reference point selection strategy (ARNSGA-III) to solve the optimization model. The superiority of this method was proven by comparing it with three other methods, namely, NSGA-III, MOSPO, and MOEA/D. The model was applied to optimize the allocation of water resources in Wusu City in China. The results show that the new multi-objective optimization model provides reasonable and feasible solutions for solving water conflicts. The convergence and stability of ARNSGA-III are better than those of the other three algorithms. Allocation schemes of water resources for Wusu City in normal years, dry years, and extremely dry years are proposed. In normal years, the structural water shortage risk index is reduced by 50.1%, economic benefits increased by 0.2%, and fairness is reduced by 60.5%. This study can provide new ideas for solving the multi-objective optimization of regional water resources.

Hydrological drought for marshy rivers is poorly characterized and understood. Our inability to quantify hydrological drought in marshy river environments stems from the lack of understanding how wetland loss in a river basin could potentially change watershed structure, attenuation, storage, and flow characteristics. In this study, hydrological drought in a marshy river in far Northeast China at a higher latitude was assessed with a streamflow drought index (SDI). A deterministic, lumped, and conceptual Rainfall–Runoff model, the NAM (Nedbor Afstromnings Model), was used to quantify the individual contributions of climate change, land use/land cover (LULC) change, and river engineering to hydrological drought. We found that in the last five decades, the frequency of hydrological droughts has been 55% without considering LULC change and reservoir construction in this wetland-abundant area. The frequency of hydrological drought increased by 8% due to land use change and by 19% when considering both the impacts of LULC change and a reservoir construction (the Longtouqiao Reservoir). In addition to the more frequent occurrence of hydrological droughts, human activities have also increased drought intensity. These findings suggest that LULC and precipitation changes play a key role in hydrological drought, and that the effect can be significantly modified by a river dam construction.