Urban water demand is a complex function of socio-economic characteristics, climatic factors and public water policies and strategies. Therefore a combination model is developed based on the multivariate econometric approach which considers these parameters to forecast and manage the urban annual water demand. Firstly, the factors correlative with water demand are selected, then the trend and cyclical components of the factors are calculated by the Hodrick–Prescott (HP) filter method. The multiple linear regression method is applied to simulate the trend components and the fuzzy neural network is built based on the cyclical components, and then the two models are combined to forecast the urban annual water demand. In order to illuminate the model, it is used to forecast the annual water demand of Dalian against actual data records from 1980 to 2007. By comparing with the traditional methods, the preferable model accuracy demonstrates the effectiveness of the fuzzy neural network and multiple linear regression based on the HP filter in forecasting urban annual water demand. After model testing, the sensitivities of the influence factors in the model are analyzed. The results show the model is reliable and feasible, and it also helps to make predictions with less than 10% relative error.

To realise the ecological protection and high-quality development of the Yellow River Basin and transition from extensive utilisation to intensive conservation of agricultural water, a multi-objective crop planting structure optimisation model was established. The model enabled highly efficient crop planting in terms of net income with high yield and low consumption of water. Thereafter, the game algorithm was used to balance different requirements of each objective function under each constraint, both competitively and cooperatively, to obtain an optimal crop planting structure. Finally, the proposed model and analysis method were demonstrated and verified using the Xiaolangdi south bank irrigation area as an example. The results indicated that using the competitive game algorithm produced a superior crop planting structure in terms of high net income, high yield, and low water usage, suggesting that the relationships between game players and objective functions should be considered in designing the optimisation model. Thus, the proposed approach provides a theoretical basis for the sustainable development of the agricultural industry by realising the intensive utilisation of water resources in a particular irrigation area.

The distribution of sediment grain size can record past environmental conditions and human activity. In this study, radioisotope of ²¹⁰Pb and ¹³⁷Cs and a grain size of a 41 cm core in Hulun Lake were applied to reconstruct the high-resolution sedimentation history. The profiles of the grain size of the lake sediments show that silt (4–63 µm) was the largest contribution with an average content of 84.05%, and the second largest contribution was sand (>63 µm) with an average content of 15.68%. The median grain size and the mean grain size in the whole sediment core was 22.39 μm and 36.85 μm, respectively. Correlations of the sedimentological variables with instrumental measurements were also analyzed. The peak–trough value of the mean grain size of the sediments in Hulun Lake can reflect the magnitude of rainfall intensity and river discharge. The clay and silt contents at a depth of approximately 32–38 cm was different from other depths throughout the core, which showed continuous maxima with an average content of 0.35% and 94.08%. These changes in grain size correspond to the period of dam construction in 1963–1970. Therefore, the sediment grain size of Hulun Lake effectively recorded the dam-building activity.

This study fabricated a silver-based composite photocatalytic material (Ag/AgVO₃/g-C₃N₄) for antibiotic degradation driven by visible light. The composite was prepared using the water bath method, and its morphology, structure and optical properties were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Ultraviolet-Visible (UV-vis) diffuse reflection spectroscopy. The photocatalytic activity of the composite was evaluated within 240 min under visible-light irradiation, and its degradation effect was quantified using tetracycline hydrochloride as the target pollutant, applying different conditions of composite proportions and dosage, initial concentration of the contaminant, and pH. The experimental results demonstrated that the composite doped with Ag⁺ had a higher degradation effect on tetracycline hydrochloride. The highest degradation rate of tetracycline hydrochloride (reaching 86.64%) was achieved at a composite ratio of Ag/AgVO₃/5g-C₃N₄, dosage of 0.8 g·L⁻¹, and initial concentration of tetracycline hydrochloride of 10mg·L⁻¹. This rate is approximately 1.4 times and 1.7 times those of the pure-phase g-C₃N₄ and AgVO₃, and the degradation rate remains stable at 81.52% after 4 cycles of experiments. The favorable stability of the photocatalyst was also verified through a stability test.