Wuliangsuhai Lake is the largest shore lake in the upper reaches of the Yellow River and has become an important ecological barrier and habitat for birds in northern China. In recent years, pollutants and nutrient loads have been partially reduced, and the water quality in the lake area has been alleviated to a certain extent. However, the overall water treatment of Wuliangsuhai Lake is worrying and needs to be improved urgently. In this paper, according to the current situation of water quality and the goal of ecological environment protection, the ecological water demand of Wuliangsuhai Lake was estimated by using the dynamic viewpoint. The calculation of ecological water demand mainly considered: water of evaporation and leakage in the lake, and water demand of pollutant dilution. The requirements of ecological water demand in Wuliangsuhai Lake were solved in four ways: agricultural wastewater in the irrigation area; strengthening water saving in the main canal; carrying out water-saving system reform; and transporting ecological water use for washing salt to Wuliangsuhai Lake during an irrigation gap period. For Wuliangsuhai Lake in the Mengxin Plateau, which is located in a serious water shortage area, it is of great significance to protect the ecological environment by ensuring the amount of water entering the lake, maintaining the existing water surface of the lake, and giving full play to its water ecological function.

Introduction: A new method is introduced to test the tensile strength of concrete: the cylinder transverse splitting test. Compared with the cylinder splitting (or Brazilian) test, the cylinder transverse splitting test involves different load positions and offers the advantages of doubling the data volume with the same number of specimens and improving the detection accuracy. Methods: Finite element analysis software was used to simulate the concrete cylinder transverse splitting test and the stress distribution on the failure surface was determined. Results and Discussion: The results show that the fracture of a cylinder is mainly determined by tensile stress. The splitting strength of normal concrete and crumb rubber concrete, a new environmentally friendly concrete material that has gathered considerable attention in recent years, was obtained by cylinder transverse and cube splitting tests. The cylinder transverse splitting test data show a stable correlation with the cube splitting test data and well characterize the concrete strength. The relationship between the cylinder nominal transverse splitting strength ( f ₂ ) and cube splitting strength ( f ₁ ) was established on the basis of linear analysis of the test data: f ₁ = 0.51 f ₂ . The calculated cube splitting strength is in good agreement with the test values.

Cemented sand and gravel (CSG) material is a new type of dam material developed on the basis of roller compacted concrete, hardfill, and ultra-poor cementing materials. Its main feature is a wide range of sources of aggregate (aggregate is not screened but by simply removing the large particles it can be fully graded on the dam filling) and low amounts of cementitious materials per unit volume. This dam construction material is not only economical and practical, but also green and environmentally friendly. There are many factors affecting the mechanical properties of CSG materials, such as aggregate gradation, sand ratio, water content, water–binder ratio, fly ash content, admixture content, etc. Based on the existing research results of the team, this paper focuses on the influence of fly ash content on the compressive strength of CSG materials. Through a large number of laboratory measured data, we found: (1) The compressive strength law of materials at different ages; the compressive strength of CSG material at age 90 d is generally 10%~30% higher than that at 28 d, and it is proposed that 90 d or 180 d strength should be used as the design strength in the design of CSG material dam; (2) There is an optimal value of fly ash content in CSG materials: when the fly ash content is 50% of the total amount of cementitious materials (cement + fly ash), the fly ash content is defined as the optimal content, and the test data are verified by regression analysis. The discovery of an ‘optimal dosage’ of fly ash provides an important reference for the design and construction of CSG dams.

In recent years, the shortage of water resources and the deterioration of water ecological environment have led to the increasing contradiction between supply and demand of water resources in river basins. How to realize the balanced allocation and scientific regulation of water resources in river basins is a serious challenge for China to face water resources problems. In this paper, the dynamic process and allocation scheme of water resources and water benefit allocation under different cooperative scenarios are simulated by constructing the water resources equilibrium allocation model of water benefit sharing. The influencing factors of water benefit sharing mechanism and the process of allocation compensation are studied, and the benefit relationship in regional coordinated utilization of water resources is revealed. The upstream, midstream and downstream water users of the Yellow River Basin are formed into alliances, respectively. Based on the principle of master–slave game theory, a basin system optimization problem with multi-level hierarchical structure is established. The initial allocation of water resources is carried out with the maximum overall benefit of water resources allocation, and the incremental benefits of the system optimization compared with the current individual and overall benefits are analyzed. The fuzzy cooperative alliance is used to allocate incremental benefits, improve the stability of cooperation among alliances, realize the cooperation and interaction of water resources in distribution, and finally achieve a dynamic equilibrium state. This paper focuses on the allocation mechanism of water resources competition and cooperation under water benefit sharing, which can provide a scientific basis for improving water resources security in water shortage basins and adapt to new problems and challenges brought by changing environments.