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The 5‐even subgraph cycle double cover conjecture (5‐CDC conjecture) asserts that every bridgeless graph has a 5‐even subgraph double cover. A shortest even subgraph cover of a graph G is a family of even subgraphs which cover all the edges of G and the sum of their lengths is minimum. It is conjectured that every bridgeless graph G has an even subgraph cover with total length at most 2115∣E(G)∣. In this paper, we study those two conjectures for weak oddness 2 cubic graphs and present a sufficient condition for such graphs to have a 5‐CDC containing a member with many vertices. As a corollary, we show that for every oddness 2 cubic graph G satisfying the sufficient condition has a 4‐even subgraph (1,2)‐cover with total length at most 2015∣E(G)∣+2. We also show that every oddness 2 cubic graph G with girth at least 30 has a 5‐CDC containing a member of length at least 910∣V(G)∣ and thus it has a 4‐even subgraph (1,2)‐cover with total length at most 2115∣E(G)∣. [ABSTRACT FROM AUTHOR]

Vegetation plays a key role in trapping sediments and further controlling pollutants. However, few studies were conducted to clarify the erosion and deposition laws of sediments and the influence factors caused by vegetation patch properties, which is not conducive to the revelation of riverbank protection and erosion prevention. Therefore, this study investigated the change in scouring and deposition characteristics around submerged vegetation patches of nine kinds of typical configurations and their influencing factors. Vegetation patches were assembled from three vegetation densities (G/d = 0.83, 1.3, and 1.77, representing dense, medium, and sparse, respectively), and three vegetation patch thicknesses (dn = 170, 400, and 630, representing narrow, usual, and wide, respectively), to measure vegetation patch property influences. Flow velocity, scouring, and deposition characteristics under nine patches were determined by a hydraulic flume experiment, three-dimensional acoustic Doppler velocimetry (ADV), and three-dimensional laser scanner, and then ten geometry and morphology indices were measured and calculated based on the results of laser scanning. Results showed that both vegetation patch density and thickness were positively related to the turbulence kinetic energy (TKE) above the vegetation canopy, and only vegetation patch density was negatively related to the flow velocity above the vegetation canopy. The relation between the product of density and vegetation patch thickness and erosion area in planform (EA) showed a power function (R2 = 0.644). Both density and vegetation patch thickness determined the scouring degree, but deposition location and amount did not rely on each one simply. On average, medium density showed the smallest maximum erosion length (MEL), EA, deposition area in planform (DA), and average deposition length (ADL) and a minimum of the above parameters also occurred at narrow vegetation patch thickness. The shape factor of the erosion volume (SFEV), the shape factor of the deposition volume (SFDV), ADL, and MEL of medium density and narrow thickness vegetation patch (G/d = 1.3, dn = 170) were significantly smaller than that of other types of patches. DA and equivalent prismatic erosion depth on the erosion area (EPED) were significantly linearly related (R2 = 0.766). Consequently, most sediment was deposited close to the vegetation patch edge. It is suggested that vegetation patch thickness and density should be given to control sediment transport. In particular, natural vegetation growth changes vegetation patch density and then alters vegetation patch thickness. Management and repair need to be first considered. The results of this study shed light on riparian zone recovery and vegetation filter strip mechanism. [ABSTRACT FROM AUTHOR]

As an integral part of rural built heritage, the aesthetic and recreational values of Historical Irrigation Canals (HICs) have increasingly garnered attention in recent years, providing new perspectives for heritage conservation and sustainable rural development. However, there is a scarcity of research conducted from the micro-perspective of public preferences for HICs in rural areas. The existing literature primarily focuses on how the landscape characteristics of natural and urban rivers affect public preferences, with a lack of attention to built heritage characteristics and rural settings, which are uniquely inherent to HICs in rural areas. This study aims to explore public preferences for HICs in rural areas from the perspectives of landscape characteristics and social backgrounds. The Li Canal-Gaoyou Irrigation District, one of the World Heritage Irrigation Structures, was selected as the case study. Selected HIC photos were utilized for measuring landscape characteristics and conducting survey questionnaires. Relationships among HIC landscape characteristics, social backgrounds, and aesthetic and recreational preferences were revealed through one-way ANOVA, Spearman's correlation, and stepwise regression analyses. Key findings include the following: (1) the public can derive aesthetic and recreational value from HICs; (2) canals with large water bodies, artificial banks, and artificial vegetation are considered more aesthetically pleasing; (3) larger canals, extensive water bodies, and artificial banks are deemed more suitable for recreation; (4) factors such as age, education level, income, rural living experience and knowledge of HICs influence public preferences; (5) costs influence public aesthetic and recreational preferences, with people more willing to pay for roads and hardened banks. Finally, several recommendations for the protection and management of HICs have been summarized, offering guidance for rural managers and planners. [ABSTRACT FROM AUTHOR]

This study aims to achieve coordination between regional economic development and ecological environmental protection and to mitigate issues such as competition for water use among industries and significant disparities between water supply and demand. A multi-water-source, multi-user, and multi-objective optimal water resource allocation model was developed for Ordos City using general water allocation and simulation (GWAS). This model was applied to optimize water resource allocation on a monthly scale for various users across different administrative units (banners) in both short- and long-term planning periods. The results indicate that Ordos City's allocated water volume for 2025 and 2030 is projected to be 1833.36 × 106 m3 and 1963.44 × 106 m3, respectively, with an overall water shortage rate of 5.46% and 5.67%, respectively. Water shortages are predicted in Dongsheng District, Dalad Banner, Etuoke Banner, Hangjin Banner, and Wushen Banner, primarily during the agricultural water usage period from March to November. The regional water supply structure was notably optimized, with a gradual decrease in the proportion of groundwater in the total water supply and a corresponding increase in the supply of surface water and unconventional water. These changes effectively improve local groundwater overexploitation and enhance the water supply efficiency. The research findings could offer valuable theoretical and technical support for the development and utilization of water resources, as well as for adjustments in the population–economic–industrial structure of Ordos City. Additionally, this study could provide scientific references for optimizing water resource allocation in other water-deficient cities in arid and semi-arid areas of the Yellow River Basin. [ABSTRACT FROM AUTHOR]

Investigating the influence of human activities and climate change on streamflow and sediment load is of great significance for understanding the hydrological cycle, addressing climate change, and ensuring sustainable water resource management. Based on observed data of precipitation, streamflow, and sediment load from 1990 to 2021 in the Xiliugou Basin, trend and abrupt change analyses of streamflow and sediment load were conducted using the coefficient of variation and Bayesian change point detection method. The effects of climate change and human activities on streamflow and sediment load were further examined through the double mass curve method, with a focus on the impact of land use changes on streamflow and sediment load dynamics. The results indicated that: (1) During the study period, there was a consistent decreasing trend in streamflow, sediment load, and precipitation, with respective rates of −77.76 × 104 m3/year, −55.97 × 104 Mt/year, and −0.84 mm/year. The distribution of annual streamflow and sediment load in the basin was uneven, with 61.05% of precipitation occurring during the wet season and the peak sediment discharge month being July, accounting for 58.90% of the total annual sediment load. (2) The variations in streamflow and sediment load in the Xiliugou Basin exhibited distinct stage characteristics, with abrupt changes occurring around 1997. Both streamflow and sediment load showed significant fluctuations from the reference period to the changing period, decreasing by 45.54% and 82.85%, respectively. (3) A positive correlation between precipitation and streamflow was observed in the Xiliugou Basin, with correlation coefficients (R) of 0.62 and 0.49, indicating a stimulating effect of precipitation on streamflow and sediment load. Human activities significantly reduced sediment load in the Xiliugou Basin from 1998 to 2021, contributing to a reduction of 115.08%. (4) An increase in cropland, water, and barren areas would lead to higher streamflow and sediment load, while an increase in grassland, forest, and impervious areas would decrease both streamflow and sediment load. [ABSTRACT FROM AUTHOR]