Search Results (3)

Ecological watersheds (eco-watersheds) are of great significance for boosting the construction of ecological civilization and realizing the ecological protection and high-quality development of watersheds. In order to establish a scientific eco-watershed evaluation index system, this paper refers to the river health evaluation index system, the water resources coupling evaluation index system, and the happy river evaluation index system, and reviews the development process of the ecological watershed evaluation index system. According to the eco-watershed theoretical system, combined with the relevant contents of policies and regulations, thousands of evaluation indicators that have been collected are screened using the theoretical analysis method and the frequency analysis method. Finally, a comprehensive evaluation index system of Weihe River eco-watersheds was constructed, including three first-level indicators: watershed water resources, socio-economic, and ecological. These were further subdivided into eight second-level indicators, namely water security, water resources, water economy, water management, water culture, water environment, water ecology, and water landscape. These second-level indicators were then further broken down into 60 third-level indicators. On the basis of determining the evaluation standards of Weihe River eco-watersheds, the evaluation weights were determined using the gray correlation method and the AHP-entropy comprehensive weight method (comprehensive weight), resulting in the establishment of an evaluation model and a coupling model for the eco-watersheds of the Weihe River. The results of the Weihe River eco-watershed evaluation model and the coupled coordination degree evaluation model show that, from 2019 to 2021, both the gray correlation analysis weights and comprehensive weight evaluation show a yearly increasing trend; the evaluation results are in the eligible status and below; and the evaluation grade is in the fourth-level eco-watersheds and below. Based on the evaluation results of each dimension, when comparing the gray correlation analysis weights with the evaluation of the comprehensive weights, the latter align more closely with the actual Weihe River Watershed. When comparing the evaluation results of the Henan Weihe River Watershed with those of the Handan Weihe River Watershed, the latter’s results, influenced by the scheduling of the Yuecheng Reservoir, are relatively better. Furthermore, in the evaluation of coupling coordination, the water resources subsystem is less coupled to other subsystems due to the 2021 flood. Therefore, in order to effectively improve the level of eco-watersheds, scientific and reasonable water resources scheduling programs should be developed. Full article

The excessive use of pesticides and fertilizers during agricultural production causes water pollution, which is an important type of non-point source pollution (NSP). Large amounts of harmful substances, such as nitrogen and phosphorus, flow into surface water along with farmland runoff, leading to eutrophication and other problems. However, the pollutant discharge capacity of different types of cultivated land varies greatly. Areas sensitive to NSP are areas with rich crop types, large spatial differences in crop growth, and complex planting patterns. These factors can cause different amounts of fertilizer used in and absorbed by the crops to influence the emission intensity of pollutants. NSP intensity mapping can reflect the spatial distribution of lands’ pollutant discharge capacity and it can provide a basis for pollution control. However, when estimating NSP intensity, existing methods generally treat cultivated land as a category and ignore how complex crop conditions impact pollution intensity. Remote sensing technology enables the classification and monitoring of ground objects, which can provide rich geographical data for NSP intensity mapping. In this study, we used a phenology–GPP (gross primary productivity) method to extract the spatial distribution of crops in the Yuecheng reservoir catchment area from Sentinel-2 remote sensing images and the overall accuracy reached 85%. Moderate resolution imaging spectroradiometer (MODIS) GPP data were used to simulate the spatial distribution of crop growth. Finally, a new model that is more suitable for farmland was obtained by combining this large amount of remote sensing data with existing mapping models. The findings from this study highlight the differences in spatial distributions between total nitrogen and total phosphorous; they also provide the means to improve NSP intensity estimations. Full article

As a result of the inexorable development of the economy and the ever-increasing population, the demand for water in the urban and rural sectors has increased, and this in turn has caused the water quality and eutrophication of the reservoir to become a legitimate concern in the water environment management of river basins. Phosphorus (P) is one of the limiting nutrients in aquatic ecosystems; P in the sediment is a primary factor for eutrophication. Yuecheng Reservoir is located in one of the most productive and intensively cultivated agricultural regions in North China. Detailed knowledge of the sediment is lacking at this regional reservoir. The first study to look into the different P fractions and its diffusion fluxes at the water sediment interface of the Yuecheng Reservoir makes it possible to learn about the internal P loading. According to the results, the concentrations of total phosphorus (TP) ranged from 1576.3 to 2172.6 mg kg and the P fraction concentration sequence is as follows: P associated with calcium (Ca–Pi) > organic P (Po) > P bound to aluminum (Al), ferrum (Fe) and manganese (Mn) oxides and hydroxides (Fe/Al–Pi). The results demonstrated that, although the construction of a large number of water conservancy projects in the upper reaches of the river resulted in the decrease of inflow runoff, the pollutions from terrestrial plants or materials played a key role in the sediment phosphorus fraction, and they should be emphasized on the water environment management of river basin. Full article