Search

[Display omitted] • China's large river sediment loadings and runoff have not universally synchronously changed in the past 20 years. • There were 9/13 of large river systems showed downward trends of annual sediment loadings. • Lower reaches of the Yellow River had the maximum annual average sediment loadings. • Runoff volume accounted for over 30% of sediment loading variations among all river systems. • Afforestation plays a crucial role in reducing sediment in arid regions. Understanding the relationship between sediment loading and its environmental implications in river systems is crucial for water resource management and environmental protection. This study explored the spatiotemporal characteristics of sediment loading and their environmental relationships in seven large rivers in China, aiming to quantify the contributions of various factors to changes in sediment transport. Monitoring data spanning twenty-one years (2002 to 2022) on sediments, hydrology, and the environment collected by sixty-five stations were analysed. The multivariate statistical techniques employed included Spearman's correlation analysis, principal component analysis, and multivariate regression modeling. The results show that sediment transport in various river systems exhibited spatial heterogeneity, the maximum annual average sediment loadings (1.59 × 108 t/yr) occur in the lower reaches of the Yellow River, the middle reaches have the highest sediment concentration (41.54 kg/m3), followed by the downstream of the Yellow River (5.85 kg/m3). Sediment loading and runoff changes in the basins did not adhere universally to synchronous patterns. Eleven of the thirteen basins of these river systems showed upward trends in annual runoff volume, whereas nine basins showed downward trends in annual sediment loading. Runoff volume accounted for over 30 % explanatory of sediment loading variations in all seven large river systems, with the Yangtze, Huaihe, Qiantang, and Songhua rivers surpassing 60 % of the explanatory power. The Normalized Difference Vegetation Index of all watersheds showed an increasing trend, whereas the index of nine of the thirteen watersheds was correlated negatively with sediment transport. The influence of human activities on basin sediment transport was higher than that of natural resilience, whereas afforestation significantly reduced sediment in arid regions. This study provides insight into the temporal and spatial characteristics of sediment loadings and the driving effects of environmental factors, which has great significance for watershed environmental management. [ABSTRACT FROM AUTHOR]

• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

• Unprecedented monitoring datasets are available to support land health assessments. • Benchmarks enable objective and actionable data-informed management decisions. • Framework for establishing benchmarks and illustrated examples are presented. • Potential caveats and best practices for benchmarking approaches are described. • Future research needs identified for benchmark research and applications. Soil erosion can have a multitude of negative impacts on agroecosystems and society and there remains an urgent need for tools to support its management. Quantitative benchmarks based on holistic understanding of erosion processes, ecosystem function, and land use objectives can be used with monitoring data and models to inform assessments and make objective and actionable decisions about erosion management. However, managers currently lack a framework for establishing benchmarks. Here, we present a framework and evaluation of different approaches to establishing quantitative benchmarks for soil erosion and ecological monitoring and assessment that can inform land management decisions. We use monitoring data collected across Chihuahuan Desert ecosystems in the United States and an aeolian sediment transport model to illustrate how benchmarks can be established. Approaches include establishing benchmarks from relationships between soil erosion indicators, reference states and land potential, including state-and-transition models, and desired conditions from existing monitoring data. We discuss the benefits and caveats of the different approaches and show how combining different benchmarking approaches can help users ensure that benchmarks appropriately reflect thresholds for soil erosion and achievable management outcomes. We finish by identifying future research needs to support establishment and application of erosion benchmarks across agroecosystems and recognize the opportunity to extend the benchmarking approaches to management of other agroecosystem processes and services. [ABSTRACT FROM AUTHOR]