Under a changing environment, the characteristics of precipitation-runoff hydrological response relationship and the analysis of synchronous and asynchronous encounter frequency in large river basins play a crucial role in the water resources planning and management. Under the precipitation and runoff bivariate hydrological framework, segmented joint distribution models for precipitation and runoff of the Yellow River Basin (YRB) are constructed using the copula function. The wet and dry synchronous-asynchronous encounter frequency of precipitation and runoff is quantitatively analysed, and the driving factors underlying the variations in the precipitation-runoff relationship are discussed. The results show that from 2005 to 2024, precipitation and runoff for Lanzhou (upper reaches), Longmen (middle reaches), and Lijin (lower reaches) hydrological station of the YRB exhibited an upward trend. The wet and dry synchronous frequencies between precipitation and runoff at these three stations were 55.24%, 58.26% and 57.67%, respectively, all higher than the asynchronous frequencies, indicating that the whole basin is likely to experience synchronous wet or dry hydrological regimes. Furthermore, in the YRB, the explanatory power of precipitation on natural runoff gradually decreases from upstream to downstream. Land use and land cover change induced by grain-for-green projects and urbanisation are likely the main causes of natural runoff variation and the alteration of the hydrological response mechanism in the YRB.
Historically, agricultural land in the Czech Republic was highly diverse, and fields were commonly bordered by wooded areas. However, consolidation occurred, particularly during the collectivisation phase, resulting in fields of several hundred hectares. In such a uniform landscape, the soil is threatened by water erosion. In addition, there are other negative impacts on the environment, such as a decline in biodiversity. One of the ways to enhance landscape management is to implement soil conservation measures, e.g. strip cropping, contour farming, and agroforestry systems. This article deals with the impact of soil conservation measures on erosion and runoff conditions. Forty-eight variants were proposed. In some variants broad-base terraces were considered. It was observed that the design of the measures resulted in a significant reduction in both soil loss and surface runoff. Among the evaluated measures, strip cropping proved to be highly effective in reducing sediment transport. The combination of strip cropping (winter barley and winter rapeseed), an agroforestry system featuring 6 m wide grass belts with a slight contour deviation, and two broad-base terraces mitigated erosion by approximately 84%. Nevertheless, this management practice introduces a significant spatial footprint of grass belts and unproductive land, around 27%.
