The relationship between water-sediment processes and landscape pattern changes has currently become a research hotspot in low-carbon water and land resource optimization research. The SWAT-VRR model is a distributed hydrological model which better shows the effect of land use landscape change on hydrological processes in the watershed. In this paper, the hydrological models of the Dapoling watershed were built, the runoff and sediment yield from 2006 to 2011 were simulated, and the relationship between landscape patterns and water-sediment yield was analyzed. The results show that the SWAT-VRR model is more accurate and reasonable in describing runoff and sediment yield than the SWAT model. The sub-basins whose soil erosion is relatively light are mostly concentrated in the middle reaches with a slope mainly between 0–5°. The NP, PD, ED, SPIIT, SHEI, and SHDI of the watershed increased slightly, and the COHESION, AI, CONTAG, and LPI showed a certain decrease. The landscape pattern is further fragmented, with the degree of landscape heterogeneity increasing and the connection reducing. The runoff, sediment yield and surface runoff are all extremely significantly negatively correlated with forest, which implies that for more complicated patch shapes of forest which have longer boundaries connecting with the patches of other landscape types, the water and sediment processes are regulated more effectively. Therefore, it can be more productive to carry out research on the optimization of water and soil resources under the constraint of carbon emission based on the SWAT-VRR model.

River network routing’s significance in reach-level flood forecasting over extensive domains is growing, requiring considerable computational resources for modeling networks comprising thousands to millions of reaches. Parallel computation plays a central role in timely forecasting in such cases. However, the sequentiality of upstream-to-downstream flow paths within river networks poses a significant challenge for parallelization. This study introduces a family of stream orders and an associated order-based parallel routing approach. We assign each reach an order that falls between one more than the maximum order of its upstream reaches and one less than the order of its downstream reach. This strategy enables the parallel simulation of reaches with identical orders while sequentially processing those with different orders, thus maintaining the crucial upstream-to-downstream dynamic. To further enhance parallel scalability, we strategically relax the upstream-to-downstream relationship along the longest flow paths, dividing the network into independent subnetworks and introducing halo reaches to mitigate the impact of inexact inflows. We validate our approach using China’s Yangtze River basin, the country’s largest river network with 53,600 fully connected reaches. Employing a conceptual parallel execution machine, we demonstrate that our method achieves 80% parallel efficiency with up to 25 processors. By strategically introducing breakpoints, we further enhance scalability, enabling efficient simulations on 77 processors while maintaining 80% efficiency. These results highlight the scalability and efficiency of our methods for large-scale, high-resolution river network modeling within Earth system models. Our study also lays a theoretical groundwork for optimizing stream orders and halo reach placements, crucial for advancing river network modeling.

With the development of landscape ecology and hydrology, the research in relationship between landscape pattern changes and hydrological process is pushed into a further level, and also to proposed a higher request to the development of related models. The SWAT-VRR model (Soil and Water Assessment Tool with Vegetation Runoff Regulation) is a distributed hydrological model to better show the effect of land use landscape change on hydrological processes. The Qihe watershed in Danjiangkou reservoir area was selected in a case study, and the applicability of SWAT-VRR was verified firstly, then set up two typical water-soil conservation scenario simulations to analyze the response to landscape pattern changes under SWAT-VRR. The results indicate that, the SWAT-VRR model achieved a notable improvement in monthly and daily hydrological simulation comparing to the SWAT model (Soil and Water Assessment Tool) simulation during 2003 to 2006. Compared with the two land use scenarios, the 300 m forest riparian along the Qihe River can adjust the runoff more effectively than the area greater than 15° is forest, and show a strong stability in water-soil conservation effect during different rainfall. The SWAT-VRR provides a more accurate scientific basis to estimate landscape pattern change on stream flow.