Application of a new distributed hydrological model based on soil–gravel structure in the Niyang River Basin, Qinghai–Tibet Plateau

Abstract

Abstract. The Qinghai-Tibet Plateau has a thin soil layer on top of a thick gravel layer, while its unique geological structure, combined with the snow and frozen soil in this area, significantly affect water circulation in the entire region. To investigate the mechanism of the underlying surface structure on the hydrothermal migration and water circulation process in the Qinghai-Tibet Plateau, we performed comprehensive study combining field experiments of the water and heat transfer processes and development of a Water and Energy transfer Processes model in the Qinghai–Tibet Plateau (WEP-QTP), based on the original Water and Energy transfer Processes model in Cold Regions (WEP-COR). The Niyang River Basin located on the Qinghai-Tibet Plateau was selected as the study area to evaluate the agreement between theoretical hypothesis, observation, and modeling results. This model divides the single soil into a dualistic structure of soil and gravel. In the non-freeze–thaw period, two infiltration models based on the dualistic soil-gravel structure were developed using the Richards equation in a non-heavy rain scenario and the multi-layer Green-Ampt model in a heavy rain scenario. During the freeze–thaw period, a hydrothermal coupling model based on the continuum of the snow-soil-gravel layer was constructed. The addition of the gravel layer corrected the original model’s overestimation of the moisture content below the surface soil and reduced the moisture content relative error (RE) from 33.74 to -12.11 %. The addition of the snow layer not only reduced the temperature fluctuation of the surface soil, but also, with the help of the gravel layers, revised the original model’s overestimation of the freeze-thaw speed. The temperature RE was reduced from -3.60 to 0.08 %. In the non-freeze-thaw period, the dualistic soil-gravel structure improved the regulation effect of groundwater on flow, stabilizing the flow process. The maximum RE at the flow peak and valley decreased by 88.2 and 21.3 %, respectively. In the freeze-thaw period, by considering the effect of the snow-soil-gravel layer continuum, the freezing and thawing process of WEP-QTP lagged that of WEP-COR by approximately one month. The groundwater simulated by WEP-QTP had more time to recharge the river, which better showed the "tailing" process after October. The flow simulated by the WEP-QTP model was more accurate and closer to the actual measurements, with Nash > 0.75 and |RE| < 10 %. The improved model reflects the effects of the Qinghai-Tibet Plateau special environment on the hydrothermal transport and water cycle process and can be used for hydrological simulation of the Qinghai-Tibet Plateau.

Analysis on “three-box” model of stress-strain in frozen soil porous media based on representative macroscopic Volume

“…In order to validate the feasibility of the description and selection method of RMV of frozen soil porous media involving porosity as a typical condition variable. It provides a new direction for developing permafrost resources and studying the build of roadworks in permafrost areas (Tang et al, 2019;Wang et al, 2022). It provides new ideas for investigating and studying the essential characteristics of frozen soil and the law of development and change, as well as the measures to prevent and control frost damage, and further serves for the development and economic construction in cold areas (Lai et al, 2018;Yu et al, 2020).…”

Analysis and partitioning of terrestrial water storage in the Yellow River source region

“…These subbasins were partitioned into 7380 contour bands, accounting for the influence of elevation and the flow dynamics along the overland pathway. The vertical structures of the contour bands comprise distinct layers: the interception, depression, upper soil, transition, and aquifer layers (Jia et al, 2006; Wang et al, 2023; Zhou et al, 2018). The main water and energy transfer processes of the model include evapotranspiration, runoff generation, confluence, and soil freeze–thaw processes (Wang et al, 2023).…”

“…The vertical structures of the contour bands comprise distinct layers: the interception, depression, upper soil, transition, and aquifer layers (Jia et al, 2006; Wang et al, 2023; Zhou et al, 2018). The main water and energy transfer processes of the model include evapotranspiration, runoff generation, confluence, and soil freeze–thaw processes (Wang et al, 2023). The Penman and Penman‐Monteith equations were employed to characterize the evapotranspiration processes (Monteith, 1973; Penman, 1948).…”

“…The Richards model was used to describe the movement of SM in unsaturated soils. The Green‐Ampt model was utilized to describe infiltration when the P intensity exceeded the infiltration capacity (Wang et al, 2023). The kinematic wave equation was employed to describe the flow of water over land and in rivers (Jia et al, 2001).…”

“…This limitation makes it challenging to capture the spatiotemporal differences in TWS and its components. To address these limitations, we improved the energy balance processes including the surface radiation calculations and snowmelt module, and developed a coupled energy‐water model with a physical mechanism based on a water and energy transfer processes model for the QTP (referred to as WEP‐QTP) (Wang et al, 2023). The improved WEP‐QTP model, incorporating the climate and terrain characteristics of the QTP, includes a water–heat coupled mechanism and reflects the geological characteristics of thin soil layers and thick gravel layers in the QTP.…”