Hongkai Gao

East China Normal University | ECNU

The root zone moisture storage capacity (SR) of terrestrial ecosystems is a buffer providing vegetation continuous access to water and a critical factor controlling land-atmospheric moisture exchange, hydrological response and biogeochemical processes. However, it is impossible to observe directly at catchment scale. Here, using data from 300 diver...

Understanding how explicit consideration of topographic information influences hydrological model performance and upscaling in glacier dominated catchments remains underexplored. In this study, the Urumqi Glacier No.1 catchment in northwest China, with 52% of the area covered by glaciers, was selected as study site. A conceptual glacier-hydrologica...

Reading landscapes and developing calibration-free runoff generation models that adequately reflect land surface heterogeneities remains the focus of much hydrological research. In this study, we report a novel and simple topography-driven runoff generation parameterization – the HAND-based Storage Capacity curve (HSC), which uses a topographic ind...

Increased attention directed at frozen soil hydrology has been prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impact of frozen soil on hydrological processes at the catchment scale is still unclear. However, frozen soil hydrology models have mostly been developed based on a bottom-up app...

Traditional hydrological theories are based on the assumption that soil is key in determining water's fate in the hydrological cycle. According to these theories, soil hydraulic properties determine water movement in both saturated and unsaturated zones, described by matrix flow formulas such as the Darcy–Richards equations. They also determine pla...

The Jarvis‐type model, which incorporates stress functions, is commonly used to describe the physiological behaviour of stomatal response in various vegetation species. However, the model has been criticized for its empirically formulated multiplicative equation, which may not accurately capture the mutual impact of intercorrelated stress factors,...

Water data are essential for monitoring, managing, modelling and projecting water resources. Yet despite such data—including water quantity, quality, demand and ecology—being extensively collected in China, it remains difficult to access, use and share them. These challenges have led to poor data quality, duplication of effort and wasting of resour...

Glaciers are one of the main sources of freshwater in cold regions. The glacier melting process can significantly impact the glacier mass balance (GMB) and contribute a large amount of runoff in cold regions. This study applied the recently developed semi-distributed glacio-hydrological conceptual model (FLEXG) to understand the glacier melting pro...

Hydrological models as common simulation tools for water resources management play a key role in improving our understanding of hydrological processes on the catchment and global scales. The reliability of hydrological simulations depends on the model structure, the quality of input data, and the calibration of model parameters. A large number of m...

Traditional "physically-based" hydrological models are based on the assumption that soil is key in determining water's fate. According to these models, soil properties determine water movement in both saturated and unsaturated zones, described by matrix flow formulas known as the Darcy-Richards equations. Soil properties would also determine plant...

Background On the front lines of climate change, glacier termini play crucial roles in linking glaciers and downstream ecosystems during glacier retreat. However, we lack a clear understanding of biological processes that occur in surface and basal ice at glacier termini. Methods Here, we studied the bacterial communities in surface ice and basal...

Multi-source merging is an established tool for improving large-scale precipitation estimates. Existing merging frameworks typically use gauge-based precipitation error statistics and neglect the inter-dependence of various precipitation products. However, gauge-observation uncertainties at daily and sub-daily time scales can bias merging weights a...

Glacier hydrology has profound implications for socio-economic development and nature conservation in arid Central Asia. Process-based hydrological models, which are the traditional tools used to simulate glacier melting, have made considerable contributions to advance our understanding of glacio-hydrology. Simultaneously, deep learning (DL) models...

Glaciers are retreating rapidly, exposing extensive new soil habitats in glacier forefields and providing unique areas for studying primary succession. However, understanding the variation patterns and assembly mechanisms of abundant and rare fungi subcommunities along the glacier-retreating chronosequence remains a knowledge gap, especially true f...

Understanding the role of reservoirs in the terrestrial water cycle is critical to support the sustainable management of water resources especially for China where reservoirs have been extensively built nationwide. However, this has been a scientific challenge due to the limited availability of continuous, long-term reservoir operation records at l...

Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau (TP) help to reveal basin-scale hydrological cycle characteristics under the interactions between the westerlies and Indian summer monsoon (ISM) systems and to improve our understanding on the mechanisms of water resource changes in th...

Lakes are very important for domestic use, commercial purposes, and ecosystem sustenance; nevertheless, studies on how different stressors influence water resources are limited, posing challenges in the planning and managing the water resources. Lake Babati is one of the important lakes in the East African rift valley as a source of fish, drinking...

Increased attention directed at frozen-soil hydrology has been prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impact of frozen-soil on hydrological processes at the catchment scale is still unclear. However, frozen-soil hydrology models have mostly been developed based on a “bottom-up” a...

The risk of coastal storm flooding is deteriorating under global warming, especially for the heavily urbanized deltaic cities, like Shanghai. The Nature-Based Flood Defense (NBFD), as an eco-friendly design alternative for hard infrastructure against coastal flooding, is gaining attention. Nevertheless, the vulnerability of saltmarsh due to the bio...

It is important to improve the forecasting performance of rainfall-runoff models due to the high complexity of basin response and frequent data limitations. Recently, many studies have been carried out based on deep learning and have achieved significant performance improvements. However, their intrinsic characteristics remain unclear and have not...

Groundwater is one of the most critical water resources for Sub Saharan Africa. However, the understanding of the groundwater system in the region is still lacking due to sparse groundwater observations. The influence of topography on the groundwater table is still mostly not evaluated in Sub Saharan Africa. This study applied the analytical hierar...

Glaciers are among the least explored environments on Earth, especially from a perspective of nutrient stoichiometry. Here, we documented and compared the nutrient concentrations and stoichiometric ratios in six distinct habitats of a glacier terminus in the source area of the Yangtze River, including surface ice (SI), basal ice (BI), basal sedimen...

The Storm Water Management Model (SWMM) has been globally used for stormwater management. However, the calibration and evaluation of SWMM for historical rainfall–runoff events in partially separated and combined drainage systems is rarely reported in Norway. In this study, we employed SWMM for the Grefsen catchment in Oslo, Norway. The main problem...

The effects of catchment characteristics and climate variables on water partitioning into evapotranspiration and runoff can be evaluated using the Budyko framework. However, the influence of glaciers on catchment characteristics within the framework has yet been adequately investigated. Here we extend the Budyko framework and apply the elasticity m...

Evaluating the accuracy of precipitation products is essential for many applications. The traditional method for evaluation is to calculate error metrics of products with gauge measurements that are considered as ground-truth. The multiplicative triple collocation (MTC) method has been demonstrated powerful in error quantification of precipitation...

Glaciers are among the least explored environments on Earth, especially from a perspective of nutrient stoichiometry. In this study, we documented and compared the nutrient availabilities (concentrations) and composition (stoichiometric ratios) of nutrients (C, N, and P) in six distinct habitats of a glacier terminus in the Yangtze River Source are...

Increased attention directed at permafrost hydrology has been prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impacts of permafrost on hydrological processes at the catchment scale are still unclear. Permafrost hydrology models at the catchment scale were mostly developed based on a “bott...

As one of the key elements of climate change, the temperature changes can affects the energy balance and hydrological cycle. The variations and trend of mean annual maximum temperature (T max ) and minimum temperature (T min ) were analyzed by using linear regress for 44 stations inside and surrounding the Qilian Mountains for period of 1960-2017....

Global hydrological models (GHMs) are important tools for addressing worldwide change-related water resource problems from a global perspective. However, the development of these models has long been hindered by their low accuracy. In order to improve the streamflow simulation accuracy of GHMs, we developed a GHM—the FLEX-Global—based on the region...

The paper “Large-scale afforestation significantly increases permanent surface water in China's vegetation restoration regions, Agricultural and Forest Meteorology, Volume 290, 15 August 2020, 108001” by Zeng et al. (2020) finds that northern China is greening up and that “vegetation cover is an important factor in controlling permanent water chang...

Permafrost extends 40% of the Qinghai-Tibet Plateau (QTP), a region which contains the headwaters of numerous major rivers in Asia. As an aquiclude, permafrost substantially controls surface runoff and its hydraulic connection with groundwater. The freeze–thaw cycle in the active layer significantly impacts soil water movement direction, velocity,...

Abstract Dielectric techniques are fundamental methods for measuring soil water content, and they commonly rely on the conventional laboratory calibration of the dielectric permittivity models between a dielectric constant and water content. As a non‐negligible factor, porosity has been constructed differently in some models as a calibration consta...

Model realism is of vital importance in science of hydrology, in terms of realistic representation of hydrological processes and reliability of future prediction. Here, we employed a stepwise modeling approach that leverages flexible model structures and multi-source observations for robust streamflow simulation and internal variables validation wi...

Patterns of biomass allocation among organs in plants are important because they influence many growth processes. The Yunnan-Guizhou Plateau (YGP) is considered to be one of the most sensitive areas in China to climate changes, but we know little about how current climatic gradients on the plateau influence plant biomass allocation. Gentiana rigesc...

Glacier retreat caused by global warming alters the hydrological regime and poses far-reaching challenges to water resources and nature conservation of the headwater of Yangtze River, and its vast downstream regions with dense population. However, there is still lack of a robust modeling framework of the “climate-glacier-streamflow” in this water t...

Understanding how biophysical processes respond to the surface energy partitioning and water budget is essential for modeling land surface processes. In general, evapotranspiration (ET) associated with vegetation dynamics can function as a vital nexus of the surface energy partitioning and water budget. Here, a dual-source ET model, the GIS-based P...

Infrastructures handle high-volume goods and services that require heavily capitalized, large-scale, durable, reliable, shared, interdependent, and specialized systems. Infrastructure facilitates social, economic, and environmental functions by achieving a high degree of efficiency at a low marginal cost to produce, transport, distribute, quality-c...

There has been a surge of interest in the field of urban flooding in recent years. However, current stormwater management models are often too complex to apply on a large scale. To fill this gap, we use a physically based and spatially distributed overland flow model, SIMulated Water Erosion (SIMWE). The SIMWE model requires only rainfall intensity...

Bacterial and fungal communities in biofilms are important components in driving biogeochemical processes in stream ecosystems. Previous studies have well documented the patterns of bacterial alpha diversity in stream biofilms in glacier-fed streams, where, however, beta diversity of the microbial communities has received much less attention especi...

Bacterial and fungal communities in biofilms are important components in driving biogeochemical processes in stream ecosystems. Previous studies have well documented the patterns of bacterial alpha diversity in stream biofilms in glacier-fed streams, where, however, beta diversity of the microbial communities has received much less attention especi...

Bacterial and fungal communities in biofilms are important components in driving biogeochemical processes in stream ecosystems. Previous studies have well documented the patterns of bacterial alpha diversity in stream biofilms in glacier-fed streams, where, however, beta diversity of the microbial communities has received much less attention especi...

Analyzing the impacts of climate change on hydrology and future projections of water supplies is fundamental for the efficient management and planning of water resources in large river systems on the Tibetan Plateau (TP), which is known as the “water tower of Asia.” However, large uncertainties remain in the projections of streamflow and glaciers i...

Precipitation and air temperature are key drivers of watershed models. Currently there are many open-access gridded precipitation and air temperature datasets at different spatial and temporal resolutions over global or quasi-global scale. Motivated by the scarcity and substantial temporal and spatial gaps in ground measurements in Africa, this stu...

Spatial and temporal patterns of trends in annual and seasonal precipitation over Germany during 1951‐2013 were analyzed using the ensemble empirical mode decomposition (EEMD) method. Three widely used and recognized high‐resolution observation‐based gridded precipitation products, the Climatic Research Unit time‐series data (CRU) and Global Precip...

Introduction Landscapes and water are closely linked. Water shapes landscapes, and landscape heterogeneity in turn determines water storage, partitioning, and movement. Understanding hydrological processes from an ecological perspective is an exciting and fast-growing field of research. Objectives The motivation of this paper is to review advances...

Lake Tana is the largest lake in Ethiopia, and its lake outflowis the source of the BlueNile River that provides vital water resources for many livelihoods and downstream/international stakeholders. Therefore, it is essential to quantify and monitor the water balance of Lake Tana. However, Lake Tana is poorly gauged, with more than 50% of Lake Tana...

This study highlights the features of vine copula for examining compound events involving underlying conditions that amply the compounding effects. To illustrate, we study compound floods in Texas (TX), U.S. These compound floods consist of combinations of precipitation and surface runoff with the El Niño–Southern Oscillation (ENSO) and rising temp...

Reading landscapes and developing calibration-free runoff generation models that adequately reflect land surface heterogeneities remains the focus of much hydrological research. In this study, we report a novel and simple topography-driven runoff generation parameterization – the HAND-based Storage Capacity curve (HSC), that uses a topographic inde...

High-altitude inland-drainage lakes on the Tibetan Plateau (TP), the earth's third pole, are very sensitive to climate change. Tibetan lakes are important natural resources with important religious, historical, and cultural significance. However, the spatial patterns and processes controlling the impacts of climate and associated changes on Tibetan...

Hydrological models often require calibration. Multi-objective calibration has been more widely used than single-objective calibration. However, it has not been fully ascertained that multi-objective calibration will necessarily guarantee better model accuracy. To test whether multi-calibration was effective in comparison to single-calibration in t...

Benthic biofilms in glacier-fed streams harbor diverse microorganisms driving biogeochemical cycles and, consequently, influencing ecosystem-level processes. Benthic biofilms are vulnerable to glacial retreat induced by climate change. To investigate microbial functions of benthic biofilms in glacier-fed streams, we predicted metagenomes from 16s r...

In various conceptual models, the shape parameter (β) of the storage capacity curve, representing the non-linear relationship between relative soil moisture and runoff, determines runoff yield given certain circumstances of rainfall and antecedent soil moisture. In practice, β is typically calibrated for individual catchments and for different purp...

Glacier-fed streams are highly dynamic environments that integrate upstream catchment processes and are prominent geomorphological and ecological components of alpine landscapes. In these systems, hydrological and physicochemical factors change significantly with location downstream of the glacier. Variation in microbial communities in benthic biof...

Whether coupling auxiliary information (except for conventional rainfall–runoff and temperature data) into hydrological models can improve model performance and transferability is still an open question. In this study, we chose a glacier catchment to test the effect of auxiliary information, i.e., distributed forcing input, topography, snow-ice acc...

Understanding which catchment characteristics dominate hydrologic response and how to take them into account remains a challenge in hydrological modeling, particularly in ungaged basins. This is even more so in non-temperate and non-humid catchments, where - due to the combination of seasonality and the occurrence of dry spells - threshold processe...

With remote sensing we can readily observe the Earth's surface, but direct observation of the sub-surface remains a challenge. In hydrology, but also in related disciplines such as agricultural and atmospheric sciences, knowledge of the dynamics of soil moisture in the root zone of vegetation is essential, as this part of the vadose zone is the cor...

This study presents an "Earth observation-based" method for estimating root zone storage capacity – a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data...

The Height Above the Nearest Drainage (HAND), a digital elevation model normalized using the nearest drainage is used for hydrological and more general purpose applications, such as hazard mapping, landform classification, and remote sensing. One of the essential characteristics of HAND is its ability to capture heterogeneities in local environment...