The thermodynamics of many lakes around the globe are shifting under a warming climate, affecting... more The thermodynamics of many lakes around the globe are shifting under a warming climate, affecting nutrients and oxygen transportation within the lake and altering lake biota. However, long-term variation in lake heat and water balance is not well known, particularly for regions like the Tibetan Plateau. This study investigates the long-term (1963–2019) variation in the heat balance of a large lake in the Tibetan Plateau (Nam Co) by combining the strengths of modeling and remote sensing. Remotely sensed lake surface water temperatures from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Along Track Scanning Radiometer Reprocessing for Climate: Lake Surface Water Temperature and Ice Cover (ARC-Lake) are used to calibrate and validate a conceptual model (air2water) and a thermodynamic model (LAKE) for the studied lake, for which in situ observation is limited. The results demonstrate that remotely sensed lake surface water temperature can serve as a valuable surrogate for...
This paper investigates the prediction of different streamflow characteristics in ungauged catchm... more This paper investigates the prediction of different streamflow characteristics in ungauged catchments and under climate change, with three rainfall-runoff models calibrated against three different objective criteria, using a large data set from 780 catchments across Australia. The results indicate that medium and high flows are relatively easier to predict, suggesting that using a single unique set of parameter values from model calibration against an objective criterion like the Nash–Sutcliffe efficiency is generally adequate and desirable to provide a consistent simulation and interpretation of daily streamflow series and the different medium and high flow characteristics. However, the low flow characteristics are considerably more difficult to predict and will require careful modelling consideration to specifically target the low flow characteristic of interest. The modelling results also show that different rainfall-runoff models and different calibration approaches can give sig...
Baseflow is the portion of streamflow that originates from groundwater. It is pivotal to groundwa... more Baseflow is the portion of streamflow that originates from groundwater. It is pivotal to groundwater supply as well as the interactions between groundwater and surface water. In the Loess Plateau of China, the baseflow plays a fundamental role in sustaining the aquatic ecosystem. Rational estimation of baseflow is of critical importance for understanding the functioning of the groundwater system and informing management of regional water resources. In this study, a two-well parameterised digital filter was used to separate baseflow from observed daily total streamflow on the Weihe River Basin. Two parameters (maximum baseflow index (BFI) and the recession constant) of this filter were estimated using UKIH and a recession analysis with physical meaning, respectively. The results show that the baseflow index increased from the upstream to downstream (0.27-0.32) of the Weihe River, and the baseflow of the river is summer dominant. In general, the baseflow has been increasing gradually ...
Well‐validated rainfall‐runoff models are able to capture the relationships between rainfall and ... more Well‐validated rainfall‐runoff models are able to capture the relationships between rainfall and streamflow and to reliably estimate initial catchment states. While future streamflows are mainly dependent on initial catchment states and future rainfall, use of the rainfall‐runoff models together with estimated future rainfall can produce skilful forecasts of future streamflows. This is the basis for the ensemble streamflow prediction system, but this approach has not been explored in Australia. In this paper, two conceptual rainfall‐runoff models, together with rainfall ensembles or analogues based on historical rainfall and the Southern Oscillation index (SOI), were used to forecast streamflows at monthly and 3‐monthly scales at two catchments in east Australia. The results showed that both models forecast monthly streamflow well when forecasts for all months were evaluated together, but their performance varied significantly from month to month. Best forecasting skills were obtain...
In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate ... more In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate change, but also impose substantial ecohydrological impacts on the local environment. Due to the limitation of ground observation, remote sensing has been used as an alternative tool to investigate recent changes of lake ice phenology. However, uncertainties exist in the remotely sensed lake ice phenology owing to both the data and methods used. In this paper, three different remotely sensed datasets are used to investigate the lake ice phenology variation in the past decade across the Tibetan Plateau, with the consideration of the underlying uncertainties. The remotely sensed data used include reflectance data, snow product, and land surface temperature (LST) data of moderate resolution imaging spectroradiometer (MODIS). The uncertainties of the three methods based on the corresponding data are assessed using the triple collocation approach. Comparatively, it is found that the method ba...
In order to reduce the environmental and ecological problems induced by water resources managemen... more In order to reduce the environmental and ecological problems induced by water resources management and use, this paper proposes a concept of environmenta water requirement. It is defined as the minimum water amount to be consumed by the natural water bodies to conserve its environmental and ecological functions. Based on the definition, the methods for calculating the amount of environmental and ecological water requirement are determined. In the case study on Haihe-Luanhe river system, the water requirement is divided into three parts, i.e., the basic instream flow, water requirement for sediment transfer and water consumption by evaporation of the lakes or everglades. The results of the calculation show that the environmental and ecological water requirement in the river system is about 124x108 m3, including 57x108 m3 for basic in-stream flow, 63x108 m3 for sediment transfer and 4x108 m3 for net evaporation loss of lakes. The total amount of environmental and ecological water requ...
Long-term changes in the water budget of lakes in the Tibetan Plateau due to climate change are o... more Long-term changes in the water budget of lakes in the Tibetan Plateau due to climate change are of great interest not only for the importance of water management, but also for the critical challenge due to the lack of observations. In this paper, the water budget of Nam Co Lake during 1980–2010 is simulated using a dynamical monthly water balance model. The simulated lake level is in good agreement with field investigations and the remotely sensed lake level. The long-term hydrological simulation shows that from 1980 to 2010, lake level rose from 4718.34 to 4724.93 m, accompanied by an increase of lake water storage volume from 77.33 × 109 to 83.66 × 109 m3. For the net lake level rise (5.93 m) during the period 1980–2010, the proportional contributions of rainfall–runoff, glacier melt, precipitation on the lake, lake percolation, and evaporation are 104.7%, 56.6%, 41.7%, −22.2%, and −80.9%, respectively. A positive but diminishing annual water surplus is found in Nam Co Lake, imply...
The thermodynamics of many lakes around the globe are shifting under a warming climate, affecting... more The thermodynamics of many lakes around the globe are shifting under a warming climate, affecting nutrients and oxygen transportation within the lake and altering lake biota. However, long-term variation in lake heat and water balance is not well known, particularly for regions like the Tibetan Plateau. This study investigates the long-term (1963–2019) variation in the heat balance of a large lake in the Tibetan Plateau (Nam Co) by combining the strengths of modeling and remote sensing. Remotely sensed lake surface water temperatures from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Along Track Scanning Radiometer Reprocessing for Climate: Lake Surface Water Temperature and Ice Cover (ARC-Lake) are used to calibrate and validate a conceptual model (air2water) and a thermodynamic model (LAKE) for the studied lake, for which in situ observation is limited. The results demonstrate that remotely sensed lake surface water temperature can serve as a valuable surrogate for...
This paper investigates the prediction of different streamflow characteristics in ungauged catchm... more This paper investigates the prediction of different streamflow characteristics in ungauged catchments and under climate change, with three rainfall-runoff models calibrated against three different objective criteria, using a large data set from 780 catchments across Australia. The results indicate that medium and high flows are relatively easier to predict, suggesting that using a single unique set of parameter values from model calibration against an objective criterion like the Nash–Sutcliffe efficiency is generally adequate and desirable to provide a consistent simulation and interpretation of daily streamflow series and the different medium and high flow characteristics. However, the low flow characteristics are considerably more difficult to predict and will require careful modelling consideration to specifically target the low flow characteristic of interest. The modelling results also show that different rainfall-runoff models and different calibration approaches can give sig...
Baseflow is the portion of streamflow that originates from groundwater. It is pivotal to groundwa... more Baseflow is the portion of streamflow that originates from groundwater. It is pivotal to groundwater supply as well as the interactions between groundwater and surface water. In the Loess Plateau of China, the baseflow plays a fundamental role in sustaining the aquatic ecosystem. Rational estimation of baseflow is of critical importance for understanding the functioning of the groundwater system and informing management of regional water resources. In this study, a two-well parameterised digital filter was used to separate baseflow from observed daily total streamflow on the Weihe River Basin. Two parameters (maximum baseflow index (BFI) and the recession constant) of this filter were estimated using UKIH and a recession analysis with physical meaning, respectively. The results show that the baseflow index increased from the upstream to downstream (0.27-0.32) of the Weihe River, and the baseflow of the river is summer dominant. In general, the baseflow has been increasing gradually ...
Well‐validated rainfall‐runoff models are able to capture the relationships between rainfall and ... more Well‐validated rainfall‐runoff models are able to capture the relationships between rainfall and streamflow and to reliably estimate initial catchment states. While future streamflows are mainly dependent on initial catchment states and future rainfall, use of the rainfall‐runoff models together with estimated future rainfall can produce skilful forecasts of future streamflows. This is the basis for the ensemble streamflow prediction system, but this approach has not been explored in Australia. In this paper, two conceptual rainfall‐runoff models, together with rainfall ensembles or analogues based on historical rainfall and the Southern Oscillation index (SOI), were used to forecast streamflows at monthly and 3‐monthly scales at two catchments in east Australia. The results showed that both models forecast monthly streamflow well when forecasts for all months were evaluated together, but their performance varied significantly from month to month. Best forecasting skills were obtain...
In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate ... more In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate change, but also impose substantial ecohydrological impacts on the local environment. Due to the limitation of ground observation, remote sensing has been used as an alternative tool to investigate recent changes of lake ice phenology. However, uncertainties exist in the remotely sensed lake ice phenology owing to both the data and methods used. In this paper, three different remotely sensed datasets are used to investigate the lake ice phenology variation in the past decade across the Tibetan Plateau, with the consideration of the underlying uncertainties. The remotely sensed data used include reflectance data, snow product, and land surface temperature (LST) data of moderate resolution imaging spectroradiometer (MODIS). The uncertainties of the three methods based on the corresponding data are assessed using the triple collocation approach. Comparatively, it is found that the method ba...
In order to reduce the environmental and ecological problems induced by water resources managemen... more In order to reduce the environmental and ecological problems induced by water resources management and use, this paper proposes a concept of environmenta water requirement. It is defined as the minimum water amount to be consumed by the natural water bodies to conserve its environmental and ecological functions. Based on the definition, the methods for calculating the amount of environmental and ecological water requirement are determined. In the case study on Haihe-Luanhe river system, the water requirement is divided into three parts, i.e., the basic instream flow, water requirement for sediment transfer and water consumption by evaporation of the lakes or everglades. The results of the calculation show that the environmental and ecological water requirement in the river system is about 124x108 m3, including 57x108 m3 for basic in-stream flow, 63x108 m3 for sediment transfer and 4x108 m3 for net evaporation loss of lakes. The total amount of environmental and ecological water requ...
Long-term changes in the water budget of lakes in the Tibetan Plateau due to climate change are o... more Long-term changes in the water budget of lakes in the Tibetan Plateau due to climate change are of great interest not only for the importance of water management, but also for the critical challenge due to the lack of observations. In this paper, the water budget of Nam Co Lake during 1980–2010 is simulated using a dynamical monthly water balance model. The simulated lake level is in good agreement with field investigations and the remotely sensed lake level. The long-term hydrological simulation shows that from 1980 to 2010, lake level rose from 4718.34 to 4724.93 m, accompanied by an increase of lake water storage volume from 77.33 × 109 to 83.66 × 109 m3. For the net lake level rise (5.93 m) during the period 1980–2010, the proportional contributions of rainfall–runoff, glacier melt, precipitation on the lake, lake percolation, and evaporation are 104.7%, 56.6%, 41.7%, −22.2%, and −80.9%, respectively. A positive but diminishing annual water surplus is found in Nam Co Lake, imply...
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