scholarly journals The value of water isotope data on improving process understanding in a glacierized catchment on the Tibetan Plateau

2021 ◽  
Author(s):  
Yi Nan ◽  
Lide Tian ◽  
Zhihua He ◽  
Fuqiang Tian ◽  
Lili Shao
Keyword(s):  
Tibetan Plateau ◽  
Isotopic Composition ◽  
Water Samples ◽  
Stream Water ◽  
The Tibetan Plateau ◽  
Snow Cover Area ◽  
Isotope Data ◽  
Process Understanding ◽  
Precipitation Water ◽  
Water Isotope

Abstract. This study integrated a water isotope module into the hydrological model THREW which has been successfully used in high and cold regions. Signatures of oxygen stable isotope (18O) of different water inputs and stores were simulated coupling with the simulations of runoff generations. Isotope measurements of precipitation water samples and global precipitation isotope product, as well as assumed constant isotope signature of ice meltwater were used to force the isotope module. Isotope signatures of water stores such as snowpack and subsurface water were updated by an assumed completely mixing procedure. Fractionation effects of snowmelt and evapotranspiration were modeled in a Rayleigh fractionation approach. The isotope-aided model was subsequently applied for the quantifications of runoff components and estimations of mean water travel time (MTT) and mean residence time (MRT) in the glacierized watershed of Karuxung River on the Tibetan Plateau. Model parameters were constrained by three different combinations of observations including a single-objective calibration using streamflow measurement solely, a dual- objective calibration using both streamflow measurement and MODIS estimated snow cover area, and a triple- objective calibration using additionally isotopic composition of stream water. Modeled MTT and MRT was validated by estimate of a tracer-based sine-wave method. Results indicate that: (1) the proposed model performed quite well on simultaneously reproducing the observations of streamflow, snow cover area, and isotopic composition of stream water, despite that only precipitation water samples were available for tracer input; (2) isotope data helped to estimate more plausible contributions of runoff components (CRCs) to streamflow in the melting season, and improved the robustness of MTT and MRT estimations; (3) involving isotope data for the model calibration obviously reduced uncertainties of the quantification of CRCs and estimations of MTT and MRT, through better constraining the strong competitions among different runoff processes induced by meltwater and rainfall. Our results inform high value of water isotope data on improving process understanding in a glacierized basin on the Tibetan Plateau.

scholarly journals The value of water isotope data on improving process understanding in a glacierized catchment on the Tibetan Plateau

2021 ◽  
Vol 25 (6) ◽  
pp. 3653-3673
Author(s):  
Yi Nan ◽  
Lide Tian ◽  
Zhihua He ◽  
Fuqiang Tian ◽  
Lili Shao
Keyword(s):  
Tibetan Plateau ◽  
Isotopic Composition ◽  
Water Samples ◽  
Stream Water ◽  
The Tibetan Plateau ◽  
Snow Cover Area ◽  
Isotope Data ◽  
Process Understanding ◽  
Precipitation Water ◽  
Water Isotope

Abstract. This study integrated a water isotope module into the hydrological model THREW (Tsinghua Representative Elementary Watershed) which has been successfully used in high and cold regions. Signatures of oxygen stable isotope (18O) of different water inputs and stores were simulated coupling with the simulations of runoff generation. Isotope measurements of precipitation water samples and assumed constant isotope signature of ice meltwater were used to force the isotope module. Isotope signatures of water stores such as snowpack and subsurface water were updated by an assumed completely mixing procedure. Fractionation effects of snowmelt and evapotranspiration were modeled in a Rayleigh fractionation approach. The isotope-aided model was subsequently applied for the quantification of runoff components and estimations of mean water travel time (MTT) and mean residence time (MRT) in the glacierized watershed of Karuxung river on the Tibetan Plateau. Model parameters were calibrated by three variants with different combinations of streamflow, snow cover area and isotopic composition of stream water. Modeled MTT and MRT were validated by estimates of a tracer-based sine-wave method. Results indicate that (1) the proposed model performs well on simultaneously reproducing the observations of streamflow, snow cover area and isotopic composition of stream water, despite the fact that only precipitation water samples were available for tracer input; (2) isotope data facilitate more robust estimations on contributions of runoff components (CRCs) to streamflow in the melting season, as well as on MTT and MRT; (3) involving isotope data for the model calibration obviously reduces uncertainties in the quantification of CRCs and estimations of MTT and MRT, through better constraining the competitions among different runoff processes induced by meltwater and rainfall. Our results inform scientists on the high value of water isotope data for improving process understanding in a glacierized basin on the Tibetan Plateau.

scholarly journals Can we use precipitation isotope outputs of Isotopic General Circulation Models to improve hydrological modeling in large mountainous catchments on the Tibetan Plateau?

2021 ◽  
Author(s):  
Yi Nan ◽  
Zhihua He ◽  
Fuqiang Tian ◽  
Zhongwang Wei ◽  
Lide Tian
Keyword(s):  
Tibetan Plateau ◽  
General Circulation ◽  
Hydrological Modeling ◽  
General Circulation Models ◽  
Model Parameters ◽  
The Tibetan Plateau ◽  
Cold Regions ◽  
Isotope Data ◽  
Mountainous Catchments ◽  
Macro Scale

Abstract. Issues related to large uncertainty and parameter equifinality have posed big challenges for hydrological modeling in cold regions where runoff generation processes are particularly complex. Tracer-aided hydrological models coupling modules to simulate the transportation and fractionation of water stable isotope are increasingly used to constrain parameter uncertainty and refine the parameterizations of specific hydrological processes in cold regions. However, commonly unavailability of site sampling of spatially-distributed precipitation isotope hampers the practical applications of tracer-aided models in large scale catchments. This study, taken the precipitation isotope data (isoGSM) derived from the Isotopic General Circulation Models (iGCM) as an example, explored its utility in driving a tracer-aided hydrological model in the Yarlung Tsangpo River basin (YTR, around 2 × 105 km2) on the Tibetan Plateau (TP). The isoGSM product was first corrected based on the biases between gridded precipitation isotope estimates and limited site sampling measurements. Model simulations driven by the corrected isoGSM data were then compared with those forced by spatially interpolated precipitation isotope from site sampling measurements. Our results indicated that: (1) spatial precipitation isotope derived from the isoGSM data helped to reduce modeling uncertainty and improve parameter identifiability in a large mountainous catchment on the TP, in comparison to a calibration method using discharge and snow cover area fraction without any information of water isotope; (2) model parameters estimated by the corrected isoGSM data presented higher transferability to nested sub-basins and produced higher model performance in the validation period than that estimated by the interpolated precipitation isotope data from site sampling measurements; (3) model calibration procedure forced by the corrected isoGSM data successfully rejected parameter sets that overestimated glacier melt contribution and gave more reliable contributions of runoff components, indicating the corrected isoGSM data served as a better choice to provide informative spatial precipitation isotope than the interpolated data from site sampling measurements at macro scale. This work suggested plausible utility of combining isoGSM data with measurements from a sparse sampling network in improving hydrological modeling in large mountainous catchments.

scholarly journals Can we use precipitation isotope outputs of isotopic general circulation models to improve hydrological modeling in large mountainous catchments on the Tibetan Plateau?

2021 ◽  
Vol 25 (12) ◽  
pp. 6151-6172
Author(s):  
Yi Nan ◽  
Zhihua He ◽  
Fuqiang Tian ◽  
Zhongwang Wei ◽  
Lide Tian
Keyword(s):  
Tibetan Plateau ◽  
General Circulation ◽  
Hydrological Modeling ◽  
General Circulation Models ◽  
Model Parameters ◽  
The Tibetan Plateau ◽  
Global Spectral Model ◽  
Cold Regions ◽  
Isotope Data ◽  
Macro Scale

Abstract. Issues related to large uncertainty and parameter equifinality have posed big challenges for hydrological modeling in cold regions where runoff generation processes are particularly complicated. Tracer-aided hydrological models that integrate the transportation and fractionation processes of water stable isotope are increasingly used to constrain parameter uncertainty and refine the parameterizations of specific hydrological processes in cold regions. However, the common unavailability of site sampling of spatially distributed precipitation isotopes hampers the practical applications of tracer-aided models in large-scale catchments. This study, taking the precipitation isotope data (isotopes-incorporated global spectral model – isoGSM) derived from the isotopic general circulation models (iGCMs) as an example, explored its utility in driving a tracer-aided hydrological model in the Yarlung Tsangpo River basin (YTR; around 2×105 km2, with a mean elevation of 4875 m) on the Tibetan Plateau (TP). The isoGSM product was firstly corrected based on the biases between gridded precipitation isotope estimates and the limited site sampling measurements. Model simulations driven by the corrected isoGSM data were then compared with those forced by spatially interpolated precipitation isotopes from site sampling measurements. Our results indicated that (1) spatial precipitation isotopes derived from the isoGSM data helped to reduce modeling uncertainty and improve parameter identifiability in a large mountainous catchment on the TP, compared to a calibration method using discharge and snow cover area fraction without any information on water isotopes; (2) model parameters estimated by the corrected isoGSM data presented higher transferability to nested subbasins and produced higher model performance in the validation period than that estimated by the interpolated precipitation isotope data from site sampling measurements; (3) model calibration forced by the corrected isoGSM data successfully rejected parameter sets that overestimated glacier melt contribution and gave more reliable contributions of runoff components, indicating the corrected isoGSM data served as a better choice to provide informative spatial precipitation isotope than the interpolated data from site sampling measurements at the macro scale. This work suggested plausible utility of combining isoGSM data with measurements, even from a sparse sampling network, in improving hydrological modeling in large high mountain basins.

scholarly journals The isotopic composition and fluxes of particulate organic carbon exported from the eastern margin of the Tibetan Plateau

2019 ◽  
Vol 252 ◽  
pp. 1-15 ◽  
Author(s):  
Jin Wang ◽  
Robert G. Hilton ◽  
Zhangdong Jin ◽  
Fei Zhang ◽  
Alexander L. Densmore ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Organic Carbon ◽  
Isotopic Composition ◽  
Particulate Organic Carbon ◽  
The Tibetan Plateau ◽  
Eastern Margin
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