Research interests | Current Research | Past Research | Publications
Research Interests:
- Model-Data Integration of carbon and water cycles.
- Process-based model developed to quantify (model-)structural and observational uncertainties.
- Quantification of global water and carbon budget over land.
- Groundwater's importance as a water resource. It's relevance to ecosystems.
Current Research:
- Development of data-driven modeling framework for water-carbon relations
- Groundwater-vegetation interactions across spatiotemporal scales
Past research:
| Global scale land surface modeling with water table dynamics |
- Groundwater affects the partitionings of runoff and evapotranspiration. By acting as an additional source of moisture, it can affect the soil moisture and consequently ET, as well as provide low flow in the rivers. The effect on surface energy balance is, however, controlled by climate, soil, and vegetation conditions. The arid-to-wet transition regions of the world are the most sensitive to groundwater moisture flux. The influence is quantitatively significant in regions with conspicuous dry season, when the ET is limited by moisture.
| Impact of climate change in riparian flood and droughts |
- The climate change driven by anthropogenic green house gas emissions will intensify the hydrological cycle. As such, the extreme hydrological events are projected to occur more frequently in future. Using the latest outputs from CMIP5 model projections, the frequency of large floods (with > 100 years return period) are projected to increase in most of Africa, Asia, and North and South America, and decrease in southern Europe. In 11% of the world, high flow will increase, and low flow will decrease potentially affecting 11% of global population.
More detailed description of my past research can be found here.
Selected Publications
Peer-reviewed
| Koirala, S., H. Kim, Y. Hirabayashi, S. Kanae, and T. Oki, Sensitivity of global hydrological simulations to groundwater capillary flux parameterizations, Water Resources Research, doi:10.1029/2018WR023434, 2018. |
| Jung, M., Koirala, S., Weber, U., Ichii, K., Gans, F., Papale, D., ... & Reichstein, M. (2018). The FLUXCOM ensemble of global land-atmosphere energy fluxes. arXiv preprint arXiv:1812.04951. |
| Trautmann, T., Koirala, S., Carvalhais, N., Eicker, A., Fink, M., Niemann, C., & Jung, M. (2018). Understanding terrestrial water storage variations in northern latitudes across scales. Hydrology and Earth System Sciences, 22(7), 4061-4082. |
| Lim, W. H., Yamazaki, D., Koirala, S., Hirabayashi, Y., Kanae, S., Dadson, S. J., & Sun, F. (2018). Long‐term changes in global socioeconomic benefits of flood defenses and residual risk based on CMIP5 climate models. Earth's Future. |
| Koirala, S., Jung, M., Reichstein, M., de Graaf, I. E. M., Camps-Valls, G., Ichii, K., Papale, D., Raduly, B., Schwalm, C. R., Tramontana, G., Carvalhais, N., Global distribution of groundwater-vegetation spatial covariation. Geophysical Research Letters.44, 4134–4142, 2017. |
| Ikeuchi, H., Y. Hirabayashi, D. Yamazaki, M. Kiguchi, S. Koirala, T. Nagano, A. Kotera, and S. Kanae, Modeling complex flow dynamics of fluvial floods exacerbated by sea level rise in the Ganges- Brahmaputra-Meghna Delta, Environmental Research Letters, 10(12): 124011, 2015. |
| Pokhrel, Y., S. Koirala, P. J.-F. Yeh, N. Hanasaki, L. Longuevergne, S. Kanae, and T. Oki, Incorporation of Groundwater Pumping in a Land Surface Model with the Representation of Human Impacts, Water Resources Research, 51(1), 78–96, 2015. |
| Yoshikawa S., A. Yanagawa, Y. Iwasaki, P. Sui, S. Koirala, K. Hirano, A. Khajuria, R. Mahendran, Y. Hirabayashi, C. Yoshimura, and S. Kanae, Illustrating a new global-scale approach to estimating potential reduction in fish species richness due to flow alteration,Hydrol. Earth Syst. Sci., 18, 621-630, 2014. |
| Koirala, S., Y. Hirabayashi, M. Roobavannan, and S. Kanae, Global assessment of agreement among streamflow projections using CMIP5 model outputs, Environmental Research Letters, 9(6), 064017, 2014. |
| Koirala, S., P. J.-F. Yeh, Y. Hirabayashi, S. Kanae, and T. Oki, Global-scale land surface hydrologic modeling with the representation of water table dynamics, Journal of Geophysical Research Atmosphere, 119, doi:10.1002/2013JD020398, 2014. |
| Hirabayashi, Y., R. Mahendran, S. Koirala, L. Konoshima, D. Yamazaki, S. Watanabe, H. Kim and S. Kanae, Global flood risk under climate change, Nature Climate Change, 3(9), 816-821, 2013. |
| van Huijgevoort M., P. Hazenberg, H. van Lanen, R. Teuling, D. Clark, S. Folwell, S. Gosling, N. Hanasaki, J. Heinke, S. Koirala, T. Stacke, F. Voss, J. Sheffield, R. Uijlenhoet, Global multi-model analysis of drought in runoff for the second half of the 20th century, Journal of Hydrometeorology, 14, 1535–1552, 2013. |
| Hirabayashi Y., Y. Zhang, S. Watanabe, S. Koirala and S. Kanae, Projection of glacier mass changes under a high-emission climate scenario using the global glacier model HYOGA2, Hydrological Research Letters, 7(1), 6-11, 2013. |
| Koirala, S., H. Yamada, P. J.-F. Yeh, T. Oki, Y. Hirabayashi, and S. Kanae, Global simulation of groundwater recharge, water table depth, and low flow using a land surface model with groundwater representation, Annual Journal of Hydraulic Engineering, Japan Society of Civil Engineers, 56, 2012. |
| Yamada, H., S. Yoshikawa, S. Koirala, and S. Kanae, Spatial and temporal estimation of global water withdrawals from 1950 to 2000 based on statistical data, Annual Journal of Hydraulic Engineering, Japan Society of Civil Engineers, 56, 2012. |
| Gudmundsson, L., L. M. Tallaksen, K. Stahl, E. Dumont, D.B. Clark, S. Hageman, N. Bertrand, D. Gerten, N. Hanasaki, J. Heinke, F. Voss, S. Koirala, Comparing large-scale hydrological model simulations to observed runoff percentiles in Europe, Journal of Hydrometeorology, 13, 604-620, 2012. |
| Pokhrel, Y., N. Hanasaki, S. Koirala, J. Cho, P. J.-F. Yeh, H. Kim, S. Kanae, and T. Oki, Incorporating anthropogenic water regulation modules into a land surface model, Journal of Hydrometeorology, 13, 255-269, 2012. |
| Ingjerd, H., S. Koirala, and Co-authors, Multi-model estimate of the global water balance: Setup and first results, Journal of Hydrometeorology, Vol. 12, 869–884, October, 2011. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae, Fully dynamic groundwater representation in the MATSIRO land surface model, Annual Journal of Hydraulic Engineering, Japan Society of Civil Engineers, 54, 2010. |
| Pokhrel, Y., N. Hanasaki, S. Koirala, S. Kanae, and T. Oki, Extreme river discharge under present and future climate conditions using high-resolution climate model data, Annual Journal of Hydraulic Engineering, Japan Society of Civil Engineers, 54, 2010. |
Conference Presentations
| Koirala, S., M. Jung, N. Carvalhais, S. Kanae, T. Oki, and M. Reichstein, Spatio-temporal covariation of evapotranspiration, plant productivity, and groundwater dynamics, AGU Fall Meeting, 15-19 Dec. 2014, San Francisco, USA. |
| Koirala, S., M. Jung, N. Carvalhais, I. De Graaf, and M. Reichstein, Controls of groundwater dynamics and climate on evapotranspiration at the global scale, 7th International Scientific Conference on the Global Water and Energy Cycle, 14-17 July 2014, The Hague, The Netherlands. |
| Koirala, S., Y. Hirabayashi, M. Roobavannan, and S. Kanae, Changes in Streamflow Percentiles under Climate Change, AGU Fall Meeting, 9-13 Dec. 2013, San Francisco, USA. |
| Oki, T., Y. Pokhrel, N. Hanasaki, S. Koirala, and S. Kanae, , Non-renewable water use on the globe and its implication to sea level change, AGU Fall Meeting, 3-7 Dec. 2012, San Francisco, USA (Invited). |
| Pokhrel, Y., S. Koirala, N. Hanasaki, P. J.-F. Yeh, S. Kanae, and T. Oki, Estimating global groundwater withdrawal and depletion using an integrated hydrological model, GRACE, and in situ observations,AGU Fall Meeting, 3-7 Dec. 2012, San Francisco, USA (Invited). |
| Koirala, S., Y. Hirabayashi, P. J.-F. Yeh, S. Kanae, and T. Oki,Uncertainties In Global Modeling Of Groundwater-induced Increase in Evapotranspiration, AGU Fall Meeting, 3-7 Dec. 2012, San Francisco, USA. |
| Koirala, S. and Y. Hirabayashi, Effect of Soil Texture Classification on Global Hydrology, Proceedings of Annual Conference, Japan Society of Hydrology and Water Resources, Sep. 2012, Hiroshima, Japan. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae, Climate-soil-vegetation control on groundwater-supplied evapotranspiration in the global modeling context, World Climate Research Programme- Open Science Conference, October, 2011. |
| Koirala, S., H. Yamada, P. J.-F. Yeh, T. Oki, and S. Kanae, Global-scale modeling of groundwater recharge and water table depth using a land surface model with groundwater representation, Japan Geoscience UnionMeeting, 2011. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae,Evaluating influence of groundwater-supplied moisture flux in global land surface hydrologic simulations, AGU Fall Meeting, 13-17 Dec. 2010, San Francisco, USA. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae, Parameter estimation of a groundwater representation applicable in a global-scale land surface model, Proceedings of Annual Conference, Japan Society of Hydrology and Water Resources, Sep. 2010, Tokyo, Japan. |
| Koirala, S., P. J.-F. Yeh, S. Kanae, T. Oki, Analysis of groundwater-supplied evapotranspiration in global-modeling context, 2nd International Conference on Hydrology delivers Earth System Science to Society, June 2010, Tokyo, Japan. |
| Koirala, S., P. J.-F. Yeh, S. Kanae, and T. Oki, Explicit representation of groundwater process in a global-scale land surface model to improve the prediction of water resources, European Geosciences Union General Assembly, May 2010, Vienna, Austria. |
| Koirala, S., P. J.-F. Yeh, S. Kanae, and T. Oki, Estimation of groundwater-supplied evapotranspiration in the global modeling context, International Workshop on Global Change Projection: Modeling and Impact Assessment, Feb. 2010, Tsukuba, Japan. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae, The parameterization of saturated-unsaturated zone interaction in the estimation of land surface hydrological fluxes, Proceedings of Annual Conference, Japan Society of Hydrology and Water Resources, Aug. 2009, Kanazawa, Japan. |
| Koirala, S., P. J.-F. Yeh, H. Kim, S. Kanae, and T. Oki, Global hydrological simulation using MATSIRO-TRIP land surface model with groundwater representation, AGU Fall Meeting, 15-19 Dec. 2008, San Francisco, USA. |
| Koirala, S., P. J.-F. Yeh, T. Oki, and S. Kanae, A parameter estimation scheme applicable to global-scale land surface modeling (in preparation). |
| Yeh, P. J.-F., T. Oki, S. Koirala, and S.Kanae,Estimation of terrestrial water storage from global hydrological modeling, GRACE and land-atmosphere water balance analysis, World Climate Research Programme- Open Science Conference, October, 2011. |
| Pokhrel, Y., S. Koirala & co-authors, Simulating the effects of irrigation pumping on global groundwater depletion, World Climate Research Programme- Open Science Conference, October, 2011. |
| Yeh, P. J.-F., M. Yuan, H. Kim, S. Koirala, Y. Pokhrel and T. Oki, Characterization of long-term atmospheric and terrestrial hydrological cycle change using multiple data sources, AGU Fall Meeting, 13-17 Dec. 2010, San Francisco, USA. |
| Pokhrel Y., N. Hanasaki, S. Koirala, S.Kanae and T. Oki,Assessing the influence of human activities on global water resources using an advanced land surface model, AGU Fall Meeting, 13-17 Dec. 2010, San Francisco, USA. |
| Koirala, S., and N. M. Shakya, Impact of urbanization in Bagmati River basin, 2005,Proceedings of Annual Conference for Purely Ungauged Basin, 2005, Kathmandu, Nepal. |
| Kim, H., T. Oki, J. Cho, S. Koirala, S. Kanae, and P. J.-F. Yeh, Estimation of uncertainty in ensemble land surface simulations, 2nd International Conference on Hydrology delivers Earth System Science to Society, June 2010, Tokyo, Japan. |
| Pokhrel, Y., N. Hanasaki, S. Koirala, S. Kanae & T. Oki, Incorporating anthropogenic water flow assessment modules into a Land Surface Model, 2nd International Conference on Hydrology delivers Earth System Science to Society, June 2010, Tokyo, Japan. |
