Dr. Saritha Padiyedath Gopalan

 Brief Details: 

Dr. Saritha Padiyedath Gopalan is working as a Postdoctoral Fellow at the University of Tokyo. She has completed Bachelor of Technology (B. Tech) in Agricultural Engineering from the Kerala Agricultural University in November 2011. She has secured the university level first rank with a CGPA of 8.65 in B. Tech and received the ‘Sardar Patel Outstanding ICAR Institution Award-Endowment Gold Medal’ from the Kerala Agricultural University. In 2011, she appeared for the Graduate Aptitude Test in Engineering (GATE) and secured 90^th Rank in Agricultural Engineering. Soon after B. Tech, She did Master of Technology (M.Tech) in Water Management from the School of Water Resources, IIT Kharagpur from July 2012 to June 2014. She has secured a CGPA of 9.6 out of 10, which was the second best of the department after the top CGPA of 9.61. After graduation, she was interested in continuing her research and pursue PhD from a reputed institution in India or abroad. After applying for a Ph.D. position under the ‘Tokyo Human Resources Fund for City Diplomacy’ scholarship funded by the Tokyo Metropolitan Government, She joined the Hydrology and Water Resources Laboratory of the Department of Civil and Environmental Engineering, Tokyo Metropolitan University, Japan under the supervision of Emeritus Prof. Akira Kawamura in October 2016. Immediately after her PhD graduation in September 2019, She started her 1^st Postdoctoral position at the Centre for Climate Change Adaptation in the National Institute for Environmental Studies, Japan under Dr. Naota Hanasaki from October 2019 to September 2022. Currently, She is working as a Postdoctoral Fellow under Prof. Taikan Oki at the Department of Civil Engineering, University of Tokyo, Japan since October 2022, which is her 2^nd Postdoctoral position. Currently, she have 4.75 years of research experience, excluding the experience gained while pursuing PhD. Due to her Postdoctoral experiences since 2019, She is an expert modeller and have been using the H08 global hydrological model, which is based on Fortran and Shell languages. Her other software skills include MATLAB, Origin Pro, ArcGIS, QGIS, Python, R programming, etc. She also have experience in developing a new model, improving the existing model, and analysing large-scale databases. She is very much excited to start a new phase in her career in the reputed institutions in India, where she can disseminate the so far acquired knowledge.

Research: Human-water interaction modelling with explicit expressions of adaptation measures to cope with future flood and water scarcity

Climate change adaptation has become the current focus of research due to its remarkable potential to alter the spatial and temporal distribution of water availability. Despite this progress globally, what adaptation measures need to be implemented in the water sector are poorly quantified. To the author’s knowledge, a handful of papers have set up their models with infrastructures that are obviously unignorable to reproduce reality and included more than one adaptation option in future impact projection. This fundamental issue can be solved by synchronizing various anthropogenic activities and adaptation measures into the macro-scale hydrological models.

Numerous dams have been constructed in large river basins, but these are seldom explicitly incorporated in distributed hydrological models. H08 is one of the pioneering global hydrological models (GHMs) that integrated natural hydrology and human water usage (e.g., irrigation water withdrawal) and management (e.g., dam operation). Therefore, initially, the possibility of reservoir operation for regulating the future flow from an adaptation viewpoint was evaluated using the H08 GHM with the Chao Phraya River basin (CPRB) as a case study. The H08 model was developed for the CPRB by including nine significant reservoirs and evaluated their impact on river discharge. The results revealed that the changes in the magnitude of future flood flow are likely to be larger than those achieved by reservoir operation, although it can increase low flows in the basin, which indicates the need for further adaptation options.

Another adaptation measure is the water diversion systems that could assuage flood and drought risks by diverting and redistributing water within and among basins. However, the representation of diversion systems into the GHMs remains in the pioneering stage. Without incorporating diversion canals, one cannot reproduce the river flow accurately. Therefore, novel algorithms were developed to express diversion channels and retarding ponds for H08 GHM. The enhanced H08 model with adaptation measures was then applied in the CPRB. A remarkable reduction in the water risk was noted, but the risk cannot be mitigated completely.

Due to the significant impact of climate change on water resources, individual adaptation measures failed to mitigate the risk completely. Hence, we proposed a flexible and efficient way to incorporate a package of multiple adaptation options, termed adaptation portfolio, into the H08 model. We found that the portfolios were primarily effective in mitigating the water scarcity to the present level, but extreme floods may prevail in historically flood-prone regions.

Teaching: Concept of the Unit hydrograph

1.   Theory of unit hydrograph - A unit hydrograph is defined as the hydrograph of direct runoff resulting from one unit depth (1 cm) of rainfall excess occurring uniformly over the basin and at a uniform rate for a specified duration (D hours). The term unit here refers to a unit depth of rainfall excess which is usually taken as 1 cm. The duration, being a very important characteristic, is used as a prefix to a specific unit hydrograph. Thus, one has a 6-h unit hydrograph, 12-h unit hydrograph, etc., and in general, a D-h unit hydrograph applicable to a given catchment. Two basic assumptions constitute the foundations for the unit-hydrograph theory. These are: (i) the time invariance and (ii) the linear response.

2.    Application of unit hydrograph - Using the basic principles of the unit hydrograph, one can easily calculate the direct runoff hydrograph (DRH) in a catchment due to a given storm if an appropriate unit hydrograph is available. Let it be assumed that a D-h unit-hydrograph and the storm hyetograph are available. The initial losses and infiltration losses are estimated and deducted from the storm hyetograph to obtain the effective rainfall hyetograph (ERH). The ERH is then divided into M blocks of D-h duration each. The rainfall excess in each D-h duration is then operated upon the unit hydrograph successively to get the various DRH curves. The ordinates of these DRHs are suitably lagged to obtain the proper time sequence and are then collected and added at each time element to obtain the required net DRH due to the storm.

Google Scholar Link:

https://scholar.google.co.jp/citations?user=U369IlEAAAAJ&hl=en