My current focus is how to provide the hydrostratigraphy of volcanic aquifers in Bandung area. The research is based on environmental isotope measurement in groundwater and morphometry. My work consists of hydrochemical measurements. I am using multivariate statistical methods to provides more quantitative foundation for the analysis and more insight into the groundwater behavior, especially its interaction with surface water. I use open source apps like R and Python to do the job. In my spare time, I also have a side project to promote open science in Indonesia's research workflow. One of my current focus is promoting INARxiv, as the first preprint server of Indonesia (osf.io/preprints/inarxiv) and serving as ORCID and OSF (osf.io) ambassador. Research interest: Hydrochemistry, multivariate analysis, and R programming. Blog: dasaptaerwin.net, derwinirawan.wordpress.com. (https://orcid.org/0000-0002-1526-0863)