This repository contains the processed datasets, Python scripts, figure-source data, model inventory records, figures, tables, software requirements, and documentation supporting the associated study of climate variability, extreme rainfall, and rainwater harvesting system performance. The repository includes reproducible workflows for observed-rainfall preparation, climate-model screening, seasonal peaks-over-threshold and generalized Pareto analyses, bias-correction diagnostics, historical and future rainwater harvesting simulations, variance partitioning, and bootstrap sensitivity analysis. Original CHIRPS archives, CORDEX NetCDF files, and restricted gauge observations are not redistributed; processed analytical derivatives required to reproduce the principal figures and tables are included.