I'm thinking of using Precipitation Runoff Modelling System (PRMS) model to simulate and predicts climate variability and river discharge relationship, but I may wish to have more suggest as to the best model to use in this study
The SPI drought index is also used for this purpose. In the same way, you can use SPEI.
Zhai, J., Su, B., Krysanova, V., Vetter, T., Gao, C., & Jiang, T. (2010). Spatial variation and trends in PDSI and SPI indices and their relation to streamflow in 10 large regions of china. Journal of Climate, 23(3), 649–663.
Beguería, S., Vicente-Serrano, S. M., Reig, F., & Latorre, B. (2014). Standardized precipitation evapotranspiration index (SPEI) revisited: Parameter fitting, evapotranspiration models, tools, datasets and drought monitoring. International Journal of Climatology, 34(10), 3001–3023.
VIC (Liang et al., 1994) is a macroscale hydrologic model that solves full water and energy balances, originally developed by Xu Liang at the University of Washington. VIC is a research model and in its various forms it has been applied to most of the major river basins around the world, as well as globally.