The data sets contain the monthly rainfall volume from manual rain gauge stations spread across the study area. There are 11 rainfall stations. The rain unit is mm. In addition, the dataset contains the chloride concentration in mg/l of the rainfall, for each month. Blank data (-) means data not available due to not enough rain volume, no rainfall or problems when transporting the samples from Kenya to Barcelona. The data available is only from April 2016 to November 2017. This data is useful to calculate the recharge volume by chloride mass balance (CMB) methodology. https://www.hydrol-earth-syst-sci-discuss.net/11/307/2014/hessd-11-307-2014-print.pdf