Simplified method for rainwater harvesting tank sizing using long day-resolution rainfall time series

This work aims to develop a simplified method for rainwater harvesting tank sizing using long dayresolution rainfall time series. The developed method, also considers heterogeneous contributing catchments and water demand flow rates. In order to estimate the tank capacities it is proposed to take into account the probability to supply the water demand, as well as the most probable time step needed and their respective variabilities. This method was applied to a specific case study (campus of the Pontificia Universidad Javeriana, Bogota –PUJ– university rainwater harvesting tank sizing), with 73 years of daily-resolution rainfall information (between 1936 and 2010, without years 1969 and 1988 with no data). The method was applied using different time periods from data-set and the results obtained are: (i) for the whole data series - 76 years: 395 m3 (28 days, probability: 78%); (ii) for the last ten years: 494 m3 (35 days, probability: 89%); (iii) for the last five years: 346 m3 (25 days, probability: 84%); (iv) for the last year: 155-198 m3 (11-14 days, probability: 89-90%).