On how rainfall characteristics affect the sizing of rain barrels in Slovakia

The study area (Slovakia) is to a great extent a part of the Carpathian mountainous system, where lowlands dominate the southwest and southeast of the region and are part of the Pannonian basin. Rainwater harvesting can reduce vulnerability of urban areas to climate change by storing water for rainless periods and by reducing surface runoff. The efficiency and reliability of water harvesting systems depends on the local climate. Analysing rainfall characteristics is therefore essential for a proper sizing of any rainwater collecting project. A total of 84 rainfall records from climatologically distinct regions of Slovakia were separated into statistically independent episodes to derive event-based statistical characteristics. A considerable spatial and seasonal variability has been observed in the statistics of rainfall events. Inter-event times decrease with elevation, whereas event volume and annual incidence of rainfall events increase with elevation. The applicability of the derived rainfall statistics was illustrated by simulations for a typical residential house using the analytical probabilistic approach. Empirical relationships between tank size and site elevation have been a developed to estimate tank sizes for un-gauged locations. The simulations show that rain barrels in the southern parts of Slovakia require larger storage capacities than those located in the mountainous regions. The presented annual and seasonal estimates of rainfall characteristics are published for the first time.