Dear Dr Singh. This is question we often get asked and there is a very handy method for considering the size and computing the chances that such a pond will run dry (climate variability) and how big it may need to be to reduce the risk of it running dry (with the proviso that some climate events are beyond management for some types of infrastructure i.e. you may not be able to build a small farm-based reservoir big enough for your purposes if drought runs for years (California until recently). We have a software product and impact model that considers historical daily rainfall patterns, size of catchment area, yield required (how much irrigation water you wish to extract) and how much risk you wish to carry for the pond running dry. Not only does the tool help to define the size (storage volume) of the reservoir it can be run with the consideration of climate change with a full range of GCM/RCM data (we have post processed that for all countries and regions) that is used to perturb historical rainfall data from your local area (that data is derived from a number of sources depending on your location). Get in touch with us for a demo version of the software info@climsystems.com. We have published papers and full documentation available. All the best. Peter