The participation of non-scientist local stakeholders in scientific processes that involve data collection, interpretation, and analysis is generally known as citizen science (CS). CS is receiving increasing attention in many disciplines. Hydrology remains a highly data-scarce; in many regions, if data exists, the lengths of the time series are not sufficient. To adequately manage water resource, the application of CS in hydrology (observation of water levels, precipitation and water availability etc.) is a great contribution to help reduce hydrological data gap. The increased availability of Information and Communication Technology (ICT) - in particular, mobile phone - opens up new ways of data acquisition and dissemination.

Smartphones for water (S4W)-Nepal has started CS utilizing mobile technology for hydrological data measurement. This paper has attempted to analyse S4W-Nepal CS based precipitation data of Kathmandu valley for the year 2017. Altogether 139 stations (volunteer observations) placed at different locations of the valley are utilized. The average no. of days with precipitation recorded in a station is found to be 35 days. Almost 40% of the stations shows the precipitation recorded days <= 10 days. 20 stations have recorded the precipitation for more than 75 days. In any case, huge spatial gaps for local variability are fulfilled by these data.

This paper attempts to compare day wise CS data with national hydro-met data (maintained by Department of Hydrology and Meteorology) and satellite-based rainfall product obtained from soil moisture data through the SM2RAIN algorithm (Brocca et al., 2014). This rainfall product has daily temporal resolution, 12.5 km spatial resolution and is available for the year 2017. With this comparison, the reliabilities of these data could be tested.

Note: The day wise comparison is still going on. The final results will be shared during the presentation.