Altered precipitation characteristics in two Polish Carpathian basins, with implications for water resources

I investigated changes in long-term characteristics of precipitation and river flow, as well as changes in their repeatability over a 60 yr period (1955-2014). The study area is located in the Western Carpathians in Poland, a region with highly dynamic hydrological processes. This region is crucial for fresh water availability in the country, providing a considerable volume of runoff, which affects the magnitude of river flow across Poland. I identified significant changes in precipitation for 5 months (March, May, July, August and September), as well as largely consistent changes in long-term river flow in the studied mountain river catchments. I also investigated the repeatability of precipitation and river flow (discharge) processes from year to year by using a coefficient of repeatability (CR), a relative measure that is useful in estimating the extent to which a process behaves reproducibly. While there was a generally high repeatability of precipitation, relative to stream flows, a decrease of several percent (6.2-8.6%) in repeatability was observed for both variables for the most recent 30 yr period (1985-2014), in comparison with the preceding 30 yr. This decrease in the repeatability of the 2 considered variables seems undesirable from both a water management perspective and a predictive perspective. Overall, the marked changes in stream flow characteristics, largely consistent with changes in precipitation characteristics, imply the need for adaptive management of water resources in the studied region, especially during summer months.