River lengths in Croatia determined from a topographic map at a scale of 1:25,000

This study presents methodologically consistent length measurements of rivers with a total length of 40 kilometres or more in the Republic of Croatia. These measurements were performed by vectorising river channels from a topographic map at a scale of 1:25,000. Contemporary orthophoto maps were used as additional cartographic sources for verification. The approaches used to determine the starting and ending points of rivers, i.e. sources and mouths or confluences, have been explained and their spatial coordinates were listed. The results showed that in terms of total river length, the 21 rivers in this study differed from the available official data by less than 5%. Considerable differences were found for rivers where significant river engineering works had been carried out to channelize and divert flow, as well as for rivers in the Adriatic Basin where there have been methodological differences in determining the river mouth, and for large lowland rivers where changes in channel planform are common due to natural dynamics and engineering interventions. Moreover, this research revealed that the longest Croatian river, with its source, confluence, and both river banks situated entirely within the territory of Croatia, is the Karašica River, with a total length of 148 km.