Applying the Index of Watershed Integrity to the Western Balkan Region (ISRS 2019)

In 2014, the western Balkans' heaviest recorded rains triggered extensive flooding affecting approximately 29,600 km2, or the equivalent of 75% of thestudy area. Rapid urbanization and the increasing regularity of late-summer droughts in the region likely exacerbated these floods.Study AreaIn response, the Regional Environmental Center (REC) for Central and Eastern Europe and the U.S. Environmental Protection Agency (US EPA) adaptedthe US EPA's Index for Watershed Integrity (U.S. IWI; Flotemersch et al. 2016) for application to the Drin River, Drina River, Skadar Lake and PrespaLake watersheds (Figure 1).The U.S. IWI evaluates six watershed functions (hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity,temperature regulation, habitat provision) based on a suite of 19 stressor variables (e.g., road-stream intersections, atmospheric deposition, impervioussurfaces, fertilizer application) (Thornbrugh et al., 2018). For the western Balkan IWI (W.B. IWI), individual stressors required adaptation to account for theregion's topography, land use trends, and data availability.Stressor AccumulationA key feature of the Index of Watershed Integrity is that scores at any location in a watershed are a product of all cumulative upstream activities. Oncemapped, results can be used to visualize the connections between upstream and downstream stressors and thereby support cooperative managementacross these transboundary watersheds. W.B. IWI scores calculated for the 1084 catchments of the study area indicate high integrity in the Alpine region(central to the study area), and intermediate and low integrity within the Mediterranean and Continental regions (SW and NE of the study area). Further,the W.B. IWI accounts for 64% of the variation in the nitrogen and phosphorus model- "Modelling Nutrient Emissions in River Systems".Management ApplicationsRegulation services, such as river flood mitigation, are most often managed at the international scale while cultural services, such as recreation, are oftenmanaged at the regional or local scale. We present the W.B. IWI values at the Watershed (International or the Index of Watershed Integrity), Catchment(Regional or Functional Component), and Stream (Local or Stressor) scales (Figure 2).Such information provides local, regional and international entities with the ability to deconstruct the W.B. IWI to identify driving stressors and increasetheir effectiveness managing transboundary watersheds.