Analysis of the potential of the Hydromorphological Index for Rivers (HIR) in the hydromorphological assessment of watercourses in the Central European Plain

The assessment of hydromorphological conditions of watercourses is a requirement of the Water Framework Directive (WFD) and of many national river status monitors. This paper evaluates the hydromorphological status of 10 watercourses (30 measurement sections) in Poland based on the calculated multimetric HIR. A new approach to the delineation of the riparian zone of rivers (small watercourses) was proposed. An analysis of the influence of river valley management on the value of HIR and its components was carried out using the statistical methods (descriptive statistics, ANOVA method with Scheffé's test). In addition, an analysis of the relationship between the component the WRH (Hydromorphological Diversity Index) and WPH (Hydromorphology Transformation Index) was performed (Spearman’s Rank Correlation Coefficient). HIR values for the studied watercourse sections ranged from 0.553 to 0.825. WRH values ranged from 27.5 to 75.5 and WPH from 2.0 to 17.5. The results of the basic statistical analyses showed no significant differences between the two riparian zone delineation methods. The one-way ANOVA showed a significant difference in the test significance level of the WRH, WPH and HIR for the riparian zone delineation methods. Spearman's rank correlation analysis confirmed that the WRH parameter has a significant influence on the HIR index. The juxtaposition of the two methods for delineating a river's riparian zone and its influence on the HIR allows for a better understanding of the interdependence between the parameters of this indicator.