Dendrohydrological Reconstructions Based on Tree-Ring Width (TRW) Chronologies of Narrow-Leaved Ash in the Sava River Basin (Croatia)

Abstract

Current flood risk management is based on statistical models and assessments of the risk of occurrence over a given time period, although with very short measurement periods, usually following catastrophic events. Ongoing monitoring of basic hydrological (river-water level and streamflow) and climate data are the basis for sustainable water management and long-term flood control planning. The lack of data has proven to be particularly negative during this period of global climate change, when non-seasonal flooding (during summer) is becoming increasingly frequent, and the resulting damage greater. The aim of this study was to analyse the possible use of tree ring width chronologies of trees growing in floodplain areas to reconstruct hydrodynamic variables (river-water level and streamflow). The study analysed the influence of climatic and hydrological variables on the growth of narrow-leaved ash (Fraxinus angustifolia Vahl) in the Sava River basin. The results indicate the significant potential of narrow-leaved ash tree-ring width chronologies to reconstruct the summer streamflows of the Sava River (R2 = 0.45). These results can serve to develop long-term data series on the summer streamflows of the river, thereby enabling better insight into its spatial and temporal dynamics with the goal of more successful, sustainable management of floodplain areas.

Streamflow Reconstructions Using Tree-Ring-Based Paleo Proxies for the Sava River Basin (Slovenia)

“…Of note, positive and significant correlations were observed for scPDSI and streamflow from March to October. The correlations of July scPDSI (and August scPDSI) and streamflow exceeded those observed with the correlations of the narrow-leaved ash tree-ring chronology and streamflow for the same months [7]. Thus, reconstructed scPDSI should be considered a proxy to develop SRB streamflow reconstructions.…”

“…The research consisted of collecting samples, developing a new tree-ring chronology for narrow-leaved ash trees, and correlating the tree-ring chronology with both monthly and seasonal streamflow from a gauge near Jasenovac (Croatia). Significant (positive) correlations were identified between May, July, and August streamflow and the narrow-leaved ash tree-ring chronology, while the May-June-July-August (MJJA) fourmonth streamflow season showed similarly significant and stable correlations [7]. Of note, positive and significant correlations were observed for scPDSI and streamflow from March to October.…”

“…In addition to precipitation, temperature, and streamflow records, [5] incorporated data from the Old Water Drought Atlas (OWDA) [6], which includes soil moisture data, specifically the self-calibrated Palmer Drought Severity Index (scPDSI) developed from summer-related tree-ring proxies dating from 0 to 2012. Perhaps the most important contribution to date in this region has been the reconstruction of SR summer streamflow in Croatia [7].…”

“…Ref. [7] stated that "to the extent of our knowledge, no such reconstructions have been conducted in Southeast Europe", thus highlighting the novelty and importance of their research efforts. The research consisted of collecting samples, developing a new tree-ring chronology for narrow-leaved ash trees, and correlating the tree-ring chronology with both monthly and seasonal streamflow from a gauge near Jasenovac (Croatia).…”

“…Skillful streamflow reconstructions in the United States [12,13] and northern Italy [14,15] used the tree-ring-derived reconstructed scPDSI [6] as a proxy. Given the significant and positive correlation between scPDSI and SR streamflow [7], we will use the scPDSI as a reconstruction proxy to evaluate seasonal streamflow reconstruction potential in the SR. Thus, a contribution of the current research was the first-known streamflow reconstruction of SR headwaters (Slovenian gauges).…”