The floodplain index, an effective tool for indicating landscape level hydrological changes in the Danube river inundation area
Šporka, Ferdinand; Krno, Iľja; Matečný, Igor; Beracko, Pavel; Kalaninová, Daniela
published: Oct 1, 2016
published online: Oct 7, 2016
manuscript accepted: Sep 10, 2016
manuscript received: Mar 22, 2016
ArtNo. ESP141018804000, Price: 29.00 €
Abstract Floodplain habitats are a functionally very important part of the landscape in large alluvial rivers. Yet, methods for their ecological assessment are poorly known. In the current article, we present the evaluation of the ecological development of the middle section of the Danube (between rkm 1804 and rkm 1841) as related to the Gabčíkovo water works, which had a significant impact on the hydromorphology of the Danube in Slovakia. At our seven sites (two in the main channel, two in the parapotamal side arms and three in the plesiopotamal side arms), we evaluated the ecological state by calculating the floodplain index (FI) based on benthic Oligochaeta, Polychaeta, Isopoda, Amphipoda and Mysidacea over a long-term period (1990 –1997). Change-point analysis was used to evaluate the development of the FI, which closely reflected discharge related changes. We identified three main patterns: 1) The major changes were associated with a shift of the FI values by one or more habitat zones, especially after damming in 1993: Considerable water level decline caused the increase of the FI values by one habitat zone at the Istragov parapotamal site and in the eupotamal Danube lower stretch (which shifted even to the plesiopotamal zone after 1996). On the contrary, a shift from the original parapotamal to eupotamal zone indicated the decreased FI values in the Bodícka brána after this arm became free-flowing in 1996. 2) The minor changes accompanied only a slight water level decline in the Danube upper stretch, maintaining the FI values in the original eupotamal zone. Similarly, the fluctuating FI values form parapotamal to plesiopotamal in the Kráľovská lúka site, reflecting the alternating presence/absence of a water connection with the adjacent anabranch system, did not show any obvious trend. 3) No changes were found at the Sporná sihoť, where hydromorphological conditions remained relatively stable during the whole monitored period. The FI thus proved to be highly effective for the indication of spatial and temporal changes in hydrological connectivity, based on the selected taxa groups. Our results suggest that the FI can be used as an important tool to assess the ecological state of the floodplain systems of large alluvial rivers.