Estimation of a Suitable Range of Discharges for the Development of Instream Flow Recommendations

Abstract

Hydrological variability is of great importance for water resources management. Regardless of how rivers are individually managed, numerous research studies have concluded that aquatic organisms are highly dependent on flow regime variability. Nevertheless, natural streamflow regimes are being altered due to human-induced pressures and climate change/variability, and sufficient biological information in not incorporated in efforts to minimize these effects. Thus, there is an urgent need to develop sustainable environmental flow management guidelines to manage the risk associated with alterations to the flow regime particularly in areas where flow-ecology relationships have not been well studied. This study focuses on a stream with high natural flow regime variability, typical in Mediterranean countries. The major finding of this work is that the estimated Suitable Range of Discharges (SRD) could better address environmental water requirements, rather than simply allocating single value minimum ecological flows. SRD was estimated using advocate statistical analysis of hydrological data series, coupled with habitat suitability models to balance the trade-offs between natural flow variability and human water needs. Combination of the aforementioned approaches was made using the West Balkan trout as a biological component which is a very important species for the quantification of environmental flows. Overall implementation of SRD during dry season is likely to provide large habitat areas for 58 to 67% of the time for the small-size fish and 35 to 55% of the time for the large-size West Balkan trout, according to the Weighted Usable Area0.5 threshold index.