The Effect of Flow Regulation on the Spatial Distribution and Dynamics of Channel Geomorphic Units (CGU’s) in the Soča River, Slovenia.

This research examines the impact of flow regulation on the spatial distribution and dynamics of physical habitats or channel geomorphic units (CGU) of the Soca River, an upland river system in Slovenia. In order to assess the impact of flow alteration on the spatial pattern of CGU type, size, hydraulics and distribution, a river channel survey was completed along three reaches (totalling 14.3km), i.e. an unregulated stretch and two regulated reaches (with reduced flows). In addition, one regulated reach was re-surveyed at different discharges to investigate the dynamics of CGU’s and their relationship with flow. CGU’s were classified and mapped on foot and from a boat using a combination of visual assessment and physical measurements of velocity and depth in each CGU. Mapping-grade GPS was used to locate CGU boundaries to sub-metre accuracy, and the application of GIS (MapInfo) enabled the description and analysis of the longitudinal distribution of CGU’s along each reach. The effect of flow regulation on the hydraulic character of the river becomes apparent by highlighting significant differences in the dominant types of CGU’s present between the regulated and unregulated reaches. Reduced flows from river regulation also significantly reduces the size of CGU’s, alters their hydraulic character, and affects the longitudinal distribution of types by creating greater habitat fragmentation. This work also highlights the need to assess CGU’s along continuous stretches of river in order to understand the nature and dynamics of river habitats

The Effect of Flow Regulation on Channel Geomorphic Unit (CGU) Composition in the Soča River, Slovenia.

This paper sets out to examine the effects of flow regulation on the size, spatial distribution and connectivity of physical habitats or channel geomorphic units (CGU) of an upland river system in Slovenia. A river channel survey was completed along three reaches (totalling 14.3km) of the Soča River in order compare an unregulated stretch (reach 1), with two regulated reaches with lower discharges, i.e. a bypassed section that experiences significant flow reduction (reach 2), and a stretch regulated by dam operation (reach 3). CGU’s were classified according to a modified version of the Hawkins et al (1993) system, and mapped on foot and from a boat using a combination of visual assessment and physical measurement. Mapping-grade GPS was used to locate CGU boundaries to sub-metre accuracy, and the application of GIS (MapInfo) enabled the description and analysis of the longitudinal distribution of CGU’s along each reach. Results demonstrated significant differences in the CGU composition between the unregulated and regulated reaches. The unregulated stretch (reach 1) was dominated by the glides (55%) with relatively fast-flowing and turbulent features (runs, riffles and rapids) making up the rest of the reach. The dominant feature of both of the regulated reaches were the slow flowing pool CGU’s occupying 44% of the bypassed section (reach 2), and 76% of the dam regulated section (reach 3), with glides, runs, riffles and rapids forming the remainder of the CGU’s. Physical measurements highlighted the extent to which the reduced discharge in the regulated reaches was dewatering the channel and reducing the size of the CGU’s. The average CGU size in the unregulated stretch (reach 1) was 58m2 of water area per m of channel length (m2/m) compared to 18.42m2/m in the reach 2, and 29.22m2/m in reach 3. CGU’s tended to be shorter, and hence there was greater habitat division or fragmenta-tion evident in the two regulated reaches, particularly the bypassed section. For example, there were on aver-age 6.81 CGU’s per km in the unregulated reach (reach 1), 18.12 CGU/km in reach 2, and 8.08 CGU/km in reach 3. This study suggests that in the Soča River under the flow conditions present during the survey, flow regula-tion alters the dominant types of CGU’s present (to slower flowing and less turbulent features), significantly reduces the size of CGU’s, and affects the longitudinal distribution of types by reducing habitat connectivity and creating greater habitat fragmentation

Mikroplanktonske i mikrobentoske alge obalnog boćatog jezera Fiesa i ušća Dragonje (Slovenija)

Between 1998 and 2000, microplanktonic and microbenthic algal communities were sampled and analysed in the coastal lake Fiesa and in the Dragonja estuary. The purpose of the investigation was to establish qualitative composition and the relative abundance of algal communities. In 1999 and 2000, basic physical and chemical parameters were measured. Altogether, 159 algal taxa were determined, 83 in the coastal lake Fiesa and 120 in the Dragonja estuary. Most of the taxa belonged to the Bacillariophyceae. Thirty four percent of all taxa were typical brackish taxa. Achnanthes septata, Amphora angusta, Gyrosigma tenuissimum, Gyrosigma wansbeckii and Pleurosigma strigosum (all Bacillariophyceae) were marine species. Brackish and marine taxa were almost exclusively Bacillariophyceae. Nineteen taxa were the first citations for Slovenia, 15 of them belonging to the Bacillariophyceae and four to the Cyanophyceae. Most new taxa belong to the genus Navicula (4).U razdoblju od 1998. do 2000. uzorkovane su i analizirane mikroplanktonske i mikrobentoske zajednice algi u obalnom jezeru Fiesa i na ušću Dragonje. Cilj istraživanja bio je ustanoviti kvalitativni sastav i relativnu abundanciju zajednica algi. Osnovni fizikalni i kemijski parametri mjereni su 1999. i 2000. Utvrđeno je 159 svojta algi, 83 u jezeru Fiesa te 120 u ušću Dragonje. Većina taksona pripadala je porodici Bacillariophyceae, a 34% od ukupnog broja bile su tipične vrste boćatih voda. Morske vrste bile su Achnanthes septata, Amphora angusta, Gyrosigma tenuissimum, Gyrosigma wansbeckii i Pleurosigma strigosum (sve Bacillariophyceae). Boćati i morski taksoni bili su gotovo isključivo Bacillariophyceae. Po prvi puta za Sloveniju zabilježeno je 19 svojti, 15 iz porodice Bacillariophyceae i 4 iz porodice Cyanophyceae. Većina novih svojti pripada rodu Navicula (4)

Detecting Submerged Macrophytes in a UK Chalk Stream Using Field Spectroscopy

Various studies using optical remote sensing in the marine environment have shown the possibilities of spectral discrimination of benthic macro and micro-algae. For in-land water bodies only very recently studies of have explored similar use of optical remote sensing to identify the taxonomic composition of algae and rooted plant communities. The importance of these communities for the functioning of river ecosystems warrants further research. In the study presented here, field spectroscopy is used to assess the possibilities of optically detecting macrophytes in a UK chalk streams. Spectral signatures of four common macrophytes were measured using a hand-held GER1500 spectroradiometer. Despite the strong absorption of near infrared in water, the results show that information on NIR can clearly contribute to the detection of submerged vegetation in shallow UK chalk stream environments. Observed spectra compare well with simulated submerged vegetation spectra, based on water absorption coefficients only. The field investigations, which were performed in the river Wylye, also indicate the confounding effects of specular reflection from riparian vegetation. The results of this study can inform remote sensing studies of the riverine environment using multi-spectral/low altitude sensors. Such larger scale studies will be highly beneficial for monitoring variation in chalk stream bioindicators, such as ranunculus

Evaluation and Application of Environmental Flows in Running Waters in Slovenia

Water use invariably results in major impacts on river flows. Environmental Flows (EF) are defined as the quantity and quality of water that is needed to preserve the structure and the function of the river and riparian zone ecosystem and sufficient quantity of water to enable the survival and reproduction of aquatic organisms in different hydraulic habitats. This paper describes the criteria and methods used to determine EF and experiences with their application in Slovenia. The diversity of running waters of Slovenia demand special treatment and determination of EF for each individual section of the river system. Using hydrological, morphological and ecological criteria, two different approaches are used for the determination of EF in Slovenia, a rapid assessment method and a detailed assessment method. For both methods, data are then analyzed by an expert panel in order to determine an EF. Since 1994, more than 180 study sites have been examined for research and application of EF in Slovenia. Determination of EF for existing users has prioritized their water requirements so they can remain economically viable. Where new schemes are proposed, there has been much greater scope to prioritize ecosystem requirements. EF determination is receiving growing attention and will continue to increase in importance, driven by research that aids our understanding of flow-biota relationships and recent environmental policy and legislation at both the national and European level