River Durance Research Articles

Monogenean parasites of Lepomis gibbosus Linnaeus introduced into the River Durance, France

Summary The pumpkinseed, Lepomis gibbosus Linnaeus (Centrarchidae), was introduced into the Europe from North America in late 19th century. In this study, we examine monogenean parasites of L. gibbosus from the River Durance in France. We found seven parasite species introduced together with the host: Actinocleidus recurvatus, A. oculatus, Onchocleidus similis, O. dispar, O. acer, Cleidodiscus robustus (Ancyrocephalidae) and Gyrodactylus macrochiri (Gyrodactylidae). Early diporpa (Diplozoidae), accidentally attached to the gills, represent a single parasite species acquired within the area of introduction. Three species, O. acer, C. robustus and G. macrochiri, are reported from Europe for the first time.

Environmental impacts of hydroelectric power and other anthropogenic developments on the hydromorphology and ecology of the Durance channel and the Etang de Berre, southeast France

The generation of electricity through hydropower can, along with other anthropogenic activities, degrade river hydromorphology and ecosystems. In this case, water for power generation is diverted from the River Durance to a canal, which services a chain of 17 power stations, with the lower three being in the catchment of the Etang de Berre. This means that excess water and sediments are discharged into the salt-water lagoon with enormous consequences for ecosystems there. This paper summarizes the impacts of HEP and other human activities on both the river and lagoonal systems. It also considers agency and government attempts to understand and counter the degradation of these systems, both to date and in the future, with the latter catering for the potential impacts of future human development and global warming.

Spatio‐temporal patterns of fish assemblages in a large regulated alluvial river

Summary1. The River Durance, the last alpine tributary of the River Rhône, is a large, braided alluvial hydrosystem. Following large‐scale regulation, flow downstream of the Serre‐Ponçon dam has been maintained at 1/40th of previous annual mean discharge. To assess the effects of historical disturbances, fish assemblages and habitat use were analysed during five summers in a representative reach of the middle Durance.2. Habitat availability and use were assessed with a multi‐scale approach including the variables water depth, current velocity, roughness height of substratum, amount of woody debris and lateral/longitudinal location. Eighteen fish species were sampled by electrofishing in 289 habitat sample units.3. Partial least square (PLS) regression showed that taxa were mainly distributed according to relationships between their total length and water depth/velocity variables. Fish assemblage composition was also related to roughness height as well as distance from the bank or to the nearest large woody debris. However, PLS regression revealed no significant differences in habitat selection between two periods of varying hydromorphological stability.4. Fish distribution patterns and density were related to proximity to the bank and cover, indicating that local scale variables need to be considered in conservation and restoration programmes.

An approach to the Intermediate Disturbance Hypothesis at the landscape scale: the effects of hydrodynamic disturbance on phytoplankton communities

The River Durance and its main tributary, the Verdon, are two highly regulated rivers in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different hydrodynamic characteristics. Here the effects of a human-induced hydrodynamic disturbance on the phytoplankton community were studied for the first time at the landscape scale. The level of hydrodynamic disturbance occurring in these regulated rivers varies depending on the landscape unit under investigation, the depth and area of the reservoirs and on how the systems are managed. A statistical analysis showed that the level of hydrodynamic disturbance in each reservoir could be evaluated by the residence time. At the community level, the Intermediate Disturbance Hypothesis (IDH) predicts maximum diversity at an intermediate disturbance frequency and intensity. The validity of the IDH was confirmed by the number of algal species and the total number of cells: the community with the largest numbers was found to be associated with intermediate disturbance levels. The composition of the algal community showed conspicuous variations along the hydrodynamic disturbance gradient and explanations for these variations are proposed.

Responses of the planktonic diatom Asterionella formosa Hassall to abiotic environmental factors in a reservoir complex (south-eastern France)

The River Durance and its main tributary, the Verdon, are both highly regulated rivers flowing in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different geographical, morphometric, climatic, hydrodynamic and chemical characteristics. The planktonic diatom Asterionella formosa Hassall, which has undesirable cyclic effects from the water management point of view, was studied in this complex of reservoirs located in the Mediterranean region. The results indicate that only the monomictic calcareous reservoirs show a bimodal pattern of Asterionella formosa abundance. The population dynamics of this algal species was found to depend on both the morphometric features and the hydraulic mode of management (retention time) used at each reservoir, as well as on the physical (temperature, suspended matter) and chemical (nitrogen, silica, calcium) characteristics of the water.

Structural variations of epiphytic diatom communities on three macrophytes in a regulated river (Durance), in South-East of France

L. and Cladophora glomerata Kiitz.) and one angiosperm Potamogeton densus L., were collected in the Mediterranean river Durance. Each macrophyte species was studied on the basis of three plant replicates, each of which cut into three segments. Although considerable heterogeneity was observed in density of the epiphytic populations between the plant species studied as regards, the composition of these algal populations showed a conspicuous degree of homogeneity within each macrophytic species. These observations were corroborated by the coefficients of variation calculated on the main diatoms and by the non parametric Friedman tests. The qualitative homogeneity of epiphyton on Potamogeton densus foliage made it possible to map the spatial repartition of

Réponses et stratégies d'adaptation des communautés algales épilithiques à différents régimes hydrologiques

Responses of epilithic algal communities were studied in a regulated river presenting two different hydrological regimes. Upstream of the Escale reservoir, the hydrological regime is characterized by a flow compensation with discharge continuous release responsible for the most significant disturbances occurring in the regulated River Durance. Downstream of this reservoir, the river presents a stable and low compensation flow. The analysis of the epilithic algal communities submitted to contrasting flow regimes has shown responses at different levels: a) at the level of the whole community, a global response by changes in species richness and abundance, as well as in community structure; b) at the level of the particular taxonomic groups, such as, for instance, a more important development of filamentous green algae, observed in the downstream reach; c) at the species level: the acquisition, by some diatoms, of an architectural type adapted to the flow regime.

The Intermediate Disturbance Hypothesis: application of this concept to the response of epilithon in a regulated Mediterranean river (Lower-Durance, southeastern France)

Hydrological regime is responsible for the most significant disturbances occurring in the regulated lower part of the River Durance. The present study was an attempt at determining the response of epilithon to the hydrodynamic disturbances occurring in this river. Three patterns of hydrodynamic disturbance resulting from three different types of regime were analysed. Under low stable compensation flow regimes, disturbance frequency and intensity were considered to be low. Under constant release flow regimes, disturbance frequency and intensity were considered to be severe. High compensation flow regimes with infrequent releases were considered intermediate. The validity of the Intermediate Disturbance Hypothesis (IDH) was confirmed for the number of algal species and the autotrophic index (an index for estimating the autotrophic versus heterotrophic balance). The results show that when the disturbance was of intermediate severity, the autotrophic and heterotrophic communities were balanced, which was not the case at either low or high hydrodynamic disturbance levels. The results allow to define the habitat of the epilithic algal species. Colonizer and competitor species were identified on the basis of the IDH. Several obviously ubiquious and resistant species were recorded at all three disturbance levels.

Influence of environmental variables on the growth ofLeuciscus cephalus(Linnaeus 1766), in the River Durance, South-east France

mesologic parameters. The chub, Leuciscus cephalus, colonizes the Durance river from its confluence with the Rhone river (alt. 13 m) up to the Serre Poncon dam (alt. 780 m.). The Durance has been exposed to strong human pressure, notably dam construction, reduction of flow rate and perturbation of the natural zonation patterns. The linear growth of chub was studied by scale measurement at six sta­ tions in the Durance catchment area : two of which are located in its main tributaries, the Buech river and the Verdon. An ana­ lysis (ANOVA) of the mean size of fish from one to five years of age shows significant differences between the stations. Principal Component Analysis, in which the stations are characterized by eight nosological variables associated with the density of inver­ tebrates and the number of degree-days above 12° and 22°C established a correlation between chub growth and species habitat, defined in terms of current flow rate, depth and substrate type and temperature. This correlation could be explained in two ways : 1- in slow-flowing homogenous riffle zone, the low water depth and absence of shelters limit the diversity of habitats and the biological richness; nevertheless the abundance of invertebrates does not seem to play an important role ; 2 - in zone of slow flo­ wing riffles subjected to large daily and seasonal variations in water temperature, as in this mediterranean river, temperature might be quite high. Fish older than two years, therefore prefer zones of deep water, where the thermic inertia is stronger.

Qualité des milieux aquatiques continentaux : intérêts de l'utilisation d'un marqueur biochimique chez le poisson

Biological assessment is useful in addition to conventional chemical mesures in order to monitor the water quality. Biochemical markers are early warning systems of the exposition of organisms to pollutants. Among them, the induction of the fish EROD activity enables the detection of specific compounds PAHs, PCBs. dioxines.EROD induction was evaluated for three cyprinids species in two French river sites : Durance and Moselle. In the river Durance, the closer to a chemical plant the sampling site was, the higher the measured EROD induction. In the river Moselle, the fish showed a significant induced EROD activity after industrial effluent discharges. In both cases the measure was species dependent.Although the EROD activity seems a fitted tool to assess the water quality, complementary studies are necessary to understand the effects of biotic and abiotic variables, on the results.

In situ pollution induced cytochrome P450 activity of freshwater fish: barbel ( Barbus barbus), chub ( Leuciscus cephalus) and nase ( Chondrostoma nasus)

The induction of cytochrome P450IA1 was detected in freshwater fish liver using 7-ethoxyresorufin- O-deethylase activity (EROD). Investigations took place in the river Durance in the south-east of France and revealed a strong induction downstream a chemical plant. This induction differed between the three species studied. The species Barbus barbus was more sensitive to the pollution. This might be due to the benthic feeding behaviour ofthat fish. The induction increased from February to October which was probably a concentration effect caused by the drastic drought that occurred in France in 1989.

Freshwater fish cytochrome P450-dependent enzymatic activities: A chemical pollution indicator

Fish mixed function oxidase activities were measured during four sampling campaigns in the river Durance in the southeast of France. Six hundred fish belonging to four species were caught for this study; the use of factorial analysis emphasizes the strong pollution dependence of the P450-dependent enzymatic activities which vary with the season, the species, and the sex of the fish. Regression analysis of the data allowed prediction of the type of location from which the fish came (polluted or unpolluted) for 80% of the fish. This supports use of such activities as chemical pollution indicators.

Compte rendu ornithologique camarguais pour les années 1978 et 1979

This bird report covers the years 1978 and 1979 and completes a period of 30 years of observations by a contingent of resident and visiting ornithologists in the Rhône delta and neighbouring Crau and Alpilles. It presents not only observations of rare species or unusual numbers of birds, but also indicates the results of several long term monitoring programmes concerning in particular, waterfowl and allied species. A climatological report summarizes the most important meteorological phenomena of the two years, the most striking of which were the very wet spring of 1978 and the dry summer of 1979. The winter of 1978-1979 must surely be remembered in northern and central Europe as one of the most severe this century. In the Mediterranean, however, it was much less severe and, fortunately, had none of the disastrous effects of the previous hard winters of 1956 and 1962-1963. “ La Crau ”, a unique stony desert area and former delta of the River Durance, is suffering seriously from the spread of industry and from agricultural reclamation. Some of the first census work to be carried out here shows just how important the area is for breeding Stone Curlews, Little Bustards and Pin-tailed Sandgrouse in particular. The sandgrouse population is an isolated one, the species occurring elsewhere in Europe only in parts of Spain. Observations of sea birds are not carried out systematically and more thorough sea-watching would probably show that many of the species mentioned here are regularly wintering in the “ Golfe du Lion ”. Unusually high numbers of Black-necked Grebes appear each autumn in the saline “ Etang de Lavalduc ” (up to 4,500), which makes it an internationally important site for this species. Whilst the herons as a group maintain their numbers, several notable changes have taken place in recent years. The reed-nesting Grey Heron continues to increase whilst the Purple clearly shows the opposite trend. The Cattle Egret, occuring only as an accidental visitor less than 15 years ago, appears now to have reached the peak of colonisation with the numbers of breeding pairs levelling off. Autumn roost counts show the total of individuals at close to 2,000. The first indications of roughly how many Bitterns breed in the Camargue are given whilst the second only record of White Storks breeding in the delta involved one semi-captive male and a wild female carrying a ring. This was a chick transplanted from Morocco to a nest in Alsace as part of a reintroduction programme in 1975. The flamingos again had two successful breeding seasons and the summer population for the south coast of France peaked at over 35,000 birds both years. Particularly interesting data are being gathered from the sightings of “ Darvic-ringed ” birds, 1858 of which have thus been marked over the past three years. 24 % of these have already been read outside France. Amongst the Anseriiformes, the wintering Bewick’s Swan population was the highest yet recorded with a maximum of 85 in January 1979. During this same period four species of geese were present with Greylags and Bean’s both reaching one hundred or more individuals. Counts of Shelducks have shown how important the salines are both as a breeding area and winter quarters, and a ringing programme has thrown some light on their movements. For other ducks the overall wintering population has been quite high with a peak of 122,000 in January 1979. In general the number of diving ducks was below average but this was compensated for by several of the surface feeders being present in large numbers, in particular Teal, Gadwall and Shoveler. The list of raptor observations is as impressive as ever and includes a second estimate of the breeding Marsh Harrier population with results slightly superior to those obtained ten years earlier. The eighth complete census of breeding Laro-limicoles was carried out in the brackish and salt water zone of the greater Camargue area. All species are maintaining their numbers and attention is drawn to the increasing populations of Mediterranean and Slender-billed Gulls. Nearctic waders already observed in the delta included sightings of Buff-breasted Sandpiper and Wilson’s Phalarope whilst the Pectoral was only the second reported. Eagle Owls in “ Les Alpilles ” appear to be increasing with 30 pairs recorded. Passerines have not been ignored entirely ; the continued increase of breeding Stonechats is encouraging whilst the successful nesting of a pair of Bed-billed Quelea in the Camargue adds an exotic flavour to this report.

Les terrasses de la Moyenne Durance

The terraces of the river Durance between Sisteron and Manosque are clearly marked by the coarse granulometry of their alluvions which decreases only slowly and gradually downstream. The granulometric criteria are approximately the same for all the terraces levels except one In fact in the two intermediate terraces levels, the latest has a far coarser granulometry, with cobbles whose mean size still exceeds 50 cms, 40 kms downstream from the moraines with which this level is connected up-stream. This terrace with big cobbles seems really to be connected up-stream This terrace with big cobbles seems really to be the same age as the maximum extension of the next-to-last glaciation as far as 2 kms downstream from Sisteron Round this reference level, we can notice the group of the lower terraces.whose highest is connected with the maximum extension of the last glaciation, 2 kms north to Sisteron But the deposits from the slopes show that this episode has been followed furthermore by an important period of gelification and loess deposits. Many discontinuous levels of high terraces are intercalated between the top of the Valensole Plateau (Old Quaternary) and the main two intermediate terraces. Their longitudinal sections cannot be connected together and it could be due to tectonic undulations continuing to the Middle Quaternary period.

La régulation dynamique Sa mise en oeuvre au canal de Provence

The de draws its supplies from the river Verdon, a tributary of the river Durance. Flow in the river is controlled by five dams built by Electricite de France, all equipped with power plant. The de intake is on the supply canal of the last plant down-river. The de supplies water for irrigation, urban and industrial use. Basic components of this complex system are the following : 1/ High-capacity conveying facilities totalling open-canal and tunnel lengths of 100 km and 130 km respectively. 2/ Large-bore pressure mains. 3/ Final distribution networks. Irrigation, urban and industrial water requirements to be met vary with time according to different laws. The system, therefore, must be capable of permanent optimal matching of supply to demand. The control method which has been adopted regulates the volumes of water through the canals and ducting, whilst updating reference volumes at regular intervals according to forecast consumption data. The system which has been designed on this principle transmits the necessary data from the canals and ducting to a remote operating centre, and appropriate gate or valve settings back to the network. Control works initially provided on the Canal de Provence were designed for operation on the downstream control principle. Dynamic arrangements were tested and developed to operational readiness on an existing structure scheduled for modernization. All new works were then designed for dynamic and existing works converted accordingly. The following facilities are required for an operational dynamic system : a) Remote transmission stations at suitable points along canals, pipes or tunnels, to centralize all data from instruments, gates or valves. b) Availability of public Post Office communications facilities c) A remote centre with a real-time computer programmed to produce commands from a measured data input. The cost of the remote-transmission system amounts to roughly 3 per cent of the total construction cost.

Production organique primaire dans un milieu saum�tre eutrophe (Etang de Berre). Effets d'une forte dilution (d�rivation des eaux de la Durance)

14C primary production measurements were made over a period of 5 years (1965–1969, inclusive) in the brackish lake “Etang de Berre”, near Marseilles (France). The diversion of the River Durance into the Etang de Berre took place during this period (March 1966) and introduced an important modification into the organic production ecosystem, mainly through increased and variable freshening, accompanied by substantial nutrient input. The seasonal distribution of production rates displayed 3 bloom periods: the first (short and slight) in spring, the second (the most important as regards intensity and duration) in summer, and the third in autumn (October). Before the diversion of the river in 1965, the carbon-uptake rates in the lake ranged between 25 mg/m2/day in winter and 800 mg/m2/day in summer-autumn, the mean value for the year being 150 g C/m2, which represents 2.5×104 tons of photosynthesized carbon for the whole lake. After the diversion, more than 3000 mg C/m2 day were measured; for 1968, the inclusive uptake rate was 384 g C/m2, representing 6×104 tons of synthesized carbon for the whole lake. Nevertheless, noticeable variations occurred from one year to another. From the annual nutrient input of phosphate to the Etang de Berre through the inflow of Durance waters, the quantity of potentially synthesizable elements has been calculated, in terms of carbon, according to the normal P:C ratio of organic substances; this quantity is called R. The difference between measured production, P, and R gives a measure of the “regenerated” production. This portion of production represented about 80% of the total production before 1968 but only 16% in 1969, a year of maximum fresh-water inflow. This phenomenon could be due to modifications of the ecophysiology of the phytoplankton resulting from the considerable freshening. With increasing nutrient load, eutrophication first occurs, then still greater dilution results in inhibition of production.

Distribution, Circulation et Evolution des Eléments Nutritifs, en Particulier du Phosphore Minéral, dans l'Etang de Berre. Influence des Eaux Duranciennes.

Distribution, Circulation and Evolution of Nutrients, Inorganic Phosphorus Particularly, in Lake Etang de Berre. Influence of River Durance WatersNutrients, phosphorus in particular, were studied at five locations in the brackish lake Etang de Berre's waters in order to examine vertical and horizontal distributions, seasonal and annual evolutions, and circulation.The phosphorus cycle was surveyed taking into account the extensive freshwater input from the river Durance which was recently deviated into the Etang de Berre.Of primary importance is the phenomenon of trapped nutrients in the deepest layer of the lake, corresponding to the occurrence of a pycnocline (halocline). This layer is in a steady state characterized by anoxic conditions and shows denitrification processes.

Aprovechamiento hidroeléctrico de la cuenca del Durance

The river Durance, which flows into the river Rhone, collects heavy torrential rains and has a large gradient. These are excellent circumstances to make use of its water for irrigation purposes. The water flow varies between 45 and 6,000 m 3 /sec, and this has necessitated the building of control dams. Over the higher reaches the most important section is that of Serre Poncon, which carries an average of 85 m 3 /sec. Beyond this dam, there are several others, such as Curbans and Oraison; the first of which provides a flow of 158 m 3 /sec, and drop in level of 77 m. The main water conduit at this dam has a large cross section, and its construction was preceded by a guide tunnel. Very modem high performance construction material was employed for this purpose, and the mean rate of progress was 9 m per day, in two shifts. The E. D. F. are the owners of this hydraulic enterprise, and they required from the contractors that this gallery should be lined with cement within two months of completing the excavation work. The Oraison dam takes its water from the Escale reservoir (capacity 3.5 million cubic metres), and there is a tunnel, 21 km long, to take the water to the pressure conduits of the underground power station.