DAMS AND THE SURROUNDING ENVIRONMENT

DAMS AND THE SURROUNDING ENVIRONMENT

1. Introduction

The impact, defined as action and influence upon the surrounding environment, is common and unavoidable for all human creations and activities, including the construction and exploitation of dams. Hydrotechnical constructions and dams in particular, have a specific influence upon the surrounding environment, different from that of most human creations and activities. That is dams:

act directly and decisively on the exploitation of one of the fundamental resources of the planet, the water, the sine qua non support of the development of life;

are involved in almost all of the human activities of all kinds (industry, agriculture, animal breeding, urban services, navigation etc.);

usually they are non-polluting during their exploitation, in some cases even contributing to the diminishing of the water pollution;

are the support of some ecological procedures for obtaining energy and agricultural products (hydroelectrical energy instead of the thermo-electric power station energy and the yield increase due to irrigation instead of artificial chemical fertilizer);

are an efficient mean of diminishing the catastrophic effects that some natural phenomena (high floods, land erosion, storms and hurricanes etc.) may have on the natural and/or anthropic environment;

contribute through their storage lakes to the increase of the minimal discharge of the river flows, having major beneficial effects upon the aquatic and riverside natural environment, especially during periods of severe droughts.

On the other hand, dams, which often have very large physical sizes, as big as the elements of the natural geographic environment, influence large areas and introduce changes of regional or even global importance. They usually have a certain, immediate and very obvious impact upon the environment (to which insidious or latent forms of impact are to be added). Whether this impact is beneficial or not, it certainly catches the attention of the public opinion.

The building and exploitation tradition of dams in Romania has always included the concern for the protection of the surrounding environment, due to a wide and responsible view of the board of engineers, under the leadership of some humanistic-oriented personalities, such as: Radu Priscu, Adalbert Gilbert, Alexandru Diaconu, Constantin Constantinescu, Victor Sabovici, Florin Iorgulescu, Alexandru Nourescu and others. Consequently, most dams and their storage lakes have created a convenient impact upon the surrounding environment, with few damaging effects. It is true however that, due to ignorance, lack of consultations with specialists from collateral fields or to decisions that came from above motivated by cutting costs, sometimes unfortunate solutions were adopted, causing regrettable effects upon the natural environment. Maybe one of the best known cases was the endangering of the endemic species of fish Romanichtys valsanicola, while cleaning the Lake Valsan in unfortunate conditions and an insufficient preserved discharge.

The systematic and scientific approach of the relations between hydrotechnical constructions (dams in particular) and the natural environment began at the initiative of I.S.P.H. (The Institute for Hydrotechnical Studies and Projects) through successive impact studies caused by the complex hydroenergetical arrangements on the environment, studies carried out by a team of the Institute of Biological Sciences of the Academy during 1988-1992. During this close collaboration a number of construction-engineers understood and assimilated elements of ecology and limnology, learnt to how to speak and to negotiate with the ecologists and formed a specialized group which has developed in time.

2. Categories of effects caused by dams upon the environment

Conceived and realized in order to obtain a convenient use of water as a resource and as support of many human activities, dams have numerous complex and deep effects upon the surrounding environment. An overall image of the multitude and diversity of these effects is shown in figure 1. Most of these were observed and commented upon in recent and accessible works (CROMB, 2000; Ionescu 1997,2001). The causes of this diversity lie primarily in the following aspects:

The large and evolving variety of the types of constructions;

The variety of the natural conditions in which they are placed is virtually infinite and changing in time;

The impact is very complex, having many insidious or latent forms and numerous superior effects (in a chain of successive and evolving causes);

Certainly there are still many unknown effects, especially those that latent or of a superior order.

The rational question that can be raised and which can be solved in a satisfactory manner is that of diminishing both the quantity and the quality of the impact the dams have on the surrounding environment or, in other words, to reach a convenient impact by maximizing the beneficial effects and diminishing or compensating the damaging effects.

Reaching such an objective is possible only if during the planning, executing and exploiting the hydrotechnical constructions, the persons and institutions involved are competent and aware of the impact upon the surrounding environment, have good faith and decide or act always bearing in mind specific criteria that are in accordance with the project. Such a behaviour is the essence of what we call and understand under the ecological engineering of dams. Appling this principle requires technical and scientific competence, pluridisciplinarity and a real civic and social conscience. The difficulty in reaching this goal lies in the unbreakable connection between the improvement measures of the impact upon the surrounding environment and the concepts and solutions of the planning, executing and exploiting the hydrotechnical constructions and the dams. This particularity is what makes them specifically different from many other engineering fields, in which protecting the environment is often reduced to adding installations for cleaning the air or the water in the classic technological chain.

3. The main effects of dams on the natural environment

3.1. General effects

Dams and other hydrotechnical arrangements of the same category have many direct or indirect beneficial effects upon the surrounding natural environment, such as:

Ø      Producing electrical power out of reusable sources, with non-polluting technologies, which, by comparison with other means (such as thermo electrical power plants), has great ecological advantages, by avoiding the pollution of air, water and soil; the production of hydroelectrical energy represents an ecological solution to the energy problem on a global scale;

Ø      The decrease in the usage of some fertilizers due to better irrigations made possible by the hydrotechnical constructions, which diminishes the pollution of phreatic waters and the lack of air from lakes;

Ø      Reducing high floods, creating a major mean of protection for the downstream sector, knowing that an exceptionally large high flood represents a natural catastrophe for the aquatic ecosystems, which would take up to 5 years to regain balance;

Ø      The increase of the minimum assured discharges and the modifying of the flowing regime downstream of the restitution of the used discharges, in order to level it, with remarkable beneficial effects on the aquatic and riverside ecosystems;

Ø      The creation of the "storage lake" ecosystems, which, under certain conditions, may have potential positive effects.

The effects of blocking the river flow upon the natural environment can be classified into the following homogenous groups:

q       The hydrographic basin situated upstream the lake;

q       The storage lake;

q       The basin situated downstream between storage and restitution;

q       Downstream the restitution of the stored discharges;

q       The nearby areas (including land ecosystems)

In figure no.2 are presented the most important potential effects and the measures for their diminishing or removal, for a hydroenergetical arrangement scheme with secondary catchings and subterranean derivation, often used in our country in natural areas with a low anthropology, with large natural biological potential.

Some comments are necessary. That is, for the ecological effects on the aquatic ecosystems from the basin located upstream the lake, these essentially depend on the size of the area. If it is sufficient, the effects of breaking the link (circulation) with the downstream section are minimum. The largest part of the basins from upstream of the dams in Romania keep their ecosystems virtually untouched, having a large variety and vitality of the aquatic biocoenosis. Examples such as the Timis, Bistrita, Arges, Lotru, Somes, Sebes or Dragan basins are conclusive in this matter.

The newly created lacustrian ecosystems have usually evolved favorably. The biotic instability periods from the first 3 to 5 years of exploitation are absolutely normal in the evolution of a new ecosystem, up to a state of balance, based on self-regulation.

On the river sections situated downstream from dams or captions up to the restitution sections of the used discharges or up to the first important emission (!), the liquid discharges are seriously diminished in comparison to the natural hydrological regime. This is why it is usually necessary to predict the emission of some discharges immediately downstream the dam or capture(!) (called debite de servitute or more correctly preserved discharges), which are retained from being used in the hydrotechnical arrangements. The value of these discharges is a much disputed and controversial problem, especially with regard to the natural conditions of the hill and mountain rivers in Romania, which have a relatively low average natural multiyear discharge. However, the surplus of water from the downstream basin difference leads to a rapid and satisfactory revitalization of the ecosystems, especially downstream from the secondary captures built relatively close to springs.

In the case of hydroenergetical arrangements, in order to protect the downstream ecosystems from the restitution section of the turbinated discharges, it is necessary for them to be leveled in a rectifier lake or basin because the pulsating (!) regime has negative geophysical and ecological effects. In a natural regime, the downstream ecosystems have a good tolerance towards slow, daily discharge variations (e.g. in spring, when the snow melts, the maximum to minimum daily discharge ratio is usually situated around the value of 3, but quite often it goes as high as 10). This is why the exploitation plan for the rectifying basin must be accurate to such a way that it adapts to the surplus of turbinated water daily, respectively to the functioning regime, so that the maximum to minimum daily discharge ratio should be no bigger than 3. Most of the existing arrangements have a convenient discharge rectifying mechanism. A regrettable exception are the arrangements where the execution of some downstream areas was interrupted after 1990 (Buzau, Pecineagu, Raul Mare, Poiana Marului etc.), where the discharges with a great level of un-uniformity have already caused and will keep causing important negative effects.

3.2. Particular aspects of the interaction between dams and the natural environment

First we should underline the recently risen concept of sustainable development which has gained wide-spread recognition, but applying it means a detailed knowledge of the processes involved in the "economical objective"-"natural capital" relation. This is why the administration of any natural resource must be preceded by evaluation activities of the reserves followed by management and monitoring recommendations.

In short, all the anthropic ecosystems, including hydroenergetical constructions placed in most hydrographic basins in Romania, require complex administration plans. In this context it is considered to be a priority the action of identifying and ordering the effects of blocking river flows (Tatole, 1999). These are the following:

Ø      First rang: the local disappearance and fragmentation of the lotic components; the disappearance of temporary and permanent puddles from the river meadows; the local disappearance and fragmentation of terrestrial components; shifts of the groundwater sheet;

Ø      Second rang: modifications of the season-variations in the flow of the arranged river; daily discharge fluctuations; shifts of the chemical composition of the water; modifications of the thermo regime; modification of the turbinezation degree; modifications of the downstream discharge; modifications of the microclimate;

Ø      Third rang: creating human-type aquatic ecosystems; differential impact on the ecosystems located nearby the arrangements; acceleration of the successional processes.

Rivers and lakes are ecosystems with a varied chemical and biological components, being heavily influenced by geoclimatic factors. They are self-evolving entities.

The river ecosystem consists of 3 major sub-systems: the river bed itself, the banks and the phreatic. Rivers are characterized by: - great variations of the matter and energy flow; - contacts with the Hiporeic (!), through the contribution of the springs; - the existence of a constant contribution to the World Ocean; - corrosion processes determined by the hydraulic energy and geomorphologic conditions; a reduced degree of autarchy etc. All of these characteristics determine an extremely varied aspect from spring to flow. Practically it houses a mosaic of biotopes, conditioned by: the angle of the river;- the velocity of the water (a decisive factor is the discharge); - depth; - the type of under lair (rocky, craggy, with boulders, with pebbles, sandy, muddy, etc.); - the configuration of the river bed and river banks etc.; - the physical and chemical parameters (in this case the decisive factors are the oxygen concentration, the temperature); - the presence of some hydrological characteristics, such as: the boundary lair, turbulence, dead angles etc. All of these particularities determine the existence of a wide variety of biocenosis. The organisms and the reofil communities usually settle according to the adaptations to the resources and specific conditions of each of them. A river is not only a continuous flow of water from spring to the sea, but a complex ecosystem consisting of subsystems represented by the tributaries, the floodable area, puddles, ponds, channels, dead arms etc., which interact materially, functionally and informational.

The lake ecosystem is characterized by: - different degrees of integrality; - a higher degree of autonomy in comparison to the flowing waters; - a higher degree of autarchy; - a surplus of sediments brought by mountain streams, by rain etc.; - transforming and recycling of matter, mostly within the same basin; - reduced stability (depending on the type of lake) through a faster evolution of the clogging process and the growth of the trophyc degree. Lakes are different not only by the geomorphological nature, by shape, surface and depth, but by the nature of their creation as well, that is natural or man-made. We must observe that storage lakes, as man-made ecosystems, are subjected to the same rules as the natural ones, differing from the latter by the nature of their creation and by human intervention in their function processes. The following ideas should be underlined:

lakes and rivers are a component of the interior waters diversity and are ecosystems characterized by individuality and self-evolution, which allow the setting of classification criteria in order to differentiate them;

the structural, functional and informational knowledge of the organizing and functioning rules of the river and lake ecosystems in natural functioning regime is a testimony in the action of estimating and controlling the impact of the human action.

The building and exploitation of a hydrotechnical arrangement requires, in time and space, the appearance and persistence of modifications capable to alter the historic character of land and water ecosystems, that is:

v     in the lotic ecosystem (flowing water): the local disappearance and fragmentation of the lotic ecosystems; - disruption of the fish migration; - the modification of the chemical structure of the water (which is stronger due to pollution); - modifying the thermic regime; - modifying of the turbinezation degree

v     in the lentic (!) ecosystem (non-flowing waters or with a very low flowing velocity): the disappearance of small temporary or permanent puddles from the river meadows; - the creation of new aquatic ecosystems: the problem of populating them (natural or man-made) and of using the aquatic biological resources; - the acceleration, preventing or delaying conditions of lack of oxygen in the storage lakes;

v     in land ecosystems: direct changes in the geomorphological configuration; - modifications of the microclimate; - changes of the biotic component.

4. ASPECTS OF THE REAL EVOLUTION OF ECOSYSTEMS CREATED OR INFLUENCED BY DAMS AND HYDROTECHNICAL ARRANGEMENTS

4.1. The evolution of new ecosystems in storage lakes

In order to establish the evolving tendencies of the biotic component for these man-made systems it is necessary to have an observed information and another after the exploitation has begun. We can make such an analysis in the arranged section of the river Olt, sectors Fagaras-Avrig and Cornetu-Dunare.

The estimates regarding the nowadays status of the aquatic biotic component of the river Olt is based on data obtained from 45 stations from the storage lakes and major tributaries in the area, from studies that were carried out before and after the arrangement (1973, 1983-85, 1986-89, 1997, 1999a, 1999b, 2000-2002, 2001-2002) and on published information. The research on the biotic component concentrated on the structural dynamic of aquatic invertebrates because, according to research data, they are considered to be the most representative elements for the bio-monitoring of surface sweet waters. The studies indicated 291 species belonging to 25 groups of aquatic invertebrates. The analysis was carried out in the two hydroenergetical arrangements of the river Olt:

The Fagaras-Avrig sector, containing 5 hydroenergetical arrangements (HEA): Voila, Vistea, Arpasu, Scoreiu and Avrig. The investigation was based on preserving samples and observations from 15 stations, in the storage lakes from Voila up to Avrig and on the tributaries from this sector.

The Cornetu-Dunare sector, containing 21 hydroenergetical arrangements. For this sector the data was obtained from observations and preserving samples from 30 stations, from the storage lakes beginning with Cornetu up to Islaz and from major tributaries.

Regarding the Fagaras-Avrig section it was noticed that a comparison between two structural overviews situated 10 years apart (1986-1989 and 1998) revealed the following characteristics: - on the bental(!) community level there are sufficient basic elements; reofil and lenitofil(!) elements coexist; - strictly reofil elements have reduced their number up to extintion; - the so called "residual fauna" populations increased their numbers.

In the sector Cornetu-Dunare three sub-sectors distinguished themselves:

Gura Lotrului-Calimanesti: the lakes maintain the same river bed on the river Olt, being narrow and sloped; a high degree of turbinezation possibility (large suspension quantities); genetic surplus from tributaries;

Daiesti-Babeni: the oldest arrangements (1974-1978); directly exposed to pollution; sediment deposits at the back of the lakes; the forming of dejection cones at the confluence of the tributaries, including the spilling channel of the Chemical Platform; sediment deposits in the perimeter of the escape channels to the next lake; changes in the liquid to solid discharge ratio; the appearance of fog due to the thermo topoclimate and smog; the increase of the density index between different masses of water and the blocking of the vertical changes of water, which stops the chemical processes of oxygen reduction of the organic matters; the growth of grass on the sediments and the appearance of willow groves and alder-tree groves, which increase the quantity of organic matter in the lake (nitrogen and phosphorus); the embedding and acceleration of the diminishing of oxygen processes; positive genetic surplus through the tributaries Caciulata, Muiereasca, Olanesti, Govora, Ramnicu Sarat, Bistrita and Topolog; the creation of a lentic(!) type of biotic component.

Ionesti-Islaz: close formation age; similar geomorphologic conditions; pollution from direct polluting sources and from upstream; a low genetic surplus (virtually non-existent) from tributaries, because many tributaries from this area do not have a permanent flow (Ursanca, Staneasca, Trepteanca, Geamana, Nisipoasa, Sterpu, Cungra); the excess development of the underwater macrofites (!); the invasion of the shell Dreissena polymorpha; the much altered biotic component by developing the species dependent on the underwater macrofites(!) which offer food and shelter for many other species.

In conclusion, the following characteristics of the structure of the aquatic invertebrate fauna for the two sectors of the hydroenergetically arranged Olt river, Fagaras-Avrig and Cornetu-Dunare, can be underlined:

There are differences between the two mentioned sectors of the river Olt because of the different age of the two arrangements (the sector Cornetu-Dunare was built 20 years than the Fagaras-Avrig section);

Most of the storage lakes are affected by the eutrofizare process, determined and accelerated by the sediment surplus supplied by the chemical-industrial, agricultural and household pollution in the area;

There is a substantial material, energetical and informational surplus brought to the river Olt by its tributaries;

In the lower section of the river there are major deviations of the material, energetical and informational fluxes due to the excess development of the underwater vegetation and the shell population species Dreissena polymorpha.

The studies carried out on the hydroenergetical arrangements on the river Olt require the implementation of a complex program of measures in order to rectify the induced crisis situations, especially from the excessive development of the above mentioned species. Some methods can be:

Ø      Mechanical: through cleaning

Ø      Chemical: by using paints that have antifuling ingredients, in order to block the shells

Ø      Biological: bio-manipulation (controlled insertion) of some predator species, mostly fish. The following species are recommended: Mylopharingodon piceus (eats shellfish), Ctenopharyngodon idella (feeds on macrofites), Cyprinus Carpio and Rutilus rutilus (consume shellfish).

4.2 The situation of the environment downstream the dams

It has been noticed water catching/catchment in hydroelectric developments designed with ..... discharge (preserved) and correctly managed do not induce major changes in their downstream. Such are the secondary water catchments Dumitreasa, Negruta, Calu from the Somesul Rece basin. After the study of the biotic (?) component in Calu catchment (second order tributary affluent of the Somesul Rece river and first order/rate tributary affluent of the river Iara, a rapid/fast river but with its river-bed "paved" with small rocks and gravel) in three stations one upstream the catchment, the second one downstream the catchment and the third one aprox. 3 km downstream the catchment, the obtained results were the following:

in all the three stations the biotic component is very well represented, as constantly there are present the main ... groups: amphipods, ......, .....,...... with one exception: from the ..., .. and ....

in the station immediately downstream the water catchment the .. disappear (these are strictly .. organisms and ..) but there appear the ... (..organisms)

the preserved discharge (minimal) and the lack of other sources for pollution assure the existence of the ecological spectrum anterior to the development.

The configuration of the invertebrate fauna taxonomical structure upstream the water catchment station is similar to the one 3km downstream the catching. Between the two biocenotical(?) components there are differences from the quantitative point of view (the relative abundance/plenty) that is the number of typical ... groups (...., ....) decreases while others ... (.....,...) increase their number or simply these differences exist because of the dynamics within the same group (......)

Hence, in this case there are no changes of the biocentical component so the development did not affect the integrity of this ecosystem.

4.3 The preserved minimal discharge and the influence of the storage lake in the downstream section

There are many cases in Romania where the water catching (be it primary or secondary) was designed without the minimal preserved discharge. It is the famous case of the Valsan river (whose catchment took place in 1967) where the lack of an optimal preserved discharge downstream the dam caused a series of effects visible first in the abiotic(?)field (the drastic diminishing of the liquid discharge, the major change of the solid discharge, the change of the under-layer , the deterioration of the water quality) and afterwards visible in the biotic field as it affected in a serious way the structure of the invertebrates fauna by the replacement of the ...... species with .... ones finally reaching the decrease of the number of fish species and implicitly of the Romanichthys vasanicola (a very valuable species: endemic and reliquary), which is now on the list of seriously endangered species according to the UICN criteria (according to the Annex II from the Convention regarding the preservation of natural habitats and the flora and fauna species from Europe - Bern, 1998). A contrastive analysis of the biotical component taxonomical structure of the of Valsan river, downstream the water catching and of the data obtained before the catching, show not only a diminution of the number of species, but also the presence in a very low percentage of the common species (18%). At the moment a LIFE Natura programme financed by the European Union is being developed and its objective is the re-ecologisation of Valsan river and the salvation of Romanichthys vasanicola species.

Another example which can clearly underline the importance of the existence of the minimally preserved discharge and also the influence of the storage lakes upon the biocenosys(?) from the downstream sector is the storage lake Gura Apelor-Raul Mare (Hydroelectric development AHE Raul Mare - Retezat). This area was chosen because it was free from any other antropic(?) influence. By comparing the taxonomical structure of the biotical component from the Lapusnicul Mare (Rotunda) river and from the Raul Mare river, both established in 1973 with the one recently established (Tatole, 2001) we can observe the following facts:

there are similarities regarding the constancy of several typical . groups, and also regarding the values of relative abundance/plenty of numerous groups (...., ...., ....., ....., partially......);

there are differencies represented by the apparition of groups which belong to the planktonical compartment of the storage lake Gura Apelor (....) and also by the dispparition of some typical .. groups (...), and by the increase of populations that belong to gropus with .... and ..... preferences (...,....)

Thus it can be noticed that the decrease of the discharge and implicitly of the speed of the water (till stagnation in certain sectors downstream) the removal of stream zones, the changes of the under-layer, the interruption of the means of supply for the river bed with the gross solid discharge and the apparition and/or the developing of alluvial deposits and smoother detritus deposits, all these cause the drastic diminution of certain associations of organisms and/or the replacement of those which already existed there. Usually in such new conditions more groups from the residual fauna of the river become the representative ones. In short we can observe that on this sector of the Raul Mare river immediately downstream the dam, the structure of the biotical component reflects the multiple effect of the storage lake influence, of the major discharge decrease and of the change in the under-layer. It is worth mentioning that the co-existence of all these elements ...., ...-..., cannot be considered as a real increase of the local biodiversity, but only a state of transition, a "temporary" form of manifestation of an extremely labile ecosystem, influenced by man.

4.4 The influence of Herculane dam upon the ecosystem from Cerna valley

There are two hydroelectrical developments in Cerna valley, one was designed to capture all the springs of this river and to direct them towards the Motru objective and the other one was designed to build the storage lake Herculane by damming the river near the "La sapte izvoare calde" spa. It is important to mention that Cerna valley is a part of the National Park Domogled - Valea Cernei and it is protected according to the existent laws (Law 462/2002). The National Park Domogled - Valea Cernei is renowned because of:

the existence of diverse biotopes(?): the greatest extension in the country of jurassic and cretaceous limestones and extremely varied and original karstic relief: caves, ..,....,...., karstic interminent springs etc.;

the influence of the south mediterranean climate which brought to the installation of its characteristic ecosystems, rich in flora and fauna.

The storage lake Herculane dates back in 1986 and the surface that was transformed for the construction is relatively small. The data that were obtained after studies realized in 1995 and 1998 allow a contrastive analysis of the biotical component structure in all the three areas (upstream the construction, from the very storage lake Herculane and downstream the lake) each of them having well defined characteristics. It is appreciated that the ...... of the lake has been enriched by trout repopulation campaigns (information received from the Forest Ward Baile Herculane - 50,000-100,000 .../for eac repopulation); there is also an intetion to repopulate the Herculane lake with hucks (Hucho hucho). For reproduction many of the up mentioned species depend on tributary affluents, where they mount in order to reproduce. The most "crowded" places in the lake are those near the shores and near the tributaries' mouths, where they can find trophical(?) resources.

Regarding the downstream sector of the storage lake Herculane it is worth mentioning that one of the most important species has disappeared - the umber. (?) Cerna keeps its characteristics as a hill river also downstream the Herculane storage lake up to Toplet, where short rapid sectors and a rocky under-layer alternate with slow sectors, deep waters and mainly sandy even oozy under-layer; each sector has its specific ichtiofauna/fish fauna.

Hence we should bear in mind that the construction of the dam and of the storage lake Herculane triggered several changes at the aquatic ecosystem levels:

in the Herculane storage lake perimeter, Cerna has lost its .... ecosystem qualities, becoming a .... ecosystem.

between the two structures of the biotic component upstream and downstream the storage lake there are great resemblances first of all because of the same conditions of discharge, under-layer etc.

the careful surveillance of the area is required because several dysfunctions, considered as accidents such as: - the loss of the fish population three years ago, including the trout population introduced in the lake through the repopulation campaigns because of a technical problem which caused the sudden emptying of the lake; -the presence of big quantities of Spyrogira (water weed) in the lake, organisms that endanger the development of fish; if these dysfunctions should repeat they can endanger the integrity of the ecosystem, which is already vulnerable because of human intervention. At the level of terrestrial ecosystems, due to the small dimensions of the lake, there were no special problems.

Thus, based on organisms associations structure, we can appreciate that the .. character of the biotic component is maintained because of the existence of the .... discharge downstream the storage lake Herculane. The fact that the construction is placed in a protected area can prevent and limit many of the unwanted effects by monitoring the region. All the above mentioned lead to the following recommendations:

-the revision of Cerna discharge values, downstream the Iovanu lake;

-the supervision of the Herculane storage lake from the water quality point of view, mainly in the dam area, in relation with Tierna hotel;

-the supervision of the level oscillations amplitude, the coordination of the filling chart and of the methodology of emptying with the critical periods of the development cycle of the fish and/or the cycle of maintenance of the biotical component;

-the supervision of the downstream discharge, which is meant to assure the survival of . fish species, as some are in a critical situation;

-the re-analysis of the storage Cornereva by the catching of river Belareca and directing it in the Herculane lake storage.

4.5. The effects of the lack of rectifying discharges downstream Hydroelectrical Plant (CHE) Clabucet on river Dambovita

In the Arges system Dambovita is considered to be the most important tributary affluent not only because of the discharges but also as a hydrographical unit. Dambovita river is the limit of the National Park Piatra Craiului. Starting from Saului valley (km 11) there are a series of components of the hydroenergetic subsystem Pecineagu - Valea Dambovitei, part of the hydroenergetical complex Arges. CHE Calbucet which functions in peak and demi-peak regime and which is serviced by the Pecineagu storage lake with V_b =63 mil.m³ is, due to its placement and construction, the first hydroelectric development (AHE) in the hydroenergetic system of Dambovita. The work interruption at Satic-Dragoslavele from downstream determines the discharges from the turbine to be evacuated downstream without ... . That caused daily level oscillations downstream CHE Clabucet. This way there were observed noticeable differences during 6 hours such as: - at 10 o'clock the water was so shallow that one could see the round rocks that paved the river bed and the water speed was very slow; - at 18 o'clock the level and the water speed grew very fast.

Proofs were taken and observation were made upstream and downstream the Clabucet development. .According to position of the studied sector, upstream and downstream the AHE, one could notice differences such as: - upstream: at the confluence with Valea Dragoslavenilor the water speed was faster, the banks were full of grass up to the water, there were ferns; downstream: at Valea Scheilor (Satic) the banks can be either full of vegetation up to the water or form collateral branches where the water is almost stagnating.

The analysis of the discharge changes influence upon the aquatic invertebrates has been done on the basis of the structural configuration of the two stations placed upstream and downstream CHE Clabucet. After the data processing 11 taxonomical groups have been identified, and their relative abundance/plenty has been calculated. There are no noticeable differences between the two stations from the quality point of view, which means that the biotical component of both stations is made up of representatives from the same taxonomical groups. The presence in both sections of the main components of the aquatic invertebrates fauna can be explained by the maintenance downstream the CHE Clabucet of the main conditions that define the flowing water ecosystem: slope inclination, water speed (stream), depth, under-layer diversity, the river bed and the banks' configuration, the physical-chemical parameters (decisive factor: concentration of the dissolved oxygen; temperature), hydraulic parameters (limit layer, turbulence, dead angles etc). There are however notable differences regarding the level of representation expressed by the difference in value of the relative abundance/plenty. Thus, taking into consideration only the case of the groups specific for the mountain rivers, such as ....(7,71% as compared to 4,02%) ... (30,95% as compared to 18,75%), ....(17,32% as compared to 4,02%) and ... (7,37% as compared to 4,25%) one can observe their decrease downstream the AHE Clabucet station.

Based on the elements from the European Council and Parliament Direction 60/2002/EC regarding the establishment of a European framework in the field of water policy which refers to the definition of the ecological state of the river, upstream and downstream the construction, we can note the followings:

-....and .... are in a very good condition; the ...composition corresponds almost totally with the unchanged conditions

-the .....invertebrates fauna is in a very good condition; the ...composition corresponds to the unchanged conditions, but the abundancy does not correspond; in the downstream station there are representatives of the same groups of aquatic invertebrate organisms as in the upstream station; from the quantitative point of view the structural components of the aquatic biotical component in the downstream sector of the CHE Clabucet are less than the values upstream the development.

-the fish fauna is generally in a good condition; there are changes regarding the ...abundance/plenty as compared to the unchanged conditions, because of the human impact; the impact is visible on the more sensitive species (for example the trout)

4.6 The impact of dirt-heaps, with examples from AHE Raul Mare-Retezat

One of the biggest problems of the dams' impact and of all hydrotechnical constructions which imply great volumes of excavations is the problem of dirt-heaps; no matter of origin the problems are similar.

Monitoring the structural dynamics at the biotical component level from several perimeters affected by the hydroelectrical developments Raul Mare-Retezat, has been under way since 1992. The monitoring network includes the following stations: -the Barlii brook (upstream dirt-heap and downstream dirt-heap); -Dobrun river; -Zlatuia river; -Netis river (upstream dirt-heap and downstream dirt-heap); Rausor river in front of the dirt-heap; -Begut - Nucsoara river, (upstream dirt-heap and downstream dirt-heap); -Valea Seaca river in front of the ventilation window/hole(?). For this presentation we have chosen two cases: the case of Barlii - Valereasca dirt-heap, which is placed in the National Park Retezat at the very border of the Scientific Reservation Gemenele, and the one on Netis river which has already been stabilized.

From the stations that are being monitored, Barlii station downstream the dirt-heap has developed and is still developing problems as the technical solution which was proposed and applied in order to prevent or to diminish the impact, proved to be faulty and these faults were solved improperly. There was placed a settling tank with filter, filter which was rapidly obstructed, and this situation was solved either by sectioning the filter or by letting out the residual materials direct in the river bed. The situation got worse after the June 1999 storn when Gafu brook grew and sectioned the dirt-heap. At the moment the river bed is "paved" with dirt and on the banks there are small deposits made of the same material. To all these we can add leaks of oil or other fuels used for the tools and work equipment. Because of this conditions the structural component of the aquatic invertebrates fauna downstream Barlii station has become poorer and poorer not only from the quality point of view (number of species) but also from the quantity point of view (number of population) so that the only representative groups are now ...and... which are well known for their great ecological adaptability. By comparison in the station upstream the dirt-heap the configuration of the aquatic invertebrates fauna structure is different as here we can notice all the groups that are specific for the unpolluted mountain rivers, organisms that require special conditions of ... and under layer. A more detailed analysis was possible on the basis of determinations(?) for every species. Thus, in the upstream station there are 36 taxons(?) present while in the downstream station there are only 8.

The situation is different in the case of the Netis dirt-heap which is 25 years old: downstream the biotic component has become even better represented as the number of ...,.. and...increased considerably. More than that the determination for every species has shown 16 taxonomical units upstream as compared to 21 downstream. This fact demonstrates that if the discharge/flow is optimal and if there are no impurifying sources, the biotical component in the rivers where dirt-heaps were deposed can recover.

5. THE CHARACTERISATION OF AQUATIC ECOSYSTEMS INFLUENCED BY DAMS

The construction of dams and hydroelectrical developments modifies the associated aquatic ecosystems and determines effects and complex evolutions with favourable and unfavorable aspects. How big is the modification of the whole ecosystem and in what sense did its quality evolved? To answer at this question of outmost importance it is necessary to define one characteristic complex size/volume/dimension and its unit of measure.

Many specialists involved in the complex problem of the environmental engineering have resorted to the use of different parameters or biological values which they considered to

be crucial for the estimation of the impact: the diversity of species, the dynamics of the composition of species, the trophic(?) relations, the energy flux, the population abundance/plenty and the reproduction process. To all these one could add the functional values such as the energetical flux and the recycling of nutritive factors(?). The biological values are based on the sensitivity or tolerance degree (expressed by score or points) of some species or of some taxons(?) superior to the pollution factors. By summing up the points given to every present group the total value of the biotical index for the given byocenosis(?) is obtained.

Experience has lead to the necessity of establishing some standard values. Thus a series of solutions appeared, many of which are based on the ... macro invertebrates which present several advantages: - ....invertebrates are generally abundant, sedentary and have a relatively long cycle of life which makes them compatible with the role of index for a long period of time; -as the..communities are heterogeneous, there is a chance that at least some groups of organisms to be sensitive to the changes of the aquatic environment; with the exception of great rivers, the biological tests/proofs can be drawn/taken without great difficulties especially because in many impact studies qualitative samples/proof/tests are being used.

So, at the European Community level at the moment 20 different indexes are being used. That is why the creation of a standard system, applicable in all European states has become more and more urgent. From all these, for the natural conditions in Romania the most appropriate is I.B.G.N (The Normalized Global Biological Index), which has been drawn out/elaborated and standardized in France. From the Technical Book published by the GAY Cabinet from Grenoble one can see that the I.B.G.N. methodology was elaborated in more steps: 1967 (Indice Biotique), 1976 (Indice de Qualit Biologique Globale), 1985 (IBG - experimental) and afterwards 1992 (IBGN standardized). This index is applicable in the case of appreciation of the aquatic environment, mainly in the case of flowing waters and it is based on the general principle according to which to a certain environment corresponds a certain byocenosis(?) (the total living population of an ecosystem). It starts from/with the premise that the population of a habitat can be considered as the synthetic expression of all ecological factors that condition the system. If the condition of the environment alters then there will be evolution processes of several factors that modifies in a greater or smaller degree the living component of the given ecosystem. In accordance to the requirements of such an instrument, this guide describes in detail the whole problem specifying clearly the steps:- how to choose the drawing(?) stations; -how in which to make samples; -how to realize the sorting of samples; -how to identify the organisms; -how to process an interpret the obtained data.

On the basis of a rich bibliography, which presupposes a similar experience ....macro invertebrates have been selected as indexes for the flowing water ecosystem because: -they are good integrators of the global quality of the ecosystem; - they are spread in all the aquatic ecosystems; - they have a great taxonomic diversity (150 families, 700 types and more than 2000 species in France); - they show a great stability in time and space because they are sedentary populations; - organisms develop sensitivity towards the quality of the water and of the under layer; - they have their place in different trophic levels of the ecosystem: primary and secondary consumers ...; they are easy to...and preserve.

Because the conditions in which this index is applied, and because the resemblance with the ecosystem in Romania (especially the great resemblance regarding the ...communities) can satisfy the correct evaluation of the impact it is considered that IBGN is the most appropriate monitoring system which must be endorsed(?) and used in our country also. An application at the secondary water catchment Calu from the Somesul Rece basin (AHE Somes-Mariselu) realized without preserved flow downstream, on a value scale IBGN from 1 to 20 the following results upstream the catching were obtained: IBGN = 17,8, immediately downstream the catching: IBGN = 9, and 3 Km downstream the catching: IBGN = 18,5. These results point that:

-the ecosystem state from our mountain rivers in natural state is very good;

-without the preserved flow immediately downstream the catching the state of the ecosystem degrades/worsens, but they are still in a medium state;

-while the flows recover from ......, the state of the ecosystem improves at small distances downstream

In the end we must specify that: - all these indexes represent indispensable instruments in order to realize the monitoring process; - it is advisable to use all these indexes while monitoring the quality of natural and antropic aquatic ecosystems; - these indexes must succeed to complex studies realized through a systemic approach which would allow the elaboration of management and integrated monitoring plan fundaments. Realizing and the official endorsement of such an instrument used for the characterization of the state of the aquatic ecosystem (and particularly thos einfluenced by dams) is a priority for which it is necessary that all the interested to make all the needed approaches, among which are also all the factors and the persons implied in the design, the promotion, the execution and the exploitation of dams and great hydro technical construction.