LETNIK 17, št. 25 (julij 1999) / VOLUME 17, No.25 (July 1999)          (full paper pdf)

Izvleček
Izgradnja hidroelektrarne (HE) Vrhovo je povzročila nastanek rečnega akumulacijskega jezera na reki Savi in s tem spremembo njenega naravnega vodnega režima, ki se odraža tudi v spremenjenih pogojih nebioloških in bioloških procesov samočiščenja vode in tako vpliva na njene kakovostne spremembe. Posledice energetske zajezitve reke na kakovost voda so lahko pozitivne ali negativne. V nalogi so obravnavani procesi evtrofikacije, biokemični in fizikalni procesi v rekah in jezerih, posledice zajezitev rek ter teoretični temelji matematičnega modeliranja in uporabljenega večparameterskega enodimenzionalnega modela QUAL2E. Model je bil uporabljen za modeliranje in napovedovanje možnih sprememb kakovosti vode v nastali zajezitvi. Opravljena je bila analiza občutljivosti modela. Številni parametri modela so bili določeni z umerjanjem modela tako, da je doseženo najboljše ujemanje rezultatov modela z izmerjenim stanjem. Potrditev modela je bila izvedena z rezultati meritev v letih 1996 in 1998. Na temelju dobljenih rezultatov je bil model uporabljen za kvantitativne napovedi raztopljenega kisika in biokemijske potrebe po kisiku v akumulaciji HE Vrhovo za ekstremne in povprečne hidrološke pogoje. Glede na rezultate modela in terenske meritve, izvedene pri nizkih pretokih in v pogojih poteka intenzivne primarne produkcije v zajezitvi, lahko zaključimo, da v akumulacijskem jezeru HE Vrhovo ne prihaja do prekomernega znižanja koncentracije raztopljenega kisika, ki bi povzročala negativne vplive na kakovost zajezene vode.

Ključne besede: evtrofikacija, matematični modeli, modeliranje kakovosti voda, površinske vode, hidroelektrarna Vrhovo.

UDK 504.4:519.87:556.55(282.243.743)

Abstract
The river impoundment on the Sava River was formed as a consequence of the construction of the Vrhovo Hydroelectric Power Plant (HEPP). The river impoundment changed the natural water circulation of the Sava River, a disruption which is also reflected in the changed conditions of the biological and non-biological self-purification processes in the water. Thus, it influences the water quality of the Sava River. River impoundments can affect water quality positively or negatively. This Thesis deals with the eutrophication, biochemical and physical processes in rivers and lakes, the impacts of river impoundments, the theoretical base of mathematical modelling and the employed multiparametric one-dimensional model QUAL2E. The QUAL2E model was used to model and predict the possible changes in water quality in the impoundment. A sensitivity analysis provided insight into the model operation and showed how the results of the model change when changing separate parameters. Many model parameters were determined by calibrating the model in such a manner that the best agreement between the results of the model and the measured state was achieved. The model validation was performed using the results of the measurements in 1996 and 1998. Based on the results obtained, the model was used for the quantitative prediction of dissolved oxygen and biochemical oxygen demand in the Vrhovo impoundment for extreme and average hydrological conditions. With regard to the model results and field measurements performed at low discharges and under conditions of intensive primary production in the dam, it can be concluded that an excessive decrease in concentrations of dissolved oxygen which could have negative influence on the dammed water quality does not appear in the Vrhovo impoundment.

Key words: eutrophication, mathematical models, water quality modelling, surface water, hydroelectric power station Vrhovo.

UDC 504.4:519.87:556.55(282.243.743)