## Wpływ retencji zbiornikowej na wybrane elementy środowiska, ze szczególnym uwzględnieniem zmian reżymu przepływów w rzece poniżej zbiornika (na przykładzie dorzecza Sanu)

### Stanisław Krzanowski

#### Abstract

This work adopts a monographic approach to the influence of man-made reservoir retention on selected elements of a geographical environment. The study is divided into two main parts. The first one discusses the impact of reservoir retention on climatic elements in the immediate vicinity of a reservoir, such as precipitation, air temperature, wind and air humidity relationships, and on environmental factors: reservoir silting, thermic and river ice phenomena, changes in the physical and chemical properties of water. The second part is concerned with the impact of reservoir retention on the changes of discharge in the river and on the range and efficiency of this influence downstream from the reservoir. The area under study is the basin of the San river. This area includes four dam reservoirs that were constructed during the period 1961-1978 with the total useful capacity of 318.2 • 106 m3, among them the largest reservoir in Poland, located at Solina, with the total useful capacity of 296.8 • 106 m3. An analysis consisting in numerical evaluation of the possibility of flow regulation was done by examining flow differences in two periods: 1948-1967 (before the construction of the dam at Solina) and 1969-1988 (after the dam was completed) at the following gauge stations on the San river: Lesko, Jaroslaw, Rzuchow and Radomygl, located downstream from the Solina — Myczkowce system of water reservoirs. Detailed investigation covered the matrices of daily discharges in the analysed two periods (1948-1967 and 1969-1988), which, after charting and summing in diminishing order, created flow-duration curves of daily discharges separately for each year. From these curves, discharges QT for T = 2, 10, 30, 60, 90, 120, 180, 182.5, 240, 270, 300, 330, 355 and 364 days were estimated. The evaluation of the homogeneity of discharge series for the analysed duration T was conducted using the test of ranking sum (TRS), also called the Kruskal-Wallis test. The T-day discharges were treated as random variables and described by Pearson's Type III distribution. The distribution parameters were assessed by the method of maximum likelihood. The empirical curves of random variables for the described duration fit well the Pearson's Type III theoretical probability curves. The T-day discharge values differ considerably between the two periods under study. Based on Pearson's Type III probability distribution for the years of exceedance probability of mean annual discharge p = 5, 25, 50, 75, 85, and 95 %, the ordered the flow-duration curves of daily discharges in the years of different water resources were drawn for each analysed gauge station and for each studied period (1948-1967 and 1969-1988, separately). The curves intersect at the point separating the reduction and the regulation zone of the reservoir. Drawing the ordered flow-duration curves of daily discharges at the considered gauge stations enabled the prediction of the required compensation retention in the years of different water resources to be made for the assumed discharges resulting from different water management needs (at the existing dam system in the basin). Statistical analysis of the matrices of daily discharges from the two periods compared provides the basis for the introduction of the parameters of random variables which describe the long-term variation of discharges of specified duration T. The totalled frequencies of flows, n, and the probability of exceedance of the year of a given characteristic, p, were shown in the shape of the unit square of time space. The area of the unit square is equal to the combined probability P = n • p = 1 (conjunction of the probability of discharge occurrence during a year, n, and the probability of exceedance of the year of a described characteristic, p), while the probability of exceedance of the predicted discharge corresponds with the area above the line of this discharge and the lines described by the equations p = 1 and n = 0. Using the ordered flow-duration curves of daily discharges, the duration of the analysed flows in different years (dry/wet) was established, enabling the lines characterises the compensation ability of the reservoir in the defined zone of discharge and describes its impact on the hydrological regime of the river downstream from the dam in different years. Based on the introduced time space square, the curves of totalled frequencies of discharge P = f(Q) for the analysed gauge stations on the San river were drawn for each considered period. The curves intersect at point "S" with coordinates Q and P. The areas under the curves P = f(Q), limited by the point of their intersection "5", abscissa x = Q (in m3/s) and ordinate y, correspond with the values of the combined probability P = n • p and show the mean annual runoff in the given period, while the area included between the curves corresponds with the volume of the required compensation retention at the analysed gauge station. By expressing graphically the estimated volumes of runoff on the longitudinal section of the river in relation to the increase in the catchment area (A in sq km), two curves of mean annual volumes of runoff were obtained (for the periods 1948-1967 and 1969-1988), which increased with increasing area. By eliminating the influence of the catchment area on the increase in runoff, mean volumes of runoff downstream from the dam were calculated for each period under consideration. The volume of retention contributing to the flow regulation of the San river at gauge stations below the Solina — Myczkowce system of water reservoirs (314 • 106 m3) corresponds with the difference between mean volumes of runoff in the catchment in the periods 1969-1988 and 1948-1967. The estimated volume of compensation retention is very close to the total useful capacity of the reservoirs operated in the basin of the San river in the years 1969-1988, amounting to 318.2 • 106 m3. The estimates which were made using independent methods prove the distinctive influence of reservoir retention on the regulation of discharges in the San river downstream from the Solina — Myczkowce system of water reservoirs. Detailed analysis of the effect of the Solina — Myczkowce system of water reservoirs on the discharges with specified duration QT along the river course shows that the range of significant influence of reservoir retention on the reduction in maximum discharges (apart from incidental cases) and on the increase in minimum ones, diminishing with the course of the river with increasing catchment area, may reach, depending on the character of the year, up to the mouth of the San river to the Vistula river. This demonstrates great runoff control possibilities of the Solina — Myczkowce system of water reservoirs.Other language title versions | The influence of reservoir retention on selected environmental elements with particular consideration given to the changes in downstream discharge regimes (a case study of the San river basin) |

Book type | Monograph |

Other categories | ROZPRAWA_HABILITACYJNA |

Author | |

Publisher | Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW [80] |

Publishing place (Publisher address) | Kraków |

Issue year | 2000 |

Book series /Journal (in case of Journal special issue) | Zeszyty Naukowe Akademii Rolniczej im. H. Kołłątaja w Krakowie. Rozprawy, ISSN 1233-4189, (0 pkt) |

No | 259 |

Pages | 156 |

Publication size in sheets | 18.3 |

Language | pl polski |

Score (nominal) | 20 |

Citation count* |

* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.

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