Increasingly, and often mutually conflicting requirements for the use of water resources, there is a need for more complex management methods, including the management of the volume of reservoirs. Silt filling of reservoirs is one of the most well-known problems of river hydraulics. Dams and reservoirs, created by damming river flows, cause the retention of river sediment (drag and floating sediment) that comes from the gravitating basins, or sub-basins of the reservoir's tributaries. By analyzing the sediment transport on the tributaries, and the total amount of sediment deposited in the Modrac multi-purpose reservoir, real data are obtained on the amount of sediment introduced into the Modrac multi-pupose reservoir, the dynamics of sediment input, and the degree of pollution of this type of water body. The Modrac multi-purpose reservoir is the only available water resource in the region of Tuzla and its surroundings. Acknowledging the fact that the useful volume of the reservoir is limited, and that over time the reservoir is filled with dragged sediment and coal dust as floating sediment, and that consumers - the population, industry and others must be provided with a water supply with a high degree of safety. Excess water needs to be used to the maximum for the purpose of electricity production, and there is a need to optimize the system, i.e. more efficient management of the water resources of the reservoir, i.e. to prove the maximum utilization of the reservoir while continuously providing all the necessary amounts of water to which the Modrac multi-purpose reservoir is connected.

Multi-purpose reservoir Modrac is the most important water resource in Tuzla canton. Ecologically acceptable flow on dam Modrac is not adjusted with the latest Rulebook about methods of determining ecologically acceptable flow. This article shows the methods used to determine ecologically acceptable flow on the Modrac dam, respecting the fact that reservoir Modrac is declared as protected water resource. The given calculation of ecologically acceptable flow is made for II level of evaluation.

This paper examines the long-term changes in temperature and precipitation in the karst region of Imotski, Croatia, which is of particular interest due to its abundance of karst phenomena. This study analyses temperatures and precipitation on monthly and annual scales at two climatological stations in the region, Imotski and Ričice. Linear regression, the Theil–Sen estimator (β), and the Mann–Kendall test were used to determine the trends and statistical significance. The homogeneity of the data was checked using the Standard Normal Homogeneity Test (SNHT), and the F-test and t-test were used to test the significance of the mean shift between the two subseries. Additionally, the coefficient of variability, standardized rainfall anomaly, and precipitation concentration index were employed to analyze the precipitation variability. The study found a statistically significant (p < 0.05) upward trend in the mean (β = 0.0437) and maximum (β = 0.0590) annual air temperature at the Imotski station and the mean (β = 0.0387) annual temperature at the Ričice station. The SNHT test showed a statistically significant (p < 0.05) shift in the mean annual temperatures after 2007 and maximum annual temperatures after 1998 at the Imotski station. Similarly, a statistically significant (p < 0.05) shift in the mean annual temperatures after 2011 and the maximum annual temperatures after 1998 was found at the Ričice station. A seasonal distribution of precipitation is observed at both the Ričice and Imotski stations, with a downward trend (β = −2.7693) at Ričice and an upward trend (β = 6.0575) at Imotski; however, neither trend is statistically significant (p > 0.05). An increase in the intensity of dry periods and the occurrence of extreme events was also noted. The climatological analysis, conducted for the first time in this area, is a crucial step toward understanding local climate patterns and making informed decisions toward sustainable development and adaptation strategies.

Mufid Tokić1 Anadel Galamić2 Jasmin Hrnjadović3 Omer Kovčić4 UDK: 556.1:627.81 DOI: 10.14415/konferencijaGFS2019.072 Summary: According to the available existing documentation and various previous studies, the flow of water into the "Modrac" accumulation is not defined directly, by measuring the flows on the main creek Spreca and Turija, but indirectly, over the level and volume of the accumulation, as well as data on the discharge of water from the reservoir. In this way, a series of average daily values of inflow into accumulation was obtained for the period from 1980 to 2012. year. Interpretation of these data was done in the form of variation of annual inflows in the observed period, as well as average flow curve curves. By reviewing the previous measurements and surveys, it can be concluded that there is a more pronounced cyclicality of inflows over a longer period of time, with driers of dry and rainy periods. On the other hand, having in mind the natural correlation between the inflow of water and the spread of the deposit, it is logical to hypothesize that at the time of the hydrological maximum, the input is higher in the accumulation. Another important indicator of the hydrological regime of the lake is the duration of the inflow into the accumulation "Modrac". This curve points to the vast hydrological regime of the watercourse in the basin of the reservoir. In this regard, it should be noted that all watercourses in Bosnia and Herzegovina and the region, with a basin area of up to 1000 km2, have such a regime. Bearing in mind the similarity of physical and geographical conditions in the region, this analogy is quite logical. The hectic hydrological regime is characterized by a short duration of large waters and a very long duration of small water, as well as a large flow range (Qmax / Qmin).

The major task of multi-purpose reservoir „Modrac“ operation is to decide how much water should bereleased now and how much should be retained for future use given some available and/or forecastedinformation at the beginning of the current time period. In practice, reservoir operators usually followrule curves, which stipulate the actions that should be taken conditioned on the current state of thesystem. Through construction of the dam Modrac in 1964, the reservoir of the same name was formed.Its primary objectives were the provision of technological water for industries in the Tuzla region andmitigation of downstream floods as well as recreation and other purposes. The multi-purpose reservoirModrac is currently a drinking water source for the municipality Tuzla. In order to better manage of themulti-purpose reservoir „Modrac“, certain analyzes are presented in this paper.This paper presents an analysis of annual precipitation, mean annual inflows in the catchment area ofthe multi-purpose reservoir „Modrac“ for the period 1967 - 2016. In this paper there are presentedstatistical datas on the maximum amount of precipitation for the dry season period (May to October) fordifferent return periods, for different distribution curves, as well as the maximum amount ofprecipitation for the wet season (November to April) for different return periods for different curvesdistribution.This paper provides information on the movement of precipitation changes in the catchment area ofmulti-purpose reservoir “Modrac” for the period from 1967. – 2016.