Hydrological characteristics of the river in the Karlovac area

U povijesti, ali i danas rijeke su vrlo bitan ekološki sustav za državu u kojoj se nalazi. Rijeke se koriste za navodnjavanje polja, za hidoelektrane, po njima se i plovi, a isto tako su stanište mnogih raličitih životinjskih i biljnih vrsta. No, s druge strane, rijeke predstavljaju i prijetnju vezanu uz pojavu poplava u uvjetima trajanja velikih voda. Cilj rada je analizirati hidrološke značajke rijeka na širem području Karlovca, pri čemu su korišteni podaci višegodišnjih razdoblja s mjernih stanica: Brodarci na rijeci Kupi, Mrzlo polje na rijeci Donja Mrežnica, Stative Donje na rijeci Donja Dobra te mjerna stanica Velemerić na rijeci Korani. Metodologija koja je primjenjena u radu zasnovana je na osnovnim statističkim metodama obrada mjesečnih i dnevnih podataka – analiza homogenosti, analiza hoda i trenda za maksimalne, srednje i minimalne protoke, korelacijska analiza, unutargodišnja raspodjela protoka, krivulje učestalosti i trajnosti te usporedni prikaz rezultata analiza vrijednosti protoka za maksimalne i minimalne protoke. Uz navedeno, još su uspoređene trajnosti srednjih dnevnih protoka s analiziranih stanica. Pomatrajući minimume protoka došli smo do saznanja da niti jedna od četiri rijeke na promatranim postajama ne presušuju, ali i da velike vode znaju poprimiti iznimno velike vrijednosti – čak nekoliko stotina m³s¯¹. Unutargodišnja raspodjela protoka pokazuje sličnost kod svih četriju postaja – reprezenata vodnog režima pojedinih rijeka: najmanje protoke tijekom ljeta (srpanj i kolovoz), a najveće tijekom zime (prosinac) i proljeća (travanj), kada se zapaža utjecaj otapanja snijega na povećanje vodne bilance otjecanja. Ovim se radom dokazalo da promatrane rijeke, naročito Kupa može doprinijeti osiguranju potrebnih količina vode u svim sezonama godine, ali i da postoji rizik od pojava ekstremnih poplavnih voda.In history, but still today, the rivers are a very important ecological system for the country in wich they are located. Rivers are used for irrigation of fields, for hydroelectric power plants, also used for sailing, and at the same time they are habitat for many species of animals and plant species. But, on the other hand, the rivers are also a threat to flooding in the conditions of large waters. The aim of the study is to analyze the hydrological characteristics of the rivers in the wider area of Karlovac, where long-term data from measuring stations were used: Brodaci on the river Kupa, Mrzlo polje on the river Donja Mrežnica, Stative Donje on the river Donja Dobra and Velemerić on the river Korana. Statistical method which was applied in a study is based on a basic statistical methods, such as homogenety analysis, walktrough and trend analysis for maximum, medium and minimum flows, correlation analysis, annual flow distribution, frequency cureve and durability, and comparative representation of the flow rate analysis for maximum and minimum flow rates. In addition, the medium daily flow of the analyzed stations are compared. By watching the minimum flow rates, we came to find out that none of the four rivers at the stations observed were dry up, but also that large water can reach extremely high values – even several hundred m³s¯¹. The annual distribution of flows shows similarity to all four stations – representative of the water regime of individual rivers: at least during summer (July and August), and most during winter (December) and spring (April), when the impact of snow melting on the increase of the water balance. This study proved that the observed rivers, in particular the Kupa can contribute to ensuring the required amount of water in all seasons of the year, but there is also a risk of extreme floods