IV. IMCOFE / ROME Young Scholars Union 405 Analysis of Streamflow Trends in the Kızılırmak River Basin Burcu ERCAN Asist. Kilis 7 Aralık University, Turkey ġimal YÜCE Phd Student, Gaziantep University, Turkey Mehmet Ġshak YÜCE Assoc. Prof. Dr. Gaziantep University, Turkey Abstract Trend analysis of annual average streamflow are indispensable in water resources management, developing hydraulic engineering projects. In this study, analyses were conducted to determine if there are any trends in the annual average streamflow data of 21 flow measurement stations situated on Kızılırmak River , Turkey. Mann-Kendall and Sperman's Rho tests, which are non-parametric trend analysis methods, were employed in order to perform a research for a period of about 30 years ranging from 1975 to 2005. The results show a decreasing trend in the majority of the streamflow data, however, no-trend was observed in a number of stations, with a significance level of 0.05. Keywords: Trend Analysis, Streamflow, Mann-Kendall, Sperman‘s Rho, Kızılırmak Basin. INTRODUCTION In recent years, studies which is done on the determination of past trends and changes of climate variables are increasing. In general, parametric and nonparametric methods are used to determine climate trends. Parametric methods provide good results if normal distribution of data is appropriate. It is better to work with nonparametric methods in situations such as non-normal distribution, presence of missing data and serial dependency. In this study, streamflow trend analysis will be done by non- parametric methods in Kızılırmak basin. The high temperature and decline of precipitation cause drought. Drought is a hidden danger of nature and one of the greatest disasters. Other variables, such as heavy wind and low humidity are effective on drought. Drought is not just a physical or a natural event. For the continuity of life, all living things need water. Therefore drought is a serious risk to human populations and the ecosystem, whatever the level is it. This risk has become more important in recent years parallel to climate change. The variability of climate conditions in Turkey indicates that it will be most affected one of the countries by a climate change due to global warming. Observational and historical hydro- meteorological data are used in the planning and design of water resources projects (Burn and Elnur, 2002:108). There is an implicit assumption, so called stationarity implying time-invariant statistical characteristics of the time series under consideration, in all water resources engineering works (Kahya and Kalaycı, β004μ1β8). As a result of global warming-related climate changes, increasing temperature and irregularities of precipitation will continue to increase in the future. This affects negative direction on entire ecosystem. It is the rainfall parameter which changes most depending on time and place from meteorological elements. Trend is defined as a significant decrease or increase in measured values of a parameter over time. In water engineering studies, a design is made assuming that long-term values do not change over time during planning. But as the accumulation of greenhouse gases are increased in the atmosphere, changes occur in the climate. In this case, the assumption is wrong. As a result, a design should be done with help of some trend tests and variable depending on the balance should be examined in the long term. These trend tests includeμ Spearman‘s Rho, Mann Kendall, Seasonal Mann