An Understanding of Hydrometeorological Trends: A Multi-Method Trend Assessment

Abstract

Climate change and anthropogenic pressures significantly affect Mediterranean water re-sources, necessitating robust trend analysis methods for effective water management. This study presents a comprehensive assessment of hydrometeorological trends in T & uuml;rkiye's largest freshwater lake system, the Beysehir Basin (1981-2016), using a multi-method analytical framework. Traditional approaches (Mann-Kendall test and Sen's slope estimator) were integrated with advanced techniques (Innovative Trend Analysis, Innovative Polygon Trend Analysis, IV-ITA, and Star-IPTA) to evaluate trends in precipitation, temperature, streamflow, lake water level, and groundwater level. The results reveal statistically significant warming trends at both stations, particularly during the summer months. The strongest increase was observed in summer at & Ccedil;umra (tau = 0.565, p < 0.0001) and Bey & scedil;ehir (tau = 0.470, p < 0.0001), with additional significant increases in spring, autumn, and an-nual temperature series (p < 0.05); However, winter trends were generally not significant. Precipitation trends exhibited considerable spatial variability at the Bey & scedil;ehir station, September precipitation showed a significant increasing trend under the Yue and Wang (2004) approach (tau = 0.231, p = 0.007), while spring precipitation at & Ccedil;umra demonstrated a significant decreasing trend (tau = -0.205, p < 0.05). Annual precipitation trends were not consistently significant across stations. Lake water levels displayed consistent declining trends across multiple temporal scales, and groundwater levels indicated systematic depletion (Sen's slope: 0.382-0.435 m/yr; Mann-Kendall tau: 0.778-0.86; ITA: 0.459-0.511). A comparative evaluation demonstrated that the innovative methods provided enhanced sensitivity in detecting subtle hydrometeorological changes compared with traditional approaches. Regular polygon patterns in temperature and groundwater analyses contrast-ed with more irregular precipitation patterns, reflecting distinct environmental response mechanisms. Overall, these findings highlight the increasing vulnerability to water scarcity in the Bey & scedil;ehir Basin and underscore the urgent need for adaptive water management strategies in Mediterranean watershed systems. The proposed methodological framework provides a replicable template for comprehensive trend assessment in regions experiencing similar climatic and anthropogenic pressures