This study examines the long-term trends of evaporative water losses at Lake Hefner and Canton Lake in Oklahoma from 1985 to 2018. Using a mixed-method approach, the research assesses annual and seasonal evaporation losses for both lakes and analyzes their correlation with various climatic factors. The findings reveal a statistically significant rise in evaporation rates, with Lake Hefner and Canton Lake experiencing annual increases of 0.31 mm and 0.42 mm, respectively. Notably, these increasing trends are more pronounced during the autumn and winter months, contrary to the expected summertime peaks. This unusual pattern is attributed to the thermal inertia of the lakes and the rising winter temperatures reported across the Western United States. The study further explores the profound impact of climate change, specifically the intensification of drought episodes in this region, such as those recorded in 2003, 2006, and 2011, which exacerbated evaporation rates. These findings underscore the increased vulnerability of water resources to climatic variability and the need for proactive solutions. In response, this thesis proposes adaptive management strategies within the framework of Integrated Water Resources Management (IWRM). It recommends the integration of evaporation suppression strategies into water management practices and the adoption of innovative technologies such as the application of wind-resistant monolayer films based on reservoir storage triggers. Policy recommendations are also discussed, emphasizing the need for robust measures that include regular evaporation monitoring and the use of financial incentives to adopt water-saving technologies. By addressing the localized impacts of climatic factors on evaporation and integrating these insights into reservoir management, this research contributes to the development of targeted strategies aimed at enhancing the sustainability of water resources in Oklahoma and similar environments globally.