Büğdüz Alt Havzasi (Burdur) Hidrolojik Modeli

Abstract

Understanding the responses of river basin flows to environmental changes is crucial for effectively managing water resources. In this thesis, the impact of human activities and water structures on the Büğdüz Basin has been assessed. For this purpose, hydrological models were developed for the periods before and after the construction of the Büğdüz Pond, which was built in 2014 on the Yayla Stream, a tributary of Büğdüz Stream, one of the main branches feeding Lake Burdur. The SWAT (Soil and Water Assessment Tool) hydrological model, commonly used in studies to evaluate the effects of human activities and climate change, was employed. Calibration and validation processes were carried out using the SUFI-2 algorithm of the SWAT-CUP program to identify the basin parameters for the 2005-2013 period when the Büğdüz Pond did not exist. Flow data observed at the Büğdüz D. (Suludere) Flow Observation Station (FOS), located at the basin outlet, were used. In the model, the years 2005-2006 were used as a warm-up period, 2007-2010 for calibration, and 2011-2013 for validation. The model performance values for the parameters obtained as a result of the calibration were statistically calculated as R² = 0.88 and NSE = 0.88, while for the validation, they were R² = 0.72 and NSE = 0.32. The low NSE value in the validation indicates that the calculated and observed flow values did not sufficiently converge. However, the hydrographs resulting from the calibration and validation processes show that the peak points of the observed and calculated flow data are generally in agreement. After obtaining the model parameters, two different models were developed for the years 2014-2018, one with and one without the Büğdüz Pond. The model inputs were used jointly for both models. For the model with the Büğdüz Pond, the reservoir module was provided with pond area, volume, and irrigation data, obtained from the report developed by the State Hydraulic Works (DSİ, 2010). Water budgets for the periods with and without the pond were calculated using the hydrological cycles obtained from the model results. As a result of the hydrological models developed for the periods with and without the Büğdüz Pond, the change in storage in the Büğdüz Basin was calculated as 9.246 x 10⁶ m³/year and 7.578 x 10⁶ m³/year, respectively. It was determined that the largest water loss in the basin occurred through evaporation and transpiration, and during the period with the pond, an additional 1.44 x 10⁶ m³/year of water was lost due to evaporation and transpiration. The hydrological models developed in this thesis aimed to reveal the effects of water structures on the hydrological cycle within the basin. Considering the uncertainties in model studies, water budget analyses should be conducted through modeling studies before the construction of water structures to minimize the impacts on water basins.