Determination of flood peak discharges in some pond watersheds and analysis of agricultural drought of Bilecik

Climate change, and the accompanying floods and droughts, significantly impact water resources. Since the agricultural sector is the largest consumer of these resources, comprehensive agricultural water management plans must be developed for the basins. This study examined the interactions between the main agricultural products cultivated in the Bilecik districts and the effects of both floods and droughts. For this purpose, agricultural product data for Bilecik were obtained from TÜİK (Turkish Statistical Institute). Climatic data for the Bilecik districts were acquired from the Bilecik Meteorology Directorate, and basin data were supplied by the State Hydraulic Works (DSİ) Regional Directorate. For the flood analysis, the following basins were used: the Arap Stream and the Delikbağ Stream in Gölpazarı; the Gümüşdere in Pazaryeri, and the Çöte Basin in Yenipazar. Basin characteristics (area, length, slope, curve number) and climatic data were prepared and utilized within the WinTR-55 and DrinC models. The results showed that the R2 value for the relationship between the RDI drought index and hop yield reached its highest value among the compared districts in Bilecik Center, with a value of 0.195. Similarly, the R2 value for the relationship between the RDI drought index and wheat yield reached its highest value in Bilecik Center, with a value of 0.31. Furthermore, a significant decrease in drought index values was observed in Bilecik in 2017. The years 2006 and 2007 were determined to be the most pronounced drought years in Bozüyük. In Pazaryeri, the year 2007 was identified as having the most intense drought impact. When comparing the peak discharge values for the 100-year recurrence interval using the WinTR-55 model, the Gölpazarı-Arap Stream area presents the highest risk with 66.59 m3/s. This is followed by Gölpazarı-Gümüşdere (47.06 m3/s), Gölpazarı-Delikbağ Stream (47.00 m3/s), and Yenipazar-Çöte (26.27 m3/s). Future research should focus on examining the tolerance levels of different crop varieties to drought and the adaptation strategies that can be developed to mitigate the impacts of drought on agricultural production. Finally, risk maps for flood-drought-water pollution should be created in agricultural water management studies, and awareness and education programs should be conducted to inform farmers about these hazards.