Assessment of changes in return levels of historical and projected high and low flows of upper Euphrates basin in Turkey using nonstationary models

Aziz R., YÜCEL İ.

Environmental monitoring and assessment, cilt.195, sa.5, ss.576, 2023 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 195 Sayı: 5
  • Basım Tarihi: 2023
  • Doi Numarası: 10.1007/s10661-023-11136-6
  • Dergi Adı: Environmental monitoring and assessment
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, ABI/INFORM, Aqualine, Aquatic Science & Fisheries Abstracts (ASFA), BIOSIS, CAB Abstracts, Compendex, EMBASE, Environment Index, Food Science & Technology Abstracts, Geobase, Greenfile, MEDLINE, Pollution Abstracts, Public Affairs Index, Veterinary Science Database, Civil Engineering Abstracts
  • Sayfa Sayıları: ss.576
  • Anahtar Kelimeler: Climate change, CORDEX, Extreme flows, Hydrological modeling, Nonstationarity
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Owning to climate changes and other anthropogenic interventions, the frequency and return levels of extreme flows cannot be treated as stationary. This study quantifies the changes in return levels by fitting the stationary and nonstationary frequency distribution models for annual and seasonal high and low flows of upper Euphrates basin during historical and two projection periods. The projected flows of three selected sub-basins in the upper Euphrates were obtained using HBV-light hydrological model forced by projected daily precipitation and temperature driven from and the most representative regional climate model (RCM) for the study area within the CORDEX-Euro domain. During the historical period, analyses suggest that half of the stations exhibited an increase in return levels (up to 13.5% with GEV), while the remaining four sub-basins experience a decrease in the return levels (up to 27% with GEV). With few exceptions, most of the sub-basins experience an increase (up to 80% with GEV) in return levels of yearly low flows. With few exceptions, the return level of low flows for all seasons generally increases; however, directional variability for high flows is observed. The changes in return levels of yearly projected flows are consistent with historical results in indicating the direction of impact for both near future and far future periods. A decrease in return levels (up to 35% and 22%) in yearly high flows and an increase (up to 100% and 40%) during the near future and far future, respectively. It is projected that the floods of a given return level in the selected sub-basins are becoming milder across all three periods. However, some directional inconsistencies are noted in nonstationarity impact at seasonal scale through projection periods. On yearly basis, the decreasing high flow along with increasing low flow quantiles suggests that the range of extreme occurrences is shrinking. The nonstationarities in high flows as well as low flows should be incorporated in design and development of water resources schemes in the study area.