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Master
Oman
Simulating Climate Change Impacts on Wadi-Flow Variation in Al-Khoud Watershed
Titre : Simulating Climate Change Impacts on Wadi-Flow Variation in Al-Khoud Watershed
Auteur : Ruqaya Al Hadhrami
Université de soutenance : Sultan Qaboos University
Grade : Master of Science (MS) 2019
Résumé
Impact of climate change is one of the most important concerns nowadays since it will directly
affects various sectors such as agriculture, economy, environment and human life. This study
investigated the possible future climate change effects on precipitation pattern and resulting
changes in stream flow regimes in Al-Khoud watershed in Oman. Al-Khoud watershed was
delineated using HEC-GeoHMS tool in ArcGIS software. Wadi-flow simulation model was
developed using Hydrological Engineering Center-Hydrologic Modeling System (HEC-HMS)
software. In HEC-HMS, Soil Moisture Accounting (SMA) algorithm and User Specified Unit
Hydrograph (USUH) technique were used for calculating precipitation losses and direct runoff
generation, respectively. Parameters of the SMA method and USUH were calibrated and
verified using historical rainfall and wadi-flow records. In climate prediction, historical
precipitation data from 6 rain gage stations were used with LARS-WG6 to downscale future
daily rainfall data from two general circulation models (GCMs) (EC-EARTH and MIROC5)
and two representative concentration pathway (RCP) scenarios (RCPs 4.5 and 8.5). Predicted
daily data were disaggregated to hourly time scale using K-Nearest Neighbor method (K-NN).
These rainfall predictions were then used with the calibrated hydrological model to simulate
wadi-flow variations in the future. The parameter analysis of HEC-HMS and SMA model show
that the soil percentage, infiltration and soil percolation parameters are the most sensitive
parameters for wadi-flow simulations. The simulated wadi-flows agree with the observed ones
with the Nash-Sutcliffe efficiency value of 0.93. The model performance can potentially be
improved by calibrating the parameters seasonally. Predicted rainfall by two RCPs and two
GCMs indicate potential increases in annual total rainfall in two future periods : 2021-2040 and
2041-2060 compared to baseline period. Simulated wadi-flow events in the future show that the
peak-flow rate can be significantly higher compared to the Gonu event in 2007 due to potential
increases in rainfall intensity. Results further indicated that the base-flow amount increases as
the duration of the rainfall event extends. Moreover, higher antecedent moisture content tends to
increase the peak-flow rate and volume of the hydrograph.
Page publiée le 4 mai 2021, mise à jour le 27 mars 2022