الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
 |  | from | 294 |  |  |
| | | from | 294 | | |
Abstract
Due to the important location of Dhamar watershed (basin) with the increase in population and urbanization. In addition to the risk of high impacts of groundwater withdrawal and the risk of flash floods inundation, this study was conducted for this watershed which is located in Dhamar Governorate, the Republic of Yemen.
It mainly aims to develop an integrated hydrological model for the watershed and an analytical methodology to estimate the long-term rainfall volumes, infiltration (groundwater recharge) volumes, surface runoff volumes, groundwater abstraction volumes, etc. It also aims to assess the flash flood hazard, risk on groundwater, and urbanization risk in each sub-basin. These aims were achieved utilizingvariety of softwares, tools, methods, and developed models including RS and GIS techniques with the help of ArcHyrdo, HEC-GeoHMS, HEC-HMS,Matlab Mathworks, Hyfran plus, and three DEMs sources of (SRTM, ASTER, and AW3D30) of 1 arc-sec. resolution (30 m). The data used in this study include rainfall data for 42 years (daily-monthly 1978-2019), land use land cover (LULC) data for 11 years (2009 – 2019), Curve Number (CN) data, soil texture types data, satellite images, topographic maps, agriculture, and groundwater data for the last period.Statistical methods (e.g. NR, IDW, MIDW, LR, WLR) and ANNs with the help of Matlab Math works and Hyfran plus were used to estimate the missing rainfall data and develop the IDF curves. The estimation of hydrological model was based on the process of the NRCS-CN method. The direct runoff also estimated based on the SCS transform method.
Since Dhamar watershed is ungauged watershed, the above applicable softwares, tools and methods were selected for more validation and verifications.Along with that, this study is the first study conducted in Yemen which distinct by using not only one DEM but three different DEMs sources and the statistical with ANNs methods as an analytical methodology in which their findings would help in select the appropriate DEM and method in hydrological studies and estimating missing rainfall data in arid and semi-arid regions such as Yemen.
The results of watershed delineation and using the semi-distributed model, the watershed was divided into 10 sub basins using the three DEMs sources.Through the comparison of continuity and consistency tests between the statistical methods and ANNs to estimate the missing rainfall data, the results confirmed that the IDW method could be the appropriate method to estimate the missing rainfall data.Through the comparison between the three DEMs sourcesrelated to the results of watershed delineation,rainfall, loss, and runoff volumes. There were no big differences between the AW3D30 and SRTM but in general the AW3D30 was the best. The results confirmed that the AW3D30 source gave the maximum area (941.71 km2), the minimum and the maximum elevations (2286 – 3026 m), and maximum values of rainfall, loss, and runoff volumes. Thus the final results for Dhamar watershed using the AW3D30 DEM sources hydrological model simulation are selected and adopted for each sub-basin in Dhamar watershed from 1978-2019.