Hydroclimate Changes to Arid regions subjected to Impact of climate change, human activities, and Large-scale climate patterns by Shereif Hassan Mahmoud A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Water Resources Engineering Department of Civil and Environmental Engineering University of Alberta © Shereif Hassan Mahmoud, 2020 Abstract In recent years, many regions worldwide have suffered from natural hazards related to the impact of human activities and climate change, such as floods and droughts, sea level rise, extreme weather events and an accelerated hydrological cycle. In Africa, the driest continent on Earth, climate change has led to more frequent occurrences of droughts of greater severity. Beside climate change, human activities have also incurred negative environmental impact which in turn has likely affected the climate at a wide range of temporal-spatial scales worldwide. For example, in the Middle East, floods of greater magnitude have been occurring more frequently in recent decades, which could be attributed partly to rapid urbanization or the effect of climate change, or both. In the Nile River basin (NRB), recurring droughts and increasing population have led to rising tension between competing users for water. Therefore, to develop more effective mitigation strategies against the potential impact of climate change, there is an urgent need to better understand changes to the hydrologic cycle of arid regions and linkage to regional climate change. The objectives of this dissertation are: 1) To investigate the potential implications of urbanization and climate change to the flood risk of Egypt and Saudi Arabia of arid climate in the Middle East. 2) To develop a GIS decision support system to delineate flood susceptibility zones in the Middle East. 3) To analyze the long-term impact of rapid urbanization on urban climate in a hot and arid environment. 4) To assess how past and future anthropogenic climate change and land use change (LUC) patterns have impacted arid regions’ environment, water resources, and ecosystems. 5) To develop a remote sensing-based water management model in arid regions of Middle East to help water managers devise sustainable water use planning and management. 6) To ii analyze the interdecadal variability in the hydroclimate of the Nile River basin and possible linkages to large-scale climate patterns. 7) To investigate the key climatic changes that contributed to recent increasing aridity of the Nile river basin. Chapter 1. From analyzing the implications of urbanization and climate change to the flood risk management of two governorates in Egypt, the results show that since 1970s, urbanization has led to higher flood risk despite of the decline in precipitation, because annual surface runoff and runoff anomaly show an increasing trend of 12.7 and 14.39 mm/decade, respectively. The surface runoff time series of the two governorates is also developed, which is one of such database first developed in Egypt, and it can be used to investigate the hydrologic impact of urbanization. Chapter 2. A multi-criteria approach to map flood susceptibility zones in the Middle East was developed. An analytical hierarchy procedure was employed to derive the weight of each susceptibility factor. An analysis was done to test the sensitivity of susceptibility factors to the flood susceptibility zones of urban watersheds, and the contribution of different susceptibility factors in developing urban flood susceptibility maps. The multi-criteria methodology was applied to the Riyadh Province, the central region of Saudi Arabia, where the flood susceptibility maps developed were validated against historical flood records and re-applied in the Riyadh city of different spatial scale. The results show that the proposed methodology is useful for general urban planning and assessment of flood susceptibility. Based on results obtained from the sensitivity analysis, it is advisable to consider six or more susceptibility factors in developing urban flood susceptibility maps, especially factors related to surface runoff and flow accumulation. Chapter 3. To study the influence of rapid urbanization on urban climate of Middle Eastern countries, the long-term impact of rapid urbanization on air temperature (Ta), relative humidity (RH), vapor pressure (VP) and human thermal comfort in the Cairo governorate of Egypt was iii analyzed. Land use change (LUC) between 1973 and 2017 were derived from Landsat satellite data. Next, non-parametric change point and trend detection algorithms were applied to Ta, RH and VP over 1950-2017 to assess the impact of urbanization on the urban climate of Egypt. Three historical thermal comfort indices: temperature humidity index (THI), effective temperature index (ETI) and relative strain index (RSI) were estimated from climate data collected between 1950 and 2017 to assess the impact of urbanization on human thermal comfort. The result shows that rapid urbanization in the Cairo governorate had led to severe heat stress levels and thermal discomfort risk in urban areas with limited vegetation covers. Chapter 4. To investigate the impact of anthropogenic climate change, human activities and land use change (LUC) on the environment and ecosystem services in arid regions, Earth observation data, Markov Chain, Cellular Automata, Pettit’s and Mann-Kendall tests were used to characterize the dynamic of LUC over coastal regions of Saudi Arabia and their impacts on regional climate and environment. Future effects of LUC and climate change in the study area, were also projected. The analysis shows that human alteration from natural vegetation and forests to other land uses after 1970s had resulted in the loss, degradation, and fragmentation of forests and vegetation, all of which have significant negative effects on the biodiversity of the region. Chapter 5. Using meteorological data, gridded climate and satellite data, a water management model was developed in arid regions of Middle East. First, the FAO Penman- Monteith method was used to model the spatial distribution of potential evapotransipration (ETo) on a grid-by-grid basis over the central regions of Saudi Arabia. Then, crop coefficients (Kc) were modelled as a function of 16-day time-series MODIS normalized difference vegetation index (NDVI). Actual evapotranspiration (AET) at daily, monthly and annual time scales were estimated from a soil water balance (SWB) model, Kc maps and ETo. The analysis of NDVI-Kc relationships iv at each pixel, showed strong agreement between NDVI modeled Kc and actual Kc which fits crop growth conditions in the field. The average daily AET data show a statistically significant positive trend of 1.5 mm/decade in the study area since 1990. The positive trend in AET is expected to give rise to more severe droughts in the future. Therefore, a strategic management of irrigated water is necessary to minimize unnecessary wastage. Chapter 6. A comprehensive analysis on the interannual to interdecadal variability in the hydroclimate of the Nile River basin (NRB) and possible teleconnection to large-scale climate patterns, the spatio-temporal variability, frequency, intensity, change point and trend of monthly precipitation, precipitation anomaly, temperature, temperature anomaly, geopotential height, relative humidity, specific humidity, actual evapotranspiration (AET), and wind stresses data over the basin level was conducted. The results show significant hydroclimate changes in NRB in recent decades. Besides climate warming, statistical analysis, wavelet transform coherence (WTC) analysis, composite analysis, and detrended cross-correlation analysis (DCCA) also show that beside ENSO, IOD plays a crucial role on NRB’s hydroclimate variability over inter-decadal and longer timescales. Chapter 7. The primary driving factors that contributed to recent increased aridity of the Nile river basin (NRB) were identified. Besides climate warming, statistical and wavelet transform coherence (WTC) analysis shows that the influence of stronger ENSO and Indian Ocean dipole (IOD) in NRB has increased after 1980s, particularly the influence of IOD on NRB’s hydroclimate over inter-decadal timescales. A shift in zonal winds (westward) and meridional winds (southward) associated with stronger El Niño events has contributed to the increased aridity of NRB after 1970s, given stream function, GPH and U-wind anomalies associated with El Niño show that changes in regional atmospheric circulations during more persistent and stronger El Niño has v resulted in drier NRB. After 1970s, WTC between El Niño, IOD, sc-PDSI (self-calibrating Palmer Drought Severity Index) and SPI (Standard Precipitation Index) shows significant anti-phase relationships, which again demonstrates that more frequent and severe El Niño, IOD and SST gradient over the Arabian Sea (WTIO) in recent years has led to more severe droughts in NRB. Furthermore, from WTC and strong negative correlations between SPI, sc-PDSI and WTIO, NRB’s hydroclimate is shown to be more strongly influenced by WTIO than by IOD, and the Nile flow is more strongly teleconnected to IOD and WTIO than El Niño at inter-annual and inter- decadal time scales. Contrary to past finding, our results show that IOD and WTIO are better predictors of the Nile flow than El Niño. Climate projections suggest that under the combined impact of warming and stronger WTIO and El Niño events, future droughts of the NRB are expected to worsen. Conclusions and future