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Desert precipitations are rare but torrential, and ephemeral streams are ungauged, by which synthetic hydrograph methods become essential for flood risk assessment. This study quantifies the impact of urbanization on generating flash floods in desert watersheds. A definition of flash flood was presented in terms of the relative strength of partial storm intensity to storm design frequency for existing stormwater drainage systems. A large desert catchment was chosen to generate synthetic surface runoff hydrograph records using HEC-HMS model. The catchment characteristics were extracted using GIS tools and digital elevation data. Intensity-duration-frequency curves were used for the catchment to simulate hypothetical storms of 24-h duration for different return periods. A sensitivity analysis was performed for curve number parameter to simulate urbanization level scenarios. The results show that it is possible to employ simple models to synthesize the impact of urbanization on desert flash floods with a drastic change in hydrograph peak discharge, time to peak, and runoff volume. The former hydrograph characteristic is found to be the most sensitive, with an increase by 316% in response to increase in curve number by 10%. This finding implies that a small variation in land cover due to urbanization may significantly increase the flash flood strength and potential damage to infrastructure and human life. [ABSTRACT FROM AUTHOR]

Foum El Gherza dam is studied herein due to its considerable loss of water resources. It is progressively threatened by water leaks with an interannual leak flow estimated at 5 hm. In this study, we undertake this problem through hydrochemical methods, tracer techniques, and physicochemical characterization including pH, conductivity, and temperature variation in order to detect water leakage combining conventional, tracing, and isotope techniques and forecast the possible treatments. The obtained results by a physicochemical study showed two types of flows. The first one is vertical downward, depicted by practically constant temperature and conductivity values, whereas the second is oblique and almost horizontal resulting from the reservoir. This one was revealed by low conductivity and homogeneous of temperature values. This reflects the degraded state of the geological layers at the level of both banks of the dam. The temperature and the conductivity evolve with depth from one point to another according to the geothermal gradient and the geologic layers of the site. This variation further confirms the degraded state of these layers. Thanks to the obtained results, a leak flow variation was established according to the water level in the dam. [ABSTRACT FROM AUTHOR]

Using MODFLOW 2005, this study numerically evaluated the effects of managed aquifer recharge (MAR) using treated wastewater (TWW) in managing the Al-Khawd coastal aquifer northeast of Oman. Our primary objective is to increase the urban water supply and to sustain the aquifer service with the lowest possible damage to the aquifer. A number of managerial scenarios were simulated and progressively developed to reduce seawater intrusion and outflow of the groundwater to the sea. An economic analysis was conducted to characterize the trade-off between the benefits of MAR and seawater inflow to the aquifer under increased abstraction for domestic supply. The results show that by managing irrigation wells and relocating public wells in conjunction with MAR practices, the abstracted volume for drinking purposes could be doubled. Even though injection of TWW is more expensive (due to the injection cost), it was observed to result in greater benefits. The results indicate that managing the aquifer would produce a net benefit ranging from $8.22 million (scenario 7) to $15.21 million (scenario 4) compared to $1.57 million with the current practice. In conclusion, MAR using TWW is a feasible solution to develop water resources in arid regions, and the best scenario depends on the decision maker's preference when weighing the benefits of MAR and the level of damage to the aquifer. MAR could help manage stressed aquifer systems in arid zones to maximize the benefit of using the water for domestic purposes while minimizing the damage to the aquifer. [ABSTRACT FROM AUTHOR]

The sediment yield of a drainage basin during flood events has a remarkable impact on a desert ecosystem. While sediment yield increases the destructive impact of the flood, it also influences the recovery of disturbed surfaces downslope from source areas in desert landscapes. For environmental change and flood mitigation, it is important to evaluate the sedimentary yield of drainage basins. The current study proposes a simple method to qualitatively evaluate sediment yield of ungauged drainage basins in arid and semi-arid zones. The method evaluates basin sediment yield based on a list of factors that control detaching of detritus from bedrocks and transporting it down the hill slopes and through the drainage system. Four drainage basins: Al Ahsabah, Qanunah, Yabah, and Hali located on the Saudi Arabia Red Sea coast were selected to apply and test the new approach. The Automated Geospatial Watershed Assessment Tool (AGWA) was used to evaluate the new approach. The study found that the new method has a reasonable capability to qualitatively evaluate the sedimentary yield of ungauged drainage basins. [ABSTRACT FROM AUTHOR]

This paper presents the derivation of the design storm hyetograph patterns for the Kingdom of Saudi Arabia based on real rainfall events from meteorological stations distributed throughout the Kingdom. Two thousand twenty-seven rainfall storms for a 20-28-year period were collected and analyzed covering 13 regions of the Kingdom. Four distinct dimensionless rainfall hyetograph patterns have been obtained over the Kingdom, while two patterns have been obtained for each individual region because of the lack of data for long-duration storms in individual regions. The resulting dimensionless rainfall patterns for each region can be used to develop storm hyetographs for any design duration, total rainfall depth and return period. It has been shown that the developed storm hyetographs have different features from other storm patterns that are commonly used in arid zones. The study recommends using these curves for the design of hydraulic structures in Kingdom of Saudi Arabia and regions alike. [ABSTRACT FROM AUTHOR]

Water resources in the Algerian South are rare and difficult to reach because they are often too deep. This is the case of Guerrara which is characterized by an annual precipitation average of less than 60 mm. The water supply is warranted from groundwater, frequently too deep and badly known. The main purpose of the present study is to determine the geometry of aquifer from geophysical data. Fourteen vertical electrical soundings covering the total surface area were carried out by using an arrangement of electrodes called 'Schlumberger array.' The length of the selected transmission line (AB) was 1,000 m, which allowed a vertical investigation reaching up to 160 m of depth. The analysis of the results shows that the prospected zone is characterized by the succession of layers with different electrical resistivities. A sandstone aquifer characterized by resistivities near 100 Ω m overcoming a limestone aquifer stronger with values that exceed 1,000 Ω m, separated by a conductive layer of clay with average resistivity of 15 Ω m. Distribution map of sandstones thickness shows the structural variations of this horizon allowing an estimation of its hydraulic potential. [ABSTRACT FROM AUTHOR]