Abdulaziz S. Al-Turbak

Climate change impact and runoff harvesting in arid regions

The most significant large-scale environmental challenge that many countries, especially in the arid and semi-arid regions of the world, will face in the middle and long-term are water scarcity problems, which are attributed to climate change impacts such as temperature increase, abundance of high solar radiation, and aridity in addition to population pressure. In many countries, current water resources use already exceeds sustainable and renewable supply. Various methodologies are suggested to increase the sources of water supply, among which one of the alternatives is rainwater and runoff harvesting (ROH). Water scarcity and additional stress are among the most specific problems in arid and semi-arid regions, where vegetation cover is very weak under extensive solar irradiation effects with high evaporation rates. Present global warming, climate change impacts, and their future patterns are expected to cause increase in the evapotranspiration rates and hence reduction in the groundwater recharges. Under such circumstances, any simple but effective water storage augmentation facility as the artificial groundwater recharge gains vital importance for sustainability of water supply and survivals in desert ecosystems. Although intensive and frequent rainfall events are rare they generate significant surface water flow during occasional floods and especially flash floods with huge amounts of surface water. It is, therefore, necessary to enhance artificial groundwater recharge from consequent frequent runoffs through suitable hydraulic structures. This paper aims at assessing the importance of ROH systems for domestic supply in arid regions with specific reference to the Kingdom of Saudi Arabia. For this purpose, it presents ROH from the surface flows in depressions of Quaternary wadi deposits in arid and semi-arid regions.

Evaluation of dams as a recharge method

Dams are used for recharge purposes in many parts of Saudi Arabia. In spite of the importance of such a method, no detailed study exists on its performance. As a part of a comprehensive research project dealing with all aspects of dams as a recharge tool in the central region of the country, data on reservoirs’ water levels, meteorological parameters and observation wells were collected at two recharge dam sites. These data were used in a water budget approach to estimate efficiency. Contrary to the established belief that this method of recharge is poor, results show that between 82% and 94.5% of water stored in the two reservoirs was taken into the soil.

Geomorphoclimatic peak discharge model with a physically based infiltration component

Abstract A geomorphoclimatic model with a physically based infiltration component is presented. Previous equations were developed to calculate peak discharge and time to peak for a certain event in a particular basin given its morphological features and storm information. These equations were incorporated into a physically based infiltration model. This model calculates a ponding time for the event and finds effective rainfall intensity and duration. The entire model was calibrated using a few events in three catchments in Saudi Arabia. The most important parameters are hydraulic conductivity and effective soil capillary drive. The model was found to predict peak discharges reasonably well, at least for events for which detailed and accurate data are available.

Recharge dam efficiency based on subsurface flow analysis

ABSTRACT Dams have been used as a recharge method in Saudi Arabia. A previous study conducted on a recharge dam in Central Saudi Arabia showed that it is efficient at infiltrating water from its bed. However; water may infiltrate but not be effective downstream. In this paper groundwater flow downstream from Al-Amalih Dam in Central Saudi Arabia was calculated for a three-year period. This was then compared to the infiltrated water The components of flow around the dam for the entire three years are discussed and presented in this article.

Assessment of a water-harvesting site in Riyadh Region of Kingdom of Saudi Arabia using hydrological analysis

A potential ungauged water-harvesting site was chosen in the central Riyadh Region of Saudi Arabia. A hydrological study was carried out on the catchment area from which runoff water will be diverted to the chosen site. Rainfall depth records from three neighboring rain gauges were used. Runoff volumes and peak discharges for the 2-, 5-, and 10-year storms were estimated using three methods, namely, (a) Soil Conservation Service (SCS) Dimensionless Unit Hydrograph (DUH) method assuming Gumbel distribution for rainfall depth analysis, (b) HEC-HMS modeling, and (c) the modified Talbot formula. The results show that the modified Talbot formula yields an order of magnitude higher peak discharge values for all return periods. The SCS-DUH method and HEC-HMS modeling provide comparable estimates for the peak discharges and runoff volumes. The peak discharges obtained through the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model for the 2-, 5-, and 10-year storms are 0.17, 0.83, and 1.34 times than those obtained by the SCS-DUH, respectively. The HEC-HMS runoff volume estimates are 0.18, 0.85, and 1.36 times than those estimated by the SCS-DUH for the 2-, 5-, and 10-year storms, respectively.