THE CHARACTERIZATION OF TRANSMISSION LOSSES IN EPHEMERAL CHANNELS: CASE STUDY IN THE WADI FERRAIN BASIN SINAI PENINSULA, EGYPT

The uncertainty in temporal and spatial variations in ephemeral streamflow losses (transmission losses - TL) greatly limits our ability to accurately quantify the contributions of ephemeral recharge to overall basin recharge. This situation is amplified in hyper-arid (<60 mm/yr annual pptn.) regions such as the Sinai Peninsula of Egypt by the general paucity of data and rugged terrain. A better understanding of wadi characteristics, magnitude, and recharge amounts is required to fully evaluate the spatiotemporal variability of TL and recharge.

An integrated approach involving the collection and analysis of field and remote sensing-based observations in conjunction with statistical analyses has been developed to assess the dynamics and magnitudes of recharge in the Wadi Ferrain Basin (1,851 km²). Data collected from five vertically installed temperature probe arrays (TPA), global satellite precipitation data (TMPA), field based double ring infiltrometer tests, and empirical infiltration assessments were used to characterize and estimate infiltration rates of TL in ephemeral channels. More specifically to provide enhanced identification of the timing and duration of precipitation and streamflow events (14 major events identified during 2008-2010). Additionally, the TPA data clearly indicates the heat transport mechanisms of advection and convection driven by stream infiltration within the wadi system.

Transmission losses based on TPA data and field based infiltrometer tests have been determined within the wadi system: Bir Watia (25cm/hr, 13.08cm/hr), Wadi Sheik (20cm/hr, 13.45cm/hr), Wadi Solaf (30cm/hr, 8.97cm/hr), Wadi Akhdar (12cm/hr, 13.5cm/hr) and the lower Wadi Ferrain (20cm/hr, 13.45cm/hr). Additionally, empirically-based transmission losses were calculated using wadi soil characteristics. Effective hydraulic conductivities of >12.7 cm/hr were determined based on the high amount of very clean gravel and sands found within the wadi systems (>90% Sands & Gravel). The integration of these transmission parameters has been used in the calibration and enhancement of SWAT (Soil & Water Assessment Tool) models and empirical analysis used to accurately predict recharge for Wadi Ferrain Basin. First order transmission losses of 47.7 x 10⁶ m³ (18%) was calculated using initial model results.