INSIGHT INTO WADI PROPERTIES, DYNAMICS, AND INTERCONNECTEDNESS DURING FLASH-FLOOD EVENTS USING TRMM SATELLITE DATA AND SOIL TEMPERATURE PROBES IN SINAI PENINSULA, EGYPT

The Sinai Peninsula (SP) of Egypt is one of the more arid regions in the world receiving <60 mm/yr of annual precipitation. Watersheds within the southern SP mountain range are composed of interconnected ephemeral channels (wadi) consisting of Quaternary alluvial deposits overlying varying types of Precambrian bedrock and act as the primary conduits of groundwater recharge in the region. Despite the low amounts of annual precipitation in the SP, events often produce torrential rainfalls and flash-floods. The ability to accurately calculate precipitation, runoff, and recharge are often hindered by the absence of appropriate monitoring systems, historical datasets, and lack of knowledge on wadi characteristics.

In order to assess the dynamics and hydrologic processes involved we have developed an integrated approach involving the collection and analysis of field and remote sensing-based observations in Wadi Ferrain Watershed. HOBO temperature loggers were installed in vertical arrays throughout Wadi Ferrain (1,851 km_²). Temperature probes coupled with global satellite precipitation data (TRMM) were used to overcome the paucity of field datasets and provide insights into various hydrologic parameters associated with wadi systems in arid environments.

Over the study period (2009-2010) fourteen precipitation events were identified by TRMM using the Remote Sensing Data Extraction Module (RESDEM). Larger precipitation events were identified were correlated with soil temperature probes. Temperature fluctuations recorded by the temperature probes provided significant correlation in two of these events. First order infiltration rates have been calculated based on temperature probe data collected during a major (20mm/hr) precipitation and flash-flood event that accrued in January 2010. The following infiltration rates were calculated for the study area: Bir Watia (45cm/hr), Wadi Sheik (20cm/hr), Wadi Solaf (30cm/hr), and Wadi Ferrain (20cm/hr). The highly porous soil types (e.g., gravel, sand) along with structural features (Kamil Moussa Dyke) found within the watershed account for the high infiltration rates (up to 45cm/hr). Results demonstrate the potential for calculating first-order wadi hydrological variables during precipitation events and verifying satellite data products such as TRMM.