Monitoring of seawater encroachement in the delta of Wadi Sudr,South Sinai, Egypt

The Delta of Wadi Sudr is one of the main development coastal areas in Southern Sinai Governorate encompassing an area of 280 km2 and lies between Longitudes 32 40' 00 and 32 48 0 E and Latitudes 29 32 30 and29 45 00 N. The study area relies on groundwater as its main source for industry touristic and agricultural purposes. As the population continues to grow at an alarming rate fresh water supplies are constantly being depleted brining with it issues such as saltwater intrusion or encroachment. The main objectives of the present work are to focus on the groundwater monitoring management and conservation through two successive years (February 2009 and 2010). The present study showed that the depth to water ranges between 2.7-35.5m in 2009 and 3-38m in 2010 with general decrease westward while the water level with respect to sea level ranges between 0.6-5.8m and -0.5-5.5m in 2009 and 2010 respectively. The water salinity ranges between 1345-15131mg/l in 2009 and 1412-14975 mg/l in 2010. The present study revealed that the intensive pumping of groundwater in the concerned area leads to a decline in the groundwater level and induces seawater intrusion where groundwater level tends to have been drawn down below mean sea level at the most affected areas by seawater intrusion where it reaches to 0.5 below mean sea level. The maximum inland extent of seawater intrusion effects in the unconfined aquifer that has been observed is around 1400 m. In some limited localities in the study area recharge from rainfall flood occurred on 17- 18th January 2010 and lateral flow flushed the intruded seawater back to the sea the groundwater was gradually freshened as shown on both resultant water table and resultant salinity maps in 2009 and 2010 where there are an increase in the water level by one meter and a decrease in the water salinity by 1000 mg/l at these localities The gradient of the groundwater flow is steep at the western part Coastal area due to the excess or groundwater abstraction which attributed to the concentration of well drilling in these localities From the spatial distribution of the level of seawater intrusion shown on the monitoring maps 2009 and 2010 using the Assessment Index AI it can be concluded that in general the class of strong intrusion increased in 2010 and it existed at the coastline the class or no intrusion is at the eastern part of the study area and the class of slight intrusion is considered as the transition zone between the other two classes which also increased in 2010.