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Potential Effects Of Climate Change On Groundwater Recharge - A Case Study Of The Gaza Strip, Palestine

Congress: 2015
Author(s): Salem Gharbia, Francesco Pilla, Abdalkarim Gharbia
Trinity College, Dublin1, Institute of Water and Environment, Al-Azhar University- Gaza2

Keyword(s): Sub-theme 17: Climate change, impacts and adaptation,
Abstract

Introduction
The Gaza Strip is a part of the Palestinian coastal plain located in an arid to semi-arid region. It is bordered by Egypt from the south, the green line from the North, Nagev desert from the East and the Mediterranean Sea from the West, so the Gaza Strip is located on the south-eastern coast of the Mediterranean Sea, between longitudes 34° 2" and 34° 25" east, and latitudes 31° 16" and 31° 45" north. Groundwater is the only water resource in the Gaza Strip and in order to recharge the Gaza coastal aquifer, mainly, it depends on the recharge from rainfall, which depends on the rate and duration of rainfall, the conditions at the upper land surface boundary, soil moisture conditions, the water table depth and the soil type. Monitoring of groundwater recharge is very important because it allows the estimation of its temporal variability and areal distribution.
This work aims to study and investigate the impacts of future climate change on groundwater recharge over the Gaza strip based on projection of future climate by multi-model median approach under Geographic Information System GIS environment.

Materials and Methods
Climate change simulation
A specially distributed climate change projected maps for temperature and precipitation over Gaza Strip according to A1F1 with high sensitive case were developed based on baseline period maps for three time intervals (2020, 2050 and 2080) and used as input in this modelling work in order to investigate the impacts of climate change on groundwater recharge of the Gaza coastal area. The baseline period maps were prepared for temperature and precipitation for mean values from 1972 to 2002. Fossil energy intensive (A1F1) with high sensitivity is the emission scenario that was used for the prediction process by SimCLIM climate model. The median assembly approach was used to get the representative results from multi General Circulation Model (GCM) outputs.
WetSpass model
WetSpass (an acronym for Water and Energy Transfer in Soil, Plants and Atmosphere under quasi Steady State) is a numerical model to simulate long-term average spatial distributions of hydrological parameters and processes on basin scale(Batelaan and De Smedt, 2007). The model makes use of grid GIS technology and digital data to partition the precipitation into groundwater recharge (Gebreyohannes et all, 2013).

Results and Discussion
From climate change modelling under GIS environment the projected mean annual temperatures for years 2020, 2050 and 2080 were 20.66 celsius degrees (oC), 22.48 oC and 25.08 oC respectively, While 0.85 oC, 2.67 oC and 5.28 oC were the mean annual changes from baseline period for years 2020, 2050 and 2080 respectively. The predicted mean annual precipitation for years 2020, 2050 and 2080 were 294.68 mm/year, 243.70 mm/year and 170.82 mm/year respectively, Hence -7.48, 23.98 and -46.37 mm/year were the predicted mean annual precipitation changes from baseline period for years 2020, 2050 and 2080 respectively.
Groundwater Recharge is a naturally occurring process whereby permeable soil or rock allows water to seep readily into the aquifer. The groundwater recharge values were simulated by WetSpass to baseline period and projected years 2020, 2050 and 2080. The simulated values for ground water recharge were been for baseline period in ranges from 14.58 to 265.71 mm/yr with a mean of 125.33 mm/yr and standard deviation of 61.21 mm, so the total recharge volume 44.23 Million Cubic meter (MCm), for 2020 projected period ranges were from 11.51 to 237.5 mm/yr with a mean of 105.07 mm/yr and standard deviation of 56.88 mm, so the total recharge volume 38.35 MCm, about 2050 projected period the ranges were from 4.93 to 177.71 mm/yr with a mean of 64.44 mm/yr and standard deviation of 45.19 mm, so the total recharge volume 23.52 MCm and for 2080 projected period the were ranged from -19.72 to 94.08 mm/yr with a mean of 20.14 mm/yr and standard deviation of 23.89 mm, so the total recharge volume 8.719 MCm.

Conclusion
The degree of common variation between the COD and the BOD5 of the wastewaters from the selected wastewater treatment plant in the Gaza strip (Bait-Lahia, Rafah and Khanuonis) were highly positive, thus the two parameters are correlated with good correlation coefficients of 0.995, 0.86 and 0.974 respectively. The correlation coefficient of the fitted equation for prediction for Bait-Lahia, Rafah and Khanuonis wastewater treatment plants, may therefore be used to facilitate rapid quality assessment or optimal process control once the chemical oxygen demand (COD) is measured or vice versa.

1. Batelaan, O., De Smedt, F., 2007. GIS-based recharge estimation by coupling surface subsurface water balances. J. Hydrol. 337 (3–4), 337–355.

2. Gebreyohannes T., Florimond De Smedt, Kristine Walraevens, Solomon Gebresilassie, Abdelwasie Hussien, Miruts Hagos, Kasa Amare, Jozef Deckers, Kindeya Gebrehiwot, 2013, “Application of a spatially distributed water balance model for assessing surface water and groundwater resources in the Geba basin, Tigray, Ethiopia”, Journal of Hydrology 499 (2013) 110–123.
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