The Eastern Mediterranean region of the Middle East and North Africa (MENA) is experiencing patterns of major drought due to the effects of rising temperatures and falling precipitation levels. The multiscale drought evaluation Standardized Precipitation Evapotranspiration Index (SPEI) reveals evolving and severe drought from North Africa and the Sinai desert toward the Middle East. While there has been a period without drought between 1970 and 1990, the severity and frequency of drought increased considerably after 1990. Current drought conditions in the Eastern Mediterranean region of MENA is moderate to severe with a 60–100% likelihood of occurrence, according to time parameters. The Gaza Strip is especially vulnerable to the consequences of increasing drought because it is situated in the vicinity of the Sinai Desert; therefore, a downscaled study of drought in the region is essential to implement mitigation measures for the sustainable management and planning of coastal aquifer and agricultural activities in the Gaza Strip. Considerable availability of precipitation time series from various meteorological stations helped provide a local drought study for the Gaza Strip, in accordance with the Standardized Precipitation Index (SPI). The stochastic time-series model of (4,0,1) (5,1,1)₁₂ shows a robust simulator for modeling and forecasting the future trend of precipitation at the nine meteorological stations. In terms of correlation accuracy, the model achieves a correlation (r) of approximately 93–97% in the calibration range and a correlation (r) of about 92–99% in the validation range. In terms of measuring the difference between the values, the root mean squared error (RMSE) of the model results shows that the RMSE was between 7–21 in the calibration range and 11–21 in the validation range. The model reveals a slightly stable trend in precipitation patterns at the northern meteorological stations of Beit Hanon, Beit Lahia, Shati, and Remal. However, declining precipitation tendency was recorded at the southern meteorological stations of Mughraka, Nussirat, Beir Al-Balah, Khanyounis, and Rafah. The SPI-based drought assessment implies that the precipitation annual threshold levels at SPI = 0 drop territorially from 474 mm in the north to about 250 mm in the south of the Gaza Strip. In this study, a representative 12-month local scale SPI₁₂ at an annual precipitation threshold level of 370 mm was formulated to address the drought conditions in the Gaza Strip. Standing on the outputs of the local SPI₁₂ scale might signify that the region of the Gaza Strip risks drought status with an incidence likelihood varying from 8% in the north to 100% in the south. Regular drought is prevalent in the northern governorates, but the hazards of extreme and severe drought are high in the southern areas with an incidence risk of about 83%. Sequentially, southern governorates of Rafah and Khanyounis experience chronic annual drought, while the return period of drought is reported to be every 9–12 years in the northern governorates of the Gaza Strip. The rain-fed years of 1998 and 2010 reported the worst periods of drought, while the period of 2016 showed a good droughtless water balance. Overall, the no-drought status might define the prospective conditions in the governorates of North Gaza, Gaza, and central Gaza over the next 20 years, while Rafah and Khanyounis are anticipated to be under normal to severe drought conditions.

The non-conventional water resources of seawater desalination, wastewater treatment, and stormwater harvesting are promising water resources to enhance the water supply and to cope with the groundwater depletion of the Gaza coastal aquifer (GCA). In total, the current daily operation of the short-term low-volume (STLV) seawater desalination plants produces 36,000 m3 and, on the large-scale perspective, the seawater desalination capacity is planned to increase from 150,000 to 300,000 m3 per day by the years 2025 and 2035, respectively. The wastewater treatment and reuse activities are processed through three wastewater treatment plants with a total daily capacity of 130,000 m3 which is proposed to be increased to a capacity of 235,000 m3 by the beginning of 2025. Stormwater collecting and harvesting supply the water sector by about 550–820 cubic meters per day. The proposed stochastic and artificial intelligence model that was developed in this study to simulate the interactive conditions between the groundwater and the water intervention plan showed proper performance in terms of (r) = 0.95–0.99 and the root mean square error (RMSE) = 0.09–0.21. The model outputs reveal that the annual groundwater abstractions will reach 192 million cubic meters by 2040 with an annual increasing rate of +3%. By applying the model, the optimum utilization of the unconventional water resources contributes positively to the recovery of the GCA, which is experiencing a decline hot spot in the water level that reaches to −19 m below mean sea level (MSL) and is expected to drop to −28 m MSL by 2040. The impact of unconventional water resources interventions was investigated by simulating the water table trend using stochastic models and artificial neural networks (ANNs) through three scenarios. The first scenario, which addresses the non-intervention status, indicates that the groundwater table will decline by −1.5% in the northern governorates and by −51% in the southern governorates of the Gaza Strip within 2020–2040. The second scenario demonstrates the impact of the existing water interventions that revealed an interim recovery in the groundwater balance until 2025 in which the water consumption tended to increase rapidly. The third scenario illustrates the impact of applying the full water management intervention plan in which the depression cone in the groundwater level will be restored by about +10 m.

In the Eastern Mediterranean countries, groundwater contained in coastal aquifers is the predominant water source for supplying water. The Mediterranean Gaza coastal aquifer in Palestine is showing alarming signs of depletion due to climate change and human-caused influences that substantially impact the hydraulic performance of the Gaza coastal aquifer. The climate statistical modeling and the downscaling of the ensemble global climate model under the representative concentration pathway (RCP) scenarios of RCP 2.60, 4.50, and 8.50 refer to a future decreasing trend in the precipitation and an increasing trend in the temperature. The stochastic model refers to an average decrease of −5.2% in the rainfall every 20 years that coincides with the RCP scenarios that show a decrease in precipitation between 0 and −5%. The rate of temperature increase over the next 20 years is defined at +1 °C, which closely matches the RCP results. As a result of human fast-paced activities, groundwater consumption is expected to rise by nearly 55% by the end of 2040, to around 193 million cubic meters, with a substantial withdrawal trend in southern provinces of the Gaza Strip. Consequently, the aquifer model predicts that subsurface water levels might fall at a rate of −2.50% per year, reaching a level of around −27.77 m below the mean sea level (MSL) by 2040. Alternative water supplies, such as desalinated seawater and treated wastewater, with annual maximum volumes of 110 and 16.5 million cubic meters, respectively, are expected to perfectly recharge groundwater resources of the Gaza coastal aquifer at an annual rate of about +3.65% to meet a groundwater table level of around −5 m below the MSL by 2040.

The water supply in the Gaza Strip substantially depends on the groundwater resource of the Gaza coastal aquifer. The climate changes and the over-exploiting processes negatively impact the recovery of the groundwater balance. The climate variability is characterized by the decline in the precipitation of −5.2% and an increase in temperature of +1 °C in the timeframe of 2020–2040. The potential evaporation and the sunshine period are expected to increase by about 111 mm and 5 hours, respectively, during the next 20 years. However, the atmosphere is predicted to be drier where the relative humidity will fall by a trend of −8% in 20 years. The groundwater abstraction is predicted to increase by 55% by 2040. The response of the groundwater level to climate change and groundwater pumping was evaluated using a model of a 20-neuron ANN with a performance of the correlation coefficient (r)=0.95–0.99 and the root mean square error (RMSE)=0.09–0.21. Nowadays, the model reveals that the groundwater level ranges between −0.38 and −18.5 m and by 2040 it is expected to reach −1.13 and −28 m below MSL at the northern and southern governorates of the Gaza Strip, respectively.

HIGHLIGHTS. Drought is a dominant climate changes consequences in the Mediterranean zone.