Modeling the groundwater flow of the Agia karstic aquifer in Crete, Greece under present and future conditions

 This study examines the groundwater potential of the Agia aquifer, Crete, Greece,  under the existing water management policies.  Alternative future scenarios of groundwater abstraction and/or climate projections are also examined. The Agia Springs area is characterized by rich groundwater supplies which are used to meet water demand for drinking and irrigation  for the  Chania region. This region belongs to one of the most productive valleys on the island of Crete and plays an important role in the agricultural - food sector. It is also characterized by intensive tourist development. Therefore, the demand for water is higher in the summer season than in the rainy season, which leads to strong seasonal fluctuations. At the same time, the water supply is declining as precipitation is lower than in previous decades.  Climate scenarios presented for the island of Crete,  predict a 20% decrease in rainfall in the near future.The relevant authorities have drawn up a water management plan, which is currently being updated in order to mitigate the problems arising from the increasing demand.  According to the new scheme of the Agia Springs, the total withdrawal is 26 hm³/year, while there is a potential of 31.5 hm³/year. The aim of this study is to model the groundwater flow of the Agia aquifer in order to develop scenarios that could allow full utilization of the groundwater potential and reform the contribution of groundwater resources to the region’s water balance. The groundwater flow simulations were carried out using the Princeton Transport Code (PTC) and the ARGUS ONE 4.2.0.w program. The model considers the hydrogeological characteristics of the area, the precipitation time series, and the pumping rates of the extraction wells. The calibration of the model has shown that the Agia Springs field is a complicated confined aquifer system with large depth values (more than 400 m below sea level). The calibration shows better performance during the dry periods, with a good correlation between the modeled results and the values of the groundwater measurements on site. The final proposed scenarios refer to: 1) the short-term scenario, in which three additional pumping wells are operated alongside the existing ones, resulting in 29 hm³/year and 2) the medium -term scenario, which considers the pumping wells of the short-term scenario and four new ones, providing an additional 5 hm³/year. The results show that there is no significant impact on the response of the springs. The level of the springs deteriorates during the additional pumping. However, it recovers with the interruption of the operation of the pumping wells, which indicates the resilience of the aquifer.

 

Acknowledgment

This work was supported by OurMED “ Sustainable  water storage and distribution in the Mediterranean” project, funded by the PRIMA Programme supported by the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 2222

 

 

References

Babu, D.K, Pinder, G.F., Niemi A., Ahlfeld, D.P. and Stothoff, S.A., 2002. Chemical Transport by Three-Dimensional Groundwater Flows, argusone.com.

Perleros, C., and Vozinakis, K., 2002. Hydrological study of the Chania county, geological map, Organization for Development of West Crete (ODWC)