Document Type : Research Paper
Department of Water Science and Engineering, Bu-Ali Sina University, Hamadan, Iran
Department of Water Engineering, College of Agriculture, Razi university, , Kermanshah, Iran
Department of Water Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
One of the methods of managing groundwater water resources is to analyze the behavior of aquifers under the implementation of different exploitation scenarios using mathematical models. The purpose of this research is to investigate the effects of implementing structural measures such as levees and artificial recharge ponds on restoring the groundwater level of Famenin Plain in hamedan province and providing management strategies for better exploitation using GMS numerical model.
Materials and Methods
Famenin Plain has faced a sharp drop in the groundwater level due to the excessive withdrawal of water resources in recent years, and the decrease in rainfall has intensified the crisis in the region. Due to the subsidences that has occurred in this plain and its surroundings, in this research, the simulation of the groundwater level of this plain was done using the GMS model under different management scenarios. This research was done in 2022. The conceptual and numerical model of Famenin Plain was prepared based on information about wells and piezometers, geological map and bedrock, information on hydraulic conductivity and specific yield, rivers and recharge of the plain. First, the model was calibrated and validated in transient mode. Also, the sensitivity analysis of influential parameters in the model was done. Assuming the continuation of the current situation, the simulation of system performance was carried out from October2023 to September 2038 for 15 years. After that, in the second scenario (implementation of structural measures), the groundwater level in the plain was predicted for the next 15 years, assuming the use of storage structures or artificial recharge ponds.
Results and discussion
The results showed that if the aquifer is operated according to the existing pattern, the water level in the aquifer will drop by an average of 11.6 meters at the end of the 15-year period. It should be noted that the maximum drop in the Famenin aquifer in this scenario was around 84 meters in the areas of the southwest of the aquifer. It should be noted that the largest concentration of sinkholes is in this section. The model was re-implemented for the operation conditions of the water storage structures and artificial recharge of the plain and the prediction of the groundwater level was made in these conditions for the next 15-years. The results of the exploitation scenario of the structures showed that the average drop of the groundwater level in the entire aquifer at the end of the period will be 11.2meters. Therefore, compared to the reference scenario, this scenario indicates an adjustment of the groundwater drop by 0.4 meters. However, the largest amount of drop in this scenario will be 81.6 meters in the southwestern areas of the plain, which indicates a maximum drop adjustment of 2.4 meters. Also, the lowest amount of drop in the plain in both scenarios is related to the eastern and southeastern regions. So that in some of these areas, in the reference scenarios and exploitation of structures, the maximum amount of water level rise will be 3.1 and 3.2meters, respectively.
It can be concluded that according to the state of exploitation of the groundwater resources of the Famenin aquifer, the biggest reason for the level drop in this plain is the withdrawal of agricultural wells due to their accumulation in the center of the plain. In case of implementation and exploitation of structural measures in the plain, the amount of level drop in the region will be adjusted to some extent, but the problem will not be solved. Therefore, it is suggested that considering the increasing trend of the population and the possibility of increasing the withdrawal from these resources in the coming years, in addition to exploiting the ponds and recharge wells and completing the structural measures by building new levees and increasing the number of recharge ponds, following the modification of the cultivation pattern of the area and replacement of low consumption crops instead of high consumption crops. However, it is better to take into account the current situation of the aquifer and the creation of numerous sinkholes that indicate excessive withdrawal from the aquifer, in addition to the above measures, a comprehensive plan should be implemented with the cooperation of the government and farmers and by spending a large budget to restore the aquifer and control settlement and in the first step, by persuading the farmers to fill the unauthorized wells or rent a part of the land that is harmful to the environment by the government and remove them from the groundwater withdrawal cycle.