modflow

Excessive abstraction of groundwater aquifers in the country has caused a sharp drop in the aquifer water level and the loss of aquatic aquifers, the effects of which is the phenomenon of subsidence. In this study, simulation of groundwater level changes in Marvdasht-Kharameh basin from a validation period and processing of a large set of raw data in Modflow mathematical model was used. The output results of sensitivity analysis of effective parameters in the calibration of Marvdasht aquifer show the maximum effect of hydraulic conductivity parameters and horizontal hydraulic conductance anisotropy and a set of linear groups of water supply network. Therefore, it is in line with the statistics of the Fars Regional Water Organization that there are wells with high discharge in these areas. According to the conditions of the aquifer, if the current operation trend continues, it is predicted that the groundwater level will drop by 15 meters during the years 2019 to 2029. Also, according to the average land subsidence, which averages 0.76 meters per 10 meters. The average land subsidence with the current harvest trend in the next ten years is predictable 114.78 cm and with a 30% increase in harvest, the rate of aquifer decline over the next 20 years is about 37 meters with an annual decline of about It is 1.9 meters. Land subsidence in this case is also predicted to be about 280 cm. Finally, according to the maps prepared from Marvdasht aquifer, due to the alluvial nature of the groundwater aquifer, the effect of water level drop can be observed from a short distance. The rate of subsidence in the southern and southwestern margins of the plain due to the low thickness of sediments and in the northern and northeastern parts of the plain due to coarse-grained sediments, is less than the central parts of the plain.

One of the ways of sustainable management of groundwater resources is to model the groundwater level of the plains in order to identify water potentials and long-term planning based on the status of aquifers. In this study, MODFLOW code, which is one of the codes in GMS7.1 software, was used to simulate the groundwater flow of Minab plain aquifer. To investigate the observational and computational level of groundwater in the study area, information about the water table of 16 observation wells in the plain was used. The constructed model was initially calibrated assuming the current was constant and the parameters affecting the model including hydraulic conductivity and feed were optimized. Then, the model was calibrated assuming that the flow is unstable in 12 time steps (October 1991 to September 1992) and the specific discharge parameter was optimized. According to the calculated balance of the aquifer, the total feeding of the aquifer is 1409.443 million cubic meters, and the total discharge from the aquifer is 1640.1011.1 million cubic meters, which is negative due to the higher output of the aquifer than the input, and the balance of the plain is negative. It will cause a sharp drop in the groundwater level in the coming years.

In this study the recharge and discharge of Isfahan-borkhar aquifer was investigated. This leads to long-term management of the aquifer and will make appropriate decisions by planners. The results of this study showed that the water table was constantly decreasing over the selected statistical period. The water table level was reduced by 0.46m per year, which reflects the fact that the aquifer is in critical conditions. In the present study, the recharge rate was determined by three factors including leakage from the river, rainfall infiltration and agricultural wastewater by using MODFLOW and then the correlation coefficient above 0.97% indicated high accuracy of the simulation. According to the results, it was found that recharge by agricultural wastewater is more than recharge by rainfall (about 32% of total irrigation water), which is due to the type of irrigation in the area (check-basin irrigation) and after that the influence of rainfall (about 10% of the total rainfall), which is a low contribution to this area due to high evaporation rates in the region. Thus, it can be concluded that the most important source of aquifer recharge is agricultural wastewater, which is necessary to be accurately calculated according to the type of product, irrigation, soil characteristics and climatic conditions of the study area in hydrological modeling studies. In case study of Isfahan-Borkhar, there is no possibility of exploitation of the aquifer due to the continuous decrease of the water table of groundwater that is clearly evident in the aquifer hydrograph, as well as the negative balance of groundwater resources.

The Study area in Asadabad plain is part of the Karkhe river watershed. Reduce in rainfall and increase in exploitation of groundwater resources led to a sharp drop in groundwater levels and subsidence’s phenomenon in recent years has. The aim of this study is the hydrogeological evaluation, a better understanding of aquifer and optimal utilization of groundwater resources by using available data. In order to provide the mathematical model, geological, meteorological, hydrological and hydrogeological data were collected and then analyzed. Then according to the aquifer’s conceptual model, the mathematical model was developed with PMWIN software. The model was implemented and calibrated for 2006-2007 with 12 stress periods. The sensitivity analysis showed that model has a more sensitive to hydraulic conductivity. The model was verified with observed data for next year (2007-2008). The results show that model is unable to simulate aquifer’s natural conditions. The main reason was the uncertainty in input data and lack of piezometers in a large part of the aquifer's second layer. Study the effective factors on subsidence phenomenon (groundwater level fall, aquifer’s type, aquifer’s thickness and existence confined aquifer) showed that the central and southern parts of the plain have more vulnerable capabilities than the subsidence phenomenon.