بررسی وضعیت آب های زیرزمینی دشت مالخلیفه واقع در استان چهار محال بختیاری

Abstract

malkhalifeh aquifer is located in south of chaharmahal and bakhtiyari province , in sannadaj- sirjan zone as tectonic setting. this area very important as agricalture in the chaharmahal and bakhtiyari.This study investigated the geology and hydrogeological features of Mal-e Khalifeh in order to make more appropriate decisions about the utilization of water resources in this area based on groundwater level fluctuations and storage capacity. The research was carried out utilizing all of the reports, statistics, and data available in the archives of Chaharmahal and Bakhtiari Regional Water Company, Rural Water and Sewerage Company, as well as data obtained through measurements, experiments, and field studies.
Mal-e Khalifeh study area, study code No. 2313, is one of the Great Karun drainage basin study areas with an area of 844.6 square kilometers, located in the southeastern part of the Great Karun in Lordegan, Iran. This area is managed by Chaharmahal and Bakhtiari Regional Water Company.
The following conclusions were obtained by evaluating the features of plain aquifers, including the type of aquifer floor rock, the type of aquifer, hydrodynamic coefficients, groundwater level fluctuations, floor depth and floor rock, and groundwater exploitation status:
- According to the map made from the amount of water transfer, the amount of transferability increases from the edges to the center of the plain, and in general, the middle section of the plain is ideal for reservoir utilizing. Suitable places for exploitation can also be identified in the northern and southern areas.
- The minimum and maximum groundwater depths, according to the map, are 2.7 and 53.6 meters, respectively, with a maximum depth in the northern areas (western Amiran piezometer) and a minimum depth in the plain's southern areas (Qarah). According to the map, to reduce the groundwater level, groundwater generally flows from east to west and from north to the center and south of the plain. This changing trend is consistent with surface currents and demonstrates the impact and compliance of piezometric wells and aquifers with surface currents. The results of the above map analysis suggest that the currents created in the north of the plain are the main source of inflow to Mal-e Khalifeh Plain.
- The region's maximum water level is around 1735.13 meters to the north and northwest of the plain, while the minimum water level is around 1659 meters in the south and southwest at the drainage basin outflow. The analysis of the groundwater drop map for the long-term period (October 1988 to October 2018) also indicated that the maximum aquifer drop in the north of the plain (Milas-Kondar intersection) was 21.29 m and the lowest drop in the south of the plain was 21.29 m. (Piezometers of Kundar-Abu Ishaq and Qarah intersection). This indicates the average annual decline in water level of 0.17 meters in recent years and a drop of around 1.26 meters in the census year (2017-2018).
- The hydrograph of the groundwater unit declined by 0.84 in the water year 2017-18, resulting in a volume reduction of 0.82 million cubic meters in the aquifer reserve for that year. In addition, from October 1991 to October 2018, the average annual change in groundwater was roughly -0.24 meters, which reduced the reservoir's average annual volume by 0.24 million cubic meters. Furthermore, the overall amount of aquifer drop from the start of the long-term study period to the present was 6.59 meters, and the total volume of reservoir loss was 6.43 million cubic meters.
- The amount of this parameter dropped from the northern regions to the southern parts and the plain outflow, according to the map of electrical co-conductivity. - Hydrogeochemical studies revealed that groundwater had adequate and acceptable drinking water quality. Furthermore, for agricultural purposes, the water quality for both dry and rainy periods was in c2s1, which is adequate and useable for agricultural purposes. In the long term, the Mal-e Khalifeh aquifer chemograph revealed a rise in salinity of plain groundwater. During the statistical period, the average electrical conductivity increased. According to this graph, the average electrical conductivity improved by 40% in the last 5 years when compared to the start of the statistical period.
- The volume of the reservoir was 0.55 million cubic meters after considering and calculating the parameters of groundwater balance.
According to the findings, the quality of groundwater in the Mal-e Khalifeh Plain is generally good for drinking and agricultural usages, with the primary issue being aquifer volume loss, which should be thoroughly explored. Considering the long-term aquifer hydrograph, which shows changes in aquifer volume of 0.24 million cubic meters per year on average, it is clear that this difference is due to some assumptions in the preparation and regulation of the groundwater aquifer balance, and due to the fact that the parameters used should be estimated, it was practically impossible to calculate it accurately during the above balance studies.
In the general balance calculations, the rate of decline of groundwater reserves was 16.77 million cubic meters, which, given the aquifer's characteristics, area, and the trend of changes in the aquifer's hydrograph, reflects a considerable decrease in water reserves in the aquifer. The following items
1. Reduction of water storage in groundwater balance calculations by 16.77 million cubic meters
2. 3.5 times difference between the number of long-term aquifers and the annual number of 2017-18 water years with the average long-term
3. Decline of groundwater level in the plain with an average annual drop of about 0.84
4. Also, a 40% increase in the average electrical conductivity
are due to the decrease in rainfall in recent years and the increase in exploitation by permitted exploitation wells and unauthorized wells in the plain. This suggests salinity, which reduces the amount of groundwater supplies and necessitates additional planning for water resource management. With this in mind, basin and water resource management in this area appears to be more important than ever, and should be technically controlled by modifying aquifer exploitation and using artificial inflow and aquifer operations.
key words:
"Mal-khalifa Plain", "Hydrodynamic Coefficients", "Water Balance", "Wilcox Chart", "Chomograph"