Due to the lack of surface water resources in Bakhtgan- Maharloo basin, the amount of water withdrawn from groundwater resources has been more than the allowed limit. This amount has significantly affected surface water resources which led to some phenomena such as drying up of the Kor river, creating subsidence in 70% of basin plains, economic damages caused by reduction in the area under cultivation in downstream of kor river and drying up of Bakhtegan lake. In order to obtain a general view of this basin and optimal management of its groundwater resources, the situation of groundwater resources has been considered. In this regard, the unit hydrograph of basin plains and annual variations of the groundwater levels were studied. For preventing from further decline in the groundwater level some scenarios such as reducing the area under cultivation, changing cropping patterns, changing irrigation system and combination of these scenarios were presented. 19 out of 28 case studies which had 14 years (2002-2016) of groundwater level data were considered. The results illustrated that among 19 studied plains, all plains except Kherameh and Shiraz have the annual decline of more than 25 cm, also 68% of the plains have the annual decline of more than 50 cm, 47% of the plains have the annual decline of more than 75 cm and 26% of the plains have the annual decline are more than one meter. In this research, the plains more than 1 meter‘s annual decline including Arsanjan, Kavar- Maharloo, Sa'adat abad, Sydan- Faroogh and Marvdasht with decline values of 2.43, 1.75, 1.44, 1.09, 1.02 meter respectively, were regarded as critical plains. At the next step, by taking into account the cultivation information, crop patterns, irrigation systems, and the volume of water-supply into the farm in pumping wells, four scenarios were performed and the annual decline under new conditions were calculated and compared with the prior annual decline. From the results, it can be expressed that only the use of modern irrigation systems instead of traditional systems in all or part of the dominant crops of the area under cultivation is not alone sufficient to reduce the available decline and will not compensate the major part of aquifer ‘s annual decline of these fields. Therefore, it is necessary to change the major crop pattern into products with low water needs to be considered. The investigations showed that the second scenario (changing irrigation method for the available crop pattern) is operationally more appropriate among other scenarios but the third scenario (case b) (changing irrigation method and crop pattern Simultaneously) has a highest impact on compensating aquifer‘s decline among all scenarios. In conclusion, according to the critical conditions of this basin the third scenario is suggested.