Considering the complexity of water resource systems, nowadays managers have widely
accepted optimization models as efficient tools to reach to a useful decision in this case. The
existing optimization models provide new opportunities for better decision making in field of
water resources development and planning. Using optimization methods allows decision
makers to make the most appropriate decisions among the solutions available for water and
soil resources. Optimization is a method which the best possible answer for a problem is
determined according to the target and the existing conjugations, which are specified by
functions and mathematical relations. The optimal problem has a target function and several
constraints. Math planning is suggested as a useful and efficient way to solve resource
allocation problems, especially when decision variables, constraints and various parameters
are examined. Linear programming is one of the simplest and most practical optimization
models. This type of planning can be used for issues with simple relationships such as direct
resource allocation to complex operational and management issues. Since all the
mathematical relations contained in this model are of the first order type, it is called the linear
model. Hamedan -Bahar plain has faced many problems such as lack of water resources,
decline of underground resources and the negative balance of groundwater in the in recent
years, a part of agricultural land in Hamadan-Bahar Basin is located in Bahar city and other
part in Hamedan city. The water needed by the agricultural sector in the Bahar city is
completely extracted from underground resources and in Hamedan, about 80% extracts from
underground resources and the rest from the surface resources. In this region, the first priority
is the allocation of water resources to the drinking sector and the second priority belongs to
the industrial sector, and agriculture sector is in the third priority. Due to this priority as well
as lack of water resources in the region, the water need of crop pattern is not fully ensured. In
this research, it has been tried to compare the different methods of planning, with considering
the priorities of water resources allocation and percentage of water supply needs in
agricultural sector. So linear programming model with the goal of 1- determining the optimal
cultivation pattern, 2- determining the optimal allocation of surface water and underground
water sources, and 3- maximizing the benefit from crop production were created. This model,
based on available water resources and also with considering limitations, determines the
pattern of crop and the amount of water allocated, so the most benefit from crop production
will be obtained. So to study the cultivation pattern on this plain and water resources
management scenarios, linear program and LINGO software have been used. Objective of this model was maximization of benefit and optimized allocation of water and cultivation pattern.
Evaluating three Scenarios of optimization of cultivation pattern in current situation,
optimization of cultivation pattern in changing irrigation method and optimization of
cultivation pattern by limitation of ground water utilization, showed that, optimization of
cultivation pattern in changing irrigation method is better than two other ones and have more
benefits. Water consumption of cultivation pattern shows 23.8 % decrease and production,
area of cultivation and advantage show in order. 13.1%, 12.7% and 15.8% increase. The
results of this research consider the necessity of changing the pattern of water consumption in
agriculture as an optimal solution to overcome the problems of dehydration and reduce the
reservoirs of aquifers. Meanwhile, providing social and cultural backgrounds for modifying
the pattern of crops by replacing less-water-based products with more economic costs,
instead of high water requirements products, can reduce water use and improve conditions
and Sustainable use of water resources in the region. Due to the proper allocation of water,
demand management and water consumption patterns, especially in the agricultural sector,
can create a better and more stable economic situation. Finally, it can be said that with the
help of planning and optimization models, it is possible to examine and compare different
methods in the field of water resources management and to make the best decision. Finally, it
is suggested that other models such as nonlinear planning and more limitation and scenario,
especially changes in cultivation pattern be used, and compared with the results of this study.