ارزیابی سناریوهای تخصیص بهینه منابع آب با استفاده از مدل WEAP (مطالعه موردی: حوضه سد کلان ملایر)

Abstract

Introduction:

Proper planning and providing management solutions for sustainable use of water resources is an inevitable necessity. To manage the allocation of water resources at a basin, the WEAP model has attracted the attention of many researchers in recent years due to its integrated water resources management system and prioritization of water allocation. In this research, the supply and demand situation of the basin located upstream of the Kalan Malayer dam in Hamedan province has been investigated using the WEAP model. The purpose of the research is to investigate the sources and uses in the medium term and to provide management solutions by defining different scenarios for the integrated management of surface water resources in the basin.

Methods:

In this research, the water systems of the study basin of the Kalan Malayer Dam located in Hamedan province were modeled in the period from 2013 to 2017 with the aim of investigating management scenarios. R2, RMSE and ME for the two variables of reservoir volume of Kalan Dam of Malayer and monthly river flow at Droodgaran hydrometric station are used, and the obtained results indicate the usefulness of modeling. Then, three possible scenarios were planned in addition to the existing conditions. The investigated scenarios are: 1-non-conservative scenario (increase in consumption regardless of the amount of available water resources), 2-conservative scenario (adjustment of the agricultural sector according to the capacity of water resources) and 3- complete development scenario (scenario of structural improvement plus environmental requirement at a good level).

Existing condition includes agricultural needs of 15,000 hectares with the common cultivation pattern of the irrigation area with 56% efficiency, drinking needs of Malayer city with a population growth rate of 2.35%, industry needs of 0.73 million cubic meters per year and the minimum environmental needs of the river. The non-conservative includes the increase of the cultivated area of agricultural farms to 18000 hectares, the population growth rate of 3.6 for the region, the increase of 30% of industrial units and the minimum environmental requirement for the Kalan Malayer River. The Conservative Scenario is adjustment of the level of agricultural farms with the common cultivation pattern of the region, observing the permissible withdrawal limit from groundwater in normal and rainy years and providing the minimum environmental requirement (acceptable level) with the Montana method for the Kalan Malayer River. The Full Development Scenario includes agricultural needs of 15,000 hectares with the common cultivation pattern of the region, with an increase in the share of modern irrigated lands from 20% to 50%, the drinking needs of the city of Malayer, both rural and urban, with per capita improvement of water consumption, the needs of industry 0.73 million cubic meters per year and providing environmental needs (good level) for the river.

Results:

The model validation indices for the two variables of reservoir volume and monthly river flow showed that the R2 coefficient is at the optimal level above 0.8. Also, the ME index is close to one and this indicates the desirability of modeling and the calibration of the model. The results showed that in the agricultural sector, which is the major consumer of water resources, there will be approximately 26% water shortage in the reference scenario, 43% in the non-conservative scenario, 13% in the conservative scenario, and 9% in the full development scenario. Also, the results showed that the complete development scenario, taking into account the improvement of the structure of the water transmission and distribution network, as well as the improvement of per capita consumption and the increase of 30% share of agricultural lands that are irrigated with modern methods, has the highest reliability index (more than 90%) for each of obtained consumption segments. Also, the non-conservative increase in water needs will significantly reduce the reliability of the system, so that the groundwater storage as a vital resource of the region will be depleted within 15 years of the implementation of this scenario. The comparison of the scenarios from the point of view of groundwater consumption shows high consumption in the existing scenario and the Non-Conservative Scenario. The results of the storage level of the aquifer for these two scenarios have been obtained, which shows the maximum withdrawal from the aquifer to supply most of the consumed points.