چكيده لاتين :
Introduction: The reducing of supplies of underground water poses a serious threat to the water security of the country, a problems which seems not to have been taken seriously. Climate changes and the result that changing in water cycle have made the challenges of water supply even more complicated. Immediately soaring and unbalance growth of population (about 80 million people in 2015) has to lead a drop in per capita water. The rapid growth of urbanization, interminable migration to the metropolis for better welfare, and the need for more food have testified the need for the promotion of health and hygiene, the industrial development of water demand and consequently the pressure over water resources. Due to population growth in Iran, the annually per capita resources of renewable water which was 7000 m3 in 1956 and in 1996 dropped to 2,000 m3 and it is predicted to decrease to 800 m3 in 2020. Moreover, population settlement pattern have lost its compatibility with the temporal and spatial distribution of water resources in the country (Center Statistics and Water Resources Management, 2015). The purpose of modeling in this study is create and develop a simulation model in order raise our understanding of the resources, the uses of such resources as well as their dynamics so that some of solutions are provided for the system to retain its proper functioning.
Material and Method: This study have projected the effects of the agricultural sector on water resources depletion. For this purpose, the model is extended and simulated from 2013 to 2063 to four sections of hydrology, water demand and socio-economic. In this study, we used the econometric time series models to develop a systems dynamic modeling and used annual data from 1983 to 2012 to evaluating the effects of economic, social and environmental effects on water resources. For studying, the stationary of variables which are used in experimental models used Augmented Dickey-Fuller (ADF) and Zivot-Andrews (ZA, the unit root test with one structural break) unit root tests. The data were collected from Central Bank of the Islamic Republic of Iran, Center Statistics of Iran, Iranian Ministry of Agriculture, FAO, World Bank and Iranian Water Resources Management Organization the statistical collected and these data were analyzed by statistical softwares in term of, Stata 12, Excel, Vensim and iThink 9. Systems dynamics has developed in a wide range of issues, Forrester (1973) were used in integrated design strategy and planning. System dynamics is an approach to understanding certain types of the complex system problems. Casual-loop diagrams and the modeling process is a simple way to display the loop structures before formulating equations. Flow diagrams include the rate variables, level, auxiliary and fixed elements and a series of tests, operations, and procedures which organize for integrate network issues in management, economic, financial and industry. In this study based on iThink software, a model was developed for projected the effects of agriculture and non-agricultural sectors on the utilize water sources in Iran from 2013 to 2063. The model extended in hydrology, water demand, agricultural economics, and population sectors. To achieve this, water resources were considered as surface water resources, reservoir, groundwater and virtual water.
Results and Discussion: The result of Augmented Dickey-Fuller (ADF) and Zivot-Andrews unit root tests showed that production, import and export of agricultural products, capital of the agricultural sector, exchange rate, consumer price index, oil income, population, income per capita, acreage and water use variables, which except for the oil income and population, income per capita, other variables are rejected the null hypothesis of unit root. The results of Iran 's water resources dynamic model simulate from 2013 to 2063, as well the verification results of the surface water, groundwater aquifers and reservoir level variables from 193 to 2012. The results illustrate that Iran 's water resources are decreasing and it is projected that extremely depleting in next 50 years. It is projected that surface water discharged very severe and from 450 (billion m3) in 2013 decrease to 386 (billion m3) in 2063. As well the reservoir water shown downward trend behavior and decrease from 30 (billion m3) in 2013 to 22 (billion m3) in 2063 and the accessible groundwater aquifers decreasing from 120 (billion m3) in 2013 to 83 (billion m3) in 2063.
Conclusions: Based on simulation model, it is projected that water shortage in agricultural and non-agricultural sectors, the price index of agricultural products and waters price are soaring over time. Thus, some policies can revitalize the water resources such as reducing the number of legal and illegal withdraw ground water, importing water-intensive agricultural products, modifying the cropping pattern, adopting with climate change, importing water and increasing water use efficiency in the agricultural sector.
