In the last century (since 1900) the population of the country has increased about six-fold. The population growth rate, which was less than 0.6 percent in the beginning of this period, reached the rate of 3.19 percent in the decade from 1976-1986. Fortunately, it has considerably decreased once again in the last decade. The major changes in population growth rate, resulting from reduction of mortality and increase of natural growth rate, occurred in the 1960s and afterward. Part of the population growth of the last decade has been due to immigration of Afghan refugees. Between 1960 and 1996, about 37 million people (about 60 percent of the existing population) were added to the country’s population.

In the period from 1961-2000, the urban population increased by about 31.7 million and the rural population increased by 11 million. In 1956, there were only three cities with a population over 250,000 in Iran, while in 2000 the number of cities with a population of over one million reached seven.

The direct impact of population growth on the water resources management of the country was an increased need for potable water in population centers. Indirect impacts were increased demand for agricultural products, development of irrigated lands, and the need for job opportunities and more income, especially in the agricultural sector.

The impacts of rapid urbanization included an increased domestic use of water, especially for hygienic purposes, and the emergence of new water needs due to the expansion of cities and improvements in living standards. Under such conditions, new responsibilities have been created for water resources management, of which the most important are the increased importance of protecting population centers against drought and flood, and the ever increasing importance of water treatment to provide hygienic water, as well as collection and sound disposal of wastewater and drainage water.

Along with changes that have been described in the areas of population increase, urban development, exploitation of water resources, qualitative and quantitative limitations for these resources, economization and protection of water resources, and protection of the aquatic environment against water pollution have gained importance.

As political and administrative institutions expanded and government became more centralized, especially after the 1960s, the role of planning and budgeting in the fate of the country became more important. After the Islamic Revolution of 1979, related social and political changes revealed the need for reform in political and social systems through supporting parliament, encouraging public participation, and privatizing and liberalizing the economy. The needed changes encompass the water management system of the country, including several water resource development projects under implementation, or nearing implementation.