An Estimation of Renewable Water Using Water Budget Model in the Absence of Adequate Data

Given its low precipitations and its inappropriate spatial-temporal distribution, Iran is regarded as an arid to semi-arid country. Under these circumstances, water resources are the main development obstacles. The quantitative sustainability criterion for water resources is to keep annual consumptions of renewable water. Renewable water is defined as the amount of water that a basin (or any geographical region) can regain through a yearly hydrological cycle. Therefore, sustainable development planning needs an accurate (or even conservative) estimate of renewable water resources. This study investigates the concept of renewable water, attempting to estimate its quantity based on water budget in Kashaf-Ruod sub-basins. To establish the balance of basins, a methodology based on trial and errors was employed to find optimal values for budget parameter, with the aim of minimizing water balance (toward zero). Given the lack of sufficient and reliable data on water budget, "experts’ opinions" were an important source of information. The components of the water budget were estimated in both wet and dry years to obtain average renewable water. In this research, experts’ opinions on the reliability of the information, physical relationships governing basins, and comparison of basins in terms of different geographic and regionally conditions were sought. Accordingly, the average natural and actual renewable water at basin were 884 and 988 million m3 respectively, with the maximum and minimum of basin renewable water being 1222 and 545 million m3 in both wet and dry years.