Determination and evaluation of blue and green water footprint of dominant tillage crops in Urmia lake watershed

Background and objectives: Water footprint index is a global index which can be as an indicator of real consumptive water base on region climate condition. At first the mentioned index was presented by Hoekstra (2002) and after this concept was used extensively in the world (Faramarzi et al, 2009; Akhavan et al, 2009; Yu et al, 2010; Arabi et al, 2012; Gerbens-Leenes et al, 2013; Xu et al, 2014). The objective of the present study is to calculate water footprint for dominant crops in Urmia lake basin in two components named green and blue water. In this process, green and blue water components were separated in order to correct programing in agriculture part and saving water resources.
Materials and methods: To investigate dominant crops water footprint in different regions of Urmia lake basin, the studied basin was divided to seven regions. Then for any region one station was selected as datum station. In this direction, Salmas, Urmia, Mahabad, Tekab, Tabriz, Maragheh and Sarab stations were presented as datum stations. In this research, to investigate agricultural crops water footprint in Urmia lake basin, five dominant crops in basin containing wheat, sugar beet, tomato, alfalfa and maize were investigated and their water footprint were calculated. The evapotranspiration and water requirement for the studied crops were calculated by using CropWat 8.0 software. The requirement data for evapotranspiration calculation containing minimum temperature, maximum temperature, relative humidity, sunshine hours, wind speed and precipitation in monthly scale were obtained from meteorological organization. After arranging, the data was presented to the software and Water footprint was calculated.
Results: The results of Water Footprint calculate in two components (blue and green) showed that the mean annual consumptive water was 24834.83 m3/ton for dominant crops and green and blue water portion was calculated 25 percent and 75 percent respectively. Also the results showed that among the studied crops, wheat (13124.94 m3/ton) and alfalfa (7393.81 m3/ton) had the highest water footprint. Whereas sugar beet and forage maize had the highest blue water to green water consumption ratio. The results of zoning showed that blue water consumption was high in Tabriz and Maragheh plains whereas for Urmia and Tekab plains green water consumption was considerable.
Conclusion: The results of the present study showed that the crops such as wheat and alfalfa which have considerable green water in comparison of other crops were proposed for cultivate in the studied region. It is necessary to mention that this issue is an effective suggestion when the water footprint index is calculated in different climate and other provinces and correct integrate programing was done in agriculture part and tillage pattern.