The Impacts of Climate Variability on Spatiotemporal Water Footprint of Tomato Production in The Hormozgan

Agriculture sector, as the key consumer of fresh water resources throughout the world, is progressively more squeezed by the requirements ofother contemporary society areas and threatened by potential climatic change. Irrigation is the major part of agricultural water usage in Iran, which consumes 90% of total agricultural water use. Increasing competition for water resources use, in conjunction with climate factors change may have significant effects on water availableness for agricultural production. Climate change has already affected components of the hydrologic cycle, such as precipitation redistribution, runoff and groundwater cycling. The water footprint of a crop is the volume of freshwater both consumed during the crop production process, and it has three components consist of green water footprint (the volume of the precipitation consumed in crop production); blue water footprint (the volume of runoff or groundwater consumed in crop production); grey water footprint (the volume of freshwater that is required to assimilate the load of pollutants during the crop production process) and white water footprint (the volume of water losses during the irrigation process).
The Hormozgan is located in a hyper -arid region that is impressionable to the potential impact of climate. The data used in this research consist of climate data and agriculturaldata. The climate data (2002-2016) was taken from the Iran Islamic Republic Meteorological Organization including monthly average maximum temperature, monthly average minimum temperature, relative humidity, precipitation, wind speed and sunshine hours. The agricultural data consists of, cultivation area, crop yield and soil type weretaken from the Agricultural-Jihad Bureau of Hormozgan Province. CROPWAT model is used to estimate crop water and crop irrigation requirements using meteorological, crop and soil dates. Effective precipitation (Pe) values were calculated by USDA method and crop evapotranspiration (ETc) was calculated by FAO-Penman-Montieth method. The WFGreen (effective precipitation), WFBlue (net irrigation requirement) and WFWhite (irrigation water losses) water footprints (WF) of potato production were estimated for Hormozgan. The Mann-Kendall (M-K) trend test is used to analyze the trends and abrupt changes of the climatic factors.
The total tomato WF was estimated 0.639 m3/kg in the Hormozgan province that Jask and Bastak have maximum and minimum with 1.54 and 0.66 m3/kg, respectively. The share of green, blue and white water footprint estimated 5, 18 and 77 percent, respectively. The largest shares of water footprint were observed in Bandar- Abbas (27%). The sum of the water footprint it is 19.2 MCM, which is more than 95% of the total water footprint (70.2 MCM) in the whole province. In Bashagard a large share of water footprint is related to the blue water footprint despite having a considerable amount of seasonal precipitation. Regarding the dominance of autumn precipitation in it, changing the vegetation genotype and cultivation of varieties resistant to water deficit will increase the plausibility of dry farming and increases share of the green water footprint. The white water footprint has the largest shares (77%) of while subsidence is so serious in more than 36 plains. Hormozgan province has low precipitation and high water demand. On the other hand, improper irrigation management (number of events and the volume of irrigation) has led to decreased tomato performance in these regions and larger water footprint. The share of blue water footprint is 18% that 4 times more than from WFGreen. The considerable amounts of precipitation in this province, strategies such as cultivation of new genotypes more adapted to the wet periods, shortening the flowering period of Saffron with the aim of avoiding the dry period at the end of the growing season can be considered to reduce the share of the blue water footprint and reduce the share of the green and white water footprints. Total consumed and exported virtual water volume from the region are 10.8 MCM to 28 million Rials per year. The export of these crops imports the most pressure on groundwater and surface water resources of the region. The M-K test results of climatic factors throughout the 2002–2016 study periods in Hormozgan showed that sunshine hours during the tomato growth period experienced downward trends for the M-K statistics values were less than zero and the downward temperature trend reached statistical significance. The declining temperature and sunshine hours would result in lower crop evapotranspiration (ETc) and agricultural water consumption, while CWR donot have any trend. The trend analysis shows that the green, blue and white water footprint had significant increasing trends in the central part. Increasing theyield would result in lower water footprint.
Ground water depletion and water shortage are two problems in Hormozgan province which have occurred due to the irregular use and inappropriate management of demand and supply of water in agricultural sector. The water footprint (WF) of crop production is a comprehensive indicator that can reflect water consumption types, quantities and environmental impacts during the crop growth period. This study assesses interannual variability of green, blue and white WFs of tomato production in Hormozgan from 2001 to 2015. The share of green, blue and white WFs in the region is 5, 17 and 77 percent and 10.5 MCM year-1. Under the combined influence of climate change and water footprint variation, WFCs weredecreasing trends. In contrast, sunshine hours had decreasing trend. The statistical analysis revealed that interannual variabilities of WFCs were caused by both climatic and non-climatic factors.