Introduction
Since ancient times, agriculture has been the main economic activity in the Zahak City, mainly due to presence of the Hirmand River. Despite the importance and special status of agriculture in the region, water fluctuations of the Hirmand River have determined the cultivation status. In drought, this factor has caused a decrease in area under cultivation and crop. Thus, in terms of economic efficiency, no stable trend is assumed. During the two recent decades, draught has extended as the result of both natural and human factors, so jobs in agricultural sector have been halted or reduced. However, the area under study has very good natural, historical, and situational potentials (border and cross-border markets) for tourism development.Among the historical monuments, we can mention Dahan-e Gholaman, which is the first Achaemenid city to be discovered so far, and the life of this city was probably only 150 to 200 years and, like The Burnt City, it was evacuated with peace and order. One of the most important factors of such evacuation was the sudden drying of the Helmand riverbed. This city is probably the same as Zarank or Zarankan and it seems that Nadali, Zahedan Kohneh and Ramshahrestan are three other cities that have taken the name of Zarank throughout history. Also, the existence of other valuable historical monuments and rich culture of the people of the region can be a valuable source for tourism development. Therefore, given these potential capabilities along with drought and water shortage crisis for agriculture, rural tourism development can act as a complement for agricultural activity. The present study has identified and prioritized the tourism potentials of the villages in the arid areas of Zahak City and has attempted to find out what are the most important priorities of the rural tourism potentials of Zahak City.
 
Materials and Methods
This research is an applied research that has been conducted by descriptive-analytical method. The statistical population of this study is 197 villages of Zahak City. Using Sharp correction formula, 40 villages were selected as a sample of the villages (the criterion for selecting the 40 villages was their rural tourism capabilities). 362 households were selected as the sample of households in the villages, using the Cochranchr('39')s formula. Accordingly, the same number of questionnaires was randomly distributed by the allocation method in accordance with the percentage of households in the sample villages. Excel, ArcGIS, and SPSS software, and Optimum Deviation Model and Friedman Test were used to analyze the data. Due to the fact that matched data are required to perform statistical tests; in this research, Friedman was run for matching of indicators of different dimensions. By examining the indicators of different dimensions of research, the maximum score obtained for the dimensions was related to the economic dimension with a score of 21. Accordingly, to perform statistical tests based on matched indicators, the economic dimension was used as a benchmark for matching the other dimensions of the research, and coefficients were considered for this purpose (assuming all indicators).
 
Results and Discussion
In terms of the total average economic dimension, Qaleh No Village had the highest average of 12.00; In terms of the total average of the historical dimension, Khamak Village had the highest average of 13.98; In terms of the total average of the socio-cultural dimension, Rashid Village had the lowest average of 10.44; In terms of the total average physical dimension, Qaleh No, Gori and Shibogoreh villages had the highest average of 15.00; And in terms of the total average of the environmental dimension, Qaleh No, Shibogoreh and Khairabad villages had the highest average of 18.20. Friedman test was used to determine the most important potential of rural tourism among different dimensions. Since this test is used to compare the average ranks of several groups, it was used to rank rural tourism potentials. Comparison of the average rankings showed that among the 5 dimensions of tourism potential, the socio-cultural dimension with an average of 4.95 has the highest rank and the historical dimension with an average of 1.30 has the lowest rank.
 
Conclusions
The research results show that the most important tourism potential of the city belongs to its socio-cultural attractions with an average of 4.95, whereas historical potential with average of 1.30 has the lowest rank. The results of ranking by the model of deviation from the optimum showed that Qale No Village with its various tourism potentials and a deviation from the optimum of 0.24 has the highest level of tourism potential and Waslan Village with the deviation from the optimum of 7.75 has the lowest level of tourism potential.