Estimating the Value of Quality of Drinking Water Using Conditional Verification Method (Case Study: Kermanshah City)

Introduction
Currently, the international community has recognized the common problems associated with the quantity and quality of water. Many diseases that can be transmitted through unhealthy drinking water occur in developing countries of Asia, Central and South Africa. Therefore, provision of safe water for the community is one of the most effective and permanent technologies for improving the health of the community. According to the World Health Organization's 2008 report, the mortality rate associated with water borne diseases was more than 5 million per year. Therefore, information on water quality and pollution of resources is significant for sustainable water management strategies. The analysis of people's economic and social demands helps to anticipate health needs and deficiencies, among which these people can value the people who drink for drinking water and express it by expressing the amount of willingness to pay. Measuring the willingness to pay in social projects in developing countries is done by conditional valuation. Given the fact that there is no explicit market for improving some products such as safe drinking water, the use of non-market methods and the trading of such goods in this market is recommended. Contingent Valuation is one common method used by economists, policymakers and water organizations to improve water supply. It has also been implemented in many water supply and sanitation projects, especially in the provision of rural water in developed and developing countries.
Matherials & Methods
The present research was carried out in the north and east of Kermanshah city (elahiya, Jahad, Nobahar, Cornachi) in December and December, 2016. Data were collected using questionnaires completed and interviews by random sampling. The Cochran formula was used to calculate the number of samples needed in the sampling method. According to the formula, the number of samples required 384 questionnaires was obtained, but to achieve better results and with the probability that some filled in questionnaires were invalid 400 questionnaires were distributed among residents of Kermanshah city 39 of the questionnaires were deleted after completing the study due to mistakes and defects. Finally, 361 questionnaires were used for the final analysis. Face-to-face interviews were conducted at the respondents' place of residence. Socio-economic characteristics, population, water resources, drinking water quality, presence of suspended particles in water, willingness to pay and reasons for unwillingness to pay for respondents were questioned. Respondents were also asked about how to use tap water (boiling, filtering) before drinking water. The conditional valuation method was used to calculate the average willingness to pay the improvement of drinking water quality in the residents of Kermanshah. Also, the binary logistic regression method was used to obtain the tendency to pay. In this method, regression analysis is based on dependent variables and binary classification variables. McFadden R2 indicators and statistics likelihood ratio was used for a good fit. the right-of-proportion ratio statistic compares the right-exponential function statistic in the bound state (all coefficients of zero) and unconstrained, and shows the simultaneous meaning of all the coefficients. If this statistic is meaningful in relation to the probability of stating the right ratio, this shows that the explanatory variables in the model have been able to describe well the dependent variables.
The software packages used in this research are SPSS, Shazam, and Wolfram Alpha.
Discussion of Results
In the preliminary study, experts' opinions were used to assess the validity of the questionnaire. After reviewing and correcting, the validity of the questionnaire was assured. To assess the reliability of the questionnaire, a pre-test was performed with 55 questionnaires and the Cronbach's alpha coefficient for the questionnaire was 0.55, which indicates that the questions are highly valid. Table 1 shows the reasons for people's dissatisfaction with drinking water in Kermanshah. As shown in the table, the most reason for people's dissatisfaction with drinking water is related to the remaining salts in the container.
The results of the willingness to pay individuals show that among 361 samples, 16% of the respondents offered 5000 USD, 51% offered 4000 USD and 16.4% proposed 2000 USD for improving water quality. Also, 16.6% were not willing to pay a sum to improve the quality of drinking water. Table 2 shows the results of a lack of willingness to pay or a willingness to pay low in order to improve the quality of drinking water in the city of Kermanshah.

According to the results, unemployment among the five problems (unemployment, high living costs, low water quality, water crisis and environmental pollution), the highest and low water quality were the least significant among the respondents. Also, 76.5% of respondents believe that the quality of drinking water is fairly good and 23.5% of respondents believe that the quality of water is poor. In general, 80.2% of respondents did not rely on drinking water (piped water) and Concerned about diseases transmitted through drinking water. Considering that 95.8% of the statistical population sources their drinking water as piped water, therefore, 64.3 percent of the respondents were willing to pay a fee to improve the quality of tap water so that the water and sewage office assured them that no disease would spread through drinking water.
The results of estimating the Logit model are shown in Table 3. The dependent variable accepts a bid amount of 0 and one and variables such as recommendation rate, education, age, water quality concern, assurance of safe water quality and the quality of drinking water quality are independent variables. Also, variables that were not statistically significant were eliminated in the Logit model to help achieve better results.
Conclusions
Environmental valuation methods have been widely used to value recreational sites, but we must consider that all environmental benefits need to be valued to achieve sustainable development. Therefore, in this study, using the conditional valuation, the willingness to pay the residents of Kermanshah city was estimated to improve the quality of drinking water. Public awareness and raising public awareness about the standards of safe water and transmissible diseases through contaminated water will greatly help people's attitudes towards water quality. It is natural for people in the community to be aware of the quality of water, demand for improved drinking water quality and if such a blue is not available, they will be willing to pay for it. Regarding the results of the present study, in the logit model, the relationship between income variable and pay-as-you-go income was not significant. It can be noted that all strata of society, not just high-income people, are demanding safe and safe drinking water, and in order to achieve such a goal, they will have financial support from the government, and in particular the water and sewage administrations. considering the importance of drinking water for the residents of Kermanshah and the desire to pay them high in order to have a healthy and high quality water, it is clear that people of the community can play an important role in supplying water. Therefore, in the area of management and planning process, conscious efforts must be made to fulfill the community's needs and address their concerns regarding the quality of drinking water. Because these are people who must meet them when they are in trouble.