条件价值评估法的调查问卷格式主要有连续型(包括开放式、支付卡式)和离散型(即封闭式)两种类型。针对黑河流域张掖市生态系统退化的现状,在连续型的支付卡问卷格式调查的基础上,以离散型单边界两分式和双边界两分式的封闭式问卷格式各设计了400份调查问卷,调查了黑河流域居民对恢复张掖市生态系统服务的支付意愿。封闭式两分式问卷调查结果的分析表明,黑河流域90.2%的居民家庭对恢复张掖市生态系统服务存在支付意愿。单边界两分式和双边界两分式问卷分析的黑河流域居民家庭对恢复张掖市生态系统服务的平均最大支付意愿每户每年分别为162.82元和182.38元。按黑河流域有支付意愿的家庭数量计算,用单边界两分式和双边界两分式问卷分析,恢复张掖市生态系统服务的经济效益每年分别为7094.36×104元和7946.66×104元。由于双边界两分式问卷更能逼近市场行为,以双边界两分式问卷的结果作为条件价值评估的结果相对比较恰当,因此,未来5年时间恢复张掖市生态系统服务总经济价值的现值为3.7478×108元。由于恢复张掖市生态系统服务具有巨大的正外部效应,因此,仅就黑河流域居民家庭数量估计的经济价值是对恢复张掖市生态系统服务的经济价值的最低估价。

The Contingent Valuation Method(CVM)is a direct interview approach that uses si - mulated(hypothetical)markets to identify values similar to actual markets.CVM is a promising technique that could potentially help public decision-making.CVM has two major question formats,the continuous and discrete contingent valuation(CV).Lots of empirical studies conducted in various contexts show that the approach is well-accepted by the general public.Based on the result of payment card format,one of the continuous CV,in this paper,we take the dichotomous choice(single-ended and double-ended)question format which belongs to the discrete CV as a tool to analyze the economic benefits of restoring ecosystem service in an impaired river basin,Heihe river basin.In our survey we use a well-designed questionnaire with maps,pictures and figures depicting the reason why the ecosystem of Heihe river basin and Zhangye city has been deteriorating,the measures by which ecosystem services could be restoring from their current level,and the benefits the households in the area could get from restoring ecosystem services.Results from400in-person interviews for single-ended and double-ended dichotomous format respectively indicate that90.2%of the households in Heihe river basin would like to pay for restoring the ecosystem services of Zhangye city.The result shows that the maximum average willingness to pay(WTP)is162.82and182.38RMB yuan per household per year for single-ended and double-ended dichotomous formats respectively.The annual aggregate benefits of restoring ecosystem services of Zhangye city are at least7094.36×10 4 and7946.66×10 4 RMB yuan for single-ended and double-ended dichotomous formats respectively,calculated by the number of the households in1999in the Heihe river basin.This result is a conservative estimate for the economic value of restoring the ecosystem services of Zhangye city because of the positive externalities of restoring the ecosystem services on the outside of Heihe river basin.It has been found that double-bounded format has a tighter confidence interval for the esti-mate of mean WTP than single-bounded format,and is more closely approximate to the true WTP of respondents.Therefore,we suggested that the estimation results of double-bounded format as the total economic value of restoring Zhangye city ecosystem services.The aggregate benefit(pre-sent value)of restoring Zhangye city ecosystem to residents of the Heihe basin is3.7478×10 8 RMB Yuan in the next5years.