Study on Indexes System of Assessing Rainwater Utilization Environmental Benefit and Its Application

Taking the Loess Plateau as its study field, choosing small watershed as its study unit, taking rainwater resources as its study object, based on the systematical analysis of the previous and current correlative results about rainwater utilization environmental benefit assessment, the author makes an effort in how to select indexes, how to define weight, how to quantify the indexes and how to establish assessment model. Based on the above study, the author synthetically appraises the rainwater utilization situation of the Hangfuchuan Heimaotugou small watershed in Inner Mongolia, and validates the assessment result by the analysis results of investigation questionnaire .The main results are listed as follows:1) According to the features of the loess Plateau, the natural and Social and economical factors are considered comprehensively ,followed the principles about indexes selecting，established a set of index system including the selected 11 indexes of three types，which is based on the application results of AHP(Analytical Hierarchy Process) and Frequence Stat Analysis.The index sustem can be used in the assessment of rainwater utilization environmental benefit and dynamic monitoring. Using the indexes system, we can make lengthways parallel of single index and the systematical study on synthetical assessment.2) By analyzing deeply the rules of soil and water conservation and rainwater utilization environmental benefit, to avoid error in marking out grades, the contribution functions are set up to realize the indexes, quantification with the help of fuzzy mathematics theory. Based on this, the rainwater utilization environmental benefit comprehensive assessment model is established, the assessment result of which is comprehensive assessment index.3) Using the index system and the comprehensive assessment model , the author assesses the rainwater utilization situation of Heimaotugou small watershed , the comprehensive asses- sment index in 1994 is 0.6664，and 0.773 in 2000.Here listed the results: in the year of 2000 ＝0.9102＞＝0.8117＞＝0.3997 and ＝0.7793＞＝0.6956＞＝0.3664.IT is shown in the calculation result that ecological benefit is superior to economical benefit, economical benefit is superior to Social benefit .We can draw a conclusi- on that the local people have made great progress in rainwater utilization and the benefit is remarkable. <WP=7>4) The author selects typical small watershed to validate the above assessment results through the investigation and investigation on the spot combined with the local government statistical material .IT is indicated in the analysis result that the assessment index and model proposed in this article can preferably reflect the change of rainwater utilization comprehensive environm- ental benefit.