DEVELOPMENT OF WATERSHED ASSESSMENT PROCEDURE: A NEW APPROACH

Watershed management is required to maintain the quality and quantity of water resources. Recently, the indication of change in watershed quality has become a global concern. A better procedure is necessary for watershed assessments. This study observed the downward trend in watershed's quality in the proposed procedure through four following parameters: a) average of annual discharge, b) the coefficient of flow regime, c) the coefficient of annual runoff and d) the value of the water availability index every year. A regression technique was modified in this study to obtain a more sensible prediction of future watershed quality. The technique developed in this study was demonstrated to assess the degradation of watershed quality in Lombok Island. Hydrological data from 1994 to 2016 was used in this study. The results showed that the new modified technique of regression was reasonable to be applied. Moreover, it was found that the average of river discharge decreases by 4% per year, the coefficient of river regime increases by 9% annually, the Coefficient of runoff increases 9% annually and the Index of Water Availability decreases by 4% every year.