Water resources renewability (WRR) determines water resources sustainability. Facing the increasing serious water resources pressure over the Pearl River Delta (PRD)

this paper

constructed a multi-hierarchy and multi-index WRR assessment system and developed an assessment model based on variable fuzzy sets theory

by which the WRR level of PRD was assessed. The results show that the WRR levels of nine cities in the PRD all belong to level II

with Shenzhen and Zhaoqing being the strongest while Foshan and Dongguan being the weakest. Particularly

the WRR levels of Zhongshan

one of the nine cities

are determined by its social WRR levels and go down first then up from 2001 to 2012. The assessment results of different methods show that Grey Relation Analysis and Fuzzy Comprehensive Evaluation have almost the same results. Variable Fuzzy Evaluation gives results with one level lower than those of the above two methods

since it calculates membership grades more finely and inclines to give lower level assessment. Genetic Projection Pursuit Method produces unreasonable results when sample data vary tremendously

thus making it not applicable for assessment of WRR levels of the nine cities in the PRD. In addition

a stricter standard system was constructed based on national data and data of the PRD. Under that system

the WRR levels of nine cities of the PRD were all assessed as level III. The stricter assessment results are likely to promote measures to increase WRR of the PRD.