A study on value estimation, collection and utilization of rainwater resources in cities of northern China—A case study of Xi´an city

As an important water resource, rainfall resources play a great role in human´s production life and socio-economic development. In this paper, the northern typical city-Xi´an was taken as an example. On the basis of temporal and spatial distribution and utilization of water resources as well as the average annual precipitation statistics during 1999 to 2008 in Xi´an, the theory of rainfall frequency curve Pearson type III was established, and its economic value was estimated from aspects such as rainfall values, costs decrease and losses reduction. The results are as following. First, according to the city´s theory of rainfall frequency curve Pearson type III, it is obtained that the average annual precipitation for 732.5mm and the total precipitation for 1.89×10⁸m³ in wet years, the average annual precipitation for 511.8mm and total precipitation for 1.32×10⁸m³ in normal years, the average annual precipitation for 359.6mm and the total precipitation for 0.93×10⁸m³ in dry years. Second, in wet years, the value of rainfall resource itself is 8.26×10⁸ yuan and the decreasing costs of the city´s supply is 4.12×10⁸ yuan; in normal years, the value of rainfall resource itself is 5.78×10⁸ yuan and the decreasing costs of the city´s supply is 2.88×10⁸ yuan; in dry years, the value of rainfall resource itself is 4.06×10⁸ yuan and the decreasing costs of the city´s supply is 3.11×10⁸ yuan, while the losses caused by water shortage decreased by 0.19×10⁸ yuan. In view of the great utilized value of rainfall resources, the paper brings up an approach to use city rainfall effectively from catchments of city buildings, accumulation of City Park, and utilization of agricultural and other aspects, which has practical guiding significance for the exploitat- on and utilization of rain in future.