GB/T 20486-2026Grades of watershed areal rainfall (English PDF)

3 Terms and definitions

4 Classification of the areal rainfall levels

5 Calculation method of the areal rainfall

Foreword

This document has been drafted in accordance with the rules given in GB/T 1.1-2020, Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.

This document replaces GB/T 20486-2017, Grade of watershed areal rainfall. Compared with GB/T 20486-2017, apart from structural adjustments and editorial changes, the main technical changes are as follows:

a) the definition of watershed and its English equivalent have been changed (see 3.1; 2.1 of the 2017 edition);

b) the definition of station rainfall and its English equivalent have been changed (see 3.2; 2.2 of the 2017 edition);

c) the term and definition of gridded rainfall have been added (see 3.3);

d) the term and definition of rainfall grade have been deleted (see 2.3 of the 2017 edition);

e) the definition of areal rainfall and its English equivalent have been changed (see 3.4; 2.4 of the 2017 edition);

f) threshold ranges for 3 h and 6 h areal rainfall grades have been added (see Table 1 in Clause 4);

g) the method of calculating areal rainfall has been changed and its field of application added (see Clause 5; Clause 4 of the 2017 edition).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.

This document was proposed by the China Meteorological Administration.

This document is under the jurisdiction of the National Technical Committee on Meteorological Disaster Prevention and Mitigation of Standardization Administration of China (SAC/TC 345).

Drafting organisations of this document: National Meteorological Centre; Henan Provincial Meteorological Observatory; Information Centre of the Ministry of Water Resources; Anhui Provincial Meteorological Information Centre.

Principal drafters of this document: Xu Fengwen, Wang Meng, Bao Hongjun, Wang Li, Cao Shuang, Di Jingyue, Huang Changxing, Ye Jinyin, Wang Di, Li Yumei, Yun Xiaobo, Yang Yin.

The previous editions of this document and of the document it replaces are as follows:

- first published in 2006 as GB/T 20486-2006 and first revised in 2017;

- this is the second revision.