Statistic analysis of average annual precipitation in the areas in and around Bohai Sea

Researches on the exploitation and utilization of sea water and sea ice as a kind of fresh water resource of Bohai Sea have been conducted recently.However,the impact of such activities on the water balance of Bohai Sea has seldom been studied.This paper focuses on such an impact from the aspect of the contribution of atmospheric precipitation to the water balance of Bohai Sea.We chose Bohai Sea area and the seaward land in the watershed as the research area.Based on the average annual precipitation data from 92 meteorological stations in the researched land area from 1971 to 2000,we use Thiessen polygon theory grounding on GIS to make statistic analysis of average annual precipitation in the two areas.Statistic results show that average annual precipitation in the watershed is 63.88% of the total precipitation in the whole land area in 2000,being three times of the water required in this area.The amount of the sea water which was directly utilized from Liaodong Bay is 3.09% of the average annual precipitation in this bay,which is 15.86% in Bohai Bay,17.38% in Laizhou Bay and 8.82% in the whole Bohai Sea.And the sea ice reserve in Liaodong Bay in 2002 is 6.08% of the average annual precipitation in this bay.Results show that it is feasible to calculate average annual precipitation based on the Thiessen polygon theory in the researched area of seaward land in the watershed.Compared with(using) average annual precipitation in the whole area around Bohai Sea in calculating the(amount) of water finally flowing into Bohai Sea from land,the method of picking out the seaward land in the watershed to conduct the calculation is much more reasonable.The(approach) applied in this research of examining the relationship between the amount of the exploited and utilized sea water and sea ice and the average annual precipitation in Bohai Sea area is primary,but it is in support of further study on the relationship between the(amount) of the exploited and utilized sea water and sea ice and the water balance in Bohai Sea.