Study On Water Use In Agriculture And Water Resources Distribution In Hangzhou

During year 1997-2001, the percentage of agriculture water consumption ranged from 33% to 48% of total water withdrawal in Hangzhou, while the paddy fields were the largest water user, accounting for more than 90% of agriculture water withdrawal. Paddy is the main crop in Hangzhou, and its water use play an important role in water distribution of Hangzhou city.Based on the data of daily water withdrawal, rainfall and evaporation in 14 experimental paddy fields, which were varied in landform, soil type, drainage system, growth rule, and irrigation mode, with typical investigation, and analysis in the influence factors on water use, the research of water use regulation in paddy fields and its influence on water resources distribution was done. At the same time, the mathematical relation between the total water consumption and the growth days of paddy was founded.Through the water quality analysis on the COD TP, TN in the irrigation water and drainage water in a model experimental field, the regulation and its influence on environmental water pollution by the drainage water was also studied.According to the present situation of the agricultural irrigation and water resources status, suggestions and possible solutions for water saving, proper distribution of water resources in Hangzhou, and the reduction of water crisis as well as nonpoint source pollution were presented.The main conclusions are as following:1. The experiences, scientific knowledge and water-saving consciousness of the peasants who are in charge of irrigation have the predominant influence on agricultural water use. In some rich areas, the waste of the irrigation water is above 50%.2. The centralized growth mode will save 11%-59% of the irrigation water use comparing to those needed in separated growth mode in same acreage.3. There is a large potential space for water saving by rainfall use.4. The rule of water use for the single-season rice is fairly fit to the local rainfall distribution. However, if the growth period is one month-ahead of the present schedule, it will save 100 million m3 of water withdrawal in Hangzhou.5. The concentrations of TP, TN in drainage water respectively have a peak value and a 40-days stable period.6. The irrigation using polluted water with high organic matter and TN is good for plant growing and environmental improvement, and the clear water for irrigation is not economic.