| The agricultural water resources decrease year by year due to the fast promotion of industrialization, urbanization, modernization and ecological civilization construction. And it is a major strategic issue that guaranteeing nation grain safety from the increasingly tense contradictions between the supply and demand of agricultural water resources. With impact of the climate change, the phenological period of winter wheat will be changed, and the characteristics of the water supply and demand on different growth period will be changed thereupon. And deeply understanding these change is significant to solve the contradiction between supply and demand of agricultural water resources. And the field investigation was conducted in the Shijin irrigated district in Hebei province and the geographic information technology and numerical simulation method was used to study the issue. Integrating the future climate scenarios, the change of the irrigation demand of the winter wheat in the future was studied from the perspective of statistics. Some conclusions were showed in following:(1) The characteristic of the climate change in study area:the annual precipitation has no obvious increase or decrease trend, but there are periodic variation of 40 years,23 years, and 16.5 years; and the increase trend has been found on the spring, but the other seasons, the trend is decrease. The annual average and minimum temperature increase significantly, but there is no trend in maximum temperature; and the annual average temperature mutates in 1993, there are periodic variation of 40 years,23 years. Annual average relative humidity, sunshine duration and wind speed significantly decrease, and seasonal change trends are consistent with trends in whole year.(2) The characteristic of the phenological period of winter wheat in study area:the date of the suitable sowing of winter wheat delayed 5 d after 2000, and the dates of sowing, emerge, tillering delayed all from 1955-2012, but the date bring forward after reviving. The mutation of the maturing date was happened on 1986, and before the mutation, the date was 15th in June, and after, the date was 10th in June. a trend of decrease was appeared on the days of the winter wheat growth from 1955 to 2012, the climatic trend rate was -2.5 d/10a, the days was reduce 8 d after 1980.(3) The characteristic of the water requirement on different growth periods of the winter wheat in study area:the annual average amount of water requirement on the whole growth period of winter wheat is 604.8±62.8 mm, and there are two peaks, the one is from the green stage to jointing stage, the other is from flowering stage to filling stage. There is a significant decrease trend on the annual average amount of water requirement on each phenological period at the temporal scale, and the mutation is occurred between 1974-1985. The spatial distribution of the water requirement on the green stage, jointing stage and flowering stage has the pattern of the ’east west high low’, while on the filling stage, the pattern changes to’low in west high east’.(4) The variation of the precipitation process i in study area was made under the under climate change, and the variation includes five aspects. ① Obvious increase trend was found in the amount of precipitation in the stage of winter wheat jointing, but for other stages, the change of the rainfall amount was not significant. ② Neither heavy rainstorm nor extremely rainstorm was happened during 1955-2012 in the Shijin irrigated area, and significant decrease trend was found in the times of the light rain happened on the stages of sowing-early and filling(α=0.05), but on the stage of flowering, the trend was increase. The times of the moderate rain happened had a decrease trend on the stage of filling and a increase trend on other stage of winter wheat growth, but the trend was not significant. ③ The rainfall duration was gradually decreased with the development of the winter wheat growth, but for the rainfall intensity, it was increased. The average intensity of the precipitation on the whole stage of winter wheat growth was 0.88 mm/h, and the intensity of the light rain was 0.65 mm/h. ④ Different times at which the rain happened was found among different rains. And the light rain always happened at 15:00 to 22:00, and the heavy rain and stormy rain mainly occur at 2:00-6:00 am, for the moderate rain, the time was randomly at 0:00-24:00. ⑤ There was uniform distribution in the Shijin irrigated area of the light rain intensity at the spatial scale, and the patial pattern of "higher in northeast and lower" in southwest was appeared in study area of the moderate rain intensity on four stages of winter wheat growth. For the heavy rain, the intensity of the spatial pattern varied from homogeneity to the fragmentation, in the final, it was "higher in middle and lower surrounding". And the distribution of the storm rain intensity was randomly in the study area.(5) The curve of the probability density function of soil relative moisture on the stages of reviving, jointing, flowering and filling was "single-peak" on the rain-fed conditions. And the expected value of soil moisture was during 0.17-0.19 on the four stage of winter wheat growth. The amount of the irrigation which could made the soil moisture remained above 80% of field capacity on the stage of the reviving under any loss in irrigation activity conditions was calculated by the Laio model, and the value was 72.2±9.0 mm at the probability of 50%, for the stages of the jointing, flowering, filling, the value was 86.9±3.0 mm,78.5±10.5 mm,53.4±14.2 mm, respectively. The amount of irrigation on the stages of winter wheat growth was significant decreased in the future(2011-2050) on the IPSL-CM5A-LR model of scenarios of RCP2.6 and RCP4.5, and the rate was between 16.9%-47.2%. |
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