华北小麦-玉米轮作净灌溉需水量变化趋势——以大兴区为例

Trend of Net Irrigation Water Requirement of Wheat-maize Rotation in North China-A Case Study of Daxing District

【目的】开展不同时间序列华北小麦-玉米轮作净灌溉需水量变化趋势研究,为未来农业用水规划提供决策参考。【方法】采用Mann-Kendall非参数检验法分析了近60 a(1961―2017年)与近30 a(1988―2017年)小麦-玉米轮作的作物需水量、有效降水量、净灌溉需水量的变化趋势。【结果】不同时间序列小麦-玉米轮作的作物需水量、有效降水量及净灌溉需水量的变化趋势存在较大差异,1961―2017年小麦-玉米轮作作物需水量与有效降水量整体呈显著增加趋势,变化倾向率分别为5.3、7.8 mm/10 a;而净灌溉需水量呈不显著减少趋势,变化倾向率为-2.5 mm/10 a。1988―2017年小麦-玉米轮作作物需水量整体呈显著增加趋势,变化倾向率为11.0 mm/10 a;有效降水量整体呈显著减少趋势,变化倾向率为-7.3 mm/10 a;净灌溉需水量整体呈显著增加趋势,变化倾向率为18.3 mm/10 a。【结论】1961―2017年小麦-玉米轮作的净灌溉需水量减少,主要是平均风速与日照时间减少所致;而1988―2017年小麦-玉米轮作净灌溉需水量增加,主要是气温升高与相对湿度减少所致,且序列越短其变化趋势越显著。因而在进行灌溉用水规划时,合理选择序列长度尤为重要。

【Objective】This paper is intended to provide a decision-making reference for future agricultural water planning.【Method】In this paper, Mann-Kendall nonparametric test was used to analyze the changes of crop water requirement, effective precipitation and net irrigation water requirement in wheat-maize rotation for 60 years(1961-2017) and nearly 30 years(1988-2017).【Result】1961―2017, the water requirement and effective precipitation of wheat-maize rotation crops increased significantly at the rates of 5.3 mm/10 a and 7.8 mm/10 a respectively, while the net irrigation water requirement decreased slightly at the rate of 18.3 mm/10 a. In the past 30 years, the water requirement of wheat-maize rotation crops increased significantly at the rate of 11.0 mm/10 a, the effective precipitation decreased significantly at the rate of-7.3 mm/10 a, and the net irrigation water requirement increased significantly at the rate of 18.3 mm/10 a.【Conclusion】There were large differences in the trends of the different time series. The decrease of net irrigation water requirement in recent 60 years was mainly due to the decrease of average wind speed and sunshine hours,although the increase in the past 30 years was mainly due to the increase of air temperature and the decrease of relative humidity. The shorter the sequence was, the more significant the change trend was. Therefore, it was very important to choose the sequence length reasonably when planning irrigation water use.