泾惠渠灌区作物种植结构变化对灌溉需水量的影响

Influence of Crop Planting Structure Change on Irrigation Water Requirement in Jinghuiqu Irrigation Area

摘要:

研究种植结构变化对灌区作物需水量和灌溉需水量的影响，能够为作物生育期的灌溉用水管理和农业水资源规划提供基础数据。依据泾惠渠灌区实测降水和蒸发蒸腾等气象数据，采用FAO推荐的Penman—Monteith公式和作物系数法计算灌区主要作物需水量；通过频率计算和配线法确定灌区丰水年（25%）、平水年（50%）和枯水年（75%）的有效降水量；根据1988—2014年Landsat卫星遥感影像提取的泾惠渠灌区不同历史时期农业种植结构数据，计算典型水文年份灌区总灌溉需水量，并分析作物需水量和灌溉需水量在不同典型水文年的年际和月际变化。结果表明，随着泾惠渠灌区农业种植结构的变化，灌区总的作物需水量和灌溉需水量都呈现显著下降趋势。但泾惠渠灌区在1988—2005年间，单位面积平均作物需水量和平均灌溉需水量都基本保持不变，随后均呈小幅下降趋势。各月份作物总需水量和总灌溉需水量除6月份之外，其余各月份都呈现显著下降趋势；但在此期间，灌区单位面积平均作物需水量和平均灌溉需水量除在4、8、9月份呈下降趋势，而6月份呈显著增加趋势外，其余各月份基本保持不变。灌区总的作物需水量和灌溉需水量的下降主要是由农作物种植面积大量减少所致，种植结构的变化对其影响较小，但灌区种植结构调整后的作物需水量状况更符合区域有效降水特点。

Abstract:

Researching the effect of crop planting structure change on alteration of crop water demand and irrigation water consumption would provide basic data for irrigation water management in the period of crop growing and agricultural water resources planning. Based on the meteorological data of actual precipitation and evapotranspiration collected in Jinghuiqu Irrigation Area, the irrigation water requirement of main crops was calculated by using Penman—Monteith formula and crop coefficient method recommended by FAO, and the effective precipitations of rainy year (25%), normal precipitation year (50%) and draught year (75%) were determined through frequency calculation and fitting curve method. Then the total irrigation water requirement in typical hydrologic years was calculated according to agricultural crop planting structure data in different periods extracted from remote sensing images in Jinghuiqu Irrigation Area from 1998 to 2014. The monthly and yearly change of water demand of crop and irrigation water requirement of typical hydrologic years were analyzed. The results showed that, in Jinghuiqu Irrigation Area from 1988 to 2014, with the change of agricultural planting structure (the crop planting area was reduced by 63.5%, the orchard area was increased by more than 10.2 times, and the inhabitants area was increased by 1.63 times), the crop water demand and irrigation water requirement displayed a significant decrease. The total water demand was decreased from 780 million m3, 800 million m3 and 820 million m3 to 520 million m3, 530 million m3 and 540 million m3, and the amount of irrigation water was dropped from 290 million m3, 350 million m3 and 430 million m3 to 190 million m3, 230 million m3 and 270 million m3 in three hydrologic years, respectively. Among different planting crops, the ratio of amount of irrigation water consumption of winter wheat and summer maize was dropped from over 90% to 50%, while that of the orchard was grown from less than 5% to 50%, and that of facilitated agriculture tended to increase slightly. However, the average crop water demand of unit area of three hydrologic years from 1988 to 2005 was remained around 720mm, 700mm and 685mm, then it was decreased slightly, and later it was dropped to 700mm, 685mm and 670mm in 2014, during which period the average irrigation water requirement almost equaled to the average crop water demand of unit area. With the change of planting structure from 1988 to 2014, the total irrigation water requirement and total crop water demand of unit area in each month, apart from June, showed a significant decreasing tendency, but the average irrigation water requirement and average crop water demand of unit area were decreased in April, August and September, increased in June and remained the same in other months. It indicated that the decrease of crop water demand and irrigation water requirement was caused mainly by decrease of crop area, and slightly by change of crop structure. The result also showed that the crop irrigation water requirement after adjusted crop planting structure was more in accordance with the features of regional effective precipitation.