宁蒙灌区灌溉定额偏高成因及节水潜力分析

REASONS OF HIGH IRRIGATION QUOTA AND POTENTIAL OF WATER-SAVING IN NING-MENG IRRIGATION AREA

宁蒙灌区灌溉定额是关中地区的 6倍左右 ,因而常常遭受各方的批评。但宁蒙灌区灌溉定额高并非完全是不合理的大水漫灌的结果 ,在很大程度上有其自然规律的必然性和合理性。由于自然条件的差异 ,宁蒙灌区的作物需水量、净灌溉定额本来就要比关中地区高很多。如果不改变目前的作物品种和种植结构 ,宁蒙灌区较高的灌溉定额 60 %左右是合理的 ,只有 40 %左右是不合理的。这既说明了宁蒙灌区节水的巨大潜力 ,只要达到关中地区的水资源有效利用系数 0 5 ,就可以减少引水 40 %左右 ,减少灌溉耗水的3 0 %左右 ;同时也说明了宁蒙灌区节水的限度 :在目前的作物品种和种植结构下 ,宁蒙灌区的灌溉定额不可能降低到与黄河中下游地区相同的水平 ,仍将维持在关中地区目前灌溉定额 (2 70 0m3 hm-2 左右 )的 3倍以上。要想进一步降低宁蒙灌区的灌溉用水 ,只有在改变灌溉方式 (如改普通地面灌为喷灌、滴灌 )以降低作物需水量。

The irrigation quota in Ningxia Plain irrigation area is 6 times higher than that of Guanzhong Plain irrigation area, while the irrigation quota in Hetao Plain irrigation area, Inner Mongolia, is 4 times higher than that of Guanzhong. So it is no doubt that the high irrigation quota in Ning Meng irrigation area (abbreviation for irrigation areas in Ningxia Plain, Ningxia and Hetao Plain and Inner Mongolia) is criticized strongly. But our analyses have shown that: More than 60% of the high irrigation quota in Ning Meng irrigation area is rational under present crop structure due to natural conditions such as higher crop water requirement and lower efficient precipitation. Only less than 40% of present irrigation quota is irrational because of lower water use efficiency. If not to change crop varieties cultivated, only by promoting the irrigation water use efficiency in Ning Meng irrigation area to advanced level of Guanzhong area, about 40% of water withdraws in Ningxia Plain can be saved while about 30% of net water depletion can be saved. In Hetao irrigation area, Inner Mongolia, the corresponding figures are 32 3% and 20%. If cultivating area of water intensity crops such as rice decreases, more water can be saved. There is high potentiality to decrease water irrigation quota by 60% and water exhaustion quota by 50% in this area through all kind of water saving measures.